o & m manual

OPERATION & MAINTENANCE

MANUAL

FOR 2 X 282.5 TPH

TRIPPLE PRESSURE NATURAL CIRCULATION, SINGLE DRUM,UNFIRED HEAT

RECOVERY STEAM GENERATOR WITH REHEAT

SUPPLIED TO

LANCO KONDAPALLI — STAGE III

THERMAX PROJECT NO.: PH 0401/02

THERMAX BABCOCK & WILCOX

A DIVISION OF THERMAX LIMITED

PUNE, INDIA

0 VSD 30.12.2011 AA 30.12.2011 NS 30.12.2011 0

REV PREPARED BY CHECKED BY APPROVED BY REVISIONDESC. /

REMARK

Operation & Maintenance Manual

Contents

Volume 1 — Boiler Description ....................................................................................................1Section A................................................................................................................................2

1 Design Specifications of Steam Generator ....................................................................32 Design Code...............................................................................................................43 Levels With Respect To Center Line .............................................................................44 Material Specifications — Pressure Parts .....................................................................45 Evaporating Heating Surface Area ...............................................................................66 Exhaust Gas Analysis .................................................................................................6

6.1 Continuous Blowdown........................................................................................67 Recommended Boiler Water Quality .............................................................................78 Recommended Feed Water Quality ..............................................................................79 Utilities .......................................................................................................................810 Chemicals for Dosing ................................................................................................911 Site Condition............................................................................................................912 Recirculation Pump .................................................................................................1013 HP/IP/LP Dosing System .........................................................................................1014 Gauge Glass ..........................................................................................................1215 Stack Damper .........................................................................................................1316 Safety Valves ..........................................................................................................1317 Relief Valves ...........................................................................................................15

Section B..............................................................................................................................161 Brief Description of the HRSG....................................................................................162 Description of HRSG Operation .................................................................................163 Steam & Water System .............................................................................................17

3.1 HP Boiler Components Description ...................................................................173.2 IP Section Components Description ..................................................................263.3 LP Section Components Description .................................................................333.4 Operational Control..........................................................................................393.5 Water And Steam Quality Control And Monitoring ..............................................403.6 Maintaining Quality Of Steam ..........................................................................42

4 Flue Gas System ......................................................................................................434.1 AIM.................................................................................................................434.2 Detailed Description.........................................................................................43

5 Drain & Dosing System..............................................................................................456 HRSG System Protection ..........................................................................................517 Automatic Controls....................................................................................................53

7.1 Drum Level Control ..........................................................................................537.2 CBD Drain Temperature Control .......................................................................597.3 Stack Temperature (CPH Bypass 3- Way) Control .............................................597.4 LP Drum Pressure Control ...............................................................................607.5 LP Drum Pressure Control ...............................................................................607.6 HP Attemperator Control ..................................................................................607.7 RH1 Attemperator Control ................................................................................607.8 CPH Recirculation Temperature Control ............................................................617.9 IP Line Back Pressure Control ..........................................................................617.10 Start up Vent (HP, IP & LP) Control .................................................................61

Section C .............................................................................................................................631 Section Overview ......................................................................................................632 HRSG Start Up and Shut Down .................................................................................633 Startup of a Cold HRSG ............................................................................................63

3.1 Walk Down Check ...........................................................................................633.2 Valve Lineup....................................................................................................643.3 System Lineup ................................................................................................65

i


3.4 Valve Positions Chart For HP, IP & LP Section (Before Light Up) ........................663.5 Filling Water in Boiler .......................................................................................753.6 HRSG Start Up & Pressurisation.......................................................................753.7 HRSG Cold Start Up Curve ..............................................................................783.8 Taking Reheater On Line .................................................................................793.9 Charging & Operation of CPH...........................................................................803.10 Parallel HRSG to the Plant Steam Mains.........................................................80

4 Hot and Warm Start up of HRSG ...............................................................................815 HRSG Shutdown.......................................................................................................86

5.1 Planned Shutdown...........................................................................................865.2 HRSG Emergency Trips ...................................................................................86

6 Cooling of a Shutdown Boiler .....................................................................................876.1 Natural Cooling................................................................................................876.2 Forced Cooling ................................................................................................87

7 HRSG Operation Walk Down Checks ........................................................................878 Do’s and Don’ts For HRSG Operation........................................................................879 Boiler Log Sheet .......................................................................................................89

9.1 Log Sheet for HRSG........................................................................................8910 Boiler Emergency Safety Procedures .......................................................................93

10.1 Emergency Procedures..................................................................................9310.2 Alarms and Trips............................................................................................9510.3 Operational Precautions for Safety .................................................................9510.4 Tube Failures ................................................................................................9510.5 Safety in Boiler House....................................................................................95

11 Trouble Shooting Chart ............................................................................................96Section D ........................................................................................................................... 100

1 Section Overview .................................................................................................... 1001.1 Recommended Maintenance Practices ........................................................... 100

2 Welding Procedure Specifications (WPS) ................................................................. 1073 Boiler Preservation Procedure.................................................................................. 107

3.1 Definitions of Water Quality ............................................................................ 1073.2 Dry Storage Preservation ............................................................................... 1083.3 Wet Storage .................................................................................................. 1093.4 Nitrogen Blanket ............................................................................................ 1103.5 Boiler Lay Up Procedures............................................................................... 1113.6 Preservation of Rotating Equipments .............................................................. 1113.7 Preservation of Instruments ........................................................................... 111

4 Tube Failures.......................................................................................................... 1124.1 Tube Failure Investigation / Analysis Method ................................................... 1124.2 Window Patch Welding .................................................................................. 114

5 General Principal of Weld Repairs............................................................................ 1166 Failure Reporting Format ......................................................................................... 1277 Water Chemistry ..................................................................................................... 128

7.1 Undissolved and Suspended Solid Materials ................................................... 1287.2 Dissolved Salts and Minerals.......................................................................... 1287.3 Dissolved Gases............................................................................................ 1297.4 Other Materials.............................................................................................. 1297.5 pH Value of the Water and its Importance........................................................ 1297.6 Effects of Impurities ....................................................................................... 129

8 Feed & Boiler Water Conditioning............................................................................. 131Section E............................................................................................................................ 134

Volume 2 — Drawings.............................................................................................................. 1 35List of Drawings .................................................................................................................. 135

Volume 3 — E & I Specifications.............................................................................................. 136

ii


Section 1 ............................................................................................................................ 137Section 2 ............................................................................................................................ 137Section 3 ............................................................................................................................ 137Section 4 ............................................................................................................................ 137Section 5 ............................................................................................................................ 137Section 6 ............................................................................................................................ 137Section 7 ............................................................................................................................ 137Section 8 ............................................................................................................................ 137Section 9 ............................................................................................................................ 137Section 10 .......................................................................................................................... 137Section 11 .......................................................................................................................... 137Section 12 .......................................................................................................................... 138Section 13 .......................................................................................................................... 138

Volume 4 — Vendor Manuals ................................................................................................... 139Section 01 .......................................................................................................................... 140

Recirculation Pump - Sulzer .......................................................................................... 140Section 02 .......................................................................................................................... 140

Dosing System - Metapow ............................................................................................ 140Section 03 .......................................................................................................................... 140

HP Drum Level Gauge Glass – Hi tech. ......................................................................... 140Section 04 .......................................................................................................................... 140

IP & LP Drum Transparent Level Gauge Glass - Chemtrols............................................. 140Section 05 .......................................................................................................................... 141

Blow Down Tank Reflex Level Gauge Glass - Chemtrols................................................ 141Section 06 .......................................................................................................................... 141

Stack Damper — Indira Damper.................................................................................... 141Section 07 .......................................................................................................................... 141

Spring Hanger – Pipe Support....................................................................................... 141Section 08 .......................................................................................................................... 141

Flow Nozzle — Micro Precision ..................................................................................... 141Section 09 .......................................................................................................................... 141

Safety Valve — Tyco Sanmar........................................................................................ 141Section 10 .......................................................................................................................... 142

Relief Valve — Tyco Sanmar......................................................................................... 142Volume 5 — Vendor Manuals ................................................................................................... 143

Section 01 .......................................................................................................................... 1441.1 Differential Pressure Transmitter (EJA) – Yokogawa.................................................. 1441.2 Absolute & Gauge Pressure Transmitter (EJA) – Yokogawa ...................................... 1441.3 HART Protocol (EJA Series) - Yokogawa.................................................................. 144

Section 02 .......................................................................................................................... 1442.1 Temperature Transmitter (YTA Series) - Yokogawa ................................................... 1442.2 HART Protocol (EJA) – Yokogawa ........................................................................... 144

Section 03 .......................................................................................................................... 1443.1 O2 Analyser (ZR 402G) — Yokogawa ...................................................................... 1443.2 HART Protocol — Yokogawa ................................................................................... 144

Section 04 .......................................................................................................................... 145Motor for Recirculation Pump - Siemens ........................................................................ 145

Section 05 .......................................................................................................................... 145Thermocouple - Pyroelectric ......................................................................................... 145

Section 06 .......................................................................................................................... 145Electronic Level Switch – Levelstate .............................................................................. 145

Section 07 .......................................................................................................................... 145DO2 Analyser - Emerson .............................................................................................. 145

Volume 6— Vendor Manuals .................................................................................................... 146

iii


Section 01 .......................................................................................................................... 147In-Situ Stack Gas Analysers - CODEL .......................................................................... 147

Section 02 .......................................................................................................................... 147Process Valve – Xomox Sanmar ................................................................................... 147

Section 03 .......................................................................................................................... 147Motorised Valve – Xomox Sanmar................................................................................. 147

Section 04 .......................................................................................................................... 147Motorised Actuator - Auma ........................................................................................... 147

Section 05 .......................................................................................................................... 147Blow Down Valve - BHEL.............................................................................................. 147

Section 06 .......................................................................................................................... 148Pressure Gauge - Bourdon ........................................................................................... 148

Section 07 .......................................................................................................................... 148Temperature Gauge – General Instrument .................................................................... 148

Section 08 .......................................................................................................................... 148Control Valve – Fisher .................................................................................................. 148

Index.................................................................................................................................. 149

iv


Volume 1 — Boiler Description

Chapters Covered in this Part

♦ Section A♦ Section B♦ Section C♦ Section D♦ Section E

Volume 1 — Boiler Description 1


Section A

Topics Covered in this Chapter

♦ Design Specifications of Steam Generator♦ Design Code♦ Levels With Respect To Center Line♦ Material Specifications — Pressure Parts♦ Evaporating Heating Surface Area♦ Exhaust Gas Analysis♦ Recommended Boiler Water Quality♦ Recommended Feed Water Quality♦ Utilities♦ Chemicals for Dosing♦ Site Condition♦ Recirculation Pump♦ HP/IP/LP Dosing System♦ Gauge Glass♦ Stack Damper♦ Safety Valves♦ Relief Valves

Section A 2


Number and Type of Boiler

2X 282.5 TPH (HP) 98.7 Bar (a), 40.2 TPH (IP) 26.1 Bar (a) and 32.3 TPH (LP) 4.37 Bar (a) TriplePressure, Natural Circulation, Single Drum, Unfired Heat Recovery Steam Generator With Reheat

1 Design Specifications of Steam Generator

PARAMETERS UNIT VALUE

HP Boiler Rating [MCR] TPH 282.5

IP Boiler Rating [MCR] TPH 40.2

LP Boiler Rating [MCR] TPH 32.3

HP Steam Pressure at Main SteamStop Valve Outlet from minimumLoad upto MCR

Bar (a) 98.7

IP Steam Pressure at Main SteamStop Valve Outlet from minimumLoad upto MCR

Bar (a) 26.1

LP Steam Pressure at Main SteamStop Valve Outlet from minimumLoad upto MCR

Bar (a) 4.37

HP Steam Temperature at the MainSteam Stop valve at MCR

° C 567.3± 3

IP Steam Temperature at the MainSteam Stop valve at MCR

° C 313.7

LP Steam Temperature at the MainSteam Stop valve at MCR

° C 286.5

Water temp at FW control valveinlet/Economiser inlet

° C 151

Design HP Pressure Bar (a) 112

Design IP Pressure Bar (a) 31

Design LP Pressure Bar (a) 9

Boiler Performance TestingProcedure

ASME PTC 4.4

Section A 3


2 Design CodeBoiler & Economiser /Pressure Parts: As per IBR 1950 with latest amendments

Piping: IBR, ANSI B 31.3

3 Levels With Respect To Center Line

For the High Pressure Steam Drum

PARAMETER ALARM VALUE

Normal Water Level NWL + 25 mm

Level Alarm High LAH + 225 mm

Level Alarm Low LAL – 225 mm

Level Trip Low Low LLLT – 330 mm

Level Trip High High HHLT + 300 mm

For the Intermediate Pressure Steam Drum


Normal Water Level NWL 0 (Center line of Drum)


Level Alarm Low LAL – 125 mm

Level Trip Low Low LLLT – 215 mm


For the Low Pressure Steam Drum


Normal Water Level NWL + 300 (Center line of Drum)


Level Alarm Low LAL - 300 mm

Level Trip Low Low LLLT - 1050 mm

BFW Pump Trip FWPT - 1350 mm


4 Material Specifications — Pressure Parts

Description Details Size In Mm Material

Shell 2000 I.D. x 100 ThkHP Steam Drum Dished end for S.D.

(Hemispherical)2000 I.D. x 100 Thk

SA 516 Gr.70

Shell1375 I.D. x 25 Thk

x 12500 LIP Steam Drum Dished end for S.D.(Hemispherical)

1375 x 25 ThkSA 516 Gr. 70

Shell 3000 I.D. x 20 ThkLP Steam Drum Dished end for S.D.

(Hemispherical)3000 I.D. x 20 Thk

SA 516 Gr. 70

HP Drum Risers 24 Nos. of Tube 200 NB x SCH 120 SA 106 Gr. B

IP Drum Risers 14 Nos. of Tube 150 NB x SCH 40 SA 106 Gr. B

LP Drum Risers 30 Nos. of Tube 150 NB x SCH 40 SA 106 Gr. B

Section A 4


Description Details Size In Mm Material

HP Drum Downcomers 4 nos. of Tube 350 NB x SCH 120 SA 106 Gr. B

IP Drum Downcomers 4 nos. of Tube 200 NB x SCH 40 SA 106 Gr. B

LP Drum Downcomers 4 nos. of Tube 300 NB x SCH 40 SA 106 Gr. B

Spiral Solid Tube 38.1 OD x 4.3 THK. SA 213 T91HP Superheater 3

Top & Bottom Header 200 NB x 45 THK. SA 335 P91

Serrated 44.5 OD x 3 ThK. SA 213 T91Reater 2


Serrated 38.1 OD x 3.2 THK. SA 213 T91HP Superheater 2


Serrated 44.5 OD x 3 THK. SA 213 T22Reater 1

Top & Bottom Header 200 NB x SCH 160 SA 335 P22

Serrated 38.1 OD x 3 THK. SA 213 T11

Top Header 200 NB x 25 THK. SA 335 P22HP Superheater 1

Bottom Header 200 NB x 25 THK. SA 335 P11

Top Header 250 NB x 30 THK. SA 106 Gr. BHP Evaporator

Bottom Header 250 NB x 30 THK. SA 106 Gr. B

Serrated 38.1 OD x 2.6 THK. SA 201 A1IP Superheater

Top & Bottom Header 200 NB x SCH 100 SA 106 Gr. B

Serrated 38.1 OD x 2.6 THK. SA 201 A1LP Superheater


Serrated 38.1 OD x 2.6 THK. SA 201 A1

250 NB x 30 THK.HP Economiser 3Top & Bottom Header

200 NB x 25 THK.SA 106 Gr. B

Serrated 38.1 OD x 2.6 THK. SA 201 A1Top & Bottom Header-1

250 NB x SCH 80 SA 106 Gr. BIP EvaporatorTop & Bottom Header-2

200 NB x SCH 100 SA 106 Gr. B

Serrated 38.1 OD x 2.6 THK. SA 201 A1HP Economiser 2

Top & Bottom Header 250 NB x 30 THK. SA 106 Gr. B

Serrated 38.1 OD x 2.6 THK. SA 201 A1HP Economiser 1A


Serrated 38.1 OD x 2.6 THK. SA 201 A1HP Economiser 1B


Top & Bottom Header 200 NB x 120 SCH SA 106 Gr. BIP Economiser

Serrated 38.1 OD x 2.6 THK. SA 201 A1

Serrated 38.1 OD x 2.6 THK. SA 201 A1LP Evaporator


Serrated 38.1 OD x 2.6 THK. SA 201 A1Top & Bottom Header(CPH A)

250 NB x SCH 100 SA 106 Gr. BCPHTop & Bottom Header(CPH B)

250 NB x SCH 80 SA 106 Gr. B

Section A 5


5 Evaporating Heating Surface Area

Zone Unit Value

HP Superheater 3 M 2 2727.57

Reheater 2 M 2 5150.00


Reheater 1 M 2 11274.00


HP Evaporator M 2 48730.00

IP Superheater M 2 3742.00

LP Superheater M 2 834.00

HP Economiser 3 M 2 48670.00

IP Evaporator M 2 24725.00


IP Economiser M 2 7453.00


LP Evaporator M 2 33524.00

CPH M 2 58805.00

Total Heating Surface Area M 2 294812.60

6 Exhaust Gas Analysis

Exhaust Gas

PARAMETERS UNIT FIRED 100% GT

N2 + AR % VOL 74.641

O2 % VOL 13.6367

CO2 % VOL 4.2678

H2O % VOL 7.4448

CO % VOL 0.0006

SO2 % VOL 0.0018

6.1 Continuous Blowdown

Design : 3 % / Hr

Operating : 0 %/ Hr

Section A 6


7 Recommended Boiler Water Quality

Parameter Units HP Section IP Section LP Section

SodiumPhosphate asPO4

ppm 16 –13 40 – 34 -

Alkalinity asCaCO3

ppm < 10 < 60 Nil

pH 9.7 — 10.2 10.8 – 11.4 –

Oil & Organic ppm Nil Nil Nil

Total dissolvedsolids

ppm < 50 < 300 < 300

Silica as SiO2 ppm < 0.9 < 21 < 60

8 Recommended Feed Water Quality


GeneralAppearance

Clear &Colourless

Clear &Colourless

Clear &Colourless

Total Hardness asCaCO3

ppm Commercial zero Commercial zero Commercial zero

Total Fe ppm < 0.01 < 0.01 < 0.01

Total Cu ppm < 0.005 < 0.005 < 0.005

Oxygen ppm < 0.007 < 0.007 < 0.007

Oil & organics ppm Nil Nil Nil

pH 9.3-9.5 8.5-9.5 8.5-9.5

Total Dissolvedsolids

ppm < 0.1 < 0.1 < 0.1

ElectricalConductivity

µs/cm < 0.2 < 0.2 < 0.2

Silica SiO2 ppm < 0.02 < 0.02 <0.02

Section A 7


9 Utilities

Electrical Power

Parameters Units Value

For HT Motors (above 160 KW)

Voltage V 6600

Frequency Hz 50

Combined Variation % 10

Type AC, 3 Phase

For LT Motors (upto 160 KW)

Voltage V 415

Frequency Hz 50

Combined Variation % 10

Type AC, 3 Phase

For Instrumentation (Field Switches, Level Gauge illumination, solenoid valves etc)

Voltage V 220

Frequency Hz 50

Type AC, 1 Phase

For Field Transmitters

Voltage V 24

Type DC

Instrument Air

Parameters Unit Value

Pressure Barg 7.0

Temperature Deg C 26

Dew Point Deg C – 20

Quality Dry & Oil free

Duty Instruments

Nitrogen

Section A 8



Pressure (min/normal/design) Barg 6/7/10

Temperature(min/normal/max/design) Deg C 0/30/35/40

Quality % 99.9 % Pure

Duty HRSG Preservation

Service Water for Quenching


Pressure Barg 2.0

Duty Quenching

10 Chemicals for Dosing

HP Dosing: Tri sodium phosphate

IP Dosing: Tri sodium phosphate

LP Dosing: Hydrazine

11 Site Condition

Parameter Units Details

Site Location Kondapalli, Andhra Pradesh

Temperatures

Ambient Temperature(min/max/design) Deg. C 15/45/30

For Performance Testing Deg. C 30

Relative Humidity

Relative Humidity(min/max/design) % 45/81/60

For Performance Testing % 60

Seismic Design

Basic Horizontal Seismicco-efficient 0.05

Importance Factor 1.75

Soil Condition Factor 1.0

Altitude m 35 m above MSL

Area Classification Safe & Non Hazardous

Environment Non-Corrosive

HRSG Location Outside

Number of HRSGs 2

Section A 9


12 Recirculation Pump

Description Units Recirculation Pump

Pump

Make Sulzer Pumps

Pump Type ZE 100–3315

Pump Speed RPM 2980

Flow m3/hr 191

Differential Head m 100

Temperature °C 148

Suction Pressure kg/cm2 11.7

Shut off Head at 50 HZ m 115

Rated power KW 64.32

Efficiency % 74.4

Motor

Make Siemens

Motor type Sqirrel Cage Induction Motor

Rating KW 90

Speed rpm 2975

Frame Size 280M/2 Pole

CouplingUnique Metaflex, Size:

80 SPL-162

13 HP/IP/LP Dosing System

Description HP Dosing for HP Drum HP Dosing for IP DrumLP Dosing for LP

Drum

Make Metapow Industries Metapow Industries Metapow Industries

Reference DrawingNo.

A-1109 Rev 02 A-1110 Rev 03 A-1111 Rev 02

Tank DetailsID 950 X 1125 X 3 THK

(Capacity 600 lit)ID 700 X 1000 X 3 THK

(Capacity 300 lit)ID 950 X 1125 X 3 THK

(Capacity 600 lit)

Chemical Dosed Tri-Sodium Phosphate Tri-Sodium Phosphate Hydrazine

Dosing Pump

Make VK Pump VK Pump VK Pump

Model PR 20 PR 10 PR 10

Flow0–15 LPH by Stroke

Adjustment0–10 LPH by Stroke

Adjustment0–15 LPH by Stroke

Adjustment

Discharge pressure110.5 kg/cm2 g (Normal),118 kg/cm2 g (Design)

31.7 kg/cm2 g (Normal),36 kg/cm2 g (Design)

8.5 kg/cm2 g (Normal),14 kg/cm2 g (Design)

Relief valve setpressure

138 kg/cm2 g 46 kg/cm2 g 11 kg/cm2 g

Motor for Dosing Pump

Section A 10


Description HP Dosing for HP Drum HP Dosing for IP DrumLP Dosing for LP

Drum

Make CGL CGL CGL

MotorM- 120A & M-120B,

TEFC IP 55M- 123A & M-123B,

TEFC IP 55M- 126A & M-126B,

TEFC IP 55

Rating1 HP, 1500 RPM,

415± 10% V0.5HP, 1500 RPM,

415± 10% V0.5 HP, 1500 RPM,

415 ± 10% V

Motor for Agitator

Make CGL CGL CGL

MotorM-120, Frame Size

— ND90LM-123, Frame Size

— ND90SM-126

Rating1.5 HP, 1000 RPM,

415±15% V1 HP, 1000 RPM,

415±10% V1.5 HP, 1000 RPM,

415 ± 10% V

Section A 11


14 Gauge Glass

HP Drum Level Gauge Glass

Description Details

Make Hi Tech System and Services

Type Bicolour Duco Gauge Glass

Tag No. LI 016A & LI 016B

Location HP Steam drum

Operating pressure 103.5 Bar (g)

Design pressure 111 Bar (g)

C/c distance 1000 mm

Visibility range 606 mm

Operating temperature Saturated

Design Temperature 320 °C

IP & LP Drum Level Gauge Glass

Description IP Drum Level GaugeGlass Details

LP Drum Level GaugeGlass Details

Make Chemtrols samil Chemtrols samil

TypeTransparent Level Gauge

GlassTransparent Level Gauge

Glass

Tag No. LI 059A & LI 059B LI 082A & LI 082B

Location IP Steam drum LP Steam drum

Operating pressure 26.7 kg/cm2 5.7 kg/cm2

Design pressure 30 kg/cm2 8 kg/cm2

C/c distance 550 mm 1900 mm

Visibility range 320 mm 1650 mm

Operating temperature Saturated Saturated

Design Temperature 236 °C 176 °C

Blow Down Tank Level Gauge GLass

Description Details

Make Chemtrols samil

Tag No. LI 096

Location Blow Down Tank

Operating pressure 1.5 kg/cm2

Design pressure 3 kg/cm2

C/c distance 1900 mm

Visibility range 1468 mm

Operating temperature 144 °C

Section A 12


15 Stack Damper

Description Units Stack Damper Details

Design Data

Make Indira Damper Industries

Medium Exhaust Gas

Gas Flow kg/sec 624.83

Gas Temperature Deg C 100

Design Temperature Deg C 200

Structural Design Pressure mmWc 500

Sealing Efficiency % 99

Flow Direction Vertical — Upward

Operation Electrical

Duty On — Off

Pressure Drop mmWc 5

Quantity no. 1 per boiler

Operating Time Seconds 60

Gear Box Details

Make Auma (I) Pvt Limited

Type GSD 200+GZ16

Reduction Ratio 424:1

Torque

Actuator Details

Make Auma (I) Pvt Limited

Type SA12E180

Rating KW 1.1

Supply415±10% V, 50±5% Hz,

3Phase, AC

16 Safety Valves

HP Boiler

DESCRIPTION UNIT DRUM LHS DRUM RHSMAIN STEAM

LINE

Type - Spring Loaded Spring Loaded Spring Loaded

Make Tyco Sanmar Tyco Sanmar Tyco Sanmar

Tag No - PSV 006A PSV 006B PSV 027

Size Orifice - 3.0 M2 6.0 3.0 M2 6.0 3.0 L2 6.0

Set pressure Bar (g) 117 118 109.7

Relieving Temperature Deg.C Saturated Saturated 573

Required Valve Capacity kg/hr 117200 117200 73300

Section A 13



LINE

Quantity - 1 no. / Boiler 1 no. / Boiler 1 no. / Boiler

Fluid - Saturated SteamSaturated

SteamSuperheated

Steam

IP Boiler


LINE




Size Orifice - 3.0 L 4.0 3.0 L 4.0 3.0 K 4.0

Set Pressure Kg/Cm2 29.57 30.59 28.96





SteamSuperheated

Steam

LP Boiler


LINE




Size Orifice - 4.0 P 6.0 4.0 P 6.0 6.0 Q 8.0






SteamSuperheated

Steam

Reheater

DESCRIPTION UNIT REHEATER INLETREHEATER

OUTLETType - Spring Loaded Spring Loaded Spring Loaded


Tag No - PSV 302 PSV 302A PSV 072

Size Orifice - 6.0 RR 10.0 6.0 RR 10.0 6.0 RR 10.0


Relieving Temperature Deg.C 410 410 572

Required Valve Capacity kg/hr 125000 125000 90,000

Section A 14


DESCRIPTION UNIT REHEATER INLETREHEATER

OUTLETQuantity - 1 no. / Boiler 1 no. / Boiler 1 no. / Boiler

Fluid -Superheated

SteamSuperheated

SteamSuperheated

Steam

17 Relief Valves

DESCRIPTION UNIT CPHAfter

RecirculationPump

IPECONOMISER



Tag No - PSV 109 PSV 111 PSV 078

Size Orifice - 4.0 N 6.0 3.0 J 4.0 2.0 H 3.0

Set pressure Kg/Cm2 24.50 27.00 71.30


Relieving Temperature Deg.C 250 250 290


Fluid - Water Water Water

Section A 15


Section B


♦ Brief Description of the HRSG♦ Description of HRSG Operation♦ Steam & Water System♦ Flue Gas System♦ Drain & Dosing System♦ HRSG System Protection♦ Automatic Controls

1 Brief Description of the HRSG

The HRSG is designed to extract maximumrecoverable heat from the exhaust gas of the gasturbine. For this purpose the exhaust gas flowfrom the gas turbine is arranged in a directioncounter to the water / steam circuit of HRSG. Theexhaust gas from the gas turbine enters HP, IP& LP section of the Boiler. All the three sectioninclude the secondary and primary superheaters,evaporators, economisers & finally through CPHmodule before exhausted to the atmosphere bythe stack.

The steam drum placed above the evaporatorsserves as a balancing vessel for water and steam.It receives feed water from the economiser andmaintains positive water supply to the evaporatormodules. Drum receives the mixture of steamand water from the evaporator modules by theheat transfer. After separating water from thesteam / water mixture at drum, the saturatedsteam is supplied to the main steam line throughsuperheaters.

Generation Capacity

Generation capacity of the HRSG

• HP steam of 282.5 TPH / 98.7 Bar (a) at atemperature of 567.3 ±3°C

• IP steam of 40.2 TPH /26.1 Bar (a) at atemperature of 313.7°C

• LP steam of 32.3 TPH / 4.37Bar (a) at atemperature of 286.5°C

General Description of HRSGInstrumentation

The latest generation of the field instrumentsis used to facilitate monitoring and control ofthe process variables, generating alarms andtrips. Differential pressure Transmitters for themeasurement of process variables like pressure,drum level and flow are used. Thermocoupleswith transmitters are used for the measurementof temperature. Control valves with position

transmitter and proximity switches form a part ofcontrol system and act as final control elementto control the process variables. Positiontransmitters allow the monitoring of the controllingelement position. Closed control loops areconfigured in DCS.

Process switches and transmitters monitor theprocess variables and generate alarms and safeshutdown of HRSG.

Analyzers are used for the measurement ofConductivity and pH of feed water, boiler waterand steam to maintain the required quality.

Control Loops:

• HP Steam Drum level control

• IP Steam Drum level control

• LP Steam Drum level control

• CBD Drain Temperature Control

• Stack Temperature (CPH Bypass 3- Way)Control

• LP Drum Pressure Control

• HP Attemperator Control

• RH1 Attemperator Control

• CPH Recirculation Temperature Control

• IP Line Back Pressure Control

Control philosophy of these loops is described insection of Automatic control

2 Description of HRSG Operation

HRSG Operation

HRSG is filled with cold DM water through theback filling line provided at the drain headers.Valves line up and procedure for boiler fill up willbe described later in operation instruction manual.

On satisfying the necessary safety interlocks,gradually admit turbine exhaust gas into HRSG.Cold start up curve has to be followed topressurize the boiler.

HRSG is pressurized by modulating the GTload and by establishing the steam flow throughthe start up vent and also modulating it. Onattaining the rated pressure and temperature ofsuperheated steam, main steam stop valve canbe opened and steam shall be admitted to header.Start up vent will be closed, once the flow throughMSSV is established.

Control loops will be selected into auto operationmode with their corresponding set points.

Section B 16


This is a brief overview of the HRSG. Details ofequipments, their operational and maintenancefeatures will be elaborated in the subsequentchapters of the manual.

3 Steam & Water System

AIM

The water and steam system covered in thischapter describes the components of the HRSGwhich transfer heat from the exhaust gas of thegas turbine to the feed water flowing from the feedwater main to convert it to HP steam of 282.5 TPH/ 98.7 Bar (a) at a temperature of 567.3 ± 3°C, IPsteam of 40.2 TPH /26.1 Bar (a) at a temperatureof 313.7°C and LP steam of 32.3 TPH /4.37 Bar(a) at a temperature of 286.5°C.

The components in the serial order of water flowof path for HP section are,

• HP Boiler Feed water Control Station

• HP Economizer I

• HP Economiser II

• HP Economiser III

• HP Drum

• HP Evaporator

• HP Superheater I

• HP Superheater II

• Attemperator

• HP Superheater III

The components in the serial order of water flowof path for IP section are,

• IP Economizer

• Boiler IP Feed water Control Station

• IP Drum

• IP Evaporator

• IP Superheater

• Reheater 1

• Attemperator

• Reheater 2

The components in the serial order of water flowof path for LP section are,

• CPH

• Boiler LP Feed water Control Station

• LP Drum/Dearator

• LP Evaporator

• LP Superheater

The exhaust gas from the Gas Turbine flows in adirection counter to the water / steam flow pathwith the hottest gas entering the sequence below

• HP Superheater 3

• Reheater 2

• HP superheater 2

• Reheater 1

• HP Superheater 1

• HP Evaporator

• IP Superheater

• LP Superheater

• HP Economiser 3

• IP Evaporator

• HP Economiser 2

• IP Economiser

• HP Economiser 1

• LP Evaporator

• CPH

3.1 HP Boiler Components Description

3.1.1HP Boiler Feed water Control Station

During normal operating HRSG, it must be keptcontinuously supplied with feed water to maintainnear normal level in the drum. The HRSG trips ifwater level in the drum is either too low or too high.Feed water is obtained from the HP BFW from theclient. There are three feed control valves, out ofwhich at least one must be in service when theHRSG is operational.

HP Boiler Feedwater Regulating Station

The feed water flow control station consists

• 30% capacity control valve [FCV 003A]

• 100 % capacity control valve [FCV 003B]

• 100 % capacity control valve [FCV 003C]

Both 30% & 100% control valves are provided withmotorised isolation valves [M 003A ,M 003B & M003C] and manual isolation valve at downstreamof control valve [GT 028, GT 027 & GT 026]. Thefeed water flow control valve is a globe type valve,pneumatically actuated by a spring opposeddiaphragm actuator and positioned by the feedwater flow indicating controller [HIC 003A,HIC003B & HIC 003C] in order to maintain the normalwater level at boiler steam drum.

Out of the above, 30% level control [FCV 003A] isused during start up and is capable of feeding theboiler only when the steam flow from HRSG is less

Section B 17


than 30%. A special feature of 30% level controlvalve [FCV 003A] is that it enables the regulationof feed water to the HRSG to be on auto modefrom the very start of HRSG.

The 100% flow control valve [FCV 003B] iscapable of feeding the HRSG when the steamflow from HRSG is from 20% to MCR. [FCV 003C]is an identical stand by to [FCV 003B].

The following are installed in the common inletline from the HP BFW line to the feed regulationStations.

• Tap off for Attemperator spray water withelectrically operator Isolating valve M 026A.

• An isolation valve GT 038.

• Temperature elements TE-001A & TE 001B forindicating temperature of inlet feed water. Asignal is fed to the FX 003.

• Pressure elements PT-002A & PT 002B forindicating pressure of inlet feed water. A signalis fed to the FX 003.

• Flow nozzle FE 003A with impulseconnections to flow transmitter FT-003A,FT-003B & FT-003C.

• Pressure indicator PI 004 for indicatingpressure of inlet HP feed water.

The flow transmitters provide feed flow signal tothe feed Indicating controller FIC-003 (which willbe described later).

After the above, the common inlet line branchesinto three parallel paths, on which are installed thethree feed regulating stations mentioned earlier tobe connected to a common line for feeding waterto the HP Economizer 1. The feed regulatingstations are now described.

30% or Start up Feed Regulation Station

The 30% feed regulating valve [FCV 003A] is usedduring HRSG start up and up to 30% steam flow ofHRSG. The valve can be operated either on autoor manual mode. The positioning of [FCV 003A]on auto is controlled only by the level signal fromthe Drum and the pressure transmitters, which isacceptable at low loads.

Valve [FCV 003A] is a globe type control valvePneumatically actuated by a spring opposeddiaphragm actuator. The characteristic of thevalve is linear, with equal increase in flow forequal valve opening. On loss of control air, thevalve opens full. There is no manual override forcontrolling the valve.

The valve [FCV 003A] is arranged between anelectrically operated inlet Isolating valve M 003A

and a manually operated outlet Isolating valve GT028. The valve GT 028 is normally kept open.After the control valve [FCV 003A] , two drainvalves (GT 025 & GT 024) are installed. The drainvalves normally remain closed and opened only todrain the line when valve [FCV 003A] has to beopened for inspection/maintenance.

The electrically operated 30% feed Isolating valveM 003A can be interlocked for opening or closingunder the following conditions.

• The valve [M 003A] can be opened for usingthe valve [FCV 003A] if the HRSG steam flowis less than 25% MCR and if the drum level isnot high.

• The valve [M 003A] closes automatically whenthere is a HRSG trip and closure of main steamstop valve M 029A.

• The valve [M 003A] gets a permission forclosing when any of the Isolating valves [M003B] or [M 003C] of the 100% feed regulatingstations are open.

• The valve closes when the drum level is veryhigh.

The valve [FCV 003A] can be positioned onmanual mode from the DCS to provide therequired quantity of water to maintain normalwater level. In the auto mode, the level indicatingcontroller HIC-003A positions the valve [FCV003A]. Level transmitters LT-003A , B & Ccontinuously monitors the steam drum water level.A signal from two out of two of these transmittersfeed a level signal to LIC-003A through a specialdrum level control macro. These level signalsare compensated for drum steam pressure at themacro. The set point of the controller LIC-003A is0 (i.e. normal level). When LIC-003A is switchedon the auto mode, the controller compares thelevel signal with the set point and generates anerror signal if there is a deviation and positionsthe valve FCV 003A through the positioner tocorrect the deviation.

FCV 003A and its automatic control are adequateduring HRSG startups & low steam flows, whenrapid changes of drum level (except duringswelling) is not envisaged. The operation of FCV003A can be sluggish and cannot respond to rapidwater level changes due to large load changes.

100% Feed Controller FCV 003B

The inlet, outlet and drain arrangements of FCV003B are similar to the low load control valve FCV003A described earlier.

Electrically operated valve M 003B is theinlet-isolating valve. GT 027 is the outlet-isolating

Section B 18


valve, which normally remains open. Drain valvesGT022 & GT 023 normally remain closed and areopened for draining only when the line is isolatedfor inspection/maintenance of valve FCV 003B

The inlet isolating valve M 003B is interlocked inthe following manner.

• The isolating valve M 003B (or M 003C as peroperator choice) opens automatically when theHRSG steam flow exceeds 25%

• Valve M 003B (or M003C) closes when,

– There is an HRSG trip or

– MSV (M 029A) closes or

– When the drum level is very high.

Three-element feed water control system isprovided to regulate the quantity of feedwaterflowing into the boiler to maintain the requiredwater level in the steam drum. In three-elementcontrol, the drum level is controlled by themeasurement of three process parameters(elements) - drum level, feedwater flow & steamflow.

The drum level is measured by using differentialpressure type level-transmitter LT 003A/B/Cinstalled on the steam drum. The measuredsignal is taken as the process variable (PV) tothe drum level controller [LIC 003B]. This processvariable (PV) is compared with the fixed set point(SP) in the drum level indicating controller blockand a control signal (CV) is generated. Thelevel controller control output (CV) is added withsteam flow signal from the main steam line ina feed forward block. This is done to achievea better level control by taking corrective actionin anticipation. The output of the feed forwardblock is used as a variable set point to the waterflow-indicating controller [FIC-003]. This variableset point is compared to the actual feed waterflow signal from [FE 003A], which acts as themeasured variable for the controller [FIC-003].The control output signal (CV) from the controller[FIC-003] will position the feed water control valvethrough a current-pneumatic converter. Action ofthe control valve is air/ signal FAIL to OPEN.

The valve position is transmitted to the DCS. Onthe DCS, current drum level, steam flow, feed flow& the feed control valve position can be monitored.

The three element control adopted for the 100%flow control valves FCV 003B & C takes intoaccount the drum level, steam flow and feed waterflow for positioning the control valve whereas the30% level controller FCV 003A takes only thedrum level for its operation.

100% Feed Controller FCV 003C

It is exactly similar to FCV 003B described aboveexcept for its valve tag numbers.

The feed water control station is connected to theHP economizer 1 through a feed water controlstation. Pressure gauge [PI 008] installed inthe line provide the economiser inlet feedwaterpressure and a NRV 031 is provided in the inletof the HP Economiser 1.

3.1.2HP Economiser

HP Economiser 1

There are 2 modules of Economizer (HPEconomizer- 1) located on the last stages ofthe exhaust gas path of the HRSG, before LPEvaporator. The Economiser modules consist ofa top and bottom header of size 200 NB x 25.4Thk and Serrated tubes of size 38.1 O.D. x 2.6Thk.

The water leaving HP economiser 1 passesthrough the HP economiser 2.

All the drains of Economizer-1 have been groupedtogether and connected to the HP drain headerthrough three isolating valves.

Air vent valves are located on the cross over pipesof the top headers (which are the high points of themodules). Air vents of Economizers modules areindividually grouped together.

Inlet piping to HP Economiser 1 is provided withfollowing:

• A pressure transmitter (PI 008) for localindication.

• A NRV 031 is provided.

Outlet piping of the HP Economiser 1 is providedwith following:

• A temperature transmitter (TE 009A & B ) forhigh temperature remote indication.

• A pressure and temperature indicator PI 010A& B and TI 047B for local indications

HP Economiser 2

There is 1 module of Economizer (HPEconomizer- 2) located on the last stages ofthe exhaust gas path of the HRSG, before IPEconomiser. The Economiser module consists ofa top and bottom header of size 250 NB x 30 Thkand Serrated tubes of size 38.1 O.D. x 2.6 Thk.

The water leaving HP economiser 2 passesthrough the HP econmiser 3.

Section B 19





• A temperature transmitter (TE 011A & B) forhigh temperature remote indication.

• A pressure and temperature indicator PI 012A& B and TI 046B for local indications

HP Economiser 3

There are 3 modules of Economizer (HPEconomizer- 3 ) located on the last stages ofthe exhaust gas path of the HRSG, before IPEvaporator. The Economiser modules consist ofa top and bottom header of size 250 NB x 30 Thkand Serrated tubes of size 38.1 O.D. x 2.6 Thk.

The water leaving HP economiser 3 is fed to theHP Drum in two feed lines.




• A temperature transmitter (TE 013A/B) for hightemperature remote indication.

• A pressure and temperature indicator PI014A/B and TI 042A/B for local indications

3.1.3HP Drum

The Steam Drum is 14500mm long weldedcylindrical vessel made of SA-516 Grade 70material. The cylindrical portion and the twohemispherical dished ends are made of thickplates respectively. The steam drum is supportedby a saddle and sliding arrangement on top ofthe HRSG structure over beams. The slidingarrangement permits a limited shift due to thermalexpansion through the oblong holes for mountingthe saddle. The drum is insulated by lightly resinbonded mineral wool mats. Two manholes ateither end of the drum provide access to the drum.The drum is closed tight at either end by thick

cover plates bolted against the manhole rim bytwo holding bars. A gasket is fitted between thecover plate and the mating machined surfaces inthe dished ends. The cover plates swing inside,for convenience during opening.

Steam Drum is fitted with several componentsto perform important functions, which are listedbelow:

• Steam Drum receives feed water from the HPEconomizer 3 outlet through two feed pipes &4 nos. of (2 on each side) cyclone separatorscalled hydroclones (to take care of economisersteaming) to maintain a near constant level(Normal water level) and for continuous supplyto the evaporator through down comer pipes.While flowing through the evaporator modules,by absorbing heat from the gas turbine exhaustgas, the hot water gets converted to water /steam mixture and flows back to the Drumbehind the baffles through riser tubes.

• Steam drum receives the water – steammixture from the evaporator modules throughthe riser tubes behind the baffles. Fromthe baffles, the water – steam mixture flowstangentially through the 50 nos. cycloneseparators installed in the steam drum. Inthis tangential flow, water, which is heavier,is separated from steam and trickle down tomix with the water in the steam drum. Steamrises upward to flow through the primaryscrubber and secondary scrubber providedat the top portion of the steam drum. Thescrubber provides a tortuous path to the steamand during its passage, strips any traces ofmoisture from steam. Saturated dry steam iscollected at the top of the drum and distributedto the HP Superheater 1.

• Conditioning of Boiler Water: Due tocontinuous evaporation of boiler water in thedrum, minor impurities present in the feedwater, concentrate to high impermissible levelsin the boiler water. Rise in hardness of water(conductivity), content of chlorides, silica etc.,have to be kept to a minimum to prevent scaleformation or deposits in the evaporator tubesand drum. While Quality Control of water isdescribed in the manual, a brief outline of thecontrol strategy is stated and the provisionsmade in the Drum to execute the control isindicated. Sample of Boiler water is collectedfrom the continuous blow down line to theSWAS. An analyzer continuously analyses thesample for pH & conductivity. If the analysisindicate high conductivity (chlorides, silica)etc., small pre-determined amount of wateris continuously drained from the steam drum

Section B 20


through the continuous Blow down valve M040 with isolating valves for controlling the flowto reduce their concentration to permissiblelevels in the steam drum.

Tri-Sodium phosphate is dosed into steamin the boiler drum to maintain a phosphateconcentration and a pH of 8 to 10. ThePhosphate has the capacity to converthardness producing insoluble calcium/magnesium salts to soluble sodium salts, whichare drained through the blow down. A typicalreaction can be as follows.

3 CaSO4 + 2 Na3 PO4→ Ca3 (PO4)2 ↓ + 3Na2SO4

The dozed phosphate also provides desiredalkalinity to the boiler water. An alkaline pHminimizes the possibilities of corrosion.

The following facilities have been provided inthe steam Drum for the above operations:

Continuous Blow Down (CBD) Line

To enable the water drained from the drum toreflect the true composition of Boiler water, aperforated is laid along the water space of thedrum below the normal water level (axis of thedrum) and connected through the CBD line to theBlow down tank. There is a isolating valves onthe upstream of a blow down valve M 040 and anon-return valve NRV676 on the line. The valvefor Boiler water continuous Blow down (CBD) ispositioned to drain continuously a pre-calculatedquantity.

HP Steam drum is fitted with several componentsto perform important functions, which are listedbelow:

Sampling Line

The CBD line provided to the SWAS throughtwo isolating valves GT726 & GT727. Water &Steam quality control is described elsewhere inthis manual.

HP (Phosphate) Dosing Line

Dosing of phosphate to the Boiler water is to bedone in a manner that it quickly mixes with thewhole of Boiler water. To enable this, a perforatedpipe has been laid along the length of the drumand connected to the HP dosing line througha non-return valve NRV 053 and an isolatingvalve GT 052. HP dosing system is described insubsequent pages of this manual.

Emergency Blow Down (EBD)

During HRSG startup situations arise resultingin high drum water levels. As high drum waterlevels are not permissible and may lead to aboiler trip, provision has been made for quicklydraining some water from the boiler drum underthis condition. The EBD line, drawn from theentire length of the drum consists of a manuallyoperated inlet isolating valve GT 765, an inchingtype motor operated blow down valve M 039A &B followed by a non return valve NRV 677. TheEBD line drains to the blow down tank. Manualisolating valves are normally kept closed and areopened only when emergency blow down has tobe done by opening M 039A & B.

GAUGES & TRANSMITTERS

Level Gauges, Level Indicators, LevelTransmitters

As maintaining normal water level in the steamdrum is one of the important parameters to bemonitored and controlled, elaborate provisionsfor level instrumentation has been made on theSteam Drum. Brief mention of this instrumentationwill be made in this section

LEVEL GAUGES (LI 016A & LI 016B)

The Level Gauges is of multiport type. The top ofthe gauge glass is connected to the steam sideof the drum through two isolating valves. Thebottom portion of the gauge glass is connectedto the waterside of the drum through two isolatingvalves. Care is taken to ensure that the center lineof the center port coincides with the center line ofthe drum, which is the required normal water level.Twin drain valves are fitted to each gauge. Thedrains normally remain shut when the gauge isin service with steam side and waterside isolatingvalves open.

The level gauges are simple direct readinginstruments and serve for quick and accuratereading of the drum level. During the start up ofHRSG, level gauges may be the only instruments,which can be relied upon, as other instrumentsmay not be accurate. The level gauges are alsoused to verify the readings of other instruments.

The level gauges being located at the drumlevel are not convenient for regular operation ofthe Boiler. The level gauges however must bemaintained in service, as IBR requires that atleast one of the level gauges must be in serviceto operate the HRSG.

Control of water Level in the steam drum relies onthe following Instruments.

• Level Transmitters LT 003A, B & C andindicators LI 016 A & B and LI 017 (Hydrastep).

Section B 21


Level transmitters LT 003A,B & C provide inputsfor Drum level indication at DCS and Low Drumlevel, High drum level alarms,

A median of the three level transmitters is taken.

• The level transmitter LT 003A,B & C providedrum level signal to the single element andthree element controllers. The above levelinstruments are connected to the steam drum,steam and water space through twin isolatingvalves. The reading of the steam drum waterlevel by the above instruments is sensitive tothe drum pressure.

Transmitters PT- 003A ,B & C (through twinisolating valves) mounted on the steam drum,provide a pressure compensation signal tothe level transmitters, so that their signalsrepresent true level neutralizing variations dueto pressure changes. They also provide steamdrum pressure signal to DCS. for low and highsteam drum pressure.

• PI- 015A & B are two local instrumentsindicating Drum pressure at the drum level,

A 4 nos. of Skin metal temperature transmitterTE 037A- TE 037D are provided on the drumto measure the Drum metal temperature andgenerate the high alarm in remote.

Drum Safety Valves (PSV- 006A AND PSV-006B)

Figure 1

To protect the boiler and personnel againstconsequences of abnormal pressure increasescaused by sudden load decrease, malfunction offiring system, closure of steam valves etc., twospring loaded safety valves have been fitted onthe drum. On increase of steam pressure beyonda pre-determined set value (117 & 118 kg/cm2),the safety valves opens automatically to relievesteam from the drum to the atmosphere. Thesafety valve closes when the steam pressure fallsby around 4% of the set value. IBR prescribesnorms for installation, care and testing of thesafety valves, which are mandatory. Safety valve,PSV- 006A and PSV- 006B along with the safetyvalve PSV- 027 (on the super heated steam line)have the capacity, as per IBR, to relieve steamfrom the HRSG in such a manner that pressurerise above 103% of the working pressure isprevented on any condition.

As the spring-loaded safety valves result in highnoise levels when they open, the exhaust of thesafety valves are connected through a silencer tosubstantially reduce the noise level.

Installation, adjustment and maintenanceinstructions for safety valves are enclosed whichmay be referred for a full understanding of thesafety valves.

Silencers

Figure 2

Exhaust of various safety valves, steam dump &startup valves are exhausted through Silencers.

Section B 22


The Silencers are acoustically & mechanicallydesigned to attenuate the large noise made duringoperation of these valves.

The silencers are made out of suitable casing inwhich the sound absorbing materials are packedin a certain pattern & wrapped by scrim cloth andwire mesh to avoid ‘fly off’ of sound absorbingmaterials during operation of silencer at high flowrates.

The process fluid enters the annular spacebetween the sound absorbing materials packingwhere the sound energy is absorbed throughoutthe length of the silencer.

The Silencers are mounted on separate structureson top of the HRSG and the exhaust pipes formthe valves are connected to the silencers. As thesilencer contain no moving parts, no operationalcare is needed except opening the drain plugprovided in the drain line, once in three monthsto drain the line.

Air Vent

An air vent (with twin valves M 005A & M 005B )has been fitted on the drum to vent out air duringinitial boiler filling, before start up and during startup. During start up, the air vents are closed at adrum pressure of 2 Kg/cm² (g) and when copioussteam is passing. The air vents are opened aftershut down of the boiler when the boiler pressurefalls to 2 kg/cm2.

N2 Filling

The N2 filling line to the HP steam drum isprovided with the Isolation valve GT 095 which isnormally closed.

A NRV 096 is provided after Isolation valve.

The Saturated steam from the steam headeris connected to the HP Superheater 1 with thefollowing

• A temperature point TP 007 is provided for theindication of the temperature of the saturatedsteam entering to the HP superheater 1.

3.1.4HP Evaporator

The Evaporators convert hot boiler water receivedfrom the HP Drum through four down comer pipesinto a steam water mixture, by absorption of heatfrom the Gas Turbine exhaust gas. The steamwater mixture is led back to the drum from theevaporators through riser pipes.

Evaporator consists of 3 modules. Two modulesconsists of four rows of tubes arranged between

a top and bottom header and one moduleconsist of three rows of tubes. The modulesare hung from the top headers in the flue gaspath, on guide supports with provision for thermalexpansion downward & in the sides. FinnedEvaporator tubes are welded between the top &bottom headers of each module to form the heatabsorption surface.

Hot water flow to the evaporators from the drumand steam/water mixture flows to the drum fromthe Evaporators through risers. A down comerheader of the Evaporator spans all the Evaporatormodules. The four down carrier pipes from theDrum connect to the down comer header. Fromthe down comer header, interconnecting pipesconnect to all the lower headers of the Evaporatormodules. The top headers of the module areconnected to the drum by riser tubes. Thecirculation through Evaporator modules takesplace as follows:

• Heated Boiler water from the drum flowsthrough the four down comer pipes to downcomer header.

• From the down comer header, the hot waterflows to the lower headers, and then throughEvaporation module tubes, to the Evaporationmodule top headers. During its passagethrough the Evaporation module tubes, thehot water absorbs heat from the exhaustgases of the gas turbine and gets convertedto a water/steam mixture. This circulation isassisted by the higher density of water in thedown comer compared to the lower density ofwater / steam mixture in evaporator and risertubes

• The water / steam mixture from the topheaders of the Evaporation module, flowsbehind the baffle chamber in the steam drum.

• In the steam drum, the steam/water mixtureflows through the cyclones where water &steam are separated and saturated steamflows to the HP Superheater 1. Separatedwater mixes with boiler water to flow throughthe Evaporator modules again.

Evaporator are of fully drainable type & drains(one for each downcomer) have been providedon the down comer header of the HRSG. Thesedrains are connected to the HP drain headerthrough three isolating valves. These drainsessentially are for draining the Evaporationmodules after shut down of HRSG. It is not to beoperated when the HRSG is in service as theiropening may interfere with the natural circulationin the modules.

Section B 23


3.1.5HP Superheater

Superheating of saturated steam from drum isdone in three stages in HP Superheater 1 , HPSuperheater 2 & HP Superheater 3. BetweenHP Superheater 2 & HP Superheater 3 anattemperator is located to control the temperatureof final steam outlet at 567.3 ± 5 °C.

Superheaters are made of modules, eachconsisting of a top header and a bottom header,with tubes between the headers. Superheatermodules are hung from their top headers withprovision for thermal expansion down wards & inthe sides.

HP Superheater 1

HP Superheater 1 Consists of 1 modules.Saturated steam from the drum flows to the firstmodule of superheater 1 lower header throughsaturated steam supply pipes from the steamheader. Steam travels up from both the endsof lower header of the first module, through themodule tubes to the top header of the samemodule, absorbing heat.

There are Serrated tubes per row; 2 rows permodule. The tubes are of size 38.1 O.D. x 3 Thk.and made of SA 213 T11 material.

The HP Superheater 1 lower headers (Lowestpoint), are provided with manual drain valve GL739 which is normally closed. HP Superheaterdrain line with two isolation valves GT680 &GT761 which are normally kept open connectedto condensate drain pot. The condensate drainpot is operated through the electrically operateddrain valve (M 038D & M 038 H) on the principleof conductivity and drain the condensate to theBD Tank. A temperature element TE 038DH isprovided in the drain line for the drain control.

The outlet line of the HP superheater1 is providedwith

• A temperature transmitter TE018A/B .

• A temperature indicator TI 045 before the HPSuperheater 2.

• A temperature point TP 008.

HP Superheater 2

HP Superheater 2 Consists of one modules.Steam from the HP superheater 1 flows to the firstmodule of HP superheater 2 lower header throughsteam supply pipes from the steam header. .Steam travels up from both the ends of lowerheader of the first module, absorbing heat andtravels to the top header of the HP Superheater2..

There are Serrated tubes per row; 3 rows permodule; 3 module in HP superheater 2. The tubesare of size 38.1 O.D. x 3.2 Thk. and made ofSA213 T91 material. .

The HP Superheater 2 header (Lowest point),are provided with drain line with two isolationvalves each. These drains are operated to drainthe HP Superheater 2 drain header. The drainsare opened before light up of the boiler to drainHP Superheater 2 . They are closed at a drumpressure of 2 To 5 Kg/cm².

The outlet line of the HP superheater 2 is providedwith

• A temperature transmitter TE 020. It transmitsthe HP superheater 2 outlet temperature signalfor the high alarm.

• A pressure Indicator PI 019.

• A temperature indicator TI 044 before theAtttemperation.

• A temperature point TP001.

Attemporator

The function of the attemporator is to control thetemperature of main steam at HP Superheater3outlet to 567.3 ± 3°C.

Water sprayed into steam evaporates, drawingheat from the steam and completely mixes withsteam. Attemporator is a header connectingfrom the bottom header of the module of HPSuper-heater 2 to the lower header of the moduleof HP Super-heater 3 with an inner sleeve. Spraynozzle is held across the header on to the headernozzle . The spray nozzle at the blind end restson a guide to with stand the force of steam. Holesare drilled on the spray nozzle in the direction ofsteam flow.

The spray water for the Attemperator is obtainedfrom the HP Boiler Feed water main, before theflow transmitter FT 034. The spray water lineconsists of the following.

• A Solenoid operated Shut off valve TV 034.

• A flow Element FE-034 to measure spraywater flow and indicate on flow transmitterFT034.

• A Control station consists of the twoPneumatically operated flow control valveTV-026A & TV-026B (100 %). The flow controlvalve is provided with inlet/outlet isolatingvalves. Motorised inlet isolation valve M 026A& M 026B are provided before the controlvalves and manual outlet isolation valveGT 049 & GT 050 are provided and remain

Section B 24


normally open. The are two drain valves GT045 & GT 046 are provided after the controlvalve TCV 026A and two drain valves GT 047& GT 048 are provided after the control valveTCV 026B, which remain normally closed.These drain valves are opened after closinginlet/outlet Isolating valves, when valve TCV026A & B are to be taken for maintenance.

• A pressure indicator PI 033 with two isolationvalve.

The spray water line connects to the spray nozzleof the attemperator through a non-return valveNRV 051.

Temperature transmitter TE 020 & TE- 042provide steam temperature indication before andafter the attemperator to judge the effectiveness ofattemperation. . The temperature transmitter TE-026A &B (1out of 2) indicate the high temperaturealarm through TIC 026. A feed back signal fromTIC 026 is provided to the controller HIC 026A& B which controls the pneumatically operatedattempearation flow control valve TV-026A & B tomaintain the temperature as required.

An attemperator is provided with manual twindrain valve GL 739 & GT 683, which are normallyclosed. Attemperator drain line is connected toHP SH drain header through two isolation valvesGT 764 & GT 694 which are normally kept open.A temperature element TE 038BF is provided inthe drain line for the drain control.

HP Superheater 3

HP Super-heater 3 does third stage ofsuperheating of steam.

HP Super-heater 3 consists of one modules.The module are constructed out of Spiral SolidTube These rows screen the radiation of flamecoming from the combustion chamber and avoidfin overheating in subsequent HRSG surfacearea. The HP Superheater 3 module tubes aremade of SA213 T91 material.

Steam after attemperation enters the lowerheader of the HP Super-heater 3 first module andrises to the top header of the same module withabsorbing heat and then to HP Main steam line.

The HP Super-heater 3 lower headers (Lowestpoint), are provided with three drains with twoisolation valves . These drains valves GT 682,2 nos. are kept closed are connected to the HPSuperheater drain header.

Temperature element TE 035A to TE 035H (8nos.)are installed on the HP Superheater 3.

An air vent is provided on main steam pipingjust after HP Superheater 3 piping. Pressure &temperature indication is provided for main steampiping.

3.1.6HP Main Steam line

The HP steam line connects the top header of HPSuper-heater 3 module to the plant steam main

This line incorporates the following

• Electrically Operated HP Steam Stop ValveM 029AThis valve Isolates the HRSG from theplant HP steam main. This valve is providedwith an electrically operated, integral by passvalve M 029B.

• Safety Valve PSV-027 To take care of thepressure upset caused by sudden load cut,malfunctioning of firing system, closure ofsteam valves etc., a safety valve is provided onthe main steam line at the Superheater outlet.This is a spring-loaded, valve set at 110.6bar (a) pressure to protect the boiler againstover pressures. The safety valve is similar toDrum safety valves PSV-006A & PSV-006Bdescribed earlier. The exhaust of the safetyvalve is piped to a silencer to reduce the noiselevels when the safety valve is operating. Thesilencer is mounted on a separate structure ontop of the HRSG.

• Start Up Vent Valve Valve PCV 028 is apneumatically operated start up vent valve.

M 028 is a motor operated Isolating valve forstart up vent. The outlet of the start up ventvalve is exhausted to atmosphere through asilencer. The start up vent valve is to be keptopen while start up. It provides initial steam flowfor the cooling of superheaters.

• HP Steam Line Drain The steam line drainconsists of the following valves.

Electrically operated motorised valve M 038A& M 038E, are normally closed are connectedin the drain line with an isolation valve GT 698which is normally open.

• Flow Nozzle FE 003B Flow nozzle FE- 003Bis installed on the HP steam line after the mainstop valve to provide steam flow indication.The flow transmitter reading after steampressure & temperature compensation is usedfor the following,

1. Steam flow reading.

2. Steam flow compensation for feed waterflow

Section B 25


• HP Steam Temperature Input Temperaturetransmitter TT- 026A & 026B (1out of 2)provide the HP steam temperature input forthe following

1. Temperature Indicating controllerTIC-026 which controls positioning ofthe attemperator spray control valve asdescribed earlier.

2. Temperature compensation signal to steamflow.

A temperature gauge TI 024 is provided for thelocal indication.

• HP Steam Pressure Input Pressure transmitterPT- 025A & B (1out of 2) provide the HP steamtemperature input for the following

1. Pressure compensation signal to steamflow.

A pressure Indicator PI 022 for local indication.

• Air Vent GT 107 &GT 108 are air vent valveson the HP steam line, which may be usedduring hydro test.

• Drum Metal Temperature Monitoring When aHRSG is started after filling water to normallevel, initially drum metal temperatures onthe steam side and water side may showconsiderable difference due to slow conductiveheat transfer across the drum metal anddifference of heat inputs across the waterwashed & steam washed parts of the drum.The temperature difference, if it exceeds 50°C,may set up abnormal thermal stresses. Towarn the operator of such a situation, fourdrum skin metal thermocouples have beeninstalled, two on the water side & two on thesteam side of the drum. These thermocouplesconnect to a monitor in the DCS. When thedifferential temperature exceeds 50°C, analarm is generated in the DCS. This alarmis an indication to the operator to slow downthe startup rate. However, when the drumpressure reaches 5 to 10 Kg/cm², temperaturedifferentials disappear. A similar caution isdesired during cooling down of HRSG.

• A tapping from the HP Steam line is providedfor the Steam turbine gland sealing system.

3.2 IP Section ComponentsDescription

3.2.1IP Economiser

There are 1 modules of Economizer (IPEconomizer) located Before HP Economiser 1in the HRSG flue gas path . The Economisermodules consist of a top and bottom header and

Serrated tubes of size 38.1 O.D. x 2.6 Thk &material SA201 A1.

The water leaving IP economiser through theFeed regulating Station to the IP Steam Drum.

All the drains of Economizer have been groupedtogether and connected to the IP drain headerthrough two isolating valves.


Inlet piping to IP Economiser is provided withfollowing:

• A connection is provided for the attemperationafter the reheater 1.

• A pressure transmitter ( PT 052) for remoteindication.

• A temperature transmitter (TE 051 ) for hightemperature remote indication.

• A pressure Indicator PI 053 for local indication.

• A non return valve NRV 209.

Outlet piping to IP Economiser is provided withfollowing:

• A pressure safety valve PSV 078 is provided.

• An Export Water Connection is providedthrough a valve (GT 211) & NRV (NRV 261)and pressure indicator PI 076 & temperatureindicator TI 076 for local indication.

• A pressure relief valve PRV 050 is provided.The outlet of PRV 050 is connected to the LPsteam drum for safe relief of hot water.

• A pressure transmitter ( PT 077A & B) forremote indication and also for the pressurecompensation to maintain the IP drum level.

• A pressure transmitter ( PT 077A & B) isprovided to measure the pressure at IP EcoOutlet. A Feed back control loop with thepressure indicating controller FIC 050 isprovided for automatic pressure control to theflow control valve FCV 050A & B in the feedregulating station of the IP section..

• A temperature transmitter ( TE 075A & B) forremote indication and also for the temperaturecompensation to maintain the IP drum level..

3.2.2IP Boiler Feed water Control Station

During normal operating HRSG, it must be keptcontinuously supplied with feed water to maintainnear normal level in the drum. The HRSG trips ifwater level in the drum is either too low or too high.

Section B 26


Feed water is obtained from the IP feed water fromthe client. There are two feed control valve , outof which at least one must be in service when theHRSG is operational.

IP Boiler Feedwater Regulating Station


• 100 % capacity control valve [FCV 050A]


Both 100% control valve are provided withmotorised isolation valves [M050A & B] andmanual isolation valve at downstream of controlvalve [GT216 & GT 217]. The feed water flowcontrol valve is a globe type valve, pneumaticallyactuated by a spring opposed diaphragm actuatorand positioned by the feed water flow indicatingcontroller [HIC 050A & 050B] order to maintainthe normal water level at boiler steam drum.

The 100% flow control valve [FCV050A] capableof feeding the HRSG. [FCV 050B] is an identicalstand by to [FCV050A].

The following are installed in the common inlet linefrom the IP feed water line from IP Economiser tothe IP feed regulation Stations.

• Temperature elements TE-075A &B forindicating temperature of inlet feed water. Asignal is fed to the FI 050A.

• Pressure elements PE-077A & B for indicatingpressure of inlet feed water. A signal is fed tothe FI 050A.

• A temperature indicator TI 075 for indicatingtemperature.

• Flow nozzle FE 050A with impulse connectionsto flow transmitter FT-050A, FT-050B &FT-050C.

• Pressure indicator PI 056 for indicatingpressure of inlet IP feed water.

The flow transmitters provide feed flow signal tothe feed Indicating controller FIC-050 (which willbe described later).

After the above, the common inlet line branchesinto two parallel paths, on which are installed thetwo feed regulating stations mentioned earlier tobe connected to a common line for feeding waterto the IP Drum. The feed regulating stations arenow described.

100% Feed Controller FCV 050A

The feed regulating valve [FCV 050A] is used forlevel controlling in the IP Drum. The valve canbe operated either on auto or manual mode. The

positioning of [FCV 050A] on auto is controlled asdiscussed below.

Valve [FCV 050A] is a globe type control valvePneumatically actuated by a spring opposeddiaphragm actuator. The characteristic of thevalve is linear, with equal increase in flow forequal valve opening. On loss of control air, thevalve opens full. There is no manual override forcontrolling the valve.

The valve [FCV 050A] is arranged between anelectrically operated inlet Isolating valve M 050Aand a manually operated outlet Isolating valveGT 216. The valve GT 216 is normally kept open.After the control valve [FCV 050A] , one drainvalve (GT 214 ) is installed. The drains normallyremain closed and opened only to drain the line,when valve [FCV 050A] has to be opened forinspection/maintenance.

The electrically operated 100% feed Isolatingvalve M 050A can be interlocked for opening orclosing under the following conditions.

• The valve [M 050A] can be opened for usingthe valve [FCV 050A] if the HRSG steam flowis less than 25% MCR and if the drum level isnot high.

• The valve [M 050A] closes automatically whenthere is a HRSG trip and closure of main steamstop valve.

• The valve [M 050A] gets a permission forclosing when any of the Isolating valves [M050B] of the 100% feed regulating stations areopen.

• The valve closes when the drum level is veryhigh.

Three-element feed water control system isprovided to regulate the quantity of feedwaterflowing into the boiler to maintain the requiredwater level in the steam drum. In three-elementcontrol, the drum level is controlled by themeasurement of three process parameters(elements) - drum level, feedwater flow & steamflow.

The drum level is measured by using differentialpressure type level-transmitter LT 050A/B/Cinstalled on the steam drum. The measuredsignal is taken as the process variable (PV) tothe drum level controller [LIC 050]. This processvariable (PV) is compared with the fixed set point(SP) in the drum level indicating controller blockand a control signal (CV) is generated. Thelevel controller control output (CV) is added withsteam flow signal from the main steam line ina feed forward block. This is done to achieve

Section B 27


a better level control by taking corrective actionin anticipation. The output of the feed forwardblock is used as a variable set point to the waterflow-indicating controller [FIC-050]. This variableset point is compared to the actual feed waterflow signal from [FE 050A] with pressure andtemperature compensation from the PT 077A &B and TE 075A & B, which acts as the measuredvariable for the controller [FIC-050]. The controloutput signal (CV) from the controller [FIC-050]will position the feed water control valve through acurrent-pneumatic converter. Action of the controlvalve is air/ signal FAIL to OPEN.

The valve position is transmitted to the DCS. Onthe DCS, current drum level, steam flow, feed flow& the feed control valve position can be monitored.

The three element control adopted for the 100%flow control valves FCV 050A & B takes intoaccount the drum level, steam flow and feedwater flow for positioning the control valve.

100% Feed Controller FCV 050B

It is exactly similar to FCV 050A described aboveexcept for its valve tag numbers.

The feed water control station is connected to theIP Drum

Pressure gauge [PI056] installed in the lineprovide the IP Drum inlet feedwater pressureand a temperature element TE 055 for remoteindication of the inlet IP drum water temperature .

3.2.3IP Drum

The Steam Drum is 12500mm long weldedcylindrical vessel made of SA-516 Grade 70material. The cylindrical portion and the twohemispherical dished ends are made of thickplates respectively. The steam drum is supportedby a saddle and sliding arrangement on top ofthe HRSG structure over beams. The slidingarrangement permits a limited shift due to thermalexpansion through the oblong holes for mountingthe saddle. The drum is insulated by lightly resinbonded mineral wool mats. Two manholes ateither end of the drum provide access to the drum.The drum is closed tight at either end by thickcover plates bolted against the manhole rim bytwo holding bars. A gasket is fitted between thecover plate and the mating machined surfaces inthe dished ends. The cover plates swing inside,for convenience during opening.

Steam Drum is fitted with several componentsto perform important functions, which are listedbelow:

• Steam Drum receives feed water from the IPEconomizer outlet through single feed pipes &2nos. of (1 on each side) cyclone separators(to take care of economiser steaming) tomaintain a near constant level (Normalwater level) and for continuous supply to theevaporator through down comer pipes. Whileflowing through the evaporator modules, byabsorbing heat from the gas turbine exhaustgas, the hot water gets converted to water /steam mixture and flows back to the Drumbehind the baffles through riser tubes.

• Steam drum receives the water – steammixture from the evaporator modules throughthe riser tubes behind the baffles. Fromthe baffles, the water – steam mixture flowstangentially through the 20 nos. cycloneseparators installed in the steam drum. Inthis tangential flow, water, which is heavier, isseparated from steam and trickle down to mixwith the water in the steam drum. Steam risesupward to flow through the secondary scrubberprovided at the top portion of the steam drum.The scrubber provides a tortuous path to thesteam and during its passage, strips any tracesof moisture from steam. Saturated dry steam iscollected at the top of the drum and distributedto the IP Superheater .

• Conditioning of Boiler Water Due to continuousevaporation of boiler water in the drum,minor impurities present in the feed water,concentrate to high impermissible levels inthe boiler water. Rise in hardness of water(conductivity), content of chlorides, silica etc.,have to be kept to a minimum to prevent scaleformation or deposits, in the evaporator tubesand drum. While Quality Control of water isdescribed in the manual, a brief outline of thecontrol strategy is stated and the provisionsmade in the Drum to execute the control isindicated. Sample of Boiler water is collectedfrom the continuous blow down line to theSWAS. An analyzer continuously analyses thesample for pH & conductivity. If the analysisindicate high conductivity, (chlorides, silica)etc., small pre-determined amount of wateris continuously drained from the steam drumthrough the continuous Blow down valve M079 with isolating valves for controlling the flowto reduce their concentration to permissiblelevels in the steam drum.

Tri-Sodium phosphate is dosed into steamin the boiler drum to maintain a phosphateconcentration and a pH of 11. The Phosphatehas the capacity to convert hardness producinginsoluble calcium/ magnesium salts to soluble

Section B 28


sodium salts, which are drained through theblow down. A typical reaction can be as follows.

3 CaSO4 + 2 Na3 PO4→ Ca3 (PO4)2 ↓ + 3Na2SO4

The dozed phosphate also provides desiredalkalinity to the boiler water. An alkaline pHminimizes the possibilities of corrosion.

The following facilities have been provided inthe steam Drum for the above operations:

Continuous Blow Down (CBD) Line

To enable the water drained from the drum toreflect the true composition of Boiler water, aperforated is laid along the water space of thedrum below the normal water level (axis of thedrum) and connected through the CBD line to theBlow down tank. There is a isolating valves onthe upstream of a blow down valve M 079 and anon-return valve NRV633 on the line. The valvefor Boiler water continuous Blow down (CBD) ispositioned to drain continuously a pre-calculatedquantity.

IP Steam drum is fitted with several componentsto perform important functions, which are listedbelow:

Sampling Line

The CBD line provided to the SWAS throughtwo isolating valves GT723 & GT724. Water &Steam quality control is described elsewhere inthis manual.

IP (Phosphate) Dosing Line

Dosing of phosphate to the Boiler water is to bedone in a manner that it quickly mixes with thewhole of Boiler water. To enable this, a perforatedpipe has been laid along the length of the drumand connected to the IP dosing line througha non-return valve NRV 256 and an isolatingvalve GT 257. IP dosing system is described insubsequent pages of this manual.

Emergency Blow Down (EBD)

During HRSG startup situations arise resultingin high drum water levels. As high drum waterlevels are not permissible and may lead to aboiler trip, provision has been made for quicklydraining some water from the boiler drum underthis condition. The EBD line, drawn from theentire length of the drum consists of a manuallyoperated inlet isolating valve GT 628, an inchingtype motor operated blow down valve M 078followed by a non return valve NRV 634. The

EBD line drains to the blow down tank. Manualisolating valves are normally kept closed and areopened only when emergency blow down has tobe done by opening M 078.

GAUGES & TRANSMITTERS

Level Gauges, Level Indicators, LevelTransmitters

As maintaining normal water level in the steamdrum is one of the important parameters to bemonitored and controlled, elaborate provisionsfor level instrumentation has been made on theSteam Drum. Brief mention of this instrumentationwill be made in this section

LEVEL GAUGES (LI 059A & LI 059B)

The Level Gauges is of multiport type. The top ofthe gauge glass is connected to the steam sideof the drum through two isolating valves. Thebottom portion of the gauge glass is connectedto the waterside of the drum through two isolatingvalves. Care is taken to ensure that the center lineof the center port coincides with the center line ofthe drum, which is the required normal water level.Twin drain valves are fitted to each gauge. Thedrains normally remain shut when the gauge isin service with steam side and waterside isolatingvalves open.

The level gauges are simple direct readinginstruments and serve for quick and accuratereading of the drum level. During the start up ofHRSG, level gauges may be the only instruments,which can be relied upon, as other instrumentsmay not be accurate. The level gauges are alsoused to verify the readings of other instruments.

The level gauges being located at the drumlevel are not convenient for regular operation ofthe Boiler. The level gauges however must bemaintained in service, as IBR requires that atleast one of the level gauges must be in serviceto operate the HRSG.

Control of water Level in the steam drum relies onthe following Instruments.

• Level Transmitters LT 050A, B & C andindicators LI 059 A & B .

Level transmitters LT 050 A, B & C provide inputsfor Drum level indication at DCS and very LowDrum level, very High drum level alarms.

• The level transmitter LT 050A, B & C providedrum level signal to the three elementcontrollers. The above level instruments areconnected to the steam drum, steam andwater space through twin isolating valves. The

Section B 29


reading of the steam drum water level by theabove instruments is sensitive to the drumpressure.

Transmitters PT— 057A, B & C (through twinisolating valves) mounted on the steam drum,provide steam drum pressure signal to DCS. forlow and high steam drum pressure.

• PI- 058A & B are two local instrumentsindicating Drum pressure at the drum level

Drum Safety Valves (PSV- 060A AND PSV-060B)

Figure 3

To protect the boiler and personnel againstconsequences of abnormal pressure increasescaused by sudden load decrease, malfunction offiring system, closure of steam valves etc., twospring loaded safety valves have been fitted onthe drum. On increase of steam pressure beyonda pre-determined set value (30 & 31 Bar g), thesafety valves opens automatically to relieve steamfrom the drum to the atmosphere. The safetyvalve closes when the steam pressure falls byaround 4% of the set value. IBR prescribes normsfor installation, care and testing of the safetyvalves, which are mandatory. Safety valve, PSV-060A and PSV- 060B along with the safety valvePSV- 062 (on the super heated steam line) havethe capacity, as per IBR, to relieve steam fromthe HRSG in such a manner that pressure riseabove 103% of the working pressure is preventedon any condition.

As the spring-loaded safety valves result in highnoise levels when they open, the exhaust of thesafety valves are connected through a silencer tosubstantially reduce the noise level.

Installation, adjustment and maintenanceinstructions for safety valves are enclosed whichmay be referred for a full understanding of thesafety valves.

Silencers

Figure 4

Exhaust of various safety valves, steam dump &startup valves are exhausted through Silencers.The Silencers are acoustically & mechanicallydesigned to attenuate the large noise made duringoperation of these valves.



The Silencers are mounted on separate structureson top of the HRSG and the exhaust pipes formthe valves are connected to the silencers. As thesilencer contain no moving parts, no operationalcare is needed except opening the drain plug

Section B 30


provided in the drain line, once in three monthsto drain the line.

Air Vent

An air vent (with valves M 061 ) has been fitted onthe drum to vent out air during initial boiler filling,before start up and during start up. During startup, the air vents are closed at a drum pressure of2 Kg/cm² (g) and when copious steam is passing.The air vents are opened after shut down of theboiler when the boiler pressure falls to 2 kg/cm2.

N2 Filling

The N2 filling line to the HP steam drum isprovided with the Isolation valve GT 228 which isnormally closed.

A NRV 227 is provided after the Isolation valve.

3.2.4IP Evaporator

The Evaporators convert hot boiler water receivedfrom the IP Drum through down comer pipes intoa steam water mixture, by absorption of heatfrom the Gas Turbine exhaust gas. The steamwater mixture is led back to the drum from theevaporators through riser pipes.

Evaporator consists of 2 modules. Two modulesconsists of three rows of tubes arranged betweena top and bottom header. The modules arehung from the top headers in the flue gas path,on guide supports with provision for thermalexpansion downward & in the sides. SerratedEvaporator tubes are welded between the top &bottom headers of each module to form the heatabsorption surface.

Hot water flow to the evaporators from the drum;and steam/water mixture flows to the drumfrom the Evaporators through risers. A downcomer header of the Evaporator spans all theEvaporator modules. The down carrier pipes fromthe Drum connect to the down comer header.From the down comer header, interconnectingpipes connect to all the lower headers of theEvaporator modules. The top headers of themodule are connected to the drum by riser tubes.The circulation through Evaporator modules takesplace as follows:

• Heated Boiler water from the drum flowsthrough the down comer pipes to down comerheader.

• From the down comer header, the hot waterflows to the lower headers, and then throughEvaporation module tubes, to the Evaporationmodule top headers. During its passage

through the Evaporation module tubes, thehot water absorbs heat from the exhaustgases of the gas turbine and gets convertedto a water/steam mixture. This circulation isassisted by the higher density of water in thedown comer compared to the lower density ofwater / steam mixture in evaporator and risertubes

• The water / steam mixture from the topheaders of the Evaporation module, flowsbehind the baffle chamber in the steam drum.

• In the steam drum, the steam/water mixtureflows through the cyclones where water &steam are separated and saturated steamflows to the IP Superheater. Separated watermixes with boiler water to flow through theEvaporator modules again.

Evaporator are of fully drainable type & drains(one for each downcomer) have been providedon the down comer header of the HRSG. Thesedrains are connected to the IP drain headerthrough two isolating valves. These drainsessentially are for draining the Evaporationmodules after shut down of HRSG. It is not to beoperated when the HRSG is in service as theiropening may interfere with the natural circulationin the modules.

3.2.5IP Superheater

Superheating of saturated steam from drumis done in IP Superheater , to control thetemperature of final steam outlet at 313.7 °C.

Superheaters are made of single module, itconsists of a top header and a bottom header,with tubes between the headers. Superheatermodules are hung from their top headers withprovision for thermal expansion down wards & inthe sides.

IP Superheater

IP Superheater Consists of 1 modules. Saturatedsteam from the drum flows to the module ofsuperheater lower header through saturatedsteam supply pipes from the steam header.Steam travels up from both the ends of lowerheader of the module, through the module tubesto the top header of the same module, absorbingheat.

There are Serrated tubes per row; 1 rows permodule. The tubes are of size 38.1 O.D. x 2.6Thk. and made of SA210 A1 material.

The IP Superheater lower headers (Lowest point),are provided with manual drain valve GT 637

Section B 31


.The drains are operated through the electricallyoperated drain valve (M 076) and drain to the IPRSH drain header.

3.2.6IP Main Steam line

The IP steam line connects the top header of IPSuper-heater module to the plant steam main


• Electrically Operated HP Steam Stop ValveM 064This valve Isolates the HRSG from theplant IP steam main. This valve is with anelectrically operated valve which connects theIP main Steam to the Reheater 1.

• Safety Valve PSV-062 To take care of thepressure upset caused by sudden load cut,malfunctioning of firing system, closure ofsteam valves etc., a safety valve is providedon the main steam line at the Superheateroutlet. This is a spring-loaded, valve set at 29.4bar (a) pressure to protect the boiler againstover pressures. The safety valve is similar toDrum safety valves PSV-060A & PSV-060Bdescribed earlier. The exhaust of the safetyvalve is piped to a silencer to reduce the noiselevels when the safety valve is operating. Thesilencer is mounted on a separate structure ontop of the HRSG.

• Start Up Vent Valve Valve PCV 063 is apneumatically operated start up vent valve

M 063 is a motor operated Isolating valve forstart up vent. The outlet of the start up ventvalve is exhausted to atmosphere through asilencer. The start up vent valve is to be keptopen while start up. It provides initial steam flowfor the cooling of superheater.

• IP Steam Line Drain The steam line drainconsists of the following valves:

Electrically operated motorised valve M 077 isnormally closed connected in the drain line withan isolation valve GT 264 which is normallyopen.

• IP Pressure Control valve A PCV 129 isprovided for controlling the IP main steampressure.

The pressure controller PIC 129 receives a feedback signal from the Pressure transmitter PT129A & B .

• Air Vent GL255 is manual air vent valves onthe IP steam line, which may be used duringhydro test.

• Flow Nozzle FE 050B Flow nozzle FE- 050B isinstalled on the IP steam line before the main

stop valve to provide steam flow indication.The flow transmitter reading after steampressure & temperature compensation is usedfor the following,



• HP Steam Temperature Input Temperaturetransmitter TT- 130A & 130B (1out of 2) providethe IP steam temperature input for the following

1. Temperature compensation signal to steamflow.

• HP Steam Pressure Input Pressure transmitterPT- 129A & B (1out of 2) provide the HP steamtemperature input for the following

1. Pressure compensation signal to steamflow.

2. Pressure High and Low Alarms for theremote indications.

• A Cold reheat line is connected to the IPMain Steam line .The steam pass through theReheater 1 for further heating the steam.

3.2.7Reheaters

Superheated steam from the IP Superheaterand the Cold reheat steam from the HP turbineexhaust is again Superheated in the Reheatersto control the temperature of final steam outlet at567 ± 3°C (Hot reheat line to IP Superheater).

Reheater are made of single module, it consistsof a top header and a bottom header, with tubesbetween the headers. Reheater modules arehung from their top headers with provision forthermal expansion down wards & in the sides.

Reheater 1

Reheater 1 Consists of 1 modules. Superheatedsteam from the IP Superheater and the Coldreheat steam from the HP turbine passes throughthe module of reheater upper header throughsteam supply pipes. Steam travels down fromboth the ends of upper header of the modulethrough the module tubes to the top header of thesame module, absorbing heat.

There are Serrated tubes per row; 3 rows permodule. The tubes are of size 44.5 O.D. x 3 Thk.and made of SA213 T22 material.

The inlet line of the Reheater1 is provided with atemperature indicator TI 303.

Attemporator

Section B 32


The function of the attemperator is to control thetemperature of main steam at reheater 2 outlet to567 ± 3°C.

Water sprayed into steam from the reheater 1,drawing heat from the steam and completelymixes with steam. Attemperator is a headerconnecting from the bottom header of the moduleof Reheater 1 to the lower header of the moduleof reheater 2 . Spray nozzle is held across theheader . The spray nozzle at the blind end restson a guide to with stand the force of steam. Holesare drilled on the spray nozzle in the direction ofsteam flow.

The spray water for the Attemperator is obtainedfrom the IP Boiler Feed water main, before the flowtransmitter FE 050A. The spray water line consistsof the following:

• A Solenoid operated Shut off valve TV 074.

• A flow transmitter FE-073 to measure spraywater flow and indicate on flow indicator FI-073.

• A Control station consists of the twoPneumatically operated flow control valveTCV-068A & TCV-068B (100 %). The flowcontrol valve is provided with inlet/outletisolating valves. Motorised inlet isolation valveM 068A & M 068B are provided before thecontrol valves and manual outlet isolation valveGT 248 & GT 249 are provided and remainnormally open. The drain valve GT246 areprovided after the control valve TCV 068A anddrain valves GT 247 are provided after thecontrol valve TCV 068B, which remain normallyclosed. These drain valves are opened afterclosing inlet/outlet Isolating valves, when valveTCV 068A & B are to be taken for maintenance.

The spray water line connects to the spray nozzleof the attemporator through a non-return valveNRV 250.

Temperature transmitter TE 068A & B providesteam temperature indication after the Reheater2 to judge the effectiveness of attemperation.. The temperature transmitter TE- 068A &B (1out of 2) indicate the high & low temperaturealarm through TIC 068. A feed back signal fromTIC 068 is provided to the controller HIC 068A& B which controls the pneumatically operatedattemperation flow control valve TCV-068A & B tomaintain the temperature as required.

The Outlet line of the Reheater 1 before theattemperation consists of

• The Temperature indicator TI 065.

• The Pressure indicator PI 065.

• The temperature point TP 004.

• A temperature Element TE 065 for high alarm .

The Inlet line to the Reheater 2 after theattemperation consists of

• A temperature Element TE 066 for high alarm .

• The temperature point TP005.

• The Pressure indicator PI 066.

• The Temperature indicator TI 066.

The Attemperator header is provided with manualdrain valve GL 738 which is normally closed. Theattemperator drain line is connected to reheaterdrain header through GT646 isolation valve whichis normally open.

Reheater 2

Reheater 2 does second stage of reheating ofsteam.

Reheater 2 consists of one modules. The modulefollowing the burner/combustion chamber areconstructed out of Serrated tubes .Each moduleconsists of 3 rows of tubes. The Reheater 2module tubes 44.5 O.D. x 3 Thk are made ofSA213 T91 material.

Steam after attemperation enters the lowerheader of the Reheater 2 module and rises to thetop header of the same module with absorbingheat. and then to Hot reheat line.

The Reheater 2 lower headers (Lowest point), areprovided with three drains with two isolation valves. These drains valves GT 642, 2 no. are keptclosed connected to the Reheater 2 drain headerthrough NRV 643 to Blowdown tank..

The outlet line to Hot Reheat Line consists of

• The temperature indicator TI 067.

• The temperature transmitters TE 068A & B.

• The pressure Indicator PI 069.

• The Pressure transmitter PT 070 for lowpressure alarm.

• The flow transmitter FE 071 for flowmeasurement of the Hot reheat Steam.

3.3 LP Section ComponentsDescription

3.3.1Condensate Pre heater (CPH)

A Condensate preheater (CPH) assembly is lastmodule assembly in flue gas path to the stackfrom the boiler to recover economically feasible

Section B 33


heat from the flue gas before discharging tothe atmosphere. The recovered heat increasesthe temperature of DM water entering the LPDrum/deaerator. Thus overall efficiency of theboiler is increased.

The CPH modules consist of a top and bottomheader of size 200 NB x SCH.100 and also 250NB x SCH.80 and segmented finned tubes of size38.1 O.D. x 2.6 Thk.

The CPH assembly is fully drainable by the drainvalve provided on the bottom header. The drainline is connected to the LP drain header. Toexpel air from the CPH during charging and whiledraining air Individual vent valves are provided onthe each module and the common vent GT 609 isprovided on the top header.

DM Water from Client enters to CPH through athree-way temperature control valve TCV 102.This three-way control valve is to be throttledsuitably to maintain LP drum/deaerator wateroutlet temperature.

DM water I/L piping is provided with following:

• Pressure control valve PCV 100 at CPH inlet isprovided to delivered 15 bar pressure (at outletof PCV 100) at inlet of three way control valveTCV 102.

• Pressure transmitter PT 100 for indication/control of water pressure at the outlet of PCV100.

• Temperature Element TE 100 for remotetemperature indication .

• Pressure gauge PI 101 for local pressureindication.

• 3-way control valve TV 102 (Stack Temperatureis fed to (TIC-102) where the process variable iscompared with the local set point for generatingthe manipulated variable. Depending upon theset point three way control valve (TCV- 102)regulates the flow of DM water through bypass& CPH to control the outlet temperature.)

• NRV valve NRV304 is provided in the inlet ofthe CPH inlet header.

• Temperature transmitter TT 108A & TT 108Bare provided in the inlet of CPH. The signal isfed to the Recirculation pump discharge linecontrol valve TCV 108 which regulates thecontrol valve position accordingly to maintainthe inlet temperature of DM water to CPHaround 57°C.

• Temperature Indicator TI 048 is provided beforean isolation valve GT 305 and a NRV 328.

The 3 way control valve (TCV- 102) Bypass lineis provided with the NRV (NRV 313) and isolationvalve GT 314.

A recirculation line is provided parallel to the 3way control valve (TCV- 102) Bypass line, therecirculation line is provided to controls the inlettemperature of the DM water entering the CPHmodule.

The recirculation line consists of the following

• Isolation valve GT 306.

• Pressure transmitter PT 103 for remoteindication of the pressure.

• Pressure indicator PI 105 for local indication ofthe pressure.

• Recirculation pump FW3-PP- 302 with a motorM 106.

• A safety valve PSV 111 is provided in thedischarge line of the recirculation pump.

• Pressure indicator PI 110 for local indication ofthe pressure.

• Flow element FT 107 is used to measure theflow of the recirculating water.

• A control valve TCV 108 is provided in thedischarge of the recirculation pump.

• A NRV valve NRV 311.

• An Isolation valve GT 312.

DM water O/L piping from CPH is provided withfollowing:

• A Temperature indicator TI 049 after thetapping of the recirculation line.

• A NRV 315 is provided in the discharge of theCPH.

• An isolation valve GT327.

• Pressure transmitter PT 131 A & B are providedfor remote pressure low indication. A signal isfed to the feed regulating Controller HIC 080A.

• Temperature transmitter TE 132 A & B areprovided for remote temperature low indication.A signal is fed to the feed regulating ControllerHIC 080A.

• Flow element FE 104 is used to measure theflow of the CPH discharge line to the Dearetor/LP Drum..

• Level control regulating station is provided withthe two control valves FCV 080A & B in parallelwith a motorized isolation valve M-080A & Band manual isolation valve GT 322 & GT325

Section B 34


for LP Drum /deaerator level control . Both thecontrol valves controller HIC 080A & HIC 080Bare fed with the signal from the FIC 080.

• A NRV 329 is provided after the control valve .

3.3.2LP Feed Regulating Station

When HRSG is in service, must be keptcontinuously supplied with DM water to maintainnear normal level in the LP drum / Deareter . TheHRSG trips if water level in the drum is either toolow or too high. DM water is obtained from theclient There are two feed control stations, out ofwhich at least one must be in service when theHRSG is operational.

LP Boiler Feedwater Regulating Station


• 100 % capacity control valve [FCV 080A]


Both 100% control valve are provided withmanual isolation valve at downstream of controlvalve [ GT322 & GT325]. The DM water flowcontrol valve is a globe type valve, pneumaticallyactuated by a spring opposed diaphragm actuatorand positioned by the DM water flow indicatingcontroller [FIC-080] in order to maintain thenormal water level at LP steam drum.

The 100% flow control valve FCV 080A is capableof feeding the HRSG . FCV 080B is an identicalstand by to FCV 080A is provided.

The flow transmitters (FE104) provide feed flowsignal to the feed Indicating controller FIC-080.

After the above, the common inlet line branchesinto two parallel paths, on which are installed thetwo feed regulating stations mentioned earlier tobe connected to a common line for feeding waterto the LP Drum /Deaerator. The feed regulatingstations are now described.

100% Feed Controller FCV-080A

Motorized operated valve M080A is theinlet-isolating valve. GT322 is the outlet-isolatingvalve, which are normally open. Drain valvesGT321 normally remain closed and are openedfor draining only when the line is isolated forinspection/maintenance of valve FCV-080A.

Three-element feed water control system isprovided to regulate the quantity of feedwaterflowing into the LP drum to maintain therequired water level in the LP steam drum. Inthree-element control, the drum level is controlledby the measurement of three process parameters

(elements) - drum level, feedwater flow & steamflow.

The drum level is measured by using differentialpressure type level-transmitter LT 080A, B & Cinstalled on the LP steam drum. The measuredsignal is taken as the process variable (PV) tothe drum level controller [FIC 080]. This processvariable (PV) is compared with the fixed set point(SP) in the drum level indicating controller blockand a control signal (CV) is generated. Thelevel controller control output (CV) is added withsteam flow signal from the main steam line ina feed forward block. This is done to achievea better level control by taking corrective actionin anticipation. The output of the feed forwardblock is used as a variable set point to the waterflow-indicating controller [FIC 080]. This variableset point is compared to the actual feed water flowsignal from [FE 104], which acts as the measuredvariable for the controller [FIC-080]. The controloutput signal (CV) from the controller [FIC-080]will position the feed water control valve through acurrent-pneumatic converter. Action of the controlvalve is air/ signal FAIL to OPEN.

The valve position is transmitted. In remote,current drum level, steam flow, feed flow & thefeed control valve position can be monitored.

The three element control adopted for the 100%flow control valves FCV-080A takes into accountthe drum level, steam flow and feed water flow forpositioning the control valve for its operation.

100% Feed Controller FCV-080B

It is exactly similar to FCV-080A described aboveexcept for its valve tag numbers.

The feed water control station is connected to theLP Steam Drum/ Deaerator through a feed watercontrol station.

3.3.3LP Drum / Deaerator

Figure 5

Section B 35


LP Drum/deaerator is Integral type of Dearator.The LP Drum is connected to the LP Evaporator.

Condensate from CPH flows into LP Drum/deaerator. The level control valve FCV 080A & Bcontrol the deaerater level. LP Drum /deaeratorin this boiler is L.P. integral type.

Deaeration removes the corrosive gases such asdissolved oxygen and free carbon dioxide fromthe boiler feed water. This ensures protectionof the feed water lines, steam lines, boiler tubesand other pressure parts of the boiler againstcorrosion and pitting, saves costly boiler re-tubingand expensive plant shutdowns. Further asthe temperature of feed water/condensate israised from 57 ° C temp. to LP Drum /deaeratoroperating temperature of 147° C and then fed tothe LP Drum , the overall boiler thermal efficiencyalso increases.

Deaeration is done by heating the feedwater/condensate with steam. Vigorouslyscrubbing the water with this steam removes thelast traces of dissolved O2 and brings down wellbelow the recommended level in feed water.

LP Drum /deaerator in which DM water/condensate is heated to its boiling temperature atthe operating pressure by steam. At boiling pointall the dissolved gases such as Oxygen, CarbonDioxide, etc. are liberated as solubility of gasesdecreases with increase in temperature. Themechanical scrubbing between water and heatingsteam ensures release of the dissolved gases.

LP Drum /deaerator is of spray type, consists of astorage tank and a vapour tank. Water is sprayedfrom the top of the vapour tank by spray nozzles. Partial scrubbing of the steam and water takesplace in the storage tank water and the rest istaking place in the vapour tank with the incomingwater spray.

Vapour tank is mounted upon the Deaeretor . Boththe tanks are connected with steam connectionNozzle at the middle. This interconnectionnozzle is flushed with inner wall of the vapourtank’s dished end and embedded inside thewater level of storage tank to facilitate the feedwater flow from vapour tank to the storage tank.Interconnection accommodates concentricallythe steam balancing connection assembly. Thissteam connection is projected inside the vapourtank and masked from the water flow direction bya hood fitted at the top, thus facilitates the steamflow from Deaertor tank to vapour tank.

DM water from CPH enters into the vapour tankthrough the topside nozzle to the distribution

header. Spray nozzles are fixed on the headerto spray the water into fine particles coveringthe entire cross section of the tank so thateasy and complete scrubbing with steam ispossible. Perforated stainless steel trays at levelsare placed inside the vapour tank to provideenough delay time to scrub the feed water withthe upcoming steam. Feed water from vapourtank flows into the storage tank through theinterconnection pipe.

LP Drum /deaerator storage tank is a LP steamdrum having downcomers & riser bank tubes .Feed water/condensate after spray at vapour tankenters to LP Drum /deaerator bank assembly.LP Drum /deaerator bank assembly consist ofdowncomer supply pipes, bottom & top headersinterconnected with two modules of tube sheet& risers which supply steam to LP steam drumor storage tank. Feed water flows to bottomheaders through down comer pipes and steam& water mixture rises up through LP boiler banktubes & finally through rises to the L.P. drum. L.P.Drum is provided with perforated sheet as steamseparator all risers ends inside this perforatedplate box which separate moisture from steamthis steam rises further & enters into vapour tankwhere it scrubs the incoming water & finally toatmosphere through vent condenser vent.

Steam rises from the bottom of StorageTank, heating the water and rises throughthe interconnection pipe into the Vapor Tank.Perforated Trays inside the Vapor tank increasethe residence time of water and Heating Steam.Oxygen, Carbon dioxide and other dissolvedgases are vented out along with vent steamthrough the vent nozzle. Vent pipe has a valveGL362 to throttle or restrict the flow of ventingsteam as required in addition to this a pressurecontrol valve PCV 083 is also provided at vapourtank vent.

The dissolved Oxygen level in the feed water bymechanical deaeration can be brought to 0.02 to0.03 ppm. The residual dissolved Oxygen can befurther scavenged by the reaction with chemicalssuch as Hydrazine . By chemical scavenging thedissolved Oxygen level can be brought down toas low as 0.007 ppm. Chemical is dosed in thestorage section of the LP Drum /deaerator througha header, which is connected to the dosing systemthrough a pipe with an isolation valve GT 361.The dosing of the particular chemical is donein predetermined quantity and concentration. Asample cooler provided in the feed water outletpiping is used to collect the sample for analysisof water.

Section B 36


Platforms and ladders are provided for tanks andcondenser for O & M feasibility.

The continuous blowdown line is connected to thestorage tank through a valve GT630 and M 095and Emergency Blowdown line is connected to thestorage tank through a valve GT612 and M 094.The blowdown lines are connected to the BD Tankthrough NRV 613 & NRV 610 respectively.

LP Drum /deaerator Accessories And TheMountings

LP Drum /deaerator Level Control

The desired normal water level (NWL) of thestorage tank is maintained through a level controlvalve describe in the LP feed regulating Station.Level in the storage take is measured by thelevel transmitter LT 080A, B & C. A Feed backcontrol loop with the level indicating controllerLIC 080 is provided for automatic level control tothe level control valve FCV 080A & B. Processvariable signal for the level indicating controller isprovided by the LT 080A, B & C. Set point of thelevel controller is to be kept at ’0’ mmWC, whichcorresponds to NWL.

Level in the storage take is measured by the leveltransmitter LT 080A, B & C. A Feed back controlloop with the level indicating controller LIC 080is provided for automatic level control Processvariable signal for the level indicating controlleris provided by the LT 080A, B & C. It providesthe high high & Low Low alarm signal for remoteindication.

Apart from the remote level indication direct levelgauge ( LI 082A & LI 082B) is provided for the localindication.

Pressure Control

Flue gases leaving HP economiser I are led to theLP Evaporator where deaerated water is heated to147°C depending upon the steam demand. Thesteam generated by the LP evaporator is used fordeaerating the incoming plant condensate to ratedtemperature.

A Pressure control valve PCV 083 mounted onthe top of the vapour tank is used to control theLP Drum /deaerator pressure through pressuretransmitter PT 083A & B. It also provide the high& Low Alarm for remote indication.

Local pressure gauges PI-081A & B are alsoprovided for LP Drum /deaerator pressureindication.

Pressure Relief Valve

Two pressure relief valves (PSV 084A & PSV084B) are mounted on the storage tank . Reliefvalve would relieve the steam when there isexcessive pressure build-up inside the vessels(system) or deaerater incase of sudden reductionof water out flow/ intake to LP Drum /deaeratoror malfunctioning of pressure control loop. Setpressures of the safety valves are 8 bar (a) & 9bar (a).

Silencers

Exhaust of various safety valves, steam dump &startup valves are exhausted through Silencers.The Silencers are acoustically & mechanicallydesigned to attenuate the large noise made duringoperation of these valves.



The Silencers are mounted on separate structureson top of the HRSG and the exhaust pipes formthe valves are connected to the silencers. As thesilencer contain no moving parts, no operationalcare is needed except opening the drain plugprovided in the drain line, once in three monthsto drain the line.

Air vent

Air vent GT 359 is provided on the vapor tank.Air vent is provided with a globe Valves and thePressure relief valve PCV 083 . Through the airvent, Steam and dissolved gases are vent out tothe atmosphere.

Other Connections

• A connection from CBD tank is provided tostorage tank through a valve M 095 & an NRV613.

• A connection from EBD tank is provided tostorage tank through a valve M 094 & an NRV610.

• Feed water outlet connection . Water inlet &outlet piping going to the boiler feed waterpumps recirculation.

• A Nozzle connected to a perforated pipe in thestorage tank for chemical dosing connection.

Section B 37


• A Manhole is provided each for storage andvapour tank.

• A N2 line is provided with a GT354 & NRV 355.

• A perforated pipe has been laid along thelength of the drum and connected to the LPdosing line through a non-return valve NRV360and an isolating valve GT 361. LP dosingsystem is described in subsequent pages ofthis manual.

3.3.4LP Evaporator

The Evaporators convert hot boiler water receivedfrom the Drum through down comer pipes intoa steam water mixture by absorption of heatfrom the Gas Turbine exhaust gas. The steamwater mixture is led back to the drum from theevaporators through riser pipes.

Evaporator consists of three modules. Eachmodule consists of three rows of tubes arrangedbetween a top and bottom header. The modulesare hung from the top headers in the flue gaspath, on two guide supports with provision forthermal expansion downward & in the sides.Serrated Evaporator tubes 38.1 O.D. x 2.6 Thkand material SA201 A1 are welded between thetop & bottom headers 200 NB x SCH.120 andmaterial SA 106 Gr .B of each module to form theheat absorption surface.

Hot water flow to the evaporators from the drumand steam/water mixture flows to the drumfrom the Evaporators through risers. A downcomer header of the Evaporator spans all theEvaporator modules. The down carrier pipes fromthe Drum connect to the down comer header.From the down comer header, interconnectingpipes connect to all the lower headers of theEvaporator modules. The top headers of themodule are connected to the drum by riser tubes.The circulation through Evaporator modules takesplace as follows:

• Heated Boiler water from the drum flowsthrough the down comer pipes to down comerheader.

• From the down comer header, the hot waterflows to the lower headers and then throughEvaporation module tubes to the Evaporationmodule top headers. During its passagethrough the Evaporation module tubes, thehot water absorbs heat from the exhaustgases of the gas turbine and gets convertedto a water/steam mixture. This circulation isassisted by the higher density of water in thedown comer compared to the lower density of

water / steam mixture in evaporator and risertubes

• The water / steam mixture from the topheaders of the Evaporation module, flowsbehind the baffle chamber in the LP steamdrum.

• In the LP steam drum, the steam/watermixture flows through the cyclones wherewater & steam are separated and saturatedsteam flows to the Superheaters. Separatedwater mixes with boiler water to flowthrough the Evaporator modules again.

Evaporator are of fullly drainable type & drains(one for each downcomer) have been providedon the down comer header of the HRSG. Thesedrains are connected to the LP drain headerthrough isolating valve. These drains essentiallyare for draining the Evaporation modules aftershut down of HRSG. It is not to be operatedwhen the HRSG is in service as their openingmay interfere with the natural circulation in themodules.

3.3.5LP Superheater

Superheating of saturated steam from LP drum isdone in LP Superheater. The temperature of finalsteam outlet at 286.5 °C.

Superheaters are made of single module, itconsist of a top header and a bottom header,with tubes between the headers. Superheatermodules are hung from their top headers withprovision for thermal expansion down wards & inthe sides.

LP Superheater

LP Superheater Consists of single module.Saturated steam from the drum flows to themodule of LP superheater upper header throughsaturated steam supply pipes from the steamheader. Steam travels up from both the ends oflower header of the first module, absorbing heatand travels down through the module tubes tolower header .

There are Serrated tubes per row; 1rows permodule;1 module in LP Superheater. The tubesare of size 38.1 O.D. x 2.6 Thk and made ofSA201 A1 material.

The LP Superheater lower headers (Lowestpoint), are provided with drain with isolationvalves GT617 which is normally kept open.This drain is operated through the electricallyoperated drain valve (M 098) and drain to the IPSuperheater drain header. The air vents & drains

Section B 38


are opened before light up of the boiler to drain LPSuperheater. They are closed at a drum pressureof 2 To 5 Kg/cm².

3.3.6LP Main Steam Line

The LP steam line connects the bottom header ofLP Super-heater module to the plant steam main


• Electrically Operated LP Steam Stop ValveM092AThis valve Isolates the HRSG from theplant LP steam main. This valve is providedwith an electrically operated, integral by passvalve M092B.

• Safety Valve PSV-085 To take care of thepressure upset caused by sudden load cut,malfunctioning of firing system, closure ofsteam valves etc., a safety valve is providedon the main steam line at the Superheateroutlet. This is a spring-loaded, valve set at 6.2bar (a) pressure to protect the boiler againstover pressures. The safety valve is similar toDrum safety valves PSV-084A & PSV-084Bdescribed earlier. The exhaust of the safetyvalve is piped to a silencer to reduce the noiselevels when the safety valve is operating. Thesilencer is mounted on a separate structure ontop of the HRSG.

• Start Up Vent Valve Valve PCV 091 is apneumatically operated start up vent valve witha controller HIC-091.

M 091 is a motor operated Isolating valve forstart up vent. The outlet of the start up ventvalve is exhausted to atmosphere through asilencer. The start up vent valve is to be keptopen while start up. It provides initial steam flowfor the cooling of superheaters.

• HP Steam Line Drain The steam line drainconsists of the following valves.

Manually operated valve GT 371. The manuallyoperated valve are kept open till the condensateis removed and once the condensate isremoved it is close during normal operation ofboiler.

• Flow Nozzle FE 093 Flow nozzle FE- 093 isinstalled on the LP steam line after the MSSVvalve to provide steam flow indication. Theflow transmitter reading, after steam pressure& temperature compensation is used for thefollowing,



• HP Steam Temperature Input Temperaturetransmitter TT- 090A & B provide the LP steamtemperature input for the following

1. Temperature compensation signal to steamflow

A temperature gauge TI 088 is provided for thelocal indication.

• HP Steam Pressure Input Pressure transmitterPT- 089A & B (1out of 2) provide the LP steamtemperature input for the following

1. Pressure Indicating controller PI-089A & Bwhich provides LP steam Pressure High &low alarms .

2. Pressure compensation signal to steamflow

A pressure Indicator PI 086 for local indication.

• Air Vent GT 374 are air vent valves on the LPsteam line, which may be used during hydrotest.

• A connection to the SWAS is provided with avalve GT 376.

3.4 Operational Control

This section explains the major operational controlpoints described in this chapter.

Steam Drum

• Maintain Feed water, Boiler water quality,phosphate concentration

• Maintain water level in the drum withinpermissible low and high levels. The protectionsystem envisages boiler trip at very high andvery low levels, which should not be bypassed

• Maintain drum level gauge glasses in goodworking condition. Operators may verify thereadings of Level Transmitter with the readingsof the drum level gauge glasses once a day

• For a cold HRSG start up, DM makeup waterfrom boiler initial filling line at room temperaturemay be used to feed the HRSG by openingvalves and the drain valves in Economizersand Evaporator. When water is filled up to lowlevel in the drum, the drain valves and fillingline valve are closed. After Boiler start, thisline shall not be used and feeding is from thefeed station.

• Drain superheaters thoroughly during startup

• Thermal Stresses Thermal Stresses In DrumDuring Start Up And Shut Down

Section B 39


Steam Drum is a large cylindrical shell. Beforelight up of a boiler, the inner and outer surfacesof the drum are at the same temperature.When boiler is lighted up, the inner surfacegets heated up first by the water (and then bysteam) and transmits heat to the outer surfaceof drum. The heat transfer is by conduction andis a bit slow. For short time after light up, therecan be differences of temperature betweensteam and water surfaces of the drum. Such adifference can set up thermal stresses, whichare not desirable and an alarm sounds at DCS.To minimize the thermal stresses, the operatormust restrict the firing rate when starting theHRSG by modulating the divertor damper.Boiler water temperature rise rate must not beabove 100°C per hour till operating pressure isreached. To monitor the skin metal temperatureof the drum, instruments have been providedwhich may be checked during light ups.

• Swelling During HRSG startup, as the Boilerwater temperature reaches 90°C, there is aincrease of water level caused by increase inthe volume of hot water. Such swelling, if notcontrolled, can cause a High Level trip. Toavoid this, initial filling is normally restricted tolow level (say – 100 to 150 mm) and the smartOperator anticipates a swell and uses the EBDto drain and control the level.

• Do not operate the HRSG with safety valvesgagged. Passing safety valves must beattended during the next planned shut down.

• Evaporators Evaporator module drains mustnot normally be opened after starting theHRSG. They must be verified for tight closurebefore pressurizing.

• Super Heaters & Attemporator Super heatersmust be drained after shut down and cooling ofthe boiler. They must also be kept open beforea cold start up till 2 - 3 kg/cm2 of pressure isbuilt up. During hot light ups they are openedfor a few minutes

Super heated steam temperatures at exit of HPprimary Super Heater , HP secondary Super

Heater & main steam temperatures must bemonitored to see there is no excessive heatpick up. Compare these figures with predictedperformance values. High steam temperaturesmay mean high metal temperatures.

• General Boiler water can be drained after ashut down only after depressurizing to 2 kg/sq.cm and after cooling to 80 °C

Draining of Boiler water must preferably bedone through the blow down tank.

If a tube failure is detected, it is advisableto plan for an early shut down. It may bepossible to quickly repair the failed tubeand return to service. If the shut down isin-ordinately delayed, there are possibilities oflarger secondary damages, which may prolongthe shut down, required for repairs.

Manually operated valves must be closed handtight only. Use of levers on hand wheels is notdesired.

3.5 Water And Steam Quality ControlAnd Monitoring

Aim

This chapter describes the standards for the boilerfeed water and boiler water for corrosion and scalefree operation of the HRSG and for obtaining puresteam. Methods of control of boiler water are alsoexplained.

Important Note

This chapter must be read in conjunction with thefollowing vendor manuals

• HP/ IP /LP dosing system

• Steam and Water analysis system

Suggested quality of HP, IP & LP boiler feed water(and attemperator water) fed to the HRSG is givenin following Table:

Section B 40



GeneralAppearance

Clear &Colourless

Clear &Colourless

Clear &Colourless

Total Hardness asCaCO3

ppm Commercial zero Commercial zero Commercial zero

Total Fe ppm < 0.01 < 0.01 < 0.01

Total Cu ppm < 0.005 < 0.005 < 0.005

Oxygen ppm < 0.007 < 0.007 < 0.007

Oil & organics ppm Nil Nil Nil

pH 9.3-9.5 8.5-9.5 8.5-9.5

Total Dissolvedsolids

ppm < 0.1 < 0.1 < 0.1

ElectricalConductivity

µs/cm < 0.2 < 0.2 < 0.2

Silica SiO2 ppm < 0.02 < 0.02 <0.02

Note

• Alkaline levels of feed water minimizescorrosion of steel

• Chlorides, Silica, Iron, Copper, Organicmatter etc., present in the feed waterconcentrate further in Boiler water.Their higher concentration calls forincreased blow down (CBD) of boilerwater causing loss of useful heat

• Silica in boiler water vaporizes to SiO2and escapes through steam

• Copper present in water, deposits onthe inner surfaces of evaporator tubesand is harmful

• Chlorides in boiler water depress thepH level and renders boiler wateracidic and may cause acceleratedcorrosion

• Oxygen in boiler water promotescorrosion of boiler tubes

• Oil present in feed water depositon tubes and interferes with heattransfer. Considering all these factors,maximum permissible values forcontaminants in feed water have beensuggested in Table

Section B 41


Following Table gives the Boiler Water Quality tobe maintained in the Drum.

Recommended Boiler Water Quality


SodiumPhosphate asPO4

ppm 16 –13 40 – 34 -

Alkalinity asCaCO3

ppm < 10 < 60 Nil

pH 9.7 — 10.2 10.8 – 11.4 –

Oil & Organic ppm Nil Nil Nil

Total dissolvedsolids

ppm < 50 < 300 < 300

Silica as SiO2 ppm < 0.9 < 21 < 60

Minor permissible contaminants present in theHRSG feed water concentrate to high levels inboiler water due to continuous evaporation in thesteam drum - evaporator circuits. Two controlsare exercised on Boiler water to avoid corrosionof HRSG tubes and the drum water - washedsurfaces. The controls are:

• Continuous blow control to restrict thecontaminants to prescribed levels suggestedfor Boiler water Tri-sodium phosphate dozingto convert the hardness producing insolublecalcium, magnesium salts to soluble sodiumsalts which can be drained by CBD and tomaintain the alkalinity levels of boiler water.The controls are described below.

3.6 Maintaining Quality Of Steam

Good Quality steam is obtained if the followingrequirements are met:

• Proper assembly of baffles, cyclone separatorsin the steam drum as per erection instructions(checked before commissioning of the Boiler)

• Boiler feed water as per norms as suggestedabove. (Monitor the feed water conductivity &PH analysers)

• Control of Boiler water quality as suggestedabove.

• Monitor the saturation steam & main steamconductivity

• Increase of saturation steam conductivity maybe a warning for check of drum internals ormaintaining high water levels in steam drum.

It should be understood that if the quality of Boilerfeed water deteriorates, the steam quality isdirectly affected as the attemporator spray wateris by boiler feed water.

After several years of service, during a boilerover haul, the cyclones, baffles and demistersare checked for damage or erosion holes, whichmay bypass steam from the separation devices.Steam which bypasses the separation device,carry with it moisture & salt contaminants.

Higher than permissible levels of Silica in boilerwater will result in Silica carry over in steam.

Operational Control

• The water chemistry for determining lowlevels of impurities in water calls for specialinstruments, special analytical procedures andan experienced chemist. These should beavailable from the time of commissioning theboiler.

• In a chemical process plant, inspite of the bestavailable demineralization facilities the boilerfeed water may occasionally get contaminatedby return condensate from the system. Aprocedure to systematically check the returncondensates (particularly for contamination byFe, Chlorides and Oil) must be established andcontaminated condensate must be discarded.

• pH & Conductivity meters must be calibratedonce a month.

Phosphate dosing must be adjusted forcontinuous operation.

Section B 42


4 Flue Gas System

4.1 AIM

This chapter describes the Gas Turbine exhaustflow through the HRSG, insulation and casing ofHRSG and the Stack.

4.2 Detailed Description

The steam drum & HRSG pressure part modulesare supported on column structures. The entireHRSG is enclosed in a gas tight casing andducting enclosing the modules to provide agas tight passage for the exhaust gas from thegas turbine. The casing is properly stiffened toenhance the rigidity of the ducting and casing.The HRSG design incorporates cold casingconcept. The modules are covered fully with SS &CS sheet casing on all four sides, with appropriateopenings for penetration of feed water lines,interconnecting pipes, steam lines etc. All thesepenetrations are suitably protected by expansionbellows to maintain a gas tight passage. Speciallydesigned studs hold the Ceramic/Min woolinsulation material tightly to the ducting. Theoverlapping design of the insulation linerscovering the insulation minimises penetration offlue gases into the insulation material. The linersprevent erosion & loss of Ceramic/Min wool fibrematerial. This system permits the outer casing tobe at a very low temperature thus minimising thethermal expansion of the casing & thermal loadson GTG flange.

Exhaust gas from the gas turbine enters theHRSG through an expansion bellow.

HRSG, which receives highly turbulent gasesfrom gas turbines, gets affected drastically bygas mal-distribution. A careful design of includedangle of transition ducting has been done forproducing predictable HRSG performance &avoiding overheating of tubes. TBW carries outcomputer simulation of the gas flow distribution todecide the design of included angle of transitionducting .

Operation of the HRSG on the turbine exhaustgas (TEG) only is termed as ‘unfired mode’ ofoperation.

Following instrumentation is provided in flue gaspath of the HRSG on gas tight casing for variousindication & controls:

Before HP Superheater

• Eight temperature transmitters (TE-200 A, B, C,D, E, F, G & H) provides furnace temperaturelow & high for remote indications.

• A pressure transmitters PT 201 providesfurnace pressure low alarm for remoteindications.

• A temperature indicator TI 202 is providedfor the temperature and pressure indicatorPI 203 for pressure measurement before HPSuperheater.

• Four Pressure points (PP001A -PP001D) &Temperature points (TP 001A- 001D ) areprovided.

• The drain to the casing is provided with anisolation valve GT 161.

Temperature and Pressure Indication BeforeHP Superheater 1

• For Local indication Pressure indicator PI-205and temperature indicator TI-204.

• Temperature indication TE –206A & Bis provided before HP Superheater 1 tomeasure heat pickup in HP Superheater 2 &3 and Reheater , to check for fouling in HPsuperheater modules.

• Four pressure points (PP002A-PP002D) &Four temperature points (TP002A-TP002D)are provided .

After HP Evaporator

• For Local indication Pressure indicator PI-207and temperature indicator TI-208A.

• Two Temperature transmitters (TE-209A & B)provides temperature high & low indication forremote indications.


After HP Economiser 3

• Local pressure gauge PI- 210 & temperatureindicator TI211A.

• Temperature Indicator TE – 212A & B providestemperature high & low indication for remoteindications


After IP Economiser

• Local pressure gauge PI- 213 & temperatureindicator TI214.


Section B 43



After LP Evaporator


• Local pressure gauge PI- 217 & temperatureindicator TI218A.

After Condensate preheater

• Six Temperature Element TE – 222 A, B, C, D,E & F for the low and high remote indications.

• Local pressure gauge PI- 219 and Temperatureindicator TI 220A.


• A pressure transmitter PT 221 for remoteindication of the flue gas Stack inlet pressure.

• A provision for installation of sampling probesfor measurement of O2 (AT 226) is provided.

• A drain is provided with an isolation valveGT162.

Stack (Chimney)

The Turbine exhaust gas after CPH is exhaustedthrough the Stack. Stack is a hollow structure.

Stack is supported on concrete foundations on acircular frame fabricated. Stack has a manholeaccess at the lower end for inspection.

Aviation warning lights are fitted at top elevationson the stack. Provision for installation of samplingprobes for measurement of SOx ,CO & NOx(AT 225,AT 224 & AT 223), is provided atsuitable elevation on the Stack. There areplatforms providing access to the aviation lights,sample probes and ease of repainting the Stack.Platforms are accessible from the ground byladders. On the top side of the Stack, helicalwind-breakers are built around the outer shell, toprovide stability to the Stack against wind forces.

The inlet Flue gas connection from the HRSG tothe Stack is through expansion bellows to containthe thermal expansion of the HRSG ducts form theStack.

A temperature element TE 227A & B provides thelow and high remote temperature indication.

A Motorized Damper M 228 is provided on thestack .

A drain is provided at the bottom of the Stack withan isolation valve GT160.

Operational Control

• The anticipated figures both steam / waterand gas side has been given in followingsection. The operator shall familiarise himselfwith these figures. Elaborate instrumentationhas been provided to measure each of thesefactors. Alarms also have been provided toalert the operator in case of deviations forseveral of these readings

• Operator attention is needed particularly forthe following

– Turbine Exhaust Gas (TEG) inlet pressureand temperature -

– Gas side pressure and temperature drop,Steam/Water side heat pick up acrosspressure parts like

♦ HP Superheater 3, 2 & 1

♦ Reheater 1 & 2

♦ HP , IP & LP Evaporator Modules

♦ HP & IP Economisers

♦ Condensate Preheater

Evaluating these figures the operator shoulddecide to check during shut down.,

• Levels of CO, NOx, & SOx emissions mustbe monitored and any abnormalities must bereported to the shift in-charge.

• Healthiness of aviation warning lamps is to becheck periodically.

Section B 44


5 Drain & Dosing System

Boiler Blowdown System

Aim

This chapter describes the HRSG blow downsystem for safe draining of high pressure / Hightemperature steam and water from the boilerusing the blow down tanks

System Description

The P & I Diagram of drains & vents shows thevarious drains & vents from the HRSG, HP , IP &LP steam line, HP , IP & LP steam drum, HP , IP& LP saturated & superheated drain header.

Large quantities of steam or highpressure/temperature water are not to be drainedthrough open canals for the following reasons:

• Such draining will cause splashing of highervolumes of steam which can be a nuisanceby the noise it creates and also it affects thevisibility around the draining area

• High temperature of these drains can causescalding injures to workmen if they come intocontact with it

• The force and temperature of these drains willerode the linings of the drain canals

Table below is a summary of such drains.

Section B 45


High Pressure / High Temperature Steam AndWater Drains

SL.No

Source Sections Valve Nos Temp of drain °CFrequency ofusage

HP Drum GT 674 , M 040 Up to 310°C

IP Drum GT 631 , M 079 Up to 217°C1Continuous blowdown

LP Drum GT 630 , M 095 Up to 145°C

Continuous,quantity dependingon quality of boilerwater

HP DrumGT 675 , M 039 A& B

Up to 310°C

IP Drum GT 628 , M 078 Up to 217°C2

Emergency blowdown

LP Drum GT 612 , M 094 Up to 145°C

Occasional duringhigh levels in drum,during start up.

3HP SH Drainheader

GT 688 , NRV 689Varying from100°C to 567°C

DrainingHPsuper-heatersduring initialstartup & after ashut down.

4Reheater Drainheader

GT 650 , NRV 649Varying from100°C to 567°C

Draining Reheaterduring initialstartup & after ashut down.RHS GT 695 , NRV 697

5HP DrainHeader LHS

GT 669 , NRV 670 Varying from100°C to 310°C

Draining of HPEvaporator &HP Economisermodules aftershutdown

RHS GT 622 , NRV 623

6 IP Drain headerLHS

GT 624 , NRV 625 Varying from 60°Cto 217°C

Draining of IPEvaporator &IP Economisermodules aftershutdown

RHS GT 605 , NRV 606

7 LP Drain headerLHS

GT 607 , NRV 608 Varying from 60°Cto 145°C

Draining of CPH& LP Evaporatormodules after ashut down

The drains indicated in above table are connectedto the continuous & intermediate blow down tank.The blow down tank is capable of separatingsteam from the drain water. The drains areconnected tangentially in the upper half of thedrum to direct the drain fluid circumferentialaround the inner wall of the tank, to aid separationof steam and water by their differences indensities.

Other Drains

It can be seen that drains have been provided inthe feed water line and the attemperator spraywater lines connected to the drain canal. Asthese drains are either for operation to drain theselines after an isolation or for short time duringcharging, Their connections to the open canal isnot expected to pose a problem.

Continuous Blow Down Control (CBD)

CBD control involves the following operations

• Obtaining a sample of boiler water from thesteam drum.

• Analyzing the sample for conductivity,hardness, NaCl, Silica, Fe, etc. and workingout a rate of draining of boiler water to maintainthe concentrations as suggested in Table -Boiler water.

• Positioning the CBD valve is to be decideddepending on the sample analysis.

• Repeating the sampling, analysis andrepositioning the CBD valve after certaininterval is necessary to maintain the requiredBoiler water quality. This system of manualcontrol requires the services of a sampler, achemist and a laboratory round the clock. Thearrangement provided for CBD control is: Aperforated pipe, laid along the water space in

Section B 46


the steam drum connects through a stub to thecontinuous blow down line.

• CBD line from drum connects to the blowdown tank.

• A tap off from the CBD line is taken to thesample cooler for continuous analysis of boilerwater conductivity and also for a grab sample.

Sampling of CBD / Boiler water is done inSWAS at customer end. This package providesanalysis of the following samples to provide acomprehensive information of quality of steamand water of HRSG.

• Samples of main steam from HP , IP & LPheader of HRSG.

• Samples of boiler water (CBD) from the HP ,IP & LP steam drum of HRSG.

• Samples of HP , IP & LP feed water.

While all the samples above are analysed forconductivity by separate analysers, the CBDsample and the feed water samples are analysedin addition for pH also. CBD valve is normally keptopen to maintain small continuous flow of boilerwater to the blow down tank. This is required toensure the sample at any time to the SWAS istruly representative of the sample being analysed.This continuous flow also ensures that these linesdo not get choked for want of adequate flow.

CE & pHE are the conductivity and pH analysersinstalled on the sample line. The specificrequirements of the analyzers are that thepressure and temperature of the sample must berigidly controlled within permissive values (seevendor manual).

The Analysers are to be maintained as per vendorinstruction.

Emergency Blow Down Control (EBD)

EBD control involves the following operations

During Startup of the boiler the Drum levelwhich is maintained at NWL suddenly rises duethe swelling of the drum water. In such casewhen there is an emergency condition an EBDconnection from the Drum is provided.

EBD connection is provided with an isolating valveand an motorised valve .

The isolating valve is kept open and the motorisedvalve controls the Drum level .

The EBD connection is connected to theBlowdown tank.

Blowdown tank (BD Tank)

BD Tank is provided with the following

• A Level gauge LI 096

• A vent is provided.

• An Over flow connection is provided which isconnected at the Drain line through a valveGT708.

• After the drain valve GT 708 the Quenchingwater arrangement is provided .

• A temperature Element TE 096A & B are in theDrain line after the Quenching arrangement.

The Quenching water line consists of the following

• A Flow transmitter FE 097 for the measurementof the quenching water in the Blow down tank.

• A control valve TCV 096 with a inlet and outletisolation valve GT 704 (2 nos.) and a bypassline with a valve GT 706.

The feed back from the TE 096 A & B to the thecontroller TIC 096 controls the TCV 096 Operation.

HP Dosing

Figure 6

Tri-sodium phosphate dosing to Boiler water tomaintain its phosphate content at 8 to 10 PPM.The tri-sodium phosphate at the suggested levels,maintains the alkalinity of the boiler water (pH 10to 11) and also converts the harmful, insolublecalcium and magnesium salts which forms theresidual hardness of boiler water, to being soluble,sodium salts, in the form of a soft sludge, to bedrained by the CBD. Phosphate dosing preventscorrosion of the water washed parts of the steamdrum and the evaporator tubes. Adjusting thespeed or the stroke of the pump provided asdescribed below can control quantity of dosing.Excess as well as reduced phosphate levels in

Section B 47


Boiler water should be avoided. (The phosphatedosing is also some times called as "HP dosing"as the pump used develops high pressure to doseagainst the boiler drum pressure).

The equipment provided for phosphate dosing("HP dosing") as shown in P & I diagram consistsof:

• A 600 liter mixing tank for preparation of 5%tri-sodium solution.

• Two dosing pumps.

• DM Water source for preparation of thephosphate solution as well as for flushing.

Mixing Tank

The Mixing tank is a carbon steel with rubber liningcovered cylindrical vessel of 600 litres capacitywith a level indicating gauge glass LI-122, DMwater inlet line (with a manual isolating valve) BL561, a tank drain line with a manual isolating valveBL 565, a basket for placing required quantity oftri-sodium phosphate powder for preparation ofthe solution. A solution inlet connection to thepumps with a manual isolating valves BL 567, BL568. A motor operated stirrer M 120 is also fittedfor preparation of chemical solutions.

The level of the mixing tank is monitored by levelgauge (LI-122). Availability of a minimum level isa pre-requisite for starting or continued service ofa dosing pump.

Preparation of 5% Phosphate Solution in TheTank

• Tank drain valve BL 565 is closed.

• Gauge glass inlet cocks are opened and itsdrain is closed.

• The lid of the tank is opened, and a calculatedquantity of phosphate to prepare 600 liters ofsolution is placed in the basket and lid closed.

• The water inlet valve (BL 561) is opened toadmit water (from the DM water line). Thelevel gauge is watched and when the level inthe tank is nearly full, the water inlet valve isclosed.

• The stirrer is placed in service for 30 minutesby operating its switch in the local module.Availability of a minimum level is a preconditionfor starting and running of the stirrer.

Phosphate Dosing Pumps

Two phosphate dosing pumps have beenprovided, out of which one is for service at a timeand the other is a standby. The pumps are plungeroperated reciprocating, positive displacement

type. The stroke of the plunger can be altered.The vendor manual of the pump and gearbox isto be referred for full information on constructionand parts detail.

Each pump is connected to a common dischargeline with the following valve arrangement:

• An inlet valve with a "Y" type strainer at thepump inlet. Y strainer traps dirt or other solidparticles in its basket. The Y strainer is to becleaned once a month, after stopping the pumpand closing its inlet and outlet isolating valves.

• On the discharge side of the pump, a pressuregauge PI-120A & B and an outlet-isolatingvalve BL 577 & BL 578 is fitted before thecommon discharge line. A safety relief valvePSV 120A & B has also been fitted on thedischarge line to relieve any over pressures incase of closure of valves on the discharge line.The outlet of the relief valve is returned to themixing tank. The relief valve must be tested forits operation at the set pressure at least oncea year. The pump must not be operated withthe relief valve continuously operating (causeof relief valve operation must be found andrectified).

The common discharge line is connected to theHP dosing line of the steam drum through an NRV053 and an isolating valve GT 052. The isolatingvalve is verified open before boiler light up andnormally remains open all the time. Phosphatedosing is through a perforated pipe along the fulllength of the water space in the drum.

Availability of a minimum level in the mixing tankis a pre condition for starting or running of thedosing pumps. Out of the two pumps, one pumpis selected for service and the other is in reserve(DCS macro, Local module). The pumps areinterlocked such that when a working pump trips,the reserve pump starts automatically

A phosphate pump is placed immediately inservice after the HRSG start up in the followingmanner:

• Boiler water sample is analyzed and phosphatecontent is determined.

• The pump is prepared by opening the outletvalve from the mixing tank, opening the inletand the two outlet valves of the pump. Twominutes are allowed after opening the inletvalve for the pump to get filled with phosphatesolution. The pump is started by switching onthe motor. The pressure gauge is observed. Itshould show a reading, higher than the steamdrum pressure. An accumulator on the pumpdischarge line dampens the pulsations which

Section B 48


otherwise would be there as this is a positivedisplacement reciprocating pump.

Any abnormal noise from the pump, motoror gearbox is noted. The safety relief valveshould not also be operating. If there are noabnormalities the pump is allowed to run.

Every four hours, the phosphate content in theboiler water is checked by laboratory sampleanalysis and also by the pH meter. The pumpspeed stroke is increased or decreased tomaintain the phosphate content within 8 to 10PPM by continuous pump operation.

The phosphate solution level is observed in themixing tank by the gauge glass. If the level falls to25% of the gauge glass level, additional solutionis prepared as stated above.

Flushing the phosphate pump and the lines withwater during long stoppage of the HRSG:

If the HRSG is to be stopped for more than a fewdays for servicing or maintenance, the phosphatepumps and the line are flushed with water to keepthem clean.

IP Dosing

Tri-sodium phosphate dosing to Boiler water tomaintain its phosphate content at 30 to 35 PPM.The tri-sodium phosphate at the suggested levels,maintains the alkalinity of the boiler water (pH 10to 11) and also converts the harmful, insolublecalcium and magnesium salts which forms theresidual hardness of boiler water, to being soluble,sodium salts, in the form of a soft sludge, to bedrained by the CBD. Phosphate dosing preventscorrosion of the water washed parts of the steamdrum and the evaporator tubes. Adjusting thespeed or the stroke of the pump provided asdescribed below can control quantity of dosing.Excess as well as reduced phosphate levels inBoiler water should be avoided. (The phosphatedosing is also some times called as "IP dosing"as the pump used develops high pressure to doseagainst the boiler drum pressure).

The equipment provided for phosphate dosing("IP dosing") as shown in P & I diagram consistsof:

• A 300 liter mixing tank for preparation of 5%tri-sodium solution.


• DM Water source for preparation of thephosphate solution as well as for flushing.

Mixing Tank

The Mixing tank is a carbon steel with rubber liningcovered cylindrical vessel of 300 liters capacitywith a level indicating gauge glass LI-125, DMwater inlet line (with a manual isolating valve) BL531, a tank drain line with a manual isolating valveBL 535, a basket for placing required quantity oftri-sodium phosphate powder for preparation ofthe solution. A solution inlet connection to thepumps with a manual isolating valves BL 537, BL538. A motor operated stirrer M 123 is also fittedfor preparation of chemical solutions.

The level of the mixing tank is monitored by levelgauge (LI-125). Availability of a minimum level isa pre-requisite for starting or continued service ofa dosing pump.

Preparation of 5% Phosphate Solution In TheTank



• The lid of the tank is opened, and a calculatedquantity of phosphate to prepare 300 liters ofsolution is placed in the basket and lid closed.


• The stirrer is placed in service for 30 minutesby operating its switch in the local module.Availability of a minimum level is a preconditionfor starting and running of the stirrer.

Phosphate Dosing Pumps

Two phosphate dosing pumps have beenprovided, out of which one is for service at a time,and the other is a standby. The pumps are plungeroperated reciprocating, positive displacementtype. The stroke of the plunger can be altered.The vendor manual of the pump and gearbox isto be referred for full information on constructionand parts detail.

Each pump is connected to a common dischargeline with the following valve arrangement:

• An inlet valve with a "Y" type strainer at thepump inlet. Y strainer traps dirt or other solidparticles in its basket. The Y strainer is to becleaned once a month, after stopping the pumpand closing its inlet and outlet isolating valves.

• On the discharge side of the pump, a pressuregauge PI-123A & B and an outlet-isolating

Section B 49


valve BL 547 & BL 548 is fitted before thecommon discharge line. A safety relief valvePSV 123A & B has also been fitted on thedischarge line to relieve any over pressures incase of closure of valves on the discharge line.The outlet of the relief valve is returned to themixing tank. The relief valve must be tested forits operation at the set pressure at least oncea year. The pump must not be operated withthe relief valve continuously operating (causeof relief valve operation must be found andrectified).

The common discharge line is connected to theHP dosing line of the steam drum through an NRV256 and an isolating valve GT 257. The isolatingvalve is verified open before boiler light up andnormally remains open all the time. Phosphatedosing is through a perforated pipe along the fulllength of the water space in the drum.

Availability of a minimum level in the mixing tankis a pre condition for starting or running of thedosing pumps. Out of the two pumps, one pumpis selected for service and the other is in reserve(DCS macro, Local module). The pumps areinterlocked such that when a working pump trips,the reserve pump starts automatically

A phosphate pump is placed immediately inservice after the HRSG start up in the followingmanner:

• Boiler water sample is analyzed and phosphatecontent is determined.

• The pump is prepared by opening the outletvalve from the mixing tank, opening the inletand the two outlet valves of the pump. Twominutes are allowed after opening the inletvalve for the pump to get filled with phosphatesolution. The pump is started by switching onthe motor. The pressure gauge is observed. Itshould show a reading, higher than the steamdrum pressure. An accumulator on the pumpdischarge line dampens the pulsations whichotherwise would be there as this is a positivedisplacement reciprocating pump.


Every four hours, the phosphate content in theboiler water is checked by laboratory sampleanalysis and also by the pH meter. The pumpspeed stroke is increased or decreased tomaintain the phosphate content within 30 to 35PPM by continuous pump operation.

The phosphate solution level is observed in themixing tank by the gauge glass. If the level falls to25% of the gauge glass level, additional solutionis prepared as stated above.

Flushing the phosphate pump and the lines withwater during long stoppage of the HRSG:

If the HRSG is to be stopped for more than a fewdays for servicing or maintenance, the phosphatepumps and the line are flushed with water to keepthem clean.

LP dosing

Hydrazine is dosed to Boiler water to maintain theDissolved O2 to 0.007 ppm. The Hydrazine atthe suggested levels, maintains the alkalinity ofthe boiler water in Dearator and thus chemicaldeaeration is done in the deaerator. Adjustingthe speed or the stroke of the pump provided asdescribed below can control quantity of dosing.Excess as well as reduced Hydrazine in Boilerwater should be avoided. (The dosing is alsosome times called as "LP dosing" as the pumpused develops high pressure to dose against theboiler drum pressure).

The equipment provided for Hydrazine dosing("LP dosing") as shown in P & I diagram consistsof:

• A 600 liter mixing tank for preparation of 2.5%Hydrazine solution.


• DM Water for preparation of the Hydrazinesolution as well as for flushing.

LP Mixing Tank

The Mixing tank is a carbon steel with rubber liningcovered cylindrical vessel of 600 liters capacity;with a level indicating gauge glass LI 128. A DMwater inlet line (with a manual isolating valve) BL501, a tank drain line with a manual isolating valveBL 505, a basket for placing required quantityof Hydrazine for preparation of the solution. Asolution inlet connection to the pumps with amanual isolating valves BL 507 & BL 508 .A motoroperated stirrer M 126 is also fitted for preparationof chemical solutions.

The level of the mixing tank is monitored by levelgauge (LI 128). Availability of a minimum level isa pre-requisite for starting or continued service ofa dosing pump.

Preparation of 2.5 % Hydrazine Solution in theLP Tank


Section B 50



• The lid of the tank is opened, and a calculatedquantity of Hydrazine to prepare 600 liters ofsolution is placed in the basket and lid closed.


• The stirrer is placed in service for 30 minutesby operating its switch in the local panel.Availability of a minimum level is a preconditionfor starting and running of the stirrer.

Hydrazine LP Dosing Pumps

Two Hydrazine dosing pumps, M- 126A & B havebeen provided, out of which one is for service ata time, and the other is a standby. The pumpsare plunger operated reciprocating, positivedisplacement type. The stroke of the plunger canbe altered. The motor is provided with a variablefrequency drive through a gearbox for continuousspeed control. The vendor manual of the pumpand gearbox is to be referred for full informationon construction and parts detail.

Each pump is connected to a common dischargeline with the following valve arrangement

• An inlet valve BL 507 & BL 508 with a "Y"strainer at the pump inlet. Y strainer traps dirtor other solid particles in its basket. The Ystrainer is to be cleaned once a month, afterstopping the pump and closing its inlet andoutlet isolating valves.

• On the discharge side of the pump, a pressuregauge PI-126A & B and an outlet-isolatingvalve BL517 & BL 518 is fitted before thecommon discharge line. A safety relief valvePSV 126A & B has also been fitted on thedischarge line to relieve any over pressures incase of closure of valves on the discharge line.The outlet of the relief valve is returned to themixing tank. The relief valve must be tested forits operation at the set pressure at least oncea year. The pump must not be operated withthe relief valve continuously operating (causeof relief valve operation must be found andrectified).

The common discharge line is connected to the LPdosing line of the steam drum through an NRV 360and an isolating valve GT 361. The isolating valveis verified open before boiler light up and normallyremains open all the time. Hydrazine dosing is

through a perforated pipe along the full length ofthe water space in the drum.

Availability of a minimum level in the mixingtank is a pre condition for starting or running ofthe dosing pumps. Out of the two pumps, onepump is selected for service and the other is inreserve (DCS macro, Local panel). The pumpsare interlocked such that when a working pumptrips, the reserve pump starts automatically.

A Hydrazine pump is placed immediately inservice after the HRSG start up in the followingmanner:

• The pump is prepared by opening the outletvalve from the mixing tank, opening the inletand the two outlet valves of the pump. Twominutes are allowed after opening the inletvalve for the pump to get filled with Hydrazinesolution. The pump is started by switching onthe motor. The pressure gauge is observed. Itshould show a reading, higher than the steamdrum pressure. An accumulator on the pumpdischarge line dampens the pulsations whichotherwise would be there as this is a positivedisplacement reciprocating pump.


The Hydrazinesolution level is observed in themixing tank by the gauge glass. If the level falls to25% of the gauge glass level, additional solutionis prepared as stated above.

Flushing the hydrazine pump and the lines withwater during long stoppage of the HRSG:

If the HRSG is to be stopped for more than a fewdays for servicing or maintenance, the Hydrazinepumps and the line are flushed with water to keepthem clean.

6 HRSG System Protection

Aim

This chapter lists out various protections andinterlocks provided in the HRSG.

As the system protections and interlocks havebeen described in the preceding chapters alongwith the description of equipment, a listing of theseprotections will only be made with brief notes ontheir significance. Testing of these interlocks &protections is to be done before the first start upof HRSG and at suitable intervals subsequently.

Section B 51


Protections

Among various protections provided, ESD guidesthe operator in preparing the HRSG in an orderlymanner to ensure availability of all essentialinputs before starting the HRSG and monitoringtheir availability all the time when the HRSG is inservice.

The boiler protections are implemented throughthe emergency shut down (ESD) logics.

Heat input to HRSG is from:

• Gas turbine exhaust gas which can becontrolled by GT operation at Differentoperating mode (viz FSNL , Spinning Reserve, Full Load).

Any of the following conditions cause trippingof the HRSG

• HP Drum level very Low

• HP Steam outlet pressure very High

• IP Drum level very Low

• LP Drum level very Low

• GT Exhaust gas Pressure high

Operational Control

The interlocks are to be tested beforecommissioning. Repeat tests are advised once ayear. Any malfunction noted during operation hasto be attended early.

Section B 52


7 Automatic Controls

Aim

To describe the automatic controls provided foroperation of the HRSG.

7.1 Drum Level Control

HP Drum Level Control

The aim of this control loop is to maintain the drumLevel at the normal operating level in drum.

Two modes of operation are provided for drumlevel control.

Single element & Three element drum levelcontrol system is envisaged to regulate thequantity of feed water flowing into the drumto maintain required water level in the drum,Single-element drum level control for low loadsand Three-elements drum level control for normal& high load. 31HFW FS-003A is mode selectorswitch which changes single element control tothree elements control and three elements controlto single element control.

If steam flow increases beyond 85 TPH(30%) thencontrol will change to three elements control.

If steam flow decreases below 70 TPH(25%) thencontrol will change to single element control.

Single Element Drum Level Control In singleelement only Drum level is the reference level tocontrol the feed water flow.

The drum level signal is compared with thefixed set point in the drum level-indicatingcontroller & output of drum level controller 31HPDLIC003A is given to feed water flow controlvalve 31HFWFCV003AJYPA. Output signal isinverted due to control valve air fail action is open.Control action of the Drum level controller 31HPDLIC003A is Reverse.

Three Element Drum Level Control In Threeelements Drum level, Water flow and Steamflow are the references to control the water flow.Drum level as primary element, Feed water flowas secondary element and steam flow as thirdelement (feed forward).

In three - element control the drum levelsignal is compared with the fixed set point(+25mmWC) in the drum level indicating controller31HPDLIC003B. To achieve, better drum levelcontrol, a feed forward action is added toin the form of steam flow in function block31HPSFX003A. The feed forward output use asa remote set point to feed water flow indicating

controller 31HFWFIC003A. The feed water flowsignal is compared with the remote set point inthe feed water flow indicating controller & outputof feed water flow controller 31HFWFIC003Ais given to feed water flow control valve31HFWFCV003BJYPA & 31HFWFCV003CJYPAthrough manual loader 31HFWHIC003B &31HFWHIC003C respectively, output signal isinverted due to control valve air fail action is open.Control action of the feed water flow controller31HFWFIC003A & Drum level controller 31HPDLIC003B is Reverse.

The drum level measured by DP (DifferentialPressure) type level transmitters 31HPDLT003A,31HPDLT003B, 31HPDLT003C & measureddrum level is compensated (density) in functionblock 31HPDLY003A, 31HPDLY003B &31HPDLY003C with median drum pressure.

The drum pressure is measured by pressuretransmitter 31HPDPT003A, 31HPDPT003B,31HPDPT003C & measured drum pressure arePV for function block 31HPDPY003 (Medianblock). The compensated drum level values arethe PV for function block 31HPDLY003 (Medianblock).The median drum level is PV to drum levelcontrollers 31HPDLIC003A and 31HPDLIC003B.

The Drum level transmitter is calibrated for - 1000to 0 mmWC and correspondence indication shall0 to 100 %.

The Drum pressure transmitter is calibrated for 0to 140 Kg/Cm2 (g) and correspondence indicationshall 0 – 140 Kg/Cm2 (g).

Drum level density compensation

Computing block 31HPD LY003A, 31HPDLY003B & 31HPD LY003C shall be configuredto Pressure compensated /corrected drum levelindication can be obtained from equation belowWhere ‘Hm’ is the corrected level indication.

Hm = {Delta p + H (Da - Ds)} / (Dw - Ds )

Where:

DP = differential pressure measured by leveltransmitter (DPT). [The range of DP in aboveequation is also to be taken as (– 100 to 0 cmWC)]

Hm – Compensated drum level signal.

Dw – Density of water (To be taken from theenclosed table)

Ds – Density of Steam (To be taken from theenclosed table)

H — Water head on LP side, wet head leg whichis to be feed as constant = 100

Section B 53


Da – Wet leg density; water Density at 30 Deg.C.(Constant =0.996).

Head on HP = Hm *Dw + (H-Hm)*Ds

Head on LP = H *Da

Delta p = HP- LP

=Hm (Dw-Ds) – H (Da-Ds)

Hm = {delta p + H (Da-Ds)}/ (Dw- Ds)

Here,

H = 100 cm.

Da = 0.996 gm/cm3 at 30 deg. c

Hm calculated from above formula is densitycorrected drum level, which shall be in scalerange 0 to 100 cm (Hm output should be blockedin this range), this value shall be scaled for (-)475to (+)525 mmwc display range on DCS .

The steam flow measured by DP (DifferentialPressure) type steam flow transmitter31HPSFT003D, 31HPSFT003E & 31HPSFT003Fthese are connected across flow element 31HPSFE003B. Square root for steam flow shall be donein smart transmitter. The measured Steam flowis compensated (Average pressure & averagetemperature) in function block 31HPSFY003A,31HPSFY003B & 31HPSFY003C with averagepressure & average temperature.

The steam pressure measured by pressuretransmitter 31HPSPT025A, 31HPSPT025B &measured steam pressure are PV for functionblock 31HPSPY025 (Average block).

The steam temperature measured by temperaturetransmitter 31HPSTT026A, 31HPSTT026B withthermocouple 31HPSTE026A, 31HPSTE026B &measured steam temperature are PV for functionblock 31HPSTY026 (Average block).

The compensated steam flow values are the PVfor function block 31HPSFY003 (Median block)

The compensated steam flow is subtractedwith Attemperator water flow in function block31HFWFX003.

The Attemperator water flow measured by DP(Differential Pressure) type Attemperator waterflow transmitter 31HFWFT0034 this is connectedacross flow element 31HFWFE034. Square rootfor Attemperator water flow shall be done in smarttransmitter.

Steam flow (Pressure & temperature)compensation

Computing block 31HPSFY003A, 31HPSFY003B& 31HPSFY003C shall be configured to Pressure& temperature compensated steam flow indicationcan be obtained from equation below

Compensated Steam Flow in TPH = IndicatedSteam Flow in TPH * √ (P1 + 1.029) * (T2+273.15)/ √ (P2+1.029) * (T1+273.15)

Where:

P1 = Measured Pressure Signal in Bar (g)

T1 = Measured Temperature Signal in °C

P2 = Flow nozzle Rated Pressure Signal inKg/Cm2g

T2 = Flow nozzle Rated Temperature Signal inDeg. C

Flow nozzle Rated Pressure = 104 Kg/Cm2 (g)

Flow nozzle Rated Temp = 567.3 Deg. C

Normal Flow = 279.2 TPH

Sizing flow = 400 TPH

Feed Water Flow Controller Remote Set-point(31HPSFX003A) = Drum Level Controller (31HPDLIC003B) O/P in % + Steam flow (31HFWFX003)O/p in %- 50.

The feed water flow is measured by DP(Differential Pressure) type feed water flowtransmitter 31HFWFT003A, 31HFWFT003B &31HFWFT003C these are connected across flowelement 31HFWFE003A. Square root for feedwater flow shall be done in smart transmitter.The measured feed water flow is compensated infunction block 31HFWFY003A, 31HFWSFY003B& 31HFWFY003C with average temperature.

The feed water pressure measured by pressuretransmitter 31HFWPT002A, 31HFWPT002B &measured feed water pressure are PV for functionblock 31HFWPY002 (Average block). This isindicated in DCS as 31HFWPI002

The feed water temperature measured bythermocouple 31HFWTE001A, 31HFWTE001B& measured feed water temperature are PV forfunction block 31HFWTY001 (Average block)

The compensated feed water flow values arethe PV for function block 31HFWFY003 (Medianblock). The median feed water flow is PV to feedwater flow controller 31HFWFIC003A.

Feed water flow (Temperature) compensation

Computing block 31HFWFY003A,31HFWFY003B & 31HFWFY003C shall be

Section B 54


configured to Temperature compensated feedwater flow indication can be obtained fromequation below

Compensated FW Flow in TPH = Indicated FWFlow in TPH * √ (T2+273.15) / √ (T1+273.15)

Where:

T1 = Measured Temperature Signal in deg. C

T2 = Flow nozzle Operating Temperature Signalin deg. C

Flow nozzle design Temp = 151 deg. C



Indications and alarms to be configured as shownin the control schematic.

Water Flow Totaliser 31HFWFIQ-003 & SteamFlow Totaliser 31HPSFIQ-003 blocks to beconfigured All process value should be record forreports & trends

Drum Level high-high alarm configured in functionblock 31HPDLAHH003A, 31HPDLAHH003B& 31HPDLAHH003C. 31HPDLAHH003 isderived after 2oo3 voting from function block31HPDLX003A. Drum Level low-low alarmconfigured in function block 31HPDLALL003A,31HPDLALL003B & 31HPDLALL003C.31HPDLALL003 is derived after 2oo3 voting fromfunction block 31HPDLX003B. Whenever drumlevel high-high or low-low alarm occurs trip theboiler that is Trip the GT.

IP Drum Level Control



Single element & Three element drum levelcontrol system is envisaged to regulate thequantity of feed water flowing into the drumto maintain required water level in the drum,Single-element drum level control for low loadsand Three-elements drum level control for normal& high load. 31IFW FS-050A is mode selectorswitch which changes single element control tothree elements control and three elements controlto single element control.

If steam flow increases beyond 13TPH(30%) thencontrol will change to three elements control.

If steam flow decreases below 10TPH(25%) thencontrol will change to single element control.

Single Element Control:-

In single element only Drum level is the referencelevel to control the feed water flow.

The drum level signal is compared with the fixedset point (0 mmWC) in the drum level-indicatingcontroller & output of drum level controller 31IPDLIC050A is given to feed water flow control valve31IFWFCV050AJYPA & 31IFWFCV050BJYPAthrough manual loader 31IFWHIC050A &31IFWHIC050B respectively. Output signal isinverted due to control valve air fail action is open.Control action of the Drum level controller 31IPDLIC050A is Reverse.

Three Element Control:

In Three elements Drum level, Water flow andSteam flow are the references to control the waterflow. Drum level as primary element, Feed waterflow as secondary element and steam flow as thirdelement (feed forward).

In three - element control the drum level signalis compared with the fixed set point in thedrum level indicating controller 31IPDLIC050B.To achieve, better drum level control, a feedforward action is added to in the form of steamflow in function block 31IPSFX050A. The feedforward output use as a remote set point to feedwater flow indicating controller 31IFWFIC050A.The feed water flow signal is compared withthe remote set point in the feed water flowindicating controller & output of feed waterflow controller 31IFWFIC050A is given to feedwater flow control valve 31IFWFCV050AJYPA& 31IFWFCV050BJYPA through manual loader31IFWHIC050A & 31IFWHIC050B respectively,output signal is inverted due to control valve airfail action is open. Control action of the feedwater flow controller 31IFWFIC050A & Drum levelcontroller 31IPD LIC050B is Reverse.

The drum level measured by DP (DifferentialPressure) type level transmitters 31IPDLT050A,31IPDLT050B, 31IPDLT050C & measured drumlevel is compensated (density) in function block31IPDLY050A, 31IPDLY050B & 31IPDLY050Cwith median drum pressure.

The drum pressure is measured by pressuretransmitter 31IPDPT057A, 31IPDPT057B,31IPDPT057C & measured drum pressure arePV for function block 31IPDPY57 (Median block).

The compensated drum level values are the PVfor function block 31IPDLY050 (Median block)

The median drum level is PV to drum levelcontrollers 31IPDLIC050A and 31IPDLIC050B.

Section B 55


The Drum level transmitter is calibrated for - 550to 0 mmWC and correspondence indication shall0 to 100 %.

The Drum pressure transmitter is calibrated for 0to 35 Kg/Cm2(g) and correspondence indicationshall 0 – 35 Kg/Cm2(g).

Drum level density compensation

Computing block 31IPD LY050A, 31IPD LY050B& 31IPD LY050C shall be configured to Pressurecompensated /corrected drum level indication canbe obtained from equation below Where ‘Hm’ isthe corrected level indication.

Hm = {Delta p + H (Da - Ds)} / (Dw - Ds )

Where:

DP = differential pressure measured by leveltransmitter (DPT).

[The range of DP in above equation is also to betaken as (– 55 to 0 cmWC)]

Hm – Compensated drum level signal

Dw – Density of water (To be taken from theenclosed table)

Ds – Density of Steam (To be taken from theenclosed table)

H — Water head on LP side, wet head leg whichis to be feed as constant = 55

Da – Wet leg density; water Density at 30 Deg.C.(Constant =0.996).

Head on HP = Hm *Dw + (H-Hm)*Ds

Head on LP = H *Da

Delta p = HP- LP

=Hm (Dw-Ds) – H (Da-Ds)

Hm = {delta p + H (Da-Ds)}/ (Dw- Ds)

Here,

H = 55 cm.

Da = 0.996 gm/cm3 at 30 deg. c

Hm calculated from above formula is densitycorrected drum level, which shall be in scalerange 0 to 55 cm (Hm output should be blockedin this range), this value shall be scaled for (-)275to (+)275 mmwc display range on DCS.

The steam flow measured by DP (DifferentialPressure) type steam flow transmitter31IPSFT050D & 31IPSFT050E both areconnected across flow element 31IPS FE050B.Square root for steam flow shall be done insmart transmitter. The measured Steam flow

is compensated (Average pressure & Averagetemperature) in function block 31IPSFY050A &31IPSFY050B with average pressure & averagetemperature.

TThe steam pressure measured by pressuretransmitter 31IPSPT129A, 31IPSPT129B &measured steam pressure are PV for functionblock 31IPSPY129 (Average block).

The steam temperature measured bythermocouple 31IPSTE130A, 31IPSTE130B &measured steam temperature are PV for functionblock 31IPSTY130 (Average block)

The compensated steam flow values are the PVfor function block 31IPSFY050 (Average block)

The steam flow transmitter is calibrated for 0 to5000 mmWC and correspondence indication shall0-60 TPH.

The steam pressure transmitter is calibrated for0 – 35 Kg/Cm2(g) and correspondence indicationshall 0 – 35 Kg/Cm2(g).

Steam flow (Pressure & temperature)compensation.

Computing block 31IPSFY050A & 31IPSFY050Bshall be configured to Pressure & temperaturecompensated steam flow indication can beobtained from equation below

Compensated Steam Flow in TPH =IndicatedSteam Flow in TPH * √ (P1 + 1.029) * (T2+273.15)/ √ (P2+1.029) * (T1+273.15)

Where:

P1 = Measured Pressure Signal in Kg/Cm2(g)


P2 = Flow nozzle Rated Pressure Signal inKg/Cm2(g)

T2 = Flow nozzle Rated Temperature Signal in °C

Flow nozzle Rated Pressure = 25.49 Kg/Cm2(g)

Flow nozzle Rated Temp = 320 °C



Feed Water Flow Controller Remote Set-point(31IPSFX050A) = Drum Level Controller (31IPDLIC050B) O/P in % + Steam flow (31IPSFY050)O/p in %- 50.

The feed water flow measured by DP (DifferentialPressure) type feed water flow transmitter31IFWFT050A, 31IFWFT050B & 31IFWFT050Cthese are connected across flow element31IFWFE050A. Square root for feed water

Section B 56


flow shall be done in smart transmitter. Themeasured feed water flow is compensated infunction block 31IFWFY050A, 31IFWSFY050B &31IFWFY050C with average temperature.

The feed water pressure measured by pressuretransmitter 31IFWPT077A, 31IFWPT077B, &measured feed water pressure are PV for functionblock 31IFWPY077 (Average block). This isindicated in DCS as 31IFWPI077

The feed water temperature measured bythermocouple 31IFWTE075A, 31IFWTE075B &measured feed water temperature are PV forfunction block 31IFWTY075 (Average block)

The compensated feed water flow values are thePV for function block 31IFWFY050 (Median block)

The median feed water flow is PV to feed waterflow controller 31IFWFIC050A.

The feed water flow transmitter is calibrated for0 to 5000 mmWC and correspondence indicationshall 0-60 TPH.

The feed water pressure transmitter is calibratedfor 0 – 80 Kg/Cm2(g) and correspondenceindication shall 0 – 80 Kg/Cm2(g).

Feed water flow (Temperature) compensation.

Computing block 31IFWFY050A, 31IFWFY050B& 31IFWFY050C shall be configured totemperature compensated feed water flowindication can be obtained from equation below

Compensated FW Flow in TPH =Indicated FWFlow in TPH * √ (T2+273.15) / √ (T1+273.15).

Where:


T2 = Flow nozzle design Temperature Signal in °C

Flow nozzle Rated Temp = 218 °C




Water Flow Totaliser 31IPSFIQ-050 & Steam FlowTotaliser 31IFWFIQ-050 blocks to be configuredAll process value should be record for reports &trends

Drum Level high-high alarm configured in functionblock 31IPDLAHH050A, 31IPDLAHH050B& 31IPDLAHH050C. 31IPDLAHH050 isderived after 2oo3 voting from function block31IPDLX050A. Drum Level low-low alarm

configured in function block 31IPDLALL050A,31IPDLALL050B & 31IPDLALL050C.31IHPDLALL050 is derived after 2oo3 votingfrom function block 31IPDLX050B. Wheneverdrum level high-high or low-low alarm occurs tripthe boiler that is trip GT

LP Drum Level Control



Single element & Three element drum levelcontrol system is envisaged to regulate thequantity of feed water flowing into the drumto maintain required water level in the drum,Single-element drum level control for low loadsand Three-elements drum level control for normal& high load. 31LFW FS-093A is mode selectorswitch which changes single element control tothree elements control and three elements controlto single element control.

Single Element Control:-

In single element only Drum level is the referencelevel to control the feed water flow.

The drum level signal is compared with the fixedset point (0 mmWC) in the drum level-indicatingcontroller & output of drum level controller 31LPDLIC080A is given to feed water flow control valve31LFWFCV080AJYPA & 31IFWFCV080BJYPAthrough manual loader 31LFWHIC080A &31LFWHIC080B respectively. Output signal isinverted due to control valve air fail action is open.Control action of the Drum level controller 31LPDLIC080A is Reverse.

Three Element Control:-

In Three elements Drum level, Water flow andSteam flow are the references to control the waterflow. Drum level as primary element, Feed waterflow as secondary element and steam flow as thirdelement (feed forward).

In three - element control the drum level signalis compared with the fixed set point in thedrum level indicating controller 31LPDLIC080B.To achieve, better drum level control, a feedforward action is added to in the form of steamflow in function block 31LPSFX093A. The feedforward output use as a remote set point to feedwater flow indicating controller 31LFWFIC093A.The feed water flow signal is compared withthe remote set point in the feed water flowindicating controller & output of feed waterflow controller 31LFWFIC093A is given to feed

Section B 57


water flow control valve 31LFWFCV080AJYPA& 31LFWFCV080BJYPA through manual loader31LFWHIC080A & 31LFWHIC080B respectively,output signal is inverted due to control valve airfail action is open. Control action of the feedwater flow controller 31LFWFIC080A & Drumlevel controller 31LPDLIC080B is Reverse.

The drum level measured by DP (DifferentialPressure) type level transmitters 31LPDLT080A,31IPDLT080B, 31IPDLT080C & measured drumlevel values are the PV for function block31LPDLY080 (Median block)

The median drum level is PV to drum levelcontrollers 31LPDLIC080A and 31LPDLIC080B.

The Drum level transmitter is calibrated for -1900to 0 cmWC and correspondence indication shall 0to 100 %.

The steam flow measured by DP (DifferentialPressure) type steam flow transmitter31LPSFT093A & 31LPSFT093B both areconnected across flow element 31LPS FE093.Square root for steam flow shall be done insmart transmitter. The measured Steam flowis compensated (Average pressure & Averagetemperature) in function block 31LPSFY093A &31LPSFY093B with average pressure & averagetemperature.

The steam pressure measured by pressuretransmitter 31LPSPT089A, 31LPSPT089B &measured steam pressure are PV for functionblock 31LPSPY089 (Average block).

The steam temperature measured bythermocouple 31LPSTE090A, 31LPSTE090B &measured steam temperature are PV for functionblock 31LPSTY090 (Average block)

The compensated steam flow values are the PVfor function block 31LPSFY093 (Average block)

The compensated steam flow is added with HPcompensated feed water flow, HP Attemperatorwater flow, IP compensated feed water flow& RH1 Attemperator water in function block31LFWFX093

The RH1 Attemperator water flow measuredby DP (Differential Pressure) type Attemperatorwater flow transmitter 31IFWFT0073 this isconnected across flow element 31IFWFE073.Square root for Attemperator water flow shall bedone in smart transmitter.

The steam flow transmitter is calibrated for 0 to5000 mmWC and correspondence indication shall0-50 TPH.

The RH1 Attemperator water flow transmitteris calibrated for 0 to 2500 mmWC andcorrespondence indication shall 0-25 TPH.

The steam pressure transmitter is calibrated for0 – 10 Kg/Cm2(g) and correspondence indicationshall 0 – 10 Kg/Cm2(g).

Steam flow (Pressure & temperature)compensation.

Computing block 31LPSFY093A &31LPSFY093B shall be configured to Pressure &temperature compensated steam flow indicationcan be obtained from equation below

Compensated Steam Flow in TPH =IndicatedSteam Flow in TPH * √ (P1 + 1.029) * (T2+273.15)/ √ (P2+1.029) * (T1+273.15)

Where:

P1 = Measured Pressure Signal in Kg/Cm2(g)

T1 =Measured Temperature Signal in °C

P2 = Flow nozzle design Pressure Signal inKg/Cm2(g)

T2 = Flow nozzle design Temperature Signal in °C

Flow nozzle design Pressure = 3.16 Kg/Cm2(g)

Flow nozzle design Temp = 286.6 °C



Feed Water Flow Controller Remote Set-point(31LPSFX093) = Drum Level Controller (31LPDLIC080B) O/P in % + Steam flow (31LFWFX093)O/p in % - 50.

The feed water flow measured by DP (DifferentialPressure) type feed water flow transmitter31LFWFT104A & 31LFWFT104B both areconnected across flow element 31LFWFE104.Square root for feed water flow shall be done insmart transmitter. The measured feed water flowis compensated in function block 31LFWFY104A& 2IFWFY104B with average temperature.

The feed water pressure measured by pressuretransmitter 31LFWPT131A, 31LIFWPT131B, &measured feed water pressure are PV for functionblock 31LFWPY131 (Average block)

The feed water temperature measured bythermocouple 31LFWTE132A, 31LFWTE132B& measured feed water temperature are PV forfunction block 31LFWTY132 (Average block)

The compensated feed water flow values arethe PV for function block 31LFWFY104 (Averageblock)

Section B 58


The average feed water flow is PV to feed waterflow controller 31LFWFIC093A.

The feed water flow transmitter is calibrated for0 to 7500 mmWC and correspondence indicationshall 0-500 TPH.

The feed water pressure transmitter is calibratedfor 0 – 40 Kg/Cm2(g) and correspondenceindication shall 0 – 40 Kg/Cm2(g).

Feed water flow (Temperature) compensation.

Computing block 31LFWFY104A &31IFWFY104B shall be configured toTemperature compensated feed water flowindication can be obtained from equation below

Compensated FW Flow in TPH = Indicated FWFlow in TPH * √ (T2+273.15) / √ (T1+273.15)

Where:


T2 = Flow nozzle Rated Temperature Signal in °C

Flow nozzle design Temp =146 °C

Normal Flow =389.2 TPH

Sizing flow =500 TPH


Water Flow Totaliser 31LFWFIQ104 & SteamFlow Totaliser 31LPSFIQ93 blocks to beconfigured All process value should be record forreports & trends

Drum Level high-high alarm configured in functionblock 31LPDLAHH080A, 31LPDLAHH080B& 31LPDLAHH080C. 31LPDLAHH080 isderived after 2oo3 voting from function block31LPDLX080A. Drum Level low-low alarmconfigured in function block 31LPDLALL080A,31LPDLALL080B & 31LPDLALL080C.31LHPDLALL080 is derived after 2oo3 votingfrom function block 31LPDLX080B. Wheneverdrum level high-high or low-low alarm occurs tripthe boiler that is trip GT

7.2 CBD Drain Temperature Control

The aim of this control loop is to maintain theCBD Drain Temperature at the normal operatingtemperature in drain line.

CBD drain temperature control system isenvisaged to regulate the quantity of quenchwater flowing into the drain line to maintainrequired temperature in drain line

CBD drain temperature Control:-

CBD drain temperature is the referencetemperature to control the drain line temperature.

The CBD drain temperature signal is comparedwith the fixed set point (60°C) in the CBD draintemperature -indicating controller & output ofCBD drain temperature controller 31SWSTIC096is given to quench water flow control valve31SWSTCV096JYPA. Output signal is inverteddue to control valve air fail action is open. Controlaction of the CBD drain temperature controller31SWSTIC096 is Direct.

The CBD drain temperature measured bytemperature transmitters 31HVDTT096A,& 31HVDTT096B with thermocouple31HVDTE096A, & 31HVDTE096B & measuredCBD drain temperature are PV for function block31HVDTY096 (Average block)

The average CBD drain temperature is PV to CBDdrain temperature controller 31SWSTIC096.

The CBD drain temperature transmitter iscalibrated for 0 – 150 Deg.C and correspondenceindication shall 0 to 150 Deg.C.

Following to be taken care while configuring thisloop in DCS.

In manual mode SP tracking is required to PV.

7.3 Stack Temperature (CPH Bypass3- Way) Control

The aim of this control loop is to maintain the stacktemperature at the normal operating temperaturein stack.

Stack temperature control system is envisaged toregulate the quantity of DM water flowing into theCPH to maintain required temperature in stack.

Stack Temperature Control:-

Stack temperature is the reference temperature tocontrol the stack temperature.

The stack temperature signal is compared withthe set point in the stack temperature -indicatingcontroller & output of stack temperature controller31LFWTIC102 is given to CPH bypass flowcontrol valve 31LFWTCV102JYPA. Control actionof the Stack temperature controller 31LFWTIC102is Reverse.

The stack temperature measuredby thermocouple 31FLUETE226A &31FLUETE226B & measured stack temperatureare PV for function block 31FLUETY226 (Averageblock)

The average stack temperature is PV to stacktemperature controller 31LFWTIC102.

Section B 59




Setpoint for Various fuels is mentioned below:

7.4 LP Drum Pressure Control

The aim of this control loop is to maintain thedrum pressure at the normal operating pressurein drum.

Drum pressure control system is envisaged toregulate the quantity of steam vent to maintainrequired pressure in drum.

LP Drum Pressure Control:-

LP Drum Pressure is the reference Pressure tocontrol the drum Pressure.

The drum Pressure signal is compared with thefixed set point in the LP drum Pressure -indicatingcontroller & output of LP drum Pressure controller2LPDPIC083 is given to drum Pressure controlvalve 2LPDPCV083JYPA. . Output signal isinverted due to control valve air fail action is open,Control action of the LP drum Pressure controller2LPDPIC083 is Direct.

The drum Pressure measured by pressuretransmitter 2LPDPT083A & 2LPDPT083B &measured drum Pressure are PV for functionblock 2LPDPY083 (Average block)

The average drum Pressure is PV to drumPressure controller 2LPDPIC083.

The LP drum pressure transmitter is calibrated for0 – 10 Bar (g) and correspondence indication shall0 – 10 Bar (g).



• Natural Gas - 86°C

• Naptha - 134°C

7.5 LP Drum Pressure Control

The aim of this control loop is to regulate thequantity of steam vent to maintain requiredpressure in drum. The Vent Valve shallbe operated from DCS thro’ Manual Loader31LPDHIC083. This valve shall be kept crackopen all the time to have continuous Vent. LPDrum Pressure Control is envisaged by LP DrumPegging Steam Pressure Control Valve.

7.6 HP Attemperator Control

The aim of this control loop is to maintain theHP Steam Temperature at the normal operatingtemperature in HP steam line.

HP steam temperature control system isenvisaged to regulate the quantity of feed waterflowing into the steam line (Attemperator) tomaintain required temperature in HP steam line.

HP1 Attemperator Control

HP steam temperature is the referencetemperature to control the steam line temperature.

The steam temperature signal is compared withthe fixed set point (567°C) in the HP Attemperator-indicating controller & output of Attemperatorcontroller 31HFWTIC026 is given to Attemperatorcontrol valve 31HFWTCV026AJYPA & .31HFWTCV026BJYPA through manual loader31HFWHIC026A & 31HFWHIC026B respectively,Output signal is inverted due to control valveair fail action is open. Control action of the HPAttemperator controller 31HFWTIC026 is Direct.

The HP steam temperature measured bytemperature transmitters 31HPSTT026A,& 31HPSTT026B with thermocouple31HPSTE026A, & 31HPSTE026B & measuredsteam temperature are PV for function block31HPSTY026 (Average block)

The average HP steam temperature is PV to HPAttemperator controller 31HFWTIC026.

The HP Steam temperature transmitter iscalibrated for 0 – 800 Deg.C and correspondenceindication shall 0 to 800 Deg.C.



7.7 RH1 Attemperator Control

The aim of this control loop is to maintain theIP Steam Temperature at the normal operatingtemperature in IP steam line.

RH1 steam temperature control system isenvisaged to regulate the quantity of feed waterflowing into the steam line (Attemperator) tomaintain required temperature in IP steam line.

RH1 Attemperator Control

IP steam temperature is the referencetemperature to control the steam line temperature.

Section B 60


The steam temperature signal is comparedwith the fixed set point (567°C) in the RH1Attemperator -indicating controller & output ofAttemperator controller 31IFWTIC068 is given toAttemperator control valve 31IFWTCV068AJYPA& . 31IFWTCV068BJYPA through manual loader31IFWHIC068A & 31IFWHIC068B respectively,Output signal is inverted due to control valve airfail action is open. Control action of the RH1Attemperator controller 31IFWTIC068 is Direct.

The IP steam temperature measured bytemperature transmitters 31HRHTT068A,& 31HRHTT068B with thermocouple31HRHTE068A, & 31HRHTE068B & measuredsteam temperature are PV for function block31HRHTY068 (Average block)

The average IP steam temperature is PV to RH1Attemperator controller 31IFWTIC068.

The IP Steam temperature transmitter iscalibrated for 0 – 800 Deg.C and correspondenceindication shall 0 to 800 Deg.C.



7.8 CPH Recirculation TemperatureControl

The aim of this control loop is to maintain theCPH Water Temperature at the normal operatingtemperature in CPH tubes to avoid corrosion ofthe CPH tubes.

CPH recirculation temperature control systemis envisaged to regulate the quantity of waterrecirculate into the CPH tubes to maintain requiredtemperature in CPH tubes.

CPH Recirculation Temperature Control

CPH Water temperature is the referencetemperature to control the CPH tubestemperature.

The CPH Water temperature signal is comparedwith the fixed set point (57°C) in the CPHrecirculation temperature - indicating controller &output of CPH recirculation temperature controller31LFWTIC108 is given to CPH recirculationtemperature control valve 31LFWTCV108JYPA.Output signal is inverted due to control valveair fail action is open. Control action ofthe CPH recirculation temperature controller31LFWTIC108 is Reverse.

The CPH Water temperature measured bytemperature transmitters 31LFWTT108A,& 31LFWTT108B with thermocouple

31LFWTE108A, & 31LFWTE108B & measuredCPH Water temperature are PV for function block31LFWTY108 (Average block)

The average CPH Water temperature is PVto CPH recirculation temperature controller31LFWTIC108.

The CPH Water temperature transmitter iscalibrated for 0 – 80 Deg.C and correspondenceindication shall 0 to 80 Deg.C.



7.9 IP Line Back Pressure Control

The aim of this control loop is to maintain the IPsteam pressure at the normal operating pressurein IP line.

IP Line Back pressure control system is envisagedto regulate the CV to maintain required pressurein IP line.

IP Line Back pressure Control

IP line Pressure is the reference Pressure tocontrol the IP line Pressure.

The IP steam Pressure signal is comparedwith the fixed set point (24 Kg/Cm2g) in the IPLine Back pressure control -indicating controller& output of IP Line Back pressure controller31IPSPIC129 is given to IP Line Back pressurecontrol valve 31IPSPCV129JYPA. . Output signalis inverted due to control valve air fail action isopen; Control action of the LP drum Pressurecontroller 31IPSPIC1293 is direct.

The IP steam Pressure measured by pressuretransmitter 31IPSPT129A & 31IPSPT129B &measured IP steam Pressure are PV for functionblock 31IPSPY129 (Average block)

The average IP steam Pressure is PV to IP lineback Pressure controller 31IPSPIC129.

The IP Steam pressure transmitter is calibrated for0 – 35 Kg/Cm2(g) and correspondence indicationshall 0 – 35 Kg/Cm2(g).


In manual mode PV to SP tracking is required.

7.10 Start up Vent (HP, IP & LP) Control

Initially during boiler start up it is necessary tokeep the start up vent valve open and increase theboiler pressure & steam temperature gradually.

Section B 61


Start up vent control valve is provided to avoid burnout of tubes and to control the start uppressure.

Section B 62


Section C


♦ Section Overview♦ HRSG Start Up and Shut Down♦ Startup of a Cold HRSG♦ Hot and Warm Start up of HRSG♦ HRSG Shutdown♦ Cooling of a Shutdown Boiler♦ HRSG Operation Walk Down Checks♦ Do’s and Don’ts For HRSG Operation♦ Boiler Log Sheet♦ Boiler Emergency Safety Procedures♦ Trouble Shooting Chart

Operation

1 Section Overview

This section describes the start up, shut downprocedures of the HRSG. HRSG operation &safety are also described here.

2 HRSG Start Up and Shut Down

Operation

HRSG Start Up And Shut Down

Aim

This and subsequent chapters describes theHRSG start up and shut down procedures asapplicable for the following conditions:

• Start up of a cold HRSG

• HRSG shut down

• Start up of a warm HRSG

• Start up of a Hot HRSG

Note

• The procedures explained in thischapter apply for start up of theHRSG already commissioned.Commissioning a new HRSG call forseveral additional requirements.

• It is assumed that operators arefully familiar with the design andconstruction features described in theearlier chapters.

• It is assumed that operators are trainedin operation of high pressure HRSGsand have been licensed to operateHRSGs or HRSG by the State BoilerAuthority

3 Startup of a Cold HRSG

A HRSG startup can be termed as cold start upwhen any of the following conditions are met

• The HRSG has been idle for more than threedays

• There is no pressure in the steam drum and itsmetal temperature is less than 70°C

In a cold startup, possibilities of some inspectionor maintenance works having been done arepresumed. A walkdown checks are requiredand the HRSG and its auxiliaries are to beprepared meticulously for a startup from thecontrol room. Before a walkdown checks ensurethat all work permits have been returned, tagsremoved and maintenance permission for HRSGstartup is available. Program of Gas Turbine (GT)availability has also to be checked.

Carry out walk down checks before cold start upof HRSG & fill up water in HRSG as per Standardoperating procedure.

3.1 Walk Down Check

Using powerful torches or low voltage inspectionlamps inspect the HRSG and ensure that

1. Furnace and the exhaust gas path areclear, all maintenance personnel have beenremoved and no scaffolding or inspectiondevices have been left inside.

2. Boiler bank, Economiser & LP Boiler Bankpanels are clean and there is no evidence ofany water drips.

3. Verify that all access doors, inspection doorsare tightly closed.

4. Verify that the exhaust gas duct to stack isclear and that all maintenance personnel havebeen withdrawn.

HP ,IP & LP Main Steam Line and Reheater

1. Verify that the safety valves are not gagged.

2. Verify that nitrogen purging valves are open.If they are open, they are to be closed justbefore HRSG light up when air vents areopened.

HP, IP & LP Steam Drum

1. Verify that the safety valves are not gagged.

2. Verify that the illuminators of local levelgauges are on. Inlet valves from steam andwaterside is open and their drain valves areclosed.

Section C 63


3. Verify that the nitrogen connection line (ifused) has been isolated and the drum vent isopen.

HP, IP & LP Dosing Systems

1. Check that the solution-mixing tank of HP, IP &LP dosing system has atleast 50% tank level.If the level is low, prepare a full tank levelof solution. Check that the pump inlet andsolution inlet valves are open.

2. Check oil levels of the gearboxes of the dosingpumps and the stirrer. Top up if necessary.

3.2 Valve Lineup

The DCS is linked from field instruments toconstantly update process information (Feed flow,steam flow, steam temperature, drum pressure,water/steam temperatures, metal temperatures,gas temperatures, pressure/temperatures for pretrip alarms etc). In the DCS, the informationis processed and based on pre-set logic andset points, control commands are sent to I/Pconverters for control action. Start/Stop commandand alarm inputs etc are also from the DCS.

1. Ensure pre-purge of HRSG is done throughGT (This is carried out standard GT operationprocedure)

2. Ensure that the HRSG is lined up for start upas per cold start up procedure as mentionedabove. Ref. cold start up procedure. Line upall valves in HP, IP & LP section as per thevalve line up chart for cold start up.

3. During cold start up all the section of HRSGviz HP, IP & LP shall receive hot flue gasesfrom GT & hence undergo cold start upsimultaneously.

4. Ensure that HP Section main steam stopvalve M029A & Bypass valve M029B areclosed & start up vent valve PCV028 is fullopen.

5. Ensure that IP Section steam isolation valveM064 to reheater is closed & start up ventvalve PCV063 is full open.

6. Ensure that drain valves to Blow down Tankof HP SH Drain header (GT688), ReheaterDrain Header (GT650) are closed. The HPSHdrain header, reheater drain header & HPSH1drain operate from condensate drain potarrangement on conductivity principle.

7. Ensure that drain valves to Blow down Tank ofIP RHS Drain Header (GT 622) & IP LHS sideheader (GT 624), LP LHS side drain header

(GT 607) & LP RHS side drain header (GT605) are open.

8. Ensure that drain valves HPSH1 GL739,Reheater2 GL738, HPSH3 GL737 are closed.

9. Ensure that following manual drain valves areopen:

• HPSH-1 Drain valve (GT680)

• RH-2 Drain valve (GT642), (GT 646).

• HPSH-3 Drain valve (GT682), (GT764,GT694)

• IPSH Drain valve (GT637) to be normallyopen.

• LPSH Drain valve (GT617) to be normallyopen.

10. Ensure that following drain valves are open:

• IP super heater motorised drain valveM076 to be closed after removal ofcondensate.

• LP superheater motorised drain valveM098 to be closed after removal ofcondensate.

• All above mentioned drain valves are startup drain valves & need to be close downwhen steam pressure of respective sectionreaches near to 4 bar (g).

11. Ensure following vent valves are open

• HP Drum vent valve M005A & M005B, tobe closed when drum pressure reaches to2 bar (g).

• HP Main steam line start up vent valveM028.

• IP Drum vent valve M061 to be closedwhen drum pressure reaches to 2 bar (g).

• LP Drum (Deaerator) vapour tank ventvalve PVC 083 & isolation valve GT 359,PVC 083 to be operated as per pressurecontroller PIC 083.

12. Ensure following valves are closed

• HP Drum EBD M039, this need to be openin the event of Drum high level.

• IP Drum EBD M078, this need to be openin the event of Drum high level.

• LP Drum EBD M094, this need to be openin the event of Drum high level.

• HP Drum CBD M040, this need to be openin proportion to keep HP drum water qualityas per requirement.

Section C 64


• IP Drum CBD M079, this need to be openin proportion to keep IP drum water qualityas per requirement.

• LP Drum CBD M095, this need to be openin proportion to keep LP drum/Deaeratorwater quality as per requirement.

3.3 System Lineup

Preliminary Requirements

• Power supply ensure that the power supply isswitched ’ON’ and available for all the motorsand panels.

• Operating station - DCS is ensured forreadiness and emergency push buttons arereleased, if activated.

• As instrument air is necessary for the operationof most of the valves and actuators, chargethe instrument air header, the branch linesand instruments supply lines elsewhere. Rootvalves of all Instruments (Pressure gauges,Pressure transmitters, DP transmitters, Levelgauges, etc,) must be kept open and theirdrains if any are to be kept closed. They arenot separately listed.

• Ensure that all the transmitters are lined upmechanically / electronically

CPH

• Verify that drain valves [GT 603 & GT604] arekept locked open except for maintenance

• Verify that air vent valves [GT 609] are lockedopen. Verify that it is open & is to be closedas soon as air is purged & water comes outduring waterside charging.

• Verify that water side inlet isolating valves [GT305] is open

• Verify that bypass manual valve [GT 314] isopen .

Feedwater Control Stations

For starting a cold HRSG, DM water from thestation DM line may preferably be used. Howeverfeed lines are lined up such that the FeedRegulating stations can be taken into service fromDCS, when requirement arises.

• Verify that electrically operated isolating valve[TV 034] to spray water lines is closed (DCS)

• Verify that drain valves on the spray water lineare closed

• Verify that the root valves of Pressure gauges,pressure transmitters, pressure switches areopen.

• Verify that the 30% and the two 100% flowcontrol valves are in the closed (0%) positionin the DCS (If they are in open position, closethem by manual command from DCS)

• Verify that the Manual operated inlet & outletisolating valve of the feed regulating station isopen

• Verify that the drain valves before and after the30% & 100% flow regulating valve are closed

Feed Line from HP Economiser I

• An export water line valve GT 211 is keptclosed.

• Root valve of all the instruments are kept open.

Attemporator Spray Water Lines

• Keep open the manual isolating valves [GT049, GT050 & GT 248, GT249].

• Verify that the Attemperator spray watercontrol valve [TCV026A & B and TCV 068A &B] is in closed position (DCS).

• Verify that the drains on either side of thecontrol valve are closed.

• Keep open the inlet and outlet isolating valvesof control valves [TCV026A & B and TCV 068A& B]

• Keep the Attemporator controller [TIC-026 &TIC 068] in manual mode.

Sample System

• All the sample lines isolation valves haveto be closed. SWAS (Customer System)can be taken into service once the HRSG ispressurized

Availability of Nitrogen Gas

Nitrogen gas is used for purging the gas, oil linesbefore inspection or maintenance of any of thecomponents. No prediction can be made whenthe nitrogen gas will actually be required. To meetany eventuality, it is a good practice to charge thenitrogen gas lines up to the consuming points andkeep the gas available whenever required.

• Verify valve from plant nitrogen gas main todrums are closed.

Section C 65


3.4 Valve Positions Chart For HP, IP &LP Section (Before Light Up)

Valve Tag Number Service Open Close Remarks

FEED WATER LINE TO HP STEAM DRUM

GT-038Feed Water MainIsolation valve

YTo be closed while carryingout maintenance duringboiler shut down

M -003 A/B/CControl station inletmotorized isolationvalves


GT- 026/027/028Control station outletmanual isolationvalves

Y

To be closed while carryingout maintenance duringboiler shut down or problemin control valve operation

GT-020/21/22/23/2 4 & 25Feed water controlstation drain valves

YTo be Opened when controlvalve is under maintenance

GT- 001/002/015/016/

2 9/30/32/33/34/3536/37 /54/55

Feed water linepressure tappingisolation valves


GT – 003,004,005,006,00 7

,008,009,010,011,012,0 13 &014

Feed water flowtransmitter isolationvalves


FCV – 003 AFeed water controlstation 30% controlvalve

YTo be opened initially whenthe water is required tomaintain the drum level

FCV – 003 BFeed water controlstation 100% controlvalve

Y

To be opened when boilerload reaches above the30% to maintain the drumlevel

FCV – 003 CFeed water controlstation 100% controlvalve

YTo be opened when the100% line main controlvalve is under maintenance

FEED WATER LINE TO IP STEAM DRUM

GT - 241Feed Water MainIsolation valve


M – 050 AControl station inletmotorized isolationvalve


GT – 216,217Control station outletmanual isolation valve

Y

To be kept openpermanently & it willbe closed only duringthe boiler shutdown ormotorized valve is undermaintenance

GT – 214,215Feed water controlstation drain valve

YTo be Opened whenmotorized valve is undermaintenance

Section C 66



GT – 201,08,

GT – 59(02 NO’S)

GT – 60 & 18

GT – 58

Feed water linepressure tappingisolation valves


GT – 202,03,04,05, 06 & 07Feed water flowtransmitter isolationvalves


GT – 211 Export water line valve YTo be closed while carryingout maintenance duringboiler shut down

FCV – 050AFeed water controlstation 100% controlvalve

YTo be opened initially whenthe water is required tomaintain the drum level

FCV – 050BFeed water controlstation 100% controlvalve

YTo be opened when the100% line main controlvalve is under maintenance

FEED WATER LINE TO LP STEAM DRUM

GT - 314Feed Water MainIsolation valve


GT - 327Feed Water SecondIsolation valve


M – 080 A/BControl station inletmotorized isolationvalves


GT – 322, 325Control station outletmanual isolationvalves

Y

To be kept openpermanently & it willbe closed only duringthe boiler shutdown ormotorized valve is undermaintenance

GT – 321, 324Feed water controlstation drain valves

YTo be Opened whenmotorized valve is undermaintenance

GT – 316, 317, 318 & 319Feed water flowtransmitter isolationvalves


GT –328, 329,Feed water linepressure tappingisolation valves


GT – 326 Vent line valve YTo be open while carryingout maintenance duringboiler shut down

ECONOMIZER HP

Section C 67



GT – 671 (04 NO’S)

GT – 672 (02 NO’S)

GT - 673 (14 NO’S )

Economizer I/II/III topheader Vent IsolationValves.

YTo be open only during firstfilling of Economizer/ boiler.

GT – 651 (06 NO’S)

GT – 693 (06 NO’S)

GT – 653 (01 NO’S)

GT – 654 (01 NO’S)

GT – 655 (02 NO’S)

GT – 656 (02 NO’S)

GT – 657 (02 NO’S)

GT – 658 (02 NO’S) GT – 659(01 NO’S)

GT – 660 (01 NO’S)

GT – 696 (02 NO’S)

GT – 663 (12 NO’S)

GT – 692 (12 NO’S)

GT – 665 (01 NO’S) GT – 666(01 NO’S)

Economizer I/II/III Top& bottom header DrainIsolation Valves.

YTo be opened for draining& initial water filling theEconomizer & hydro

ECONOMIZER IP

GT – 626 (02 NO’S)Economize top headerVent Isolation Valves.


GT – 620 (02 NO’S )

GT – 621 (02NO’S )Economizer Top &bottom header DrainIsolation Valves.


DM WATER FILLING IN HRSG

GT-716,714,718,720 , 722 &712

DM water line atbattery limit valves

YTo be open only to takewater for boiler hydro test.

GT – 627 & 636 (02 NO’SEACH)

IP Evaporator drainline valves


GT – 615 & 616 (01 NO EACH)LP Evaporator drainline valves


GT – 695, 669, 622, 624, 605,& 607

All header drain valves Y

To be open duringboiler cold start up tolet water/condensate toblow down tank.

HP STEAM DRUM

M –005 A/BMotorized IsolationValves of Drum Vent

YTo be closed when drumpressure reaches 2 bar (g)during boiler pressurization.

GT – 095N2 PreservationConnection

YTo be opened only whenboiler is to be preservedwith N2

Section C 68



GT – 087,088,089, 090,091 &092

Steam drum pressuretransmitters isolationvalves


GT – 084,085 & 086Steam drum localpressure indicatorisolation valves


GT – 087, 088, 089, 090, 091,092

Steam drum localpressure transmitterisolation valves


GT-060,061,062,063,064,065,066, 067, 068,069,070,071, 072, 073,074 &075

Isolation Valvesfor manifold onSteam Drum forLevel IndicatingInstruments.


GT – 076,077,078,079,080,081,082 & 083

Isolation Valves ofSteam Drum LevelGauge Glass


HP EVAPORATOR

GT – 678 & 679 (02 NO’SEACH)

HP Evaporator drainline valves

YTo be open only during firstfilling of Economizer/ boiler.

GT – 690 (02 NO’S) Evaporator vent valve YTo be open only during firstfilling of Economizer/ boiler.

HP MAIN STEAM LINE

GT – 680HP Superheater-1Drain Isolation Valvebefore MOVs

YTo be kept lock open. Tobe closed at failure of MOVvalve.

GT – 682 (02 NO’S)

GT – 683 (02 NO’S

HP Superheater-2 & 3Drain Isolation Valves

YTo be open during boilershut down for completedraining or superheater

M – 038 B

M – 038 F

HP Superheater-2 &3 Motorized operatedDrain valves

Y

To be closed whencondensate is drainedcompletely at 4 bar (g)pressure.

M – 038 D

M – 038 H

HP Superheater-1Motorized operatedDrain valves

Y

To be closed whencondensate is drainedcompletely at 4 bar (g)pressure.

GT – 691 (02 NO’S)Superheater 2 ventvalve

YTo be open during boilershutdown

GT – 688HP SH Drain headervalve

Y To be kept lock open

GT – 698Main Steam line drainbefore MSSV


M- 038A & 038EMain steam linemotorized operateddrain valves

YTo be closed once thecondensate removed forline completely

Section C 69



GT – 107 & 108Main steam line ventvalve before safetyvalve


GT – 129Steam samplingsystem main isolationvalve


M - 028Motorized isolationValve of Startup VentValve

Y

To be kept open duringboiler start up. To be closedwhen boiler is connectedto plant mains along withPV028.

PV -028 Startup Vent valve Y

To be Closed once ratedpressure is attained andboiler is connected to Plantmains

M – 029 B

Motorised PressureEqualization Valveof Main Steam StopValve

YTo be opened forequalization of pressure.

M – 029 AMotorized Main SteamStop Valve

YTo be opened after reachingthe rated Pressure.

GT – 112 & 113 (02 NO’SEACH)

GT –110 & 111

Main steam linepressure transmitterisolation valves


GT – 114,115,116,117,118,119,120,121,122,123,124 & 125

Main steam line flowtransmitter tappingline valves


REHEATER

GT – 644 (02 NO’S)

GT – 642 (02 NO’S)

Reheater drain linevalves


M – 38CRe-heater -1 & 2 drainline motorized valve

Y

This valve to be closed oncethe condensate removedcompletely from Re-heater1 & 2.

GT - 646Re-heater -1 & 2 drainline manual valve


GT – 650Reheater Drainheader valve

Y To be kept lock open.

GL – 738ReheaterAttemperator drainvalve


FMV – D201 (Customer scope)Reheater -2 O/L tosteam header Drainvalve

YTo be closed whencondensate is drainedcompletely.

HP ATTEMPERATOR SYSTEM

Section C 70



LCV – 034Attemperator line mainisolation valve

YTo be closed during initialfill up water in boiler /Economizer

M – 026 A/B

Attemperator controlstation up streammotorized isolationvalves


GT – 049 & 050

Attemperator controlstation down streammanual isolationvalves


GT – 045,046 & 047,048Attemperator drainline isolation valves


To be open as per thesteam temperature controlrequirement.TCV – 026 A/B

Temperature controlvalve one is main linevalve and another isbypass valves

Y

One TCV kept closed andone will be use.

GT – 103 & 104Attemperator vent linevalves

YTo be opened during boilershutdown

GT – 105 & 106Attemperator drainline valve

YTo be opened during boilershutdown

M – 038B & 038FHP Attemperatormotorized drain valves

YBoth valves to be closedonce the condensateremoved completely

GT - 694HP Attemperatormanual drain valve


HP BLOWDOWN SYSTEM

M - 040HP Drum EBDmotorized valve

YThis valve need to be openin the event of Drum highlevel

GT – 674 (02 NO’S)HP Drum EBD manualisolation valves

YManual isolation valveskeep open continuously

M - 039HP Drum CBDmotorized valve

Y

This need to be open in theevent of Drum high levelor maintaining the TDS inboiler

GT – 675 (02 NO’S)HP Drum CBD manualvalves

YManual isolation valveskeep open continuously

IP STEAM DRUM

M –061Motorized IsolationValves of Drum Vent

YTo be closed when drumpressure reaches 2 bar (g)during boiler pressurization.

GT - 228N2 PreservationConnection


Section C 71



GT – 224,225 & 226Steam drum pressuretransmitters isolationvalves


GT – 219,220 & 221Steam drum localpressure indicatorisolation valves


GT-235,236,237, 238,239 &240

Isolation Valvesfor manifold onSteam Drum forLevel IndicatingInstruments.


GT – 231,232 & 234Isolation Valves ofSteam Drum LevelGauge Glass


IP EVAPORATOR

GT – 636 & 627 (02 NO’SEACH)

IP Evaporator drainline valves

YTo be open only duringinitial water filling & hydro

GT – 641 (02 NO’S) Evaporator vent valve Y

To be open during initialwater filling & hydro & to beclosed after air is expelledcompletely.

IP MAIN STEAM LINE

GT – 637 & GI – 256Superheater Inlet &Outlet Header DrainIsolation Valves

YTo be closed during boilershutdown

M – 076IP Superheatermotorized drain valve

YTo be closed once thecondensate removedcompletely

GT – 294Superheater inlet ventvalve


GI – 256Main Steam line drainvalve

Y

GI – 255Main steam line ventvalve

Y



M - 063Motorized isolationValve of Startup VentValve

YTo be closed along withPCV 063 when boiler isconnected to re-heater

PCV -063 Startup Vent valve Y

To be Closed once ratedpressure is attained andboiler is connected tore-heater

M – 064IP section to re-heaterconnecting lineisolation valve

YTo be open once the boilerpressure reaches above 5Bar

Section C 72



GT – 264IP main steam linedrain valve

Y To be kept lock open.

M -077IP main steam linemotorized operateddrain valve

YTo be closed once thecondensate removed fromline

GT – 257,258,259 & 260Main steam line flowtransmitter tappingline valves


IP ATTEMPERATOR SYSTEM

LCV – 074Attemperator line mainisolation valve

Y

M – 068 A/B

Attemperator controlstation up streammotorized isolationvalves


GT – 248 & 249

Attemperator controlstation down streammanual isolationvalves


GT – 246 & 247Attemperator drainline isolation valves


To be open as per thesteam temperature controlrequirement.TCV – 068 A/B

Temperature controlvalve one is main linevalve and another isbypass valve

Y

One TCV kept closed andone will be use.

GT – 274Attemperator headervent line valve

Y

GT – 275Attemperator drainline valve

Y

IP BLOWDOWN SYSTEM

M - 078IP Drum EBDmotorized valve

YThis need to be open in theevent of Drum high level

GT – 631IP Drum EBD manualvalve

YManual isolation valve keeplock open

GT – 628IP Drum CBD manualvalve


M - 079IP Drum CBDmotorized valve

YThis need to be opento maintain boiler waterchemistry

IP EVAPORATOR

GT – 615 & 616LP Evaporator drainline valves

YTo be open for initial waterfilling & hydro test

GT – 619 (02 NO’S) Evaporator vent valve YTo be open for initial waterfilling & hydro test

LP DRUM

Section C 73



GT – 359

PCV - 083

Air vent is providedon the vapor tank withtwin Valve

YThrough the air vent, Steamand dissolved gases arevent out to the atmosphere

GT - 362Air vent is provided onthe vapor tank

YThrough the air vent, Steamand dissolved gases arevent out to the atmosphere

GT - 354N2 PreservationConnection


GT – 353LP drum pressuretransmitters isolationvalve


GT – 356,357 & 358LP drum localpressure indicatorisolation valves


GT-341,342,343, 344 345 &346

Isolation Valves formanifold on LP Drumfor Level IndicatingInstruments.


M - 094LP Drum EBDmotorized valve

YThis need to be open in theevent of Drum high level

GT – 612LP Drum EBD manualvalve


M - 095LP Drum CBDmotorized valve

YThis need to be opento maintain boiler waterchemistry

GT – 630LP Drum CBD manualvalve


GT – 347,348 & 350,351Isolation Valves of LPDrum Level GaugeGlass


LP MAIN STEAM LINE

GT – 617LP Superheater Inlet& Outlet Header DrainIsolation Valves

Y To be kept lock open

M – 098LP Superheater drainvalve

YTo be closed oncecondensate is removedcompletely.

GT – 381Superheater inlet ventvalve

Y

GI – 371Main Steam line drainbefore MSSV

Y

GI – 374Main steam line ventvalve before MSSV

Y



Section C 74



To be opened beforeopeningM - 091

Motorized isolationValve of Startup VentValve

Y

Start up vent valve.

PV -091 Startup Vent valve YTo be Closed once ratedpressure is attained andboiler is connected to load

M – 092 B

Motorised PressureEqualization Valveof Main Steam StopValve

YTo be opened forequalization of pressure.

M – 092 AMotorized Main SteamStop Valve

YTo be opened after reachingthe rated Pressure.

GT – 379 & 380Main steam line flowtransmitter tappingline valves


3.5 Filling Water in Boiler

For filling water in a cold HRSG, cold water fromthe plant DM line is preferred through Boiler fill uplines. However when the water is not deaerated,following procedure is used for filling from theHRSG filling line.

• During this filling, for assurance of correctsteam drum water level, post an attendant atthe drum level to monitor the local level andthe hydrastep gauges and to communicate tothe control room when a level of –100 mm isreached. (Final level recommendations shallbe set at the time of commissioning).

• Filling is done by feeding D.M water to the HP,IP & LP drain headers from the plant DM main.For this,

• Open valves GT720, 722, 716, 718, 714 & 712from DM water line at battery limit.

• Ensure that all the HP & IP economiser, HP, IP& LP evaporator panel drain valves are open.

• When air is released and water comes out fromeconomiser vents GT671, GT626, GT672,GT673, these can be closed one by one.These valves need to be operated only duringinitial water filling.

• When water level of –150mm is reachedin the drum, DM water filling line valvesGT 718,716,720,722,712 & 714 anddrains of Economisers & evaporatorsGT616,615,636,621,627,620,660,654,679,666,653,659,665,678 are to closed and thedrain valves of HP ,IP & LP Drain headers toblow down tank GT669,695,622,624 605,607is opened.

• Deaerator storage tank can be filled up byusing Condensate pump & opening batterylimit isolation valve GT301. During cold start upthree way control valve TCV102 shall remainclose to CPH & direct entire water to Deaeratorthrough FCV 080A. Keep Deaerator level -50mmwc below NWL to avoid swelling effectduring initial start up.

Caution

Filling water temperature should not be more than38 deg C of the boiler metal temperature. Duringfilling of a cold boiler, the ambient temperatureshould be used as an indicator of the boiler metaltemperature. Assuming an ambient temperatureof 40 deg C, the maximum temperature of fillingwater shall be 78 deg C.

3.6 HRSG Start Up & Pressurisation

The DCS is linked from field instruments toconstantly update process information (Feed flow,steam flow, steam temperature, drum pressure,water/steam temperatures, metal temperatures,gas temperatures, pressure/temperatures for pretrip alarms etc). In the DCS, the informationis processed and based on preset logic andset points, control commands are sent to I/Pconverters for control action. Alarm inputs etc arealso from the DCS.

1. Start the HRSG preferably along with GT startup cycle. During cold start up maintained theGT on Reserve spinning mode with 7 % load& ensure that the GT exhaust temperature ismaintained below 377 Deg C.

2. Yet time HRSG also can be started afterstabilising GT operation by lowering the

Section C 75


Load on GT and by lower the GT exhausttemperature below 377 Deg C.

3. During cold start up of HRSG, as the superheaters are running dry for few minutes intransition condition. To safe guard the supperheater & reheat SH tubes it is essentialto control the GT exhaust temperature byallowing gas temperature below 377 Deg.

4. Purge the HRSG as per GT start up sequence(As recommended GT Supplier).

5. Start GT as per the GT start up sequence.

6. During cold / Warm start up, maintain GT inreverse spinning mode with 7% load on GT tillthe positive steam flow is established throughsuper heater & re-heaters. Ensure that duringcold start-up of HRSG flue gas temperature atthe inlet of HRSG should not exceed 377 DegC. Monitor the metal temperature of supperheaters (HPSH3 < 612°C) & re-heater (RH 2< 611°C). The heat transfer commences andthe water in the HRSG gets slowly convertedto steam as a result pressure of steam in thedrum starts gradually build up. The saturatedsteam temperature rise rate (and hence rateof rise in metal temperature) is controlled asper cold start-up pressurisation curve to safeguard against impermissible stress levels bymodulating respective start up vent valves.

7. After having stabilised the positive steam flowthrough superheater & reheater, increase GTload gradually to pressurise the boiler as perCold start up pressurisation curve.

8. During start up & continuous operation,monitor the skin metal temperature ofHPSH3 < 612° C , & Reheat RH 2 < 611°C for ensuring cooling. If the Skin metaltemperature reaches set point, please stopgas flow to HRSG.

9. Monitor Drum metal temperatures HP DrumTE 037 A – 037 D < 321° C. 11. Monitor thewater level in the drum. As the temperaturereaches about 90°C, a huge swelling of waterlevel in the drum takes place. The operatoranticipates this and controls the level byopening the EBD valve. When the swellingin the drum level is over, EBD valve is fullyclosed

To summarise each start up procedure needs tobe followed for following sequence:

1. Line up of water filling lines valves, HRSGsystem drains & vents.

2. Preparation/checks to be done beforeadmission of hot flue gases in HRSH

3. Purging of HRSG

4. Steaming & closure of various drains & vents

5. Pressurisation HP Bypass & Gland Sealingline charging

6. Charging of reheater

7. Charging of CPH

Operator Action required during HRSGcold start-up

• Ensuring permissible rate of heat input toHRSG during start up.

• Monitor Exhaust gas temperature in variouszones. The temperatures of gas across varioussections of HRSG will start increasing after theGT exhaust gas enters in HRSG.

• Operator can also check the local exhaust gasand temperature indications

• Monitor Drum metal temperatures.

• Monitor the water level in the drum. As thetemperature reaches about 90°C, a hugeswelling of water level in the drum takes place.The operator anticipates this and controls thelevel by opening the EBD valve. When theswelling in the drum level is over, EBD valveis fully closed

• Initially, checking the local level gauges andthe level indicators takes a careful assessmentof water level in the drum. Variations in levelsbetween gauges are possible at low drumpressures are to be relied for true drum levelindications which initiate trips at very high andvery low levels. Request Instrument Engineerto reconcile the differences in levels betweengauges if any.

• Observe the air vent on drum. Air gets expelledand steady steam starts coming out of the airvents

• Observe drum pressure at DCS as also localpressure gauge at drum

• When drum pressure shows 2 kg/cm², drumair vents can be closed

• When the steam pressure builds up to 3 –5kg/cm² , the super heater drain valves are to beclosed. (If required, manually operated drainvalves are also closed)

• When the swelling phase of drum water levelis over and the level shows a decreasing trend,the 30% feed control can be taken into serviceby opening Control valve can be positioned asrequired manually to maintain drum level

Section C 76


• Ensure CBD, feed water and super heatedsteam samples are flowing to the coolers andthe pH, conductivity meters are in operation.Verify pH and conductivity is within permissivevalues.

• Verify the HP dosing mixing tank level is morethan 50% and a 5% phosphate solution isavailable in the tank. Place one HP dosingpump in service.

• Similarly Verify the IP & LP dosing mixingtank level is more than 50% and a solution isavailable in the tank. Place one IP & LP dosingpump in service.

• Start taking feed water through 30% controlvalve as per the requirement. Water shall flowto steam drums. CPH can be taken on lineonce the flow established and the flue gas exittemperature is above acid dew point.

• Allow the HRSG steam pressure andtemperature to build up to rated temperatureand pressure by suitably modulating theindividual Start up vent valve and if requiredthe GT load.

• Monitor the steam drum water level.

• Monitor the parameters, which can cause aHRSG trip.

Section C 77


3.7 HRSG Cold Start Up Curve

HRSG Cold Start Up Pressurising Curve for HPSection

Please refer section E — Curves

The pressurisation curve for cold start upalongwith GT operation for HP section isillustrated above. The cold start up curve of IP &LP section will follow the pressurisation accordingto the heat input received based on HP sectioncurve.

Section C 78


3.8 Taking Reheater On Line

This section describes how to take Reheater online through HP & IP section. Reheater has to becharged simultaneously through HP & IP sectionas per the criteria mentioned charging procedureof reheater, only to bring upon clarity procedure isexplained here separately (section wise).

3.8.1Charging HP Steam to Reheater

1. Keep Open start up vent valve PCV 079& isolation valve GL 736 provided on hotreheat line for maintaining positive steam flowthrough re-heater.

2. Once the steam pressure at HP super heateroutlet reaches 5 bar, open HP steam stopequalization /bypass valve M029B 100%and charge HP steam line as per steam linecharging procedure after heating main steamline by HP steam stop bypass valve M029Band close the bypass valve after opening theHP steam stop valve M029A 100% .

3. When the swelling phase of HP Steam drumwater level is over and the level shows adecreasing trend, the 30% feed control canbe taken into service by opening isolatingvalves of FCV 003A, Control valve FCV 003Acan be positioned as required manually tomaintain drum level

4. Before charging the HP steam line, ensuresteam line drain valves (GT 668, GL731) areopen to drain out the condensate and closethe drain line valve. Before charging HPsteam line ensure that the turbine inlet valveis closed.

5. Once HP steam line is charged, throttleHP start up vent valve to follow HP steampressurisation curve & ensure that sufficientsteam is getting passed through Reheater.Pass entire HP steam through reheat andensure that steam temperature at cold reheatis maintained below 380 Deg. C by operatingPCH 0101 (HP to IP bypass valve) in auto /manual mode, as required.

6. Ensure reheat SH is drained properly forwater / condensate before charging byoperating motorised drain valve M038C forReheater-2 to be operated. These valve is tobe closed as soon as condensate/ water isdrained out completely & steam start comingthrough it (max for 5 min). Ensure that drainedwater led to blow down tank.

7. Control the steam temperature at outletof reheat using attemperator control valve

TCV 068A in auto / Manual mode, as perrequirement of steam turbine.

8. Vent the hot reheat steam to atmospherethrough Start up vent valve (Valve tag willbe added later ) provided on Hot Reheatline till condenser is made ready. Once theCondenser is available to dump the hot reheatsteam , line up the IP - LP bypass PRDSPCH0101 and start dumping hot reheatsteam to condenser. Once the steam flowthrough IP - LP bypass PRDS PCH0101 tothe condenser is established slowly close thestart up vent valve by looking in to the steampressure at reheater out let and allow entirehot reheat steam to go to Condenser. Placethe IP - LP bypass PRDS PCH0101 in automode. Steam comes out from Reheat Module2 is termed as Hot reheat steam.

9. Keep watch on Reheat 2 metal temperaturefor proper cooling.Caution : To safeguard theReheater Tubes, it is essential to maintainpositive steam flow either by venting steamthrough start up vent valve provided on hotreheat steam line or by dumping the steamdirectly to Condenser when it is operational.

10. Now allow HP steam to pressurize as perpressuring curve by controlling start up ventvalves opening. Once the HP steam pressurereaches near about 23 bar put the HP by passPRDS ( PCH 0101) to Reheat in auto modewith 25 bar set point.

11. PSV 302 on cold reheat & PSV 072 on hotreheat line safeguard the reheat SH from highpressure.

12. Continue the operation till HP turbine is put inoperation and ensure sufficient steam passedto cold heat line.

3.8.1.1 Charging IP steam to reheat

1. Now the cold reheat line gets HP steam fromHP section through PRDS valve PCH 0101and IP section is getting pressurised as perthe start up curve maintaining steam ventingto atmosphere through IP start up vent valvePCV063.

2. Open HP to IP bypass valve for leading CRH(Cold Reheat) flow through Reheater. KeepHP start up vent valve throttled to follow HPpressurization curve at the same time ensurepositive steam flow through Reheater. oncethe IP steam pressure reaches to 5 bar orabove CRH steam pressure (0.5 bar aboveRH pressure), synchronize the IP main steampressure with cold reheat pressure (open PCV

Section C 79


129 gradually & introduce steam to CRH. Thispressure matching can be done by positioningstart up vent valves as per the requirement onHP line PCV028 & on IP line PCV063. NRV254 in the IP main steam line shall take careof reverse flow of HP steam to IP section.Once IP section working pressure @ 24.3 baris reached put PCV 129 in auto mode with setpt of 24.3 Bar.

3. Keep watch on flue gas temperature at IP SHinlet.

Once the HP steam & HRH steam quality isachieved as per requirement , charge the steamto turbine. After rolling the turbine, once the coldRH steam starts HP turbine HP steam bypassvalve closes accordingly in auto mode and closesfully once full-fledged cold reheat steam flow isestablished from turbine.

Further loading of HRSG can be done byincreasing load on GT as per load requirement.Loading is done without firing the burners, whichis called unfired mode of HRSG operation. Boilersteam generation is limited depending uponthe GT load or the exhaust gas flow rate andtemperature (heat input to HRSG).

3.9 Charging & Operation of CPH

CPH charging can be considered as the last mostactivity in Start up procedure of entire HRSG.

During initial water fill up, drain line commonisolation valve GT603 & GT 604 will be closedand common vent valve GT 609 shall be keptopened as long as air is purged out completely& then it will be closed. Other Manual valves inthe system shall be kept locked open except formaintenance.

During cold start up of HRSG, Condensatepreheater (CPH) will be kept bypassedcompletely. This is to avoid steaming in CPH ,during transient period of start up due to high gastemperature at CPH inlet there is always chanceof steam generation in CPH . Bypassing CPHwill also help to keep the deaerator pressure /temperature rise under control.

Deaerator temperature will be high during start upand at lower loads which will lead to more ventingof steam. Admitting the DM water/Condensate atambient temperature (condensate return temp.)directly into the deaerator through the CPHbypass, will reduce the venting steam quantity.Deaerator pressure control valve will kept inauto mode during start up with pressure set

point. However the deaerator pressure will bemaintained by controlling LP start up vent valve asper LP pressurising curve. CPH can be chargedwhen once the HRSG start up stabilised andloaded.

Once, the boiler is loaded comfortably the flowthrough CPH can be modulated on observingthe deaerator pressure / temperature. Flowthrough CPH is adjusted in such a way that thedifference between Deaerator temperature andCPH outlet water temperature is around 15 DegC. Condensate is fed to CPH at around 57 Deg C& CPH heats it up to 137 Deg C.

Once the CPH is charged start the CPH watercirculation pump and put the TCV 108 in automode with a set point to maintain the flue gastemperature to stack. During cold start up keepthe circulation pump in stop condition.

Emergency action

HRSG TRIP

Close the MSSV and boxup the HP,IP & LPsection at prevailing condition.

Take out CPH from line by modulating the 3 wayvalve TCV- 102. Slowly bypass the CPH byclosing inlet and outlet valve.

The CPH bypass valve GT 314 should be open sothat the condensate bypasses the CPH.

The CPH can be taken out of line.

3.10 Parallel HRSG to the Plant SteamMains

Parallel HRSG to the Plant Steam Mains

Paralleling HRSG to the steam mains of the plantis an important operation to be carefully donewithout affecting the temperature of steam in theplant. The pre requisites for this operation are:

• Building the steam pressure in HRSG toa pressure slightly more than plant steampressure. This is controlled by modulating theStart up vent valve and if required modulatingthe GT load. Take into account the permissiblerate of drum pressure increase to position thevent valves.

• Building the steam temperature (Alternatelyone can settle for a lower steam temperatureinitially if it would not cause any problemsdown stream. To compensate for temperaturedifference increase temperature of other boilerconnected to header).

Section C 80


• With the build up of required steam pressureand temperature in HRSG, the main steamstop valve can be opened

• When the HP Steam Pressure reaches thepressure of 5 Bar(a).

• Initiate an open command for HP Main steamstop valve and observe

– Valve [M-029B] opens; The pressuredifferential across MSSV [M-029A] startsdecreasing and when ∆P at MSSV <5 bar (a)

– Valve [M-029A] opens and when open feedback is received,

– -Valve [M-029B] (MSSV by-pass) close

With the opening of valve [M-029A] , HRSG isready for supply of HP steam to the plant.

• Similarly for LP section

• Initiate an open command for LP Main steamstop valve and observe

– Valve [092B] opens; The pressure differentialacross MSSV [M-092A] starts decreasingand when ∆P at MSSV <5 bar (a)

– Valve [M-092A] opens and when open feedback is received,

– -Valve [M-092B] (MSSV by-pass) close

With the opening of valve [M-092A] , HRSG isready for supply of LP steam to the plant.

• Reduce the opening of the start up vent valveto about 15%.

• Attemperator can be taken in service ifSuperheater outlet temperature is exceedingrated value.

• Observe steam temperatures after thesuperheater of individual sections.

• Observe the feed control station. Whenoutput signal from Level Indicating Controllerexceeds 65%, full load control station comesinto service .

4 Hot and Warm Start up of HRSG

Hot Start up of HRSG

Restarting the HRSG immediately after a trip out,when the HRSG is still hot, with steam pressurenot less than 40bar (a) is termed as a hot restart.As the HRSG was in service till the trip out, therequired valve line up (as was stated for coldstart up) will be available and can be quicklyverified by visual inspection. Hot restart requiresoperations to be done fast, using the maximum

permissible heat input rates so as to obtain quicklythe required HP steam pressure and temperature.

In event of GT trip first & foremost important dutyof operator is to close all steam outlets, closechimney inlet isolation damper & maintain drumwater level as recommended. As the HRSG wasin service till the trip out, the required valve line up(as was stated for cold start up) will be availableexcept for few vent valves these valves can bequickly verified as per the below mentioned list.Hot restart requires operations to be done fast,using the maximum permissible heat input ratesso as to obtain quickly the required HP/IP sectionsteam pressure and temperatures. The HRSGhot restart sequence will comprise of variousoperations as detailed below:

The HRSG hot restart sequence will comprise ofvarious DCS and manual operations as detailedbelow

1. Start GT as per GT start up cycle. DuringHot start up maintained the GT at 15 % load& ensure that the GT exhaust temperature ismaintained at 510 Deg C.

2. During hot start up of HRSG, to avoidsuperheater & reheater running dry donot open start up vent valves of HPsection(PCV028) & IP section(PCV129).Open HP main steam stop valve & pass100% HP steam generated through cold & hotreheat & dump into condenser by opening IPbypass valve (PCH0101). Similarly dump theLP steam to condenser through LP bypassvalve (PCH0101).

3. Bypass CPH from water side to avoidsteaming during start up.

4. Ensure that drain valves to Blow down Tankof HP SH Drain header (GT688), ReheaterDrain Header (GT650), IP RHS Drain Header(GT 622) & IP LHS side header (GT 624)are open.During Hot start up of boiler superheater & atteperator motorized drain valveneed to be opened for say 1 min for removalof condensate then leave the followingvalves crack open till respective sectionsuperheater outlet temperature reaches or100% condensate is drained out.

Following are the valves need to be operated

• HP Section

– HP superheater 2 & 3 header motoriseddrain valve M038B & F

– HP Superheater 1 motorised drain valveM038D/H

Section C 81


• Reheater Section

– Reheater 1 & 2 motorised drain valveM038C, Reheater 2 drain valves FVM –D201

• IP & LP Section

– IP superheater motorised drain valveM076

– LP superheater motorised drain valveM098

• Ensure following vent valves are Closed

– HP Drum vent valve M005A & M005B

– IP Drum vent valve M061

5. Ensure that GT is maintained at 15% load& exhaust temperature is maintained at 510Deg C.

6. Ensure that during hot start-up of HRSGflue gas temperature at the inlet of HRSGis maintained at 510 Deg C. Monitor themetal temperature of super heaters (HPSH3< 612 Deg. C) & re-heater (RH 2 < 611 Deg.C). The heat transfer commences and thewater in the HRSG gets slowly converted tosteam as a result pressure of steam in the

drum starts gradually build up. The saturatedsteam temperature rise rate (and hence rateof rise in metal temperature) is controlled asper hot start-up pressurisation curve to safeguard against impermissible stress.

7. After having stabilised the positive steam flowthrough superheater & reheater, increase GTload gradually to pressurise the HRSG.

8. During start up & continuous operationMonitor the skin metal temperature of HPSH3< 612 Deg. C , & Reheat RH 2 < 611 Deg.C for ensuring cooling. If the Skin metaltemperature reaches set point please stopgas flow to HRSG.

9. Monitor Drum metal temperatures HP DrumTE 037 A – 037 D < 321 Deg. C.

10. Monitor the water level in the drum. Theremay be chance of swelling of water level inthe drum. The operator anticipates this andcontrols the level by opening the EBD valve.When the swelling in the drum level is over,EBD valve is fully closed

11. Once the HRSG operation is stabilised &steam parameters suitable for STG operationis reached supply steam to STG.

Section C 82


HRSG Hot Start-Up Curve for HP section


The pressurisation curve for hot start up for HPsection is illustrated above. The hot start up curve

of IP & LP section will follow the pressurisationaccording to the heat input received based on HPsection curve.

Section C 83


Warm Start up of HRSG

Restarting of a hot HRSG within few hours timeafter a trip or stoppage, with the HRSG steampressure of not less than 10-kg/cm² (g) is termedas a warm start .

In event of GT trip first & foremost important dutyof operator is to close all steam outlets, closechimney inlet isolation damper & maintain drumwater level as recommended. As the HRSG wasin service till the trip out, the required valve line up(as was stated for cold start up) will be availableexcept for few vent valves these valves can bequickly verified as per the below mentioned list.

The HRSG warm restart sequence will compriseof various operations as detailed below

1. Start GT as per GT start up cycle. Duringwarm start up maintained the GT on Reservespinning mode with 7 % load & ensure that theGT exhaust temperature is maintained at 430Deg C.

2. During warm start up of HRSG, to avoidsuperheater & reheater running dry donot open start up vent valves of HPsection(PCV028) & IP section(PCV129).Open HP main steam stop valve & pass100% HP steam generated through cold & hotreheat & dump into condenser by opening IPbypass valve (PCH0101). Similarly dump theLP steam to condenser through LP bypassvalve (PCH0101).

3. In case if condenser is not ready to dumpthe steam then follow the procedure asmentioned in cold start up procedure forsteam venting & pressurisation.

4. Bypass CPH from water side to avoidsteaming during start up.

5. Ensure that drain valves to Blow down Tankof HP SH Drain header (GT688), ReheaterDrain Header (GT650), IP RHS Drain Header(GT 622) & IP LHS side header (GT 624) areopen.During warm start up of boiler superheater & attemperator motorized drain valveneed to be opened for say 1 min for removalof condensate then leave the followingvalves crack open till respective sectionsuperheater outlet temperature reaches or100% condensate is drained out.

Following are the valves need to be operated

• HP Section

– HP superheater 2 & 3 header motoriseddrain valve M038B & F

– HP Superheater 1 motorised drain valveM038D/H

• Reheater Section

– Reheater 1 & 2 motorised drain valveM038C, Reheater 2 drain valves FVM –D201

• IP & LP Section

– IP superheater motorised drain valveM076

– LP superheater motorised drain valveM098

• Ensure following vent valves are Closed

– HP Drum vent valve M005A & M005B

– IP Drum vent valve M061

6. Ensure that GT is maintained at 7% reservespinning & exhaust temperature is maintainedat 430 Deg C.

7. Ensure that during warm start-up of HRSGflue gas temperature at the inlet of HRSG iamaintained at 430 Deg C. Monitor the metaltemperature of supper heaters (HPSH3 < 612Deg.C) & re-heater (RH 2 < 611 Deg. C).The heat transfer commences and the waterin the HRSG gets slowly converted to steamas a result pressure of steam in the drumstarts gradually build up. The saturated steamtemperature rise rate (and hence rate of rise inmetal temperature) is controlled as per warmstart-up pressurisation curve to safe guardagainst impermissible stress.

8. After having stabilised the positive steam flowthrough superheater & reheater, increase GTload gradually to pressurise the HRSG.

9. During start up & continuous operationMonitor the skin metal temperature of HPSH3< 612 Deg. C , & Reheat RH 2 < 611 Deg.C for ensuring cooling. If the Skin metaltemperature reaches set point please stopgas flow to HRSG.

10. Monitor Drum metal temperatures HP DrumTE 037 A – 037 D < 321 Deg. C.

11. Monitor the water level in the drum. Theremay be chance of swelling of water level inthe drum. The operator anticipates this andcontrols the level by opening the EBD valve.When the swelling in the drum level is over,EBD valve is fully closed

12. Once the HRSG operation is stabilised &steam parameters suitable for STG operationis reached supply steam to STG.

Section C 84


HRSG Warm Start up Curve for HP section


The pressurisation curve for warm start up forHP section is illustrated above. The warm

start up curve of IP & LP section will followthe pressurisation according to the heat inputreceived based on HP section curve.

Section C 85


5 HRSG Shutdown

Shutdown of HRSG can be of two types -

1. Planned shutdown for maintenance,inspection, where the operator gets advancednotice.

2. Trip on protection or a stop due to emergency.

Suggested action by the operator for the abovetypes of shutdowns are indicated below

5.1 Planned Shutdown

A planned shut down has to be coordinated withother working boilers such that loads reduced fromthe HRSG are picked up by them without affectingthe performance of the plant

• Reduce to the load to 50% MCR by reducingthe GT load.

• Depending on the GT load restrictions,continue to reduce GT load till the HRSGreaches minimum MCR mode of operation.Also reduce the steam demand from the plantor transfer the steam load to other boilers.Close the Main steam stop valve.

• Stop the gas turbine.

• On the working HP dosing pump, charge overto DM water to the pump inlet and close thephosphate solution inlet to the pump. Run theHP dosing pump for about one hour to keepthe line clear of phosphate up to the drum.

• Close CBD valve.

• Allow the HRSG to cool down naturally.Maintain water level in the drum till thepressure drops to 2-bar (g)

• At 2 bar (g) pressure (or slightly lower) openthe respective section Drum vent valves.

• If water is to be drained from HRSG, normallyit can be done only when the drum pressuredrops below 1.25 bar (g)

5.2 HRSG Emergency Trips

Emergency trips can occur in HRSG due to any ofthe following causes:

• HP Drum level very Low

• IP Drum level very Low

• LP Drum level very Low

• HP Steam O/L Pressure high-"Hi Hi PressureTrip In Case of STG Trip and HP BypassSystem Valve Not Open

• GT Exhaust gas Pressure high at inlet ofHRSG.

HRSG Trip Due to Gas Turbine Trip

In this case the operator action is to shut downthe HRSG, if restart of the Gas Turbine will bedelayed.

Close CBD valve, feed water control stationisolation valve after maintaining level in the steamdrum. Close Main steam stop valve. HRSG isstarted when the Gas Turbine comes into service.

HRSG Trip Due to Instrument Air Failure

When the HRSG trips due to instrument air failure,exercise extra caution to see that the fail-safevalves do not endanger the boiler. E.g. if feedcontrol valves remain full open, isolating valvesbefore or after the control valves are to be closed;start-up vent valve remain full open, hence closethe manual isolation valve. This scenario willlikely result into a plant blackout. HRSG to berestarted after restoration & normalising of allservices.

HRSG Trip Due to Power Failure

In an extreme case of power failure, HRSG maytrip due to tripping of Seal air fans. Instrumentsand controls may still be available as they areusually powered from UPS (please check the plantphilosophy). However the status of availabilityof instrument air, feed water supply and fuelsupply will determine the continuation of HRSGin operation.

Operation In The Event Of STG Trip & HRSGRunning Condition

When ever STG trips, while HRSG is in operation,dump the hot reheat steam to condensor throughHP, IP/LP bypass PRDS and pass the steamthrough reheat to cool the reheat. During STGtrip & hot start-up ensure that HP to cold reheatbypass PRDS is opened immediately withoutany delay during this watch the reheat metaltemperature.

Safe Gaurding the HRSG after a Trip

• Upon tripping of steam turbine, entire steamwill get dumped to condenser via HP,IP,LPBypass.

• In case of failure of bypass valve safety valvesprovided on respective section steam drum &superheater section will release the steam alsostart up vent valve shall be open to release thesteam in auto mode.

Section C 86


• Continue to supply feed water to the drum tomaintain normal level, after closing the CBDand sample line valves.

• Investigate the cause of the trip from the firstup signals and DCS data acquisition system. Ifthe cause of the trip is known, rectify the causeand opt for restart of HRSG.

6 Cooling of a Shutdown Boiler

Aim

This chapter describes the methods of cooling ashut down HRSG and the steps to be taken topreserve the HRSG to minimize corrosion.

System Description

HRSG after shut down has to be cooled carefully.It is recommended to cool the HRSG under normalcircumstances at the rate of heating. If the coolingrate is accelerated, thermal stresses develop inthe thick components such as the steam drum,Economiser, Evaporator, Super Heater headers,attemperator etc.,

A HRSG is shut down either for keeping it inreserve as a stand by unit or for maintenanceand inspection. The purpose of the shut downdetermines the method of cooling to be adopted

6.1 Natural Cooling

The HRSG after a shut down is allowed to coolslowly in a ‘boxed up condition’. The followingvalves are also closed.

• HP,IP & LP dosing to Drum

• CBD /EBD valve of all HP ,IP & LP Drum

• Sample line to HRSG water/saturated steam/ SH steams to Swas

The HRSG cools slowly, loosing its heat byradiation to the environment. Till the HP ,IP& LP steam drum pressure drops to 2-bar (g),permissible water level is maintained in the drum(+150mm to – 250mm) by intermittent feeding.After the steam drum pressure falls below 2-bar(g) maintaining water level in the drum is notessential.

When the steam drum pressure is less than 2-bar(a) , the access doors in the HRSG are kept opento create a natural draught through the HRSG tothe chimney. HRSG cools to an accessible levelin about three-four days.

6.2 Forced Cooling

If the HRSG has to be made available forinspection or repair and the shut down time has

to be reduced to a minimum, forced cooling of theHRSG is done.

After the shut down of the HRSG, the HP,IP & LPdosing, CBD, EBD and SWAS valves are closedas for natural cooling. Water level in the HP ,IP &LP drum is also maintained between permissiblelevels till the steam drum pressure falls to 2 bar(a). For 8 hours after the shut down, the HRSG isallowed to cool naturally in the boxed up condition.

After 8 hours, access doors on HRSG are openedto allow airflow through the HRSG to the stack.

De-pressurization of steam in the HRSG is alsospeeded up by controlled opening of the start upvent valve De-pressurization rate is not to exceed10kg/cm2 per hour. However forced cooling is notdone unless absolutely essential.

7 HRSG Operation Walk DownChecks

1. Check for unusual noises. This may be fromsteam or water leakages.

2. Check for steam or water leaks from valves,connections and fittings.

3. Check for unusual traces of water on floor.

4. Check for air / flue leakage from windbox,HRSG casing and ducting.

5. Walk around the furnace exterior andobserve for any hot spots or gas leaks.

6. Check for passing from safety valves atnormal operating pressure. Check that thedrain lines and drip pans are not plugged.

7. Check to see that proper water level is beingshown by the direct water level gauge. Checkfor water or steam leak from ports or drainconnections, which will cause a false waterlevel in the gauge glass. Inspect the glass fordiscoloration or fouling.

8. Check for any obstruction for thermalexpansion.

8 Do’s and Don’ts For HRSGOperation

Do’s

1. Maintain all instruments in good workingcondition.

2. All equipment interlocks should always be inline.

3. Maintain normal water level in steam drum.

4. Maintain water quality as per therecommended limits. A table showing the

Section C 87


DM water & drum water quality is included atthe end of this section .

5. Pressure raising from cold start must be doneas per the cold start up curve.

6. All the duct joints must be leak proof.

7. Use proper lubricant and maintainthe schedule as recommended by themanufacturers.

8. Operate the HRSG within the recommendedoperation limits .

9. HRSG, piping, ducts must be properlyinsulated.

10. Servicing of equipment should be done as perthe manufacturer’s schedule .

11. Maintain proper operation log sheetsregularly.

12. Maintain the instrument air free from moistureand oily matters and the pressure asrecommended .

13. Carry out regular cleaning of direct water levelgauge glasses of HRSG drum.

14. Use proper valve gland packing to avoidleakage .

15. Use proper gaskets for flange joints .

16. Operate the blowdown valves as perrecommendation.

17. In case of power failure, close the steam stopvalve.

18. If the water level goes up above the limitsoperate the emergency blowdown valveimmediately and maintain the water level tonormal .

19. Maintain the feedwater temperature ateconomizer inlet and flue gas temperature ateconomizer outlet as recommended .

20. Use genuine spares.

21. HRSG surroundings and equipments must beproperly illuminated.

Don’ts

1. Don’t bypass any instruments and safetyinterlocks

2. Don’t use raw water as HRSG feedwater

3. Don’t operate the HRSG beyond theoperation limits.

4. Don’t leave the furnace door open while theHRSG is in operation

5. Don’t mix up different lubricants

6. Don’t alter the equipment maintenanceschedule

7. Don’t leave the instrument control panelunattended

8. Don’t allow unauthorized persons to operatethe HRSG and associated equipments

Section C 88


9 Boiler Log Sheet

It is suggested to record the HRSG parametersduring startup and normal operation. Observedabnormalities (if any) recorded can be usedfor analysis, troubleshooting and maintenancepurposes.

1. Log sheet to be filled once in every hour bythe operating staff.

2. Feedwater, HRSG water quality are also to benoted once in four hours

3. Total steam production of a day to be noted.

4. Logbook should furnish the details about

5. HRSG trips with reasons and time

6. HRSG running hours.

7. HRSG shut down details (forced or planned,outage hours, jobs carried out, etc.,) Samplelog sheet is enclosed.

9.1 Log Sheet for HRSG

Date:

Shift:

SL.NO

PARAMETER UNIT TIMETIME TIME

1 GT LOAD MW

2HP DRUM

LEVELmmWC

3 IP DRUM LEVEL mmWC

4LP DRUM

LEVELmmWC

5HP MAINSTEAM PRESSURE

Bar (a)

6IP MAINSTEAM PRESSURE

Bar (a)

7LP MAINSTEAM PRESSURE

Bar (a)

8HP STEAM

FLOWTPH

9IP STEAM

FLOWTPH

10LP STEAM

FLOWTPH

11

FEED WATERPRESSURE ATHP CONTROLSTATION INLET

Bar (a)

12

FEED WATERPRESSURE ATIP CONTROLSTATION INLET

Bar (a)

13

FEED WATERPRESSURE ATLP CONTROLSTATION INLET

Bar (a)

14CONDENSATETEMP.BEFORE

CPHDEG C

Section C 89


SL.NO


15

CONDENSATETEMPERATUREAFTERCONDENSATE

PRE-HEATER

DEG C

16FEED WATERTEMP. AT HP

ECO I INLETDEG C

17FEED WATERTEMP. AT HP

ECO 1 OUTLETDEG C

18FEEDWATERTEMP. AT HPECO 2 OUTLET

DEG C

19FEED WATERTEMP. AT HPECO 3 OUTLET

DEG C

20

FEED WATERTEMP. AT IPECONOMIZER

INLET

DEG C

21

FEED WATERTEMP. AT IPECONOMIZER

OUTLET

DEG C

22FLUE GASTEMP. AT DD

OUTLETDEG C

23

FLUE GASTEMP. AT HPSUPERHEATER

3

DEG C

24FLUE GASTEMP AFTER

REHEATERDEG C

25

FLUE GASTEMPAFTER HPEVAPORATOR

DEG C

26

FLUE GASTEMP.AFTER HPECONOMIZER 3

DEG C

27FLUE GASTEMP. AFTER IPECONOMIZER

DEG C

28

FLUE GASTEMP.AFTER LPEVAPORATOR

DEG C

Section C 90


SL.NO


29

FLUE GASTEMP. AFTERCONDENSATE

PRE-HEATER

DEG C

30FLUE GAS PR.AT DD OUTLET

mmWC

31

FLUE GASPRESSUREAT HPSUPERHEATER

3

mmWC

32

FLUE GASPRESSUREAFTER

REHEATER

mmWC

33

FLUE GASPRESSUREAFTER HPEVAPORATOR

mmWC

34

FLUE GASPRESSUREAFTER HPECONOMIZER 3

mmWC

35

FLUE GASPRESSUREAFTER IPECONOMIZER

mmWC

36

FLUE GASPRESSUREAFTER LPEVAPORATOR

mmWC

37

FLUE GASPRESSUREAFTERCONDENSATE

PRE-HEATER

mmWC

38FLUE GASTEMP. AT

STACKDEG C

Section C 91


SL.NO


39

Feed WaterAnalysis

pH

Conductivity

TDS

Silica

Hardness

Oxygen

40

Drum WaterAnalysis:

pH

TDS Alkalinity asCaCo3

Silica

Phosphate asPo4

Sulphite as SO3

41

Sat. & Sh SteamAnalysis:

pH

Conductivity

TDS

Silica

Operator Name:

Signature:

Date:

Section C 92


10 Boiler Emergency SafetyProcedures

10.1 Emergency Procedures

Low Water Level

Causes

1. Feedwater control system failure.

2. BFP failure

3. Tube leak

Action

Compare control room indication with gaugeglass level. If the water level falls out of sight dueto momentary failure of water supply system, dueto negligence of the operator, due to momentaryfluctuations that might occur with extraordinarychanges in load, appropriate action should betaken at once to trip the fuel. Any decision tocontinue to operate, even if only for a short timeat a reduced rating would have to be made bysomeone in authority who is thoroughly familiarwith the circumstances that led to the emergencyand positively certain that the water level can berestored immediately without damaging the boiler.

In the absence of such a decision

1. Shut off the main steam stop valve .

Simultaneously, if feedwater has becomeavailable and the operator is assured that nopressure part has been damaged

1. Take the feedwater control system intomanual mode

2. Allow the water flow to boiler gradually tonormal water level. (Do not hurry up whichmay lead to sudden quenching and tube leak)if pressure part damage is suspected

3. Reduce the steam pressure gradually

4. Open the drum air vent when the pressuredrops below 2 kg/cm²

5. Cool the boiler so as to examine the extent ofdamage

6. Drain the boiler after cooling

7. If any tube rupture and bulging is observedrectify the same

8. If any tube leakage were observed rectify /repair the leaking tubes and after the repairsconduct hydrotest

9. Determine the cause of low water

High Water Level

Causes

1. Feedwater control malfunction

2. Operator error

3. Instrument air supply failure

Action

1. Take the drum level control loop into manualmode

2. Reduce the water level immediately byoperating the intermittent blow down tomaintain the drum level

3. Reduce the steam discharge rate, ifnecessary

4. If instrument air supply failure, then open theby manual operated pass valve to maintainedthe drum level

Boiler Explosion

Causes

1. In-sufficient purging of furnace

With the mixture of unburned fuel with air inexplosive proportions and the application of heatsufficient enough to raise the temperature of themixture to ignition point.

Action

1. Analyse the reasons for explosion and rectifythe system

2. Evacuate or clean the furnace to the possibleextend

Conditions for Boiler Restart after FurnaceExplosion

After a case of furnace/ boiler explosion, therestart of the boiler has to be carried out onlyafter a thorough and detailed investigation& understanding of the cause of explosion.Following necessary actions have to becompleted to prevent the repeat incidence ofexplosion and before restart of the boiler.

Find out the root cause for the explosion andrectify the same.

1. Inspect the furnace for any signs of bulging ordamage to the tubes.

2. Inspect the expansion bellows in the air andflue ducts for damages

3. Inspect the economizer casing for damages

4. Assess the damage if any and rectify thesame.

5. Carry out the hydro test of the boiler. In theevent of a failure of the hydro test, identify thetubes that have failed and proceed to rectify

Section C 93


the same as explained in the maintenancesection.

Section C 94


10.2 Alarms and Trips

Note

1. These Alarm and Interlock valuescan be revised at the time ofcommissioning of the boiler. The finalrevised alarms and interlocks list shallbe submitted post commissioning ofthe boiler.

10.3 Operational Precautions for Safety

Operating the HRSG with low feedwatertemperature will result in corrosion of economizercoils.

The raising and lowering of steam parametersshould be restricted to the value given in thestarting diagram. Exceeding these values willresult in reduced fatigue life of pressure parts.

In case of tube failure, which can be identifiedby hearing the noise in the HRSG galleryand increase in draught pressure, flue gasand steam temperature, the HRSG should beshutdown at the earliest by regular procedure formaintenance work. Otherwise large number ofsurrounding tubes may fail due to steam erosionand impingement.

Boiler salt in the wet steam will acceleratecorrosion.

Always use deaerated de-mineralized water forboiler feeding.

Carryover of salt in steam occurs either dueto mechanical or vapor carryover from steamdrum. Efficient drum internals can only reducemechanical carry over. Silica is always carriedover in vaporous form. Continuous monitoringof sodium and silica in boiler water and steam isdesirable.

Before operating a HRSG, ensure completeknowledge of water chemistry.

Whenever HRSG is started after a shutdown ofmore than 3 days, check all safety interlocksbefore HRSG start up for proper functioning.

The steam drum should normally be filled up to thepoint when water is showing in the bottom part ofthe gauge glass. This is to allow for the swell onheating and to reduce any blowing down resultingfrom this cause to a minimum.

Once the HRSG is boxed up, the water level inthe steam drum must be raised to the very top ofthe drum. Filling the drum like this will prevent

excessive temperature differentials along thedrum wall. The water is then shut-off and theHRSG is allowed to cool.

10.4 Tube Failures

Operating the boiler with a known tube leak is notrecommended. Steam or water escaping froma small leak at pressure can cut other tubes byimpingement and set up a chain reaction of tubefailures. Large leaks can be dangerous. Theboiler water may be lost, the ignition may be lostand boiler casing can get damaged.

Small leaks can sometime be detected by the lossof water in the cycle or system. A loss of boilerwater chemicals or by the noise made by the leak.If a leak is suspected the boiler should be shutdown as soon as possible by following the normalshutdown procedure.

After the exact location of the leak or leaks islocated, the leaks may be repaired by replacingthe failed tube or by splicing in a new section oftube, conforming to relevant ASME code.

An investigation of the tube failure is veryimportant so that the condition causing the tubefailure can be eliminated and future failures canbe prevented. This investigation should include acareful visual inspection of the failed tube and insome cases a lab analysis.

It is recommended that every effort be made tofind the cause of tube failures before operation isresumed.

10.5 Safety in Boiler House

It is expected that the final user will evolve acomprehensive safety code for all operations inthe plant. A few suggestions are listed belowwhich can form part of the plant safety code forthe HRSG.

• The boiler operation and maintenance staffmust recognize hazards of high pressure, hightemperature steam and water .

• Furnace explosion is also possible if boileroperating instructions are not followed or if theprotections are bypassed.

• Before startup of a HRSG, ensure that allmaintenance personnel, tools, scaffolding etc.have been withdrawn from the HRSG. (SteamDrum, gas ducts, stack etc.) Ensure that allmanholes, peepholes, inspection doors havebeen properly closed and pad locked.

Section C 95


• Do not attempt to open the observation portsin a working HRSG without observing propersafety procedure.

• Use a full face mask and tinted glass for safety

• For personal safety in handling hot valves,piping, oil guns etc. wear protective gloveswhile working around the HRSG.

• Never enter drums, ducts, furnace etc., untilthe HRSG has been shut down and cooled.The Natural gas, steam and water valvesshould be checked closed and tagged. Theconfined spaces where you are entering haveto be cooled, ventilated and assured safe forhuman entry.

• When you need illumination for inspection,only use low voltage extension cords with lowvoltage bulbs with the cords properly earthed.The power supply be from an earth leak circuitbreaker (ELCB)

• Before entering through gates and dampers,ensure that their drive mechanism have beenlocked.

• Before removing manholes or flanges in drumor pipeline, ensure that the drum/line has beenisolated and drained.

• Do not use toxic fluids like CTC for cleaning ina confined space without adequate ventilation.

• Install and strictly follow a system of permitsand tagging for any maintenance or inspectionwork to be done by any person in the boilerhouse.

• Operators trained in Fire fighting, First aid,handling electric shocks etc may save livesand property in an emergency.

11 Trouble Shooting Chart

The following chart is to be used for solvingproblems arising during operation.

Section C 96


Indication Probable Source Probable CauseRepair method &Preventive Measures

Remove HRSGfrom service at firstconvenient time.Hydrostatic test tobe done to locate leak.Repair by welding orsplicing as indicatedand as approved byinsurance or StateInspection. Determinecause of failure andcorrect it.

Unable to maintainHRSG waterconcentration

Tube Leak HideoutSlight leakage frompitting or cracking oftube or tube seat leak.

Operation at normalloads should putchemical back insolution.

Sound of steamblowing in furnaceor seeing visible steamfrom the stack.

Tube leak

Substantial leakfrom tube/tubes.Over-heating as fromscale or tube seatleakage.

The same as aboveplus tubes re-rolling.

Steam explosion infurnace followed byinability to maintainwater level.

Tube rupture

Failure of tube from lowwater, tube blockageor erosion of exteriormetal surface.

Remove HRSG fromthe line immediately.Inspect or determinewhether tube splicingor wholesale tubereplacement isnecessary.

High conductivity

Solids carry over inthe steam or highCO2 or NH3 in HRSGwater

High boiler waterconcentrations,excessive water levelfluctuation drum baffleleakage or deposits onscrubbers

Check for baffle leaksin steam drum whenout of service, or boilerwater contamination.Check of degasifiedsteam sample willindicate if CO2 or NH3is high

High gas temperature High excess airImproper control/adjustment of airflow.

Check excess air atfurnace HRSG outlet,and correct airflow ifrequired

Excessive water levelfluctuation

Water load or controlconditions

High boilerconcentrations,extreme load swings,varying supplypressure or controlloop adjustment

Correct conditionleading to the problem

Section C 97



Bowed water wallgenerating tubes

Overheating

Internal deposit or lowwater. Usually internaldeposits result in tubesbowing away from thefurnace & low water/starve results bowingtoward the furnace.

Severity of bowingwill determine extentof tube replacement.Internal scale will callfor internal cleaning. Iflow water is indicated athorough inspection fordrum damage and tubeseat leakage must bemade. Take steps toprevent recurrence orlow water condition

Tube blisters Localised overheating Internal deposit

Repair by retubingor welding in tubesection or by heatingand driving backblister dependingupon insurance carrieror State Inspector’sapproval. Cleaninternally by turbiningor acid cleaning.

Depth and extent ofpitting determinesneed and extent oftube replacement.Extensive drum pittingcan be welded but issubject to approval byeither the manufacturer& insurance carrier orState.

Source of oxygenmust be located andeliminated

Internal pitting sharpedged and coveredwith barnacles in drumor tubes.

Corrosion Oxygen in Boiler water

Internal loss of metalnot sharply defined andaccompanied by blackiron oxide (Fe 3 O4 )

Corrosion

Overheating resultingin breakdown of waterinto H & O2

Cause is usually fromsludge letdown orpluggage.

Individual inspectionwill determine extent orreplacement, internalcleaning and correctionof water conditions arerequired

Section C 98



Extent of repair mustbe determined byindividual inspection.In emergency tubesout of high heat zonecan be plugged, beingsure they are cut tovent and to preventdifferential expansionwith adjacent tubes.

Proper externalcleaning can preventout of servicecorrosion.

External pitting Corrosion

From corrosive ashdeposit and moistureeither from dew pointor external source suchas leaking soot blowingtube.

Locate and eliminatesource of moisture. Ifdew point is from in-service corrosion, takesteps to raise metaltemperature

When accessible andwith insurance or Stateapproval, the crackscan be ground outand welded, otherwisesplice in section orreplace tube. Locate& eliminate source ofexpansion difficultyby inspection or hotto cold expansionmeasurements.

Tube cracking

Mechanical stressor a combination ofstress corrosion or tubevariation.

Interference withexpansion ordifferential expansionwith adjacent partsto give mechanicalstress or this stressplus corrosion attack.Vibration set up byturbulent gas flowcharacteristics overtubes.

Using tube spacers canstop vibration.

External metal loss.Highly polished area

ErosionMechanical abrasionfrom soot bloweraction.

Where accessible andwith insurance or Stateapproval pad weld orsplice in a tube section.Eliminate channelingof steam from sootblowers or use tubeshields

External metal loss.Oxidized fire scalearea.

OverheatingProlonged or repeatedoverheating.

Extent of metalloss will determineextent of tube or tubesection replacement.Inspection or athermocoupleinstallation willdetermine cause ofoverheating

Section C 99


Section D


♦ Section Overview♦ Welding Procedure Specifications (WPS)♦ Boiler Preservation Procedure♦ Tube Failures♦ General Principal of Weld Repairs♦ Failure Reporting Format♦ Water Chemistry♦ Feed & Boiler Water Conditioning

1 Section Overview

This section describes the various maintenancepractices, overhauling, and preservationtechniques. Also discussed are failures andrepair techniques

1.1 Recommended MaintenancePractices

Systematic maintenance is essential to keepthe boiler and its auxiliaries in good conditionand to obtain reliable operation of the boiler withhigh availability and plant load factor. Effectivemaintenance aims at timely inspection of partsto repair or replace defective components and toprevent their failure when the boiler is in service.

Maintenance can be classified as -

• Preventive maintenance – mostly conditionbased

• Annual Boiler overhauls to clean andinspect pressure parts. The shutdown periodof the overhaul is also utilized to attend tosystems and parts which cannot be attendedduring short shutdowns or when the boiler is inoperation

The vendor manuals of the fans, motors, controlvalves with their positioners and actuators,instruments and controls, power cylindersetc., prescribe certain minimum maintenancerequirements which are to be carried out in oneof the above two maintenance categories.

1.1.1Preventive Maintenance

The objective of the preventive maintenanceprogram is to obtain trouble free service from thecomponent till the next maintenance.

Vendor manuals for various equipments suggestinspection periods, checks to be done and

recommended spares. The true objective of themaintenance program can only be realized, if amaster plan of maintenance of all the componentsis prepared as per vendor instructions.

Full benefits of maintenance can be obtained onlyif proper parts are used. Mandatory spare partlist covers most of the spares required. It may befound that in the first two years of operation dueto variations of site conditions, some additionalspares not included are also required. Action hasto be initiated to procure such spares.

Some equipment have 100% reserve standbyunits. (Feedwater pumps etc.). Maintenance ofsuch equipments can be organized even whenthe boiler is in service, although some minimumrisk is involved. Equipment such as igniters,scanners have replacement spares which can beutilized when the working equipment are to bemaintained without affecting the boiler operation.The prepared master plan for maintenance shouldbe periodically reviewed during the first threeyears of the boiler operation.

It may be found that due to varying site conditions,the frequencies and quantum of work scheduledas per vendor manuals are either too much or tooless. Based on site experience, the frequenciesand work schedules can be modified. Ascientific method of preparation of the preventivemaintenance schedules is to make them conditionbased. In condition based maintenance, theequipment and components of the plant areinspected daily, weekly monthly etc., as pera suggested schedule by the local operatorsand deteriorating conditions if any observed arereported. Suggested inspection program is givenin this section. Based on operator reports of suchinspection, maintenance works are planned forthe next available planned shut down. Mandatoryinspections prescribed by the vendors are alsotaken care of, irrespective of the equipmentcondition.

1.1.2Schedule of Inspections for ConditionBased Maintenance

The schedule of daily, weekly and monthlyinspections given in the following pages do notrequire a boiler shutdown and in fact can onlybe done when the boiler is in service. Threeand six monthly inspections are done utilizing anavailable planned shutdown approximately in thespecified time period.

Objective of these inspections is to ensurethat

• The components are in trouble free condition

Section D 100


• To carry out any minor repairs or adjustmentswhich can be done with the boiler in service

• To plan for repair of such items, which cannotbe attended when the boiler is in service,during the next available shutdown

• To collect a database to determine optimumservice life of the systems and componentsbefore maintenance is required

The schedule can be expanded, curtailed ormodified based on experience in the first twoyears of operation.

Daily Checks

To be done once a day by the local operator duringhis walkdown checks. Such walkdown checksare to be encouraged to be done in each shiftby the operators. Only those operational checksthat require maintenance work for correction havebeen included.

EQUIPMENT CHECK WORK TO BE DONE

1. Local level gauge on steam drum • Check illumination is proper.

• Leaking valve glands.

• Leaking ports.

• Blurred level.

• Replace fused bulbs

• Isolate level gauges andtighten leaking glands

• Replace leaking ports

• Steam wash mica assuggested by vendor (Notto be done too frequently)

2. Comparison of levels indicated bylocal level gauge with that of remotelevel indicators in the control room

Compare the levels afterverifying there are no leaksfrom valves, glands etc., ofthe level gauge and indicators.Report discrepancies.

If there are seriousdiscrepancies, calibrationof the remote levelindicators has to be plannedimmediately.

3. Traces of water on boiler claddingetc.

Such spots are indicative ofvalve leaks, Instrument tappingleaks, boiler tube leaks etc.,Trace the source of leak.

Maintenance to be plannedto eliminate the sourceeither immediately orduring next planned shutdown (depending on thesource and quantity ofleak and accessibility formaintenance)

4. Fans & drive motors. • Check bearing temperatures

• Check for vibration levels.

If higher than normalbearing temperaturesare noticed check forcause-proper oil level / oilcirculation, correct gradeand quality of oil, abnormalsound or vibration. Ifbearing temperatures arevery high, start the reserveequipment (if avl.) and planfor a maintenance check.

Section D 101



5. Drum safety valves. Check for passing of safetyvalves (noise or wisp of steamthrough silencer)

• Hand pop the affectedsafety valve one or twotimes to clear any dirtsticking to the valveseats.

• Lightly tap on the stem ofthe safety valves.

• If these measures donot succeed, requestfor check of the safetyvalve during next plannedshutdown.

6. Purity of Instrument air • Check by visual observationthat the instrument air is oiland moisture free

• If there is a feel by visualinspection, Oil and moisturecontent can also be checkedby laboratory examination asper standards

• Oil and moisture in theinstrument air is likelyto clog the positionersof pneumatic controllers/ solenoids and maketheir operation sluggishor unreliable.

• Open drain valves ofair-receivers for shorttime to drain condensateif any.

• If these measures arenot successful, inform theMaintenance Group

7. Scanner cooling fansuction-damper linkages andpower cylinders.

Check for their proper operation Sluggish operation offan suction dampermay be due to stucklinkage, stuck damper,faulty power cylinder,and faulty positioners.Check for possible cause.Maintenance works have tobe planned.

8. Steam or water leakages fromvalves and from flange joints

• Loose valve gland

• Loosened bolts of flange jointand / or failed gasket

• Tighten the gland nuts.If the leakage notgetting arrested, planfor maintenance duringshut down.

• Tighten the bolts. If thegasket failed then plan forthe maintenance duringshut down.

9. Boiler cladding, air duct or fluegas duct

Check for hot spots Hot spots may be due toleakage of flue gas or hotair. Source of leakage hasto be located after selectiveremoval of insulation (tobe planned for the nextplanned shut down)

Section D 102


Monthly Checks


1. Fans and blowers.

With a vibration analyzerrecord vibration and measurebearing temperature. Also notethe operating condition of theequipment at the time of theabove observations and recordthem.

By monthly recording ofdata, establish a databasefor deciding the overhaultime of the equipment. Anoverhaul once in two or threeyears may be adequate.Such a database will helpin deciding the time frame.Sharp increase in vibrationlevels bearing temperaturesor sound levels may callfor early scheduling ofoverhauls

Checks Every Six Months During a planned shut down of the boiler, thefollowing checks can be done.


1. Boiler Pre-interlock, purgeinterlocks, start permissive, boilertrip protection.

Coinciding with a plannedshut down of boiler, carryout the checks to identifymalfunctioning or sluggishpressure, temperatureswitches, solenoid operatedvalves, positioners, proximityswitches, actuators etc.,

Plan for maintenance orre-calibration of defectiveitems if any noticed, duringthe shut down period.

2. Burner refractory work.Visual check that there are noloose bricks, spalling or cracks

If any abnormalities are seenrepair works to be plannedduring next available shutdown

3. UV Scanner components

Clean UV Scanner cell andcheck its output as per vendormanual. Check its amplifierand flame relay

Replace scanner cells ifoutput is suspect. Adjustamplifier flame relay ifrequired.

Checks Every Year (Refer also work listed under Boiler overhaul)


1. Pressure temperature, Flow level,differential pressure controllers

Utilizing the boiler annual shutdown for overhaul, re-calibrateall pressure, temperature, flow,level and d/p controllers as pervendor manuals

Carry out any maintenancereplacement or adjustmentneeded to secure initialcalibration values as percommissioning records

Section D 103



2. Pressure gauges, temperaturegauges, Pressure/temperatureSwitches

Re-calibrate, Verify functioningof pressure/temperatureswitches as per design

Repairs or adjustments asnecessary

3. Positioners, actuators

Verify functioning of positionersand actuators by feedingcurrent inputs to positionersand measuring the air pressureoutput of the positioners andopening closing of actuators

Repairs or adjustmentsas necessary as pervendor manuals to obtainperformance as percommissioning records.Verify functioning ofproximity switches whereprovided. Clean filtersof air regulators. Checkfunctioning of air regulators.Verify tightness of airconnections

Section D 104


1.1.3Boiler Annual Maintenance andOverhaul

In addition to the check and inspections listedunder preventive maintenance, the boiler requiresan annual shut down of about 10 to 15 daysfor cleaning, inspection ad overhaul of boilerpressure parts. The shut down period is restrictedto a minimum by deploying adequate resources.If required, Field Engineering department of TBWcan assist the customer in carrying out the boileroverhaul.

The annual shutdown is utilized for cleaning andinspection of the pressure parts and to collectdata on the wear pattern of boiler, superheaterand economizer pressure parts. The shutdownopportunity is also utilized for overhaul of safetyvalves, regulating and isolating valves andcomponents, which can not be attended when theboiler is in service. (The valve overhauls neednot be done every year).

Annual Overhaul

Planning Before Overhaul

• Prepare a list of jobs to be done during theoverhaul based on earlier inspection reportsand the jobs listed below.

• Ensure availability of spares required for theproposed jobs.

• Ensure tools, tackles, scaffolding materialsrequired for the job.

• Ensure availability of manpower required forthe job (Own sources, contract labor etc.)Services of TBW are also available for carryingout annual overhauls and inspections.

Shutdown and Cooling the Boiler

Shutdown the boiler in a planned manner. Coolthe boiler. Open all access and inspection doors.Refer to the Section B of this volume for theshutdown procedures.

Inspection After Cooling

Carry out a preliminary inspection after cooling tocheck cleanliness and any sign of deposition onwater wall panels and the need for water wash.

Drums Inspection

• Open the access doors at either end of thedrums

• Allow the drum to ventilate for about 8 hours.If necessary two fan coolers can be fitted overtemporary stands to force air through the drum

• From the time the drum manholes are openedtill they are closed after inspection, the areaaround the drum must be cordoned to restrictentry only to specifically authorized personnel

• The names of persons who are entering thedrum for inspection, along with tools they carrymust be entered in a register. Persons comingout of the drum after inspection should beasked to account for the material they carriedinto the drum. This precaution is to preventaccidental dropping of foreign material throughthe water wall tubes, which may block watercirculation through them and can cause tubefailures

• Carry out a preliminary inspection of the drumto check for any deposits on the waterside ofthe drum

• Using nylon brushes, the deposits (which arenormally soft) are cleaned, collected on traysand disposed off outside the drum. Washingdown the deposits to the boiler tubes is notrecommended

• In case of excessive deposits, the chemist isasked to analyze the nature of the deposits. Areview of phosphate concentrations and boilerwater quality control, (high conductivity) maybe made to reduce the deposits in the nextyear of operation.

• After cleaning the following examinations aremade

– Examine the boiler drum metal for scale,pitting, corrosion and metal wastage. (Drumthickness is measured at a few selected spotsusing ultrasonic instruments and comparedto design thickness)

– Inspect fastenings of the baffles anddemisters to see that they are intact, withoutcorrosion pitting or holes. Eroded or corrodeddrum internals to be attended. No weldinghowever is permitted on the drum metal.The demisters can be examined in position.They need not to be dismantled. Reasonablewater tightness of the baffles is to be ensured

– Examine that feedwater pipe is intact withflange connections tight and discharge exitcorrectly oriented

– Examine that the continuous blowdown anddosing pipes are not plugged or corroded,their supports are normal, and their holeshave been correctly oriented

After the inspection, clean the manhole seatsand provide new gaskets. After the inspection

Section D 105


and verifying that all men and material have beenremoved from the drum, close the manholes andbolt them tight.

Inspections in the Furnace

Check the water wall tube panels in thefurnace for

• Evidence of pitting / erosion / corrosion on tubeouter surfaces (exposed to the flue gas path)

• Evidence of overheating (bulging of tubes,blue color of tubes, blisters, disturbed verticalalignment of panels)

• On suspicion of any abnormalities consult TBWor a metallurgist for advice.

• Check the duct burner & accessories as perR& V manual & its setting..

• Any loose material inside the furnace needsto be cleared.

• The scaffolding inside the furnace shouldbe removed after such inspection (if any)and manhole door to be closed tightly afterensuring that the refractory blocks is placed inthe manhole.

Safety Valves, Start Up Vent Valves andother Isolating Valves

These valves require regular overhauls, normallyonce in three years even if condition reports do notindicate any abnormality. Earlier overhauls can bescheduled if condition reports warrant. Overhaulsof the valves can be staggered after the first twoyears of operation in a manner that certain numberof valves are overhauled every year. Overhaulsof the valves are as per their vendor manualsenclosed.

Expansion Joints

Examine the expansion joints. Eroded / corrodedparts can be patched by welding. When severeerosion is noticed (after several years of service)the expansion joints are to be replaced. Collapseor stretching of the expansion joints is usuallydue to forces exerted by the connecting ducts.Readjustment of duct supports will solve theproblem and will assist the expansion joints toregain their original dimensions.

Insulation and Cladding

Verify insulation as per drawings and correctwherever necessary. Inspect cladding for

damages due pitting, hotspots, dislocation etc.Repaired as necessary.

Other Equipment

Overhaul of seal air fans, control valves, actuatorsetc., is scheduled as per vendor instructions andcondition monitoring described under preventivemaintenance

Light Up of the Boiler after Maintenanceand Overhaul

The pressure-raising rate during the first lightup after the overhaul should be slower thanusual giving time for check of equipment andcomponents. Valve flange joints and glandsmust be checked for absence of leaks andcan be re-tightened where necessary when theboiler pressure is less than 5 Kg/cm2. Burnerperformance has to be verified and its axialposition corrected if required. If overhauled,performance of the safety valves must be verifiedby floating them. The boiler expansions must beverified during pressure raising. A boiler overhaulis considered successful if it enables anothertwelve months of trouble free boiler operation.

1.1.4Tube Thickness Survey

To make a quantitative assessment of wastage oftubes (both internal and external) a tube thicknesssurvey using ultrasonic tube thickness gaugesis recommended. For a useful tube thicknesssurvey program measurement location on waterwall, super heaters and economizers’ tubesmust be specified and indicated on a drawing.Vulnerable locations are usually chosen. Onrequest, the Field Engineering Department ofTBW can establish such a program. The followingare the suggested areas for a tube thicknesssurvey -

• Boiler bank, economizer coils, deaerator paneltubes & MUWH..

Tube thickness measurements at the selectedlocations are made and recorded after waterwashing and drying, during the first annualoverhaul. The base value is the design thicknessof the tubes. Subsequent measurements aremade at the same locations, every alternate year.The tube thickness survey provides useful dataon corrosion / erosion rates and can alert theowner when serious loss of thickness is noticed.

Section D 106


2 Welding ProcedureSpecifications (WPS)

The pressure part of the boiler is made of severaltypes of steel of varying thickness. Welding isthe basic technique used in the fabrication of theboiler. The joints produced by welding shouldhave strength not less than that of the parentmetal. In the weld joint, the parent metals shouldfuse together, without cracks, blowholes, slaginclusions or defects of any kind. The weld jointapart from proving its mechanical strength intension must also be able to resist bending withoutcracking. Such requirements can only be met ifthe welding process used is strictly controlled.

ASME (and other organizations) classify materialsinto categories (P1 P2, P3, P9) as per carboncontent and alloying metals (chromium, Nickel,Molybdenum etc.) and specify the procedureto be used for welding materials of the samecategory or one category with another category.A specification of the materials and shapesadopted by TBW can be obtained on request.The welding procedure distinguishes betweenwelding of thin and thick material. The weldingprocess specification defines the following foreach category of welding.

• Edge preparation (angle, shape)

• Joint preparation (cleaning, gap) and tagging

• Joint pre-inspection before welding

• Pre-heat of the weld joint, if any required(method of pre-heating, temperature method ofchecking temperature)

• Root weld (gas welding, TIG or Arc, size ofelectrode, type of electrode)

• Radiographic inspection of root weld if required

• Subsequent runs of welding (TIG, Arc or othermethods, size of electrode, type of electrode,number of runs)

• Post weld heat treatment if any required(temperature, rate of increase of temperature,method of increasing temperature, holdingtime, rate of cooling)

• Radio graphic examination of the weld joint,indicating defects if any to be corrected

• Correction of weld defects

• Final acceptance of the weld joint

The WPS indicates compatible categories ofmaterials that can be welded. The WPS also laysdown the type of electrode to be used for each

category of welding. As the electrode depositsmaterials, the composition of the electrode mustbe compatible with the material welded and addstrength. The coating of the electrode also mustmeet specific requirements.

The WPS must be used not only during fabricationof the boiler, but also when any repair ormaintenance works are to be done. TBW hasWPS to cover every welding job connectedwith fabrication of the boiler in the factory anderection of the boiler at site, conforming to IBRrequirements. The Field Engineering Departmentof TBW will be glad to provide a WPS for any siterepair weld jobs required for maintenance.

3 Boiler Preservation Procedure

Introduction

Both the gas and waterside of a boiler should beprotected against corrosion during out of serviceperiods. It is known that many of the corrosionproblems of boiler and auxiliary equipment havetheir inception during storage. Rusting of tubesurfaces, as indicated by the formation of the redhematite (Fe2O3), not only cause a roughenedtube surface but also results in attack of parentmetal.

The advantages of efficient feedwater and boilerwater treatment during operation may be lost ifthe same diligence is not applied to protect heat.Transfer surfaces during idle periods. Protectionfrom corrosion during storage becomes vitallyimportant considering the number of times duringthe life of a boiler when it and its auxiliaryequipment are idle.

To minimize the possibility of corrosion, boiler tobe placed into storage must be carefully preparedfor the idle period and closely watched duringthe outage. There are two methods availablefor storing the unit dry storage and wet storage.Although the wet storage procedures is preferredsuch factors as availability of good quality water,ambient weather conditions, length of storageperiod, auxiliary supply of heat, etc may dictatethat the dry storage procedure is more practical.

3.1 Definitions of Water Quality

Some cleaning procedures, hydrostatic testingand storage require water of higher qualitythan others. For the purpose of economy andconvenience the lowest water quality consistentwith requirements is specified in these variousprocedures. The terms that identify the different

Section D 107


water qualities along with their definitions are listbelow: Station service water - Water normallyused for drinking, fire protection, etc.

Softened water - Filtered, sodium zeolite softenedwater with total hardness less than 1 ppm.

Two- bed demineralised water - Water thenhas been passed through cation and anion ionexchanges in series.

Mixed bed demineralised water - Water that hasbeen passed through a mixed bed demineraliser.Water from an evaporator is considered to be ofequal quality.

Treated demineralised water - Mixed beddemineralised water that has 200 ppm ofhydrazine and enough ammonia added to givefinal concentration of 10 ppm (or a pH of 10.0).In this procedure, condensate is considered to betreated demineralised water.

3.2 Dry Storage Preservation

When it is known that a boiler is to be idle fora considerable length of time and that a briefperiod will be allowed for preparation to return it toservice, the dry storage method is recommended.In this method the unit is emptied, thoroughlycleaned internally and externally dried, and thenclosed up tight to exclude both moisture andair. Trays of lime, silica gel, or other moistureabsorbent may be placed in the drums to draw offthe moisture in the air trapped by the closing upof the boiler.

The following general procedure isrecommended when placing a unit into drystorage:

1. Fire the boiler according to the normalstart-up procedure and establish upto3.5-kg/cm2G-drum pressure. Stop firing.Secure the boiler and when the pressuredecays to 1.3 kg/cm2G, immediately drainthe boiler and headers under air. As soonas possible, open the drums to allow air tocirculate for drying of all internal surfaces.This step is included for a unit that has beenin service and is to be placed into storage.For a unit that has never been in service, startwith Step 2.

2. If the unit is full of water and cold, drain theunit under air. All non-drainable boiler tubesshould be blown with compressed air. If anexternal source of heat is available such asa steam coil air heater, portable heaters, etc.,

operate these heaters to assist in drying theinternal boiler surfaces.

Install trays (of non-porous constructionand capable of passing through the drummanhole) containing the moisture absorbent(silica gel is preferred) into the drums. Insertthe trays into the drum being certain thatnone of the absorbent comes into contactwith the metal surface of the drum. Toinsure against an overflow of corrosive liquidafter the moisture has been absorbed, thetrays should not be more than ½ full of dryabsorbent. The amount of absorbent canvary but the recommended minimum is oneKg of absorbent per 1000 Kg per hour steamflow capacity of the unit.

3. Open the isolation valve for nitrogenconnection, on the steam drum, close allother vents and drains and pressurize theboiler to 0.3 to 0.6 kg/cm2G with nitrogen.The amount of nitrogen required will varyaccording to the volume of the unit.

4. With the boiler pressurized, alternately openall boiler drains to purge air from the unit untilpressure decays to zero. It may be necessaryto repeat this process several times to reducethe amount of oxygen left in the unit to aminimum.

The unit should now be stored under 0.3 to0.6-kg/cm2G nitrogen pressure maintainedat the steam drum. To maintain the nitrogenpressure, all connections and valves shouldbe blanked or tightly closed. Check gaspressure daily to ensure protection. We wouldrecommend that periodic inspection of theunit be performed every 3 months to assurethat no corrosive action is taking place andto replenish the absorbent as required. Sinceair will enter the unit during this inspection,it will be necessary to repeat Steps 3 & 4 toexpel the air.

The unit should be properly tagged and theappropriate warning signs attached notingthat the boiler is stored under nitrogenpressure and that complete exhaustion ofthe nitrogen must occur before anyoneenters the drum. Before entering drumstest to prove that the oxygen concentrationis at least 19.5 %. The above procedure isintended to include the economizer.

Section D 108


3.3 Wet Storage

The advantage of employing the wet storageprocedure is that the unit is stored completelywet with the recommended levels of chemicalsto eliminate a wet-dry interface where possiblecorrosion can occur. It is suggested that volatilechemicals be used to avoid increasing the levelof dissolved solids in the water to be used forstorage.

In preparing a unit for wet storage, the followingprocedure is recommended.

The unit should be filled with deaerated,Demineralised water treated with 200 ppmhydrazine (N2H4) for oxygen removal andsufficient ammonia (NH3) in order to attain a pHof 10 (for demineralised water, this will requireapproximately 10 ppm ammonia).

We strongly recommend pre-mixing of thechemicals with the water to insure a uniformmixture entering the boiler. This can beaccomplished by the blend-fill method. Theblend-fill method consists of blending thechemicals with the demineralised water at acontinuous rate such that a uniform mixtureis entering the boiler. Simply introducing thechemicals through the drum after establishingwater level will not insure adequate dispersion ofchemicals to all internal surfaces, unless sufficientheat is delivered to the furnace (i.e. firing theboiler) to induce natural circulation throughout theboiler.

Fill the unit with the treated demineralised waterto the normal centerline of the steam drum. Stopfilling further.

Back-fill the with treated Demineralised water untila rise in steam drum level is noted. Continue fillinguntil water exits from the steam drum vents. Afterfilling, all connections should be blanked or tightlyclosed.

A source of low-pressure nitrogen should beconnected at the steam drum to maintain 0.3 to0.6 Bar G to prevent air from entering the unitduring the storage period.

The unit should be properly tagged and theappropriate warning signs attached notingthat the boiler is stored under nitrogenpressure and that complete exhaustion ofthe nitrogen must occur before anyoneenters the drum.Before entering drums test to prove that theoxygen concentration is at least 19.5%.

If storage continues into winter, ambienttemperatures below the freezing point of watercreate a real hazard to the boiler pressure partsand it will be necessary to provide a means ofkeeping the unit warm to avoid damage.

At some later date when the unit is to be placedinto service, the boiler can be drained to normalstart-up water level and placed into operation.

In some cases, an expansion tank or surge tank(such as a 55-gallon drum) above the steamdrum elevation may be required to accommodatevolume changes due to temperature changes.This tank is equipped with a tight cover and sightglass and contains properly treated water. Thetank should be connected to an available opening,such as a vent line at the top of the steam drumin order to create a hydrostatic head. This tankwill provide a ready, visual check of water level orin leakage during lay up.

A source of low-pressure nitrogen should beconnected to the surge tank to maintain 0.3 to 0.6Bar G to prevent air from entering the unit duringthe storage period.

The treated demineralised water should beanalyzed weekly, and when necessary, sufficientchemicals should be added through thechemical feed line, to establish the proper levelsrecommended. Samples of the treated water canbe taken at the continuous blowdown line or anysuitable drain connection.

No unit should be stored wet when there is anypossibility of a temperature drop to the freezingpoint unless sufficient heat can be provided to theunit to eliminate the danger of water freezing andsubsequent damage to pressure parts.

Section D 109


3.4 Nitrogen Blanket

Nitrogen can be introduced at the followinglocations

1. Through the steam drum

2. Through the main steam line

The nitrogen required to seal the drainablecomponents may be supplied from a permanentnitrogen system or portable tanks located nearthe vent elevations. Due to differences in plantlayout, the owner should choose his own methodof piping the nitrogen, either from their permanentsystem or from portable tanks, to the vent (ordrain) locations listed.

The unit should be properly tagged and theappropriate warning signs attached notingthat the boiler is stored under nitrogenpressure and that complete exhaustion ofthe nitrogen must occur before anyoneenters the drum.Before entering drums test to prove that theoxygen concentration is at least 19.5 %

Section D 110


3.5 Boiler Lay Up Procedures

TYPE OF SHUTDOWN PROCEDURE

Short Outages 4 Days or Less. Unit Not Drained Maintain the same hydrazine and ammoniaconcentration as present during normaloperation. Establish 0.3 to 0.6 kg/cm2G nitrogencap on the steam drum

Short Outages 4 Days or Less. Unit is Drained Drain and open only those sections requirerepair. Isolate remainder of the unit under 0.3to 0.6 BarG nitrogen pressure where possible.Maintain the same nitrogen and ammoniaconcentration for water remaining in the cycle

Long Outages Longer than 4 Days Upto 15 Days.Unit is Drained

Fill the boiler with Polish water having 200 ppmof hydrazine and 10 ppm of ammonia to maintainpH 10. Establish nitrogen cap of 0.3 to 0.6kg/cm2G over the steam drum.

Long Outages More than 15 Days - Unit isDrained.

Dry storage of boiler with nitrogen alone ispreferred procedure. Nitrogen cap of 0.3 to 0.6kg/cm2G to be maintained on the steam drum.Installed silica gel tray in the steam drum to soakmoisture if any present in the drum atmosphere.

3.6 Preservation of RotatingEquipments

1. Put the rotating equipment in service once inevery 48 hours or atleast once in a week

2. If the equipment is going to be under longshutdown

a. Fill bearing block full of oil to preserve thebearing and rotate the Fan/Pump Shaft by90o once in every 48 hours

b. Cover the bearing block & uncoveredportion of shaft with plastic sheets toprevent dust/water ingress

c. Ensure no dust/water accumulates on therotating equipment

3.7 Preservation of Instruments

1. Cover all field instruments with plastic sheets

2. Power up the panel instruments and check theoperation

3. Keep the control room dust and moisture free

4. Operate control valves, power cylinders oncea week and check operation.

5. Operate quick shutoff valves frequently(Twice a week)

6. Ensure that O2 analyzer is powered up andreference air supply is given when flue gas ispresent.

7. Check operation of Ignition Transformer oncein 2 weeks

8. Check operation of Flame Scanners & FlameAmplifiers once in 2 weeks

Section D 111


4 Tube Failures

Operating a boiler with a known tube leak is notrecommended. Steam or water escaping from asmall leak can cut other tubes by impingementand set up a chain reaction of tube failures. Largeleaks can be dangerous. The boiler water may belost, the ignition may be lost, and the boiler casingmay be damaged.

Small leaks can some times be detected by theloss of water in the cycle or system, a loss in boilerwater chemicals or by the noise made by the leak.If a leak is suspected the boiler should be shutdown as soon as possible by following normal shutdown procedures (If situation permits).

After the exact locations of the leak or leaks areidentified, the leaks may be repaired by replacingthe failed tube or by splicing in a new section oftube as per relevant codes.

An investigation of tube failure is veryimportant so that the condition causingthe tube failure can be eliminated andfuture failures can be prevented. Thisinvestigation should include a carefulvisual inspection of the failed tube and insome cases a laboratory analysis.

1. It is recommended that every effort be madeto find the cause of tube failures beforeoperation is resumed.

2. It should be ensured that, whenever a spoolpiece is inserted in the failed zone, the weldjoint needs to be of proper weld quality.

3. Free from excess weld penetration to avoidany obstruction in the water / steam mixtureflow inside the tube. Excess weld penetrationcan cause internal tube erosion and results intube failures.

4. It is suggested to have all the joints arex-rayed and interpreted by qualified /experienced radiographer.

4.1 Tube Failure Investigation /Analysis Method

Investigation / analysis methodology is listed asfollows, which needs to be followed to find theactual root cause of the problems.

PLEASE FILLUP THE ENCLOSED (end of thissub-section) OBSERVATION FORM AND THE

SAME MAY BE SENT TO TBW ALONG WITHTUBE SAMPLE FOR ANALYSIS.

Objectives of Failure Investigation

Boiler tube failures are the largest cause of forcedoutages experienced by a utility. To avoid orminimize outages and the associated economicpenalties, it is important to identify the mechanismand root cause of tube failures. Informed visualinspection is often adequate for this purpose,however failure analysis involving detailedmetallurgical investigation is necessary. Tubefailures may be due to overheating, corrosion,erosion, fatigue, hydrogen damage etc. A failureinvestigation and subsequent analysis shoulddetermine the primary cause of a failure, andbased on determination, corrective action shouldbe initiated that will prevent similar failures.

Stages of Failure Analysis

Although the sequence is subject to variation,depending upon the nature of a specific failure, theprincipal stages that comprise the investigation &analysis of a failure are:

• Collection of background & selection ofsamples

• Preliminary examination of the failed part(visual examination & record keeping)

• Non destructive testing

• Mechanical testing (including hardness &toughness testing)

• Selection, identification, preservation, and/orcleaning of all specimens

• Macroscopic examination and analysis(fracture surfaces, secondary cracks, & othersurface phenomena)

• Microscopic examination and analysis

• Selection & preparation of metallographicsections

• Examination and analysis of metallographicsections

Collection of Background OperatingData:

Boiler operating data just before & at the timeof a tube failure is very important, as it will giveinformation of the service conditions faced by thetube at the time of failure. This operating datashould also be co-related with the past operationdata & abnormalities if any should be taken careoff. Water chemistry analysis, fuel analysis shouldalso form an important part of this data. This data

Section D 112


& the metallurgical analysis will help us in truesense to arrive at the exact cause of a tube failure.

Investigation of Tube Failure in aBoiler

Study the boiler log sheet & water chemistryrecord prior to tube failure and after tube failure.Preserve the copies of these log sheets. Record,if any abnormality noticed, such as mal operation,malfunction, very high or low temperature/loads,fluctuating loads, sudden increase in load ortemperature, poor water chemistry, start up ventcrack open / close etc. etc. (if possible collectand send the water samples, internal scale fromdrum & tubes, external scale samples).

After entering in boiler and before proceeding totube failure location inspect & record the conditionof boiler and pressure parts without disturbing theevidence i.e. distortion of pressure parts/coils,bulging of pressure parts, scaling / lump formationon pressure parts, blockage of flue gas path, other/ secondary failures etc. etc. In such case takingphotographs will help in great extent in analyzingof the tube failure, boiler problem. The failedpressure part tube should not be hammered, anymechanical impact should be avoided.

Inspect the failed tube and record all findings onthe same as well as its adjacent tubes. Carryout dimensional measurement of failed tube andaffected adjacent tubes.

Number mark the failed tube for its location,flue gas flow, steam flow with oil paint.After completion of inspection, recording andphotography, cut the failed tube and affectedadjacent tube, if any, with the help of HACKSAWonly. Gas cutting of the tubes should be avoidedas much as possible. The failed tube, keeping

the failed portion in middle should be cut for totallength of minimum 350 mm. Immediately aftercutting the tube sample both the ends shouldbe covered with plastic caps. While doing this,internal or external scale of tube should not falldown.

The failed tube samples should be carefullypacked in plastic bag / wooden caseaccompanying duly filled format with waterchemistry of boiler log sheets should be sent toTBW, Pune.

Removal of Failed Tube Sample

• The tube sample should be cut with a hacksawblade. Gas cutting should be avoided

• The sample should be cut approx. 8-10 inchesabove & below the affected area

• The exact location & elevation should bemarked on the tube sample

• The direction of the fluid flow should be markedon the tube sample

• Immediately after cutting the tube sample boththe ends should be covered with plastic caps.Internal or external scale of tube should not falldown

The failed tube sample nicely packed in plasticbag / wooden case accompanying duly filledformat as given below with water chemistry ofboiler log sheets should be sent to TBW H.O formetallurgical investigations.

Tube Failure Analysis ObservationSheet

SR.NO: DATE:

NAME OF THE CUSTOMER

Boiler Specifications

Capacity

Steam Pressure

Steam Temperature

Fuel Fired

Location of Tube Sample

Duration of Service of Boiler

Duration of Service of Tube Sample

Date of Failure

Sample Received on

No. of Samples Handed Over to Lab on (WithIdentification Mark/No) Nos. / Date

Visual Inspection Report

Section D 113


NAME OF THE CUSTOMER

With Sketch / Nature Of Failure

Tube Material ( Specified)

Tube OD X THK (Specified)

Orientation of Tube

Fluid Flow Direction

(With Marking)

Boiler Operating Condition

At the Time of Failure (Water

Chemistry & boiler operation log sheets)

ANY OTHER RELEVANT INFORMATION ABOUT THE FAILURE

4.2 Window Patch Welding

Purpose

The purpose of the window patching method is toallow the welding of tubes that could not otherwisebe welded because of limited access to part of thetube diameter. This procedure is restricted to thatuse.

Preparation

1. The area to be patched shall be cleaned tobare metal

2. The patch shall be made from tube materialof same type, diameter and thickness, as thetube being welded

3. The area of the tube to be removed shall becarefully marked out as close as possible tocontour of the patch. The tube section maythen be removed using an oxyacetylene gascutting torch or by mechanical means

4. The weld preparation shall be made as per theFigure #1. The fit up of the patch weld gapshall be 2.4 0.8 mm

Welding

1. A welder qualified to the requirementsof ASME shall make the tube and patchwelds in accordance with an approved weldprocedure.

2. The root pass shall be done with GTAWprocess. The weld may then be completedwith either SMAW or GTAW process. Someacceptable weld procedure specifications arelisted in Table below

Testing

1. All the tube and patch welding shall besubject to close visual inspection and100% radiography in accordance with therequirements of ASME section V. Thestandard for accepting /rejecting is specifiedin ASME section I

2. Completed welds are subject to hydrostatictest

BASE MATERIAL FILLER METAL

P1 TO P1 Carbon Steel to Carbon Steel ER 70S.2 E7018

P3 TO P3Carbon ½ Moly to Carbon ½Moly ER80S.B2 E7018A1

P3 TO P3½ Cr ½ MOLY TO ½ Cr ½MOLY ER80S.B2 E8018B2L

P4 TO P4 1-1/4 Cr TO 1-1/4 Cr ER80S.B2 E8018B2L

P5 TO P52-1/4 Cr 1 MOLY TO 2-1/4 Cr1 MOLY ER90S.B3 E9018B3L

P8 TO P8 Stainless to Stainless ER308 ER308-16

Section D 114


Figure 7

Section D 115


5 General Principal of WeldRepairs

Furnace and Boiler Tubes

• The minimum replacement tube length shouldbe not less than 150 mm. A damaged tubeshould be cut at least 75 mm each side of thedefective area.

• Backing rings must not to be used in weldingheat absorbing tubes carrying water or mixtureof steam and water.

• If a backing ring is not used, the first pass of theweld must be made with inert gas-arc or oxyacetylene. The weld passes may be completedby either process, or by a manual metal arc.

• Pre heat or post heat is not required for weldingcarbon steel furnace or boiler tubes.

• Prior to welding, clean the tube ends to brightmetal inside and outside for at least 40 mmfrom the weld area. Remove all deposits ofoxide, boiler water salts and slag to avoid gasor slag inclusions in the weld.

• Fit-up of the weld joints is important. It isdifficult to obtain accurate cuts on furnacetubes especially those in welded furnace walls.However, it is worth to spend extra time to getthe existing tube ends squared and correctlychamfered and to cut the replacement tubeto the correct length. Poor fit-up increase thepossibility of an unsuccessful weld.

• Allow for shrink in the welding, remember, theweld metal and parent metal are melted in thewelding process and the molten metal shrinksas it solidifies. A butt weld in the tube willshorten the total tube length about 1.6 mm.

• Use a clamp or guide lug to hold one end ofthe replacement tube alignment while the firstweld is made. Do not tack weld both end of thereplacement tubes particularly if the existingtubes are rigidly supported

• As a general rule, first complete the welds atthe lower end of the replacement tube. Do notstart welding the upper end of the replacementtube until both the replacement and the existingtubes have cooled to ambient temperature.

Weld Repair of Small Cracks in Tube

In the interest of saving time and cost, it is betterto weld small cracks rather than replace a lengthof the tube. The crack must be ground out to forman acceptable welding groove. The groove shouldcontinue well beyond the ends of the crack. Inert

gas arc or oxy acetylene process must make thefirst pass of the weld.

Note

This type of the repairs entails somerisk. Internal deposits. Particularlycopper, may exist under the crackwhich will result in damaging the parentand/or weld metal causing failure in ashort period of time.

Over-heating the tube may havecaused the longitudinal crack. In thiscase, the tube has swollen and theweld thickness reduced. In the modernwelded wall construction, it is difficult toaccurately measure the tube diameteror circumference to detect the minorswelling. If visual indicates swellingand reduction of wall thickness atthe crack, a complete replacement ofthe damaged tube length is the bestsolution.

A circumferential crack indicates afailure due to excessive stress appliedby expansion restriction, bending orfatigue; welding can repair such cracks.However, unless the cause of failureis diagnosed and corrected, anothersimilar failure could occur at or nearthe original crack.

Also the tube cannot be cleaned frominside and there is always a possibilityinternal deposits will contaminate theweld.

Plugging Tubes in Drums & Headers

Often after a tube failure, it is desirable to plugthe failed tube in the drum or header shell sothe boiler may be returned to service with theleast possible delay. It is recommended that thefailed tube be replaced whenever possible in lieuof plugging. If the leak is remote from the tubeseats and accessible, the faulty section of thetube should be cut out and replaced rather thanplugging.

Water wall tubes (space tube) should be replacedif possible and plugged only as a last resort. Theplugged tube must be free to expand and distortwith respect to the adjacent tubes. Membranetubes must be repaired and not plugged.

When tubes are plugged, the old tube should beremoved from the boiler setting since it probablywill burn off due to lack of cooling and couldbecome displaced and obstruct gas lanes, foul

Section D 116


up soot blowers, be dangerous to personnel aftershutdown, and etc. If the tube is not removed fromthe setting, a definite hole must be punched ordrilled in the tube to prevent a possible dangerousbuildup of pressure between the tube plugs.

A expanded tube leaking at the seat should beremoved from its seat and

1. a new tube rolled in,

2. a new short stub rolled in and plugged,

3. the tube end seal welded to the shell or, ifthe drum shell is internally counter bored, acylindrical plug must be installed and sealwelded to the drum shell.

Note

No. (1) is the preferred fix with No. (3)the least preferred.

Seal welding of tube ends, tapered plugs, orcylindrical plugs to the shell should be done insuch a manner as to minimize the heating ofadjacent tube seats, which may become loose.It is essential that the welding process should beas per standard procedure for carbon steel shellsand tubes to be followed very closely to ensuresuccess. Deviations from these parameters willnormally result in unsatisfactory connections.The major welding parameters for shells or tubesother than carbon steel may be obtained fromqualified welding procedures.

Ensure that welders are qualified in accordancewith ASME Section IX and local provincialrequirements. They must also ensure that thewelding is done to the applicable qualified weldprocedure.

It also to be ensured that the proposed repair hasbeen approved by the Boiler Inspection Branch ofthe local jurisdiction.

Machined tube stubs and plugs are used wherethe old tube can be removed from its seat withoutseat damage and for new construction that isdrilled for future addition of tubes. The rolled-intube stub extends into the shell and a solid plugis installed and seal welded to the stub. Thesestubs and plugs are standardized to have onlyone tube stub and one plug for each standardtube hole.

Before rolling stubs in, they should be cleanedinside and outside with a wire brush, abrasivepaper, or a liquid cleaner until the metal is free ofall foreign substances. In general, stubs do notrequire cleaning beyond the removal of dirt, rust,scale or foreign material.

The stub seat (tube hole) should be similarlycleaned. If a liquid solvent is used to clean eitherthe stub and/or tube hole, care must be taken todry the metal completely. Liquid trapped betweenthe stub and its seat prevents contact of the twometal surfaces.

Before the expanding tool is inserted, the insideof the stub should be lubricated with a suitablecompound. The compound selected shouldbe water soluble to facilitate cleanup. Therolling process should not be rushed since heatgenerated during rolling is detrimental to thestrength of the rolled joint. The tube stub isproperly expanded when the wall thickness in theseat is reduced by 6 to 10 percent for generatingtubes and 10 to 14 percent for other boiler tubes.The tube stub wall reduction for thin shells shouldbe less than that for thicker shells. This is toprevent over rolling which could cause adjacenttube seats to leak. Since the stub wall itselfcannot be measured after it is rolled in its seat,the only alternative is to calculate the increasein the stub ID that is necessary to prove that thewall has in fact been reduced by the requiredpercentage. This depends upon the tube seatID (hole diameter), tube stub OD, the clearancebetween these two and also the stub wall. Anexample of this conversion for a 2 ½" OD by0.150-inch wall tube stub for a 10% wall reductionis as follows

MeasureHold Dia

= 2.531

MeasureStub OD

= 2.500 / 0.031 Clearance

MeasureStub ID

= 2.200

Clearance = 0.031 / 2,231 Stub ID @Contact

StubID @Contact

= 2.231

10% of0.150 x2

= 0.030 / 2.261 Stub ID afterexpanding

Plug all internal counter bored holes in the fieldwith the cylindrical plug when the tube is still inthe seat. Some counter bores may be shallowenough that the tube ends are exposed sufficientlyto permit seal welding to a tapered plug. SeeFigure 2. If the tube seat is leaking, then the tubemust either be seal welded to the drum shell or thecounter bore can be plugged with the cylindricalplug and seal welded per Figures 3 and 4. It

Section D 117


may be necessary to machine the tube ends backin order to provide a seat for the cylindrical pluginstallation. See Figures 3 and 4.

Figure 5 shows the details of this cylindrical plugand gives instruction for the specific plug sizedesired.

Tapered plugs are used to plug existing tubeswhere it is not practical to remove the tube from itsseat and there is no internal counter bore. Theseplugs must be tailor made for each tube diameterand tube wall thickness. Figure 6 shows thedetails of this tapered plug and give instructionsfor a plug to fit tube diameters from 1-3/4" through4 ½" OD and any wall thickness. Figure 7 showsthe arrangement of the tapered plug seal weldedto the tube.

The plugs and seal welds described above aredesigned for the boiler pressure to be on the head(seal weld side) of the plug only. The ¾ inchdiameter by 1/8-inch thick button weld on the plugis to eliminate leakage through the “piping” whichcan occur at the center of some bar stock.

Figure 8 shows a tube seal welded to the shell.This arrangement may be used when the tubeseat is leaking and it is not practical to replace orremove the tube and use a rolled stub and plug.

Economizer headers and superheater headersmay be plugged as shown in Figure 9 & 10where external access is available and theconditions shown on the figures are met. If thoseconditions cannot be satisfied, tube replacementis recommended. In these two figures, thepressure is on the internal end of the plug and theexternal strength weld restrains the plug.

Plugged tubes that are below the horizontalcenterline of the shell will not drain. Therefore,after chemical cleaning it is necessary that theplug to be removed and the stub swabbed out toremove the chemicals in these stubs. The plugcan then be welded back in or in some cases itwill have been destroyed in the removal processand anew one will have to be installed. Caremust be taken in the plug removal process to notdamage or thin the tube stubs wall.

Replacement of Sections of Tubes

Experienced personnel must do the replacementof a section of failed tube. The length of thereplaced section should be a minimum of 12inches. Usual practice is to cut out the defectivesection with an oxyacetylene torch, but it ispreferable to use a saw or wafer disc. Care mustbe taken to prevent slag from entering the tube.

The ends are prepared for welding by grinding orwith special tools.

The root pass of the joint should be depositedwith the gas tungsten arc process. A 3/32-inchdiameter shielded metal arc-welding electrode isrecommended for the remainder of the joint. Thewelding parameters for tubes may be obtainedfrom qualified Welding Procedures.

Removing Tubes From Drums, Headers &Tube Plates

The removal of tubes from their tube seats mustbe done very carefully to prevent damage to thetube seats. If the tube seat is damaged, it maybe impossible to ever roll another tube in andmake a tight seal. Gouging of the tube seat couldalso affect the ligaments between tube holes andintegrity of the shell. Tubes can be removed fromtheir seats without seat damage if the followingprocedures are carefully followed.

With light- gage tubes, it is often possible to coldcrimp the tube end to loosen it in its seat, thendrive or "jack" the tube out. When the tubes aretoo heavy for cold crimping, the two-stage heatingmethod may be used. Heat is applied to the insideof the tube end with a torch. Heat is first appliedfor a short period - not long enough for it to betransferred to the tube sheet.

When the tube end cools, the joint will haveloosened enough so that the second heat willnot be transferred readily to the tube sheet.The tube end can then be heated sufficiently forcrimping and the tube can be pushed out of itsseat. If neither of these methods is applicable,the following methods may be employed.

To remove light tube tubs, it is advisable to cutgrooves about 3/4 inch apart with a round nosechisel. When the tongue (the metal between thetwo grooves) is knocked free, the tube can becollapsed and removed.

To remove heavy gage tubes, the type of groovingtool shown in figure 12 is used to prepare thetongues without damage to the tube seat. It isused with a pneumatic hammer, but it is necessarythat the tool be suited to the tube thickness sothat it will cut the grooves as deep as possibleand yet leave a minimum thickness of metal overthe tube seat. In very heavy gage tubes, a thirdgroove is often cut, as nearly opposite the tongueas possible, so that less heavy pounding will berequired to collapse the stub. These latter twomethods require that the flare on the end of thetube be crimped straight before starting, to cut thegrooves for collapsing the tube. Of course, the

Section D 118


seal weld around the end of any tube must beground or machined off before attempting to cutthe grooves for collapsing the tube. This mustbe done carefully to prevent damage to the drumshell.

Attached Figures 2 to 10

Figure 8

Section D 119


Figure 9

Section D 120


Figure 10

Section D 121


Figure 11

Section D 122


Figure 12

Section D 123


Figure 13

Figure 14

Section D 124


Figure 15

Section D 125


Figure 16

Section D 126


6 Failure Reporting Format

Enclosed is a format for reporting of failure ofequipment etc.

The enclosed formats are exclusively for the useby O & M engineers of the client for reportingany malfunctioning or failure of the boiler pressureparts and its auxiliaries. Most of the boilers atsite need to be investigated with the help of pasexperience and guidance from the O & M. TheO & M, in turn, required precise and systematicinformation on which the failure analysis will haveto be based.

TBW request the boiler users to report to TBWany problems that they may come across duringroutine O & M of the plant, immediately onoccurrence.

It is suggested that enclosed formats be used forthis purpose and help provide better and quickerservices for trouble shooting.

There may be cases when problems arisingduring the O & M are resolved on temporaryor permanent basis by the O & M engineersand there may not be any immediate need forservice of TBW or OEM. Even in such cases it isthe request of TBW with the enclosed reportingformats be filled in and faxed over to TBW, Pune.

This will go a long way to generate a data bankon the auxiliary equipments and come out withimprovement rather for the final users.

Customer Feed Back Form

CUSTOMER DETAILS:

Company Name

Communication Address

Telephone Number

Fax Number

E-Mail Address

Contact Person

Other Details (If Any)

Boiler Details:

Boiler Number :

Date of Commissioning

Boiler Capacity – MCR

Steam Pressure

Steam Temperature

Fuel Fired

Feed Back Details: Equipment Details:

SL.NO PROBLEM DETAILS OBSERVATIONSCORRECTIVEACTIONS TAKEN

COMMENTS /RECOMMENDATIONS

OtherInformations :

Expectationsfrom TBW :

Reply Awaited /Service EngineerVisit :

Signature &Date:

Section D 127


7 Water Chemistry

Introduction

The natural water contains solid, liquid andgaseous impurities and therefore, this cannot beused for the generation of steam in the boilers.The impurities present in the water should beremoved before its use for steam generation.The necessity for reducing the corrosive natureand quantity of dissolved and suspended solidsin feed water has become increasingly importantwith the advent of high pressure, critical andsupercritical boilers.

The impurities present in the feed water areclassified as given below

1. Un dissolved and suspended solid materials.

2. Dissolved salts and minerals.

3. Dissolved gases.

4. Other materials (a soil, acid) either in mixedand unmixed forms.

7.1 Undissolved and Suspended SolidMaterials

A) Turbidity and Sediment:

Turbidity in the water is suspended insolublematter including coarse particles (mud, sedimentsand etc,) that settle rapidly. Amounts rangesfrom almost zero in most ground waters and60,000 ppm. in muddy and turbulent river water.The turbidity of feed water should not exceed5 ppm. These materials can be removed bysettling coagulation and filtration. Their presenceis undesirable because heating or evaporationproduces hard stony scale deposits on theheating surface and clog fluid system. Both areobjectionable as they cause damage to the boilersystem. A standard of measurement of hardnessis taken as being the amount of calcium carbonate(CaCO3) in the water and is referred to in part permillion (ppm) or grains per gallon (grain/gallon) X17.1 = ppm.

B) Sodium and Potassium Salts:

These are extremely soluble in water and donot deposit unless highly concentrated. Theirpresence is troublesome as they are alkaline innature and accelerate the corrosion.

C) Chlorides:

Majority of the chloride causes increasedcorrosive action of water.

D) Iron:

Most common soluble iron in water is ferrousbicarbonate. The water containing ferrousbicarbonate deposits becomes yellowish andreddish sediment of ferric hydroxide if exposedto air. Majority of ground surface water containsless than 5 ppm but 0.3 ppm, can create troublein the feed water system by soft scale formationand accelerating the corrosion.

E) Manganese:

It also occurs in similar form as iron and it is alsoequally troublesome.

F) Silica:

Most natural water contains silica ranging from 1to 100 ppm. Its presence is highly objectionableas it forms very hard scale in boilers and formsinsoluble deposits on turbine blades. In modernhigh-pressure boilers its presence is reduced aslow as 10-50 ppm.

G) Microbiological Growths:

Various growths occur in surface water (lakeand river). The microorganisms include diatons,molds, bacterial slimes, algae; manganese andsulfate reducing bacteria and many others. Thesecan cause coating on heat exchanger and clogthe flow passages and reduce the heat transferrates.

H) Color:

Surface waters from swampy areas becomehighly colored due to decaying vegetation. Colorof feed water is objectionable as it causes foamingin boilers and may interfere by chlorinating ofabsorption by activated carbon.

7.2 Dissolved Salts and Minerals

A) Calcium And Magnesium Salts:

The calcium and magnesium salts present in thewater in the form of carbonates, bicarbonates,sulfates and chlorides. The presence of thesesalts is recognized by the hardness of the water(hardness of water is tested by soap test). Thehardness of water is classified as temporary andpermanent hardness. The temporary hardnessis caused by the bicarbonates of calcium andmagnesium and can be removed by boiling. Theboiling converts the soluble bicarbonates intoless soluble carbonates, which can be removedby simple blow-down method. The presenceof chlorides, sulfates and nitrates of calcium

Section D 128


cause the permanent hardness of the water andmagnesium and they cannot be removed just byboiling because they form a hard scale on heatingsurfaces.

7.3 Dissolved Gases

A) Oxygen:

It presents in surface water in dissolved form withvariable percentage depending upon the watertemperature and other solid contents in water. Itspresence is highly objectionable, as it is corrosiveto iron, zinc, brass and other metals. It causescorrosion and pitting of water lines, boilers andheat exchangers. Its effect is further acceleratedat high temperature.

B) Carbon Dioxide:

The river water contains 50 ppm & well watercontains 2-50 ppm of CO2. It also helps toaccelerate the corrosive action of oxygen.

The other gases are H2S, CH4, N2 and manyothers but their percentage are negligibleTherefore their effects are not discussed here.

7.4 Other Materials

A) Free Mineral Acid:

Usually present as sulfuric or hydrochloric acidand causes corrosion. The presence is requiredby neutralization with alkalis.

B) Oil:

Generally the lubricating oil is carried with steaminto the condenser & thorough the feed system tothe boiler. It causes sludge, scale & foaming inboilers. Strainers and baffle separators generallyremove it.

The effects of all the impurities present in thewater are the scale formation on the differentparts of the boiler system and corrosion. Thescale formation reduces the heat transfer ratesand clogs the flow passage and endangers thelife of the equipment by increasing the tempabove the safe limit. The corrosion phenomenonreduces the life of the plant rapidly. Therefore itis absolutely necessary to reduce the impuritiesbelow a safe limit for the proper working of thepower plant.

7.5 pH Value of the Water and itsImportance

The pH value of the feed water plays veryimportant controlling the corrosion. pH is a

number denoting the degree of acidity or alkalinityof a substance. It does not indicate the quantityof acid or alkali in a solution as found by filtrationmethod. It is derived by measuring the amount ofhydrogen ion (H+) in grams per liter of solution.The greater the amount of hydrogen ions presentin solution its acid reaction becomes stronger.Therefore, pure water is being neutral solution,any solution producing more hydrogen ion thanpure water will be acidic and degree is governedby difference and other solution producing lesshydrogen ions than pure water will be alkaline andthe degree is also governed by the difference.

The Role Of pH in Corrosion:

The role of pH in corrosion of metals is extremelyimportant. The corrosion rate of iron in theabsence of oxygen is proportional to pH up to avalue of 9.6. At this point, hydrogen gas formationand dissolving of iron practically stops. This isthe came pH produced by a saturated solution offerrous hydroxide Fe (OH) 2.

The Oxygen in the water unites with ferroushydroxide to form ferric hydroxide. This reactionlowers pH of the solution and levels to stimulatecorrosion.

Alkalinity adjustment and film formation areclosely related. The pH value of feed water shouldbe maintained greater than 9.6 to reduce thecorrosion effects caused by the reason mentionedabove. The required alkalinity of feed water isadjusted by adding soda ash caustic soda ortrisodium phosphate. The calcium hardness,alkalinity and pH are inter-related variables inscale control. Calcium carbonate is one of themost troublesome deposits responsible for scaleformation.

7.6 Effects of Impurities

The major troubles caused by the feeding ofwater of undesirable quality are scale formation,corrosion, foaming, caustic embrittlement,carry-over and priming. The details describedbelow: -

1. Scale Formation

Feed water containing a group of impurities indissolved and suspended form flows into theBoiler for continuos generation of Steam. Withconversion of water into steam in Boiler, solidsare left behind to concentrate the remainingwater. The scale formation tendency increaseswith the increase in temperature of feed water.Because, the solubility of some salts (as calciumsulphite) decreases with the increase in feedwater temperature. Calcium sulphite has solubility

Section D 129


of 3200 ppm. at 15 Deg. C and it reduces to 55ppm. at 230 Deg. C and 27 ppm. At 320 Deg. C.

Scale formation takes place mainly due to saltsof calcium and magnesium. Sometimes, it iscemented into a hard mass by Silica. Among all,calcium is the principal offender and particularly,Calcium sulphate, magnesium sulphate and otherChlorides are sufficiently soluble in water and arenot much troublesome. Sodium salts are highlysoluble in water and are non-scale forming.

The scale formation takes place mainly in feedwater piping and Boiler Tubes. Its first effect onthe piping system is to choke the flow of water byreducing the flow area and increases the pressurerequired to maintain the water delivery. Anothereffect of scale formation is to reduce the transferof heat form the hot gases to water. Real dangersof the scale formation exist in radiant heat zonewhere boiler tubes are directly exposed to thecombustion. The scale formation retards the flowof heat and metal temperature increases. Even athin layer of scale in high heat zone can over-heatthe metal enough to rupture the tubes. The metaltubes weakened due to over-heating yield topressure providing a protrusion known as bag.Such bag provides a pocket for the accumulationof sludge and scale, which eventually causesfailure. The over-heating of metal causes layer ofmetal to separate and form a blister.

2. Corrosion

The corrosion is eating away process of boilermetal. It causes deterioration & failure of theequipment, eventually this cause for major repairsor expensive shut -downs or replacements.

The corrosion of boilers, economizers, feedwater heaters & piping is caused by an acid orlow PH in addition to the presence of dissolvedoxygen & carbon dioxide in the boiler feed water.The presence of oxygen is mostly responsiblefor corrosion among all other factors. Thepermissible limit of oxygen content varies with theacidity of water. Generally it should not shouldexceed 0.5 cc per liter .O2 generally entersinto closed system through make up condenserleakage and condensate pump packing.

CO2 is next to O2, which is responsible forcorrosion. The CO2 comes out of bicarbonateson heating and combines with water to form weakacids known as carbonic acid. This acid slowlyreacts with iron and other metals to form theirbicarbonates. The newly formed bicarbonates ofmetals decompose by heat once more and CO2 isagain liberated. This gas again unites with water

to form carbonic acid and the cycle is repeated.Adding alkali solution to neutralize acids inwater and raise the PH value can minimize thecorrosion. The effect of CO2 is minimized by theaddition of ammonia or neutralizing the amines inwater. This is necessary because CO2 lowers thePH of the boiler feed water and dissolved solidsto leave the boiler.

The priming is a violent discharge of water withsteam from the boiler. It can be compared to thepumping of water that frequently accompaniesrapid heating in a open vessel. In priming thewater level in the boiler undergoes rapid andgreat changes and there are violent dischargesof bursting bubbles. Therefore ‘sludge’ of boilerwater is thrown over with the steam.

The priming is caused due to improper boilerdesign, improper method of firing, overloading,sudden load changing or a combination of thesefactors. The priming effect is reduced by installingsteam purifier, lowering water level in the boilerand maintains constant load on boilers.

The foaming is the formation of small andstable bubbles throughout the boiler water. Thehigh percentage of dissolved solids, excessivealkalinity and presence of oil in water areresponsible for foaming.

Boiler water solids are also carried over in themoisture mixed with steam even when there isno indication of either priming or foaming. Thisis known as ‘carry-over’. The carry-over of boilerwater solids is partly a mechanical and partly achemical problem. The amount of suspendedsolids and alkalinity in the boiler water is alsoimportant in addition to other reasons like boilerdesign, high water level, and overloading andfluctuating loads on boiler.

3. Caustic Embrittlement

The caustic embrittlement is the weakening ofboiler Steel as a result of inner crystalline cracks.This is caused by long exposure of boiler steel tocombination of stress and highly alkaline water.

The course of embrittlement takes place underfollowing condition:

a) When boiler water contains free hydroxide,alkalinity and some silica. It has been alwaysfound that the feed water was high in sodiumbicarbonate, which broke down into sodiumcarbonate in the boiler and partially hydralizedas shown by the following reaction in case ofembrittlement.

Section D 130


Na2CO3 + HOH = CO2 + 2 NaOH

b) Slow leakage of boiler water through a joint orseam.

c) Boiler metal is highly stressed at the point ofleakage. This may be caused by faulty design andexpansion etc.

The prevention of caustic embrittlement consistsof reducing the causticity or adding inhibitingagents to the feed water. The most practicalmethod of preventing caustic embrittlement is toregulate the chemical composition of the boilerwater. The obvious solution to embrittlement isto eliminate all free NaOH from feed water byaddition of Phosphates.

8 Feed & Boiler Water Conditioning

1. Introduction

The successful use of boiler is dependent onproper water conditioning and treatment. Thequality of water must have accurate for troublefree operation of boiler.

The water as available to industry is not suitablefor boiler use. A complete pre-treatment andinternal chemical treatment is necessary to makeraw water suitable for boiler feed.

The objective of the water treatment is:

• Eliminate scaling - deposition in boiler whichcause tube over heating leading to accidents.

• Control corrosion of boiler system, which causefailure of boiler tubes, leading to unscheduledshutdowns.

• Reduce carry over of water with steam, which isthe cause of deposition on super heater/turbineblades, leading to the expensive failures.

• To maintain peak boiler efficiency by keepingcomplete boiler water system clean.

In order to meet above objectives, it is necessaryto maintain certain chemical conditions in boiler,condense and feed water systems. A brief reviewof important factors is given in this section to assistthose taking charges of new boiler equipment. It isnot possible to cover the subject fully, there fore, itis recommended that the care and control of waterquality be entrusted to water treatment specialist.

2. Need for Water Treatment

A. Corrossive Control

Water is corrosive to boiler metal. Typicallycorrosion due to water will reduce thickness oftube @ 1 mm/year. Thus the life and safety of

boiler entirely depends on the rate of corrosionof boiler metal. In order to protect boiler fromcorrosion, pre-treatment is done to removeexcessive corrosion ions like chloride, sulphateetc. However, further chemical conditioning isrequired to protect boiler and auxiliary systemsfrom corrosion.

Tri sodium phosphate, caustic, ammonia andamines are used as corrosion inhibitors. Thesechemicals form a protective film over metalsurface and reduce corrosion. It is necessaryto maintain prescribed concentration of thesechemicals in boiler water systems continuously.

B. Oxygen Corrosion Inhibitor:

Oxygen is present in dissolved form in water.At high temperature, oxygen reacts with metalto cause pitting corrosion. Thus prevention ofoxygen lead to pin holes in economizer, steamdrums and steam tubes.

Most of the oxygen is removed externally bydeaerator and preheating of feed water. However,traces of residual oxygen must be removed bychemical conditioning.

Sodium sulfite, hydrazine and amines arerecommended for oxygen removal. Thesechemicals react with residual oxygen makingit inactive and protect metal against pittingcorrosion. Catalyzed oxygen scavengers areused for quick reaction.

C. Scale / Deposit Control:

Raw water contains dissolved solids, hardnesssalts and suspended matters.

External treatment is used to remove suchimpurities.

• Clarification - To remove suspended matters.

• Filtration - To remove residual turbidity

• Softening - To remove hardness salts

Dealkaliser - To remove hardness salts andexcessive alkalinity

• Demineralization - To remove residual saltsand silica

• Mixed bed - To remove residual salts and silicafrom DM water.

A combination of above equipments are used toremove undesirable impurities in raw water.

Scale Control

Hardness salts in feed water cause formation inboiler. Under temperature and pressure inside theboiler and due to concentration, hardness salts

Section D 131


precipitate in tubes as calcium carbonate, calciumsulphate and Ca/Mg silicate scales.

External treatment like softening,demineralization or de-alkalisation removes mostof the hardness salts from boiler feed water.However, malfunctioning of this equipment,occasional bypassing of the softener/DM plant orcontamination of condensate or feed water withraw water often led to ingress of hardness in theboiler.

All hardness salt precipitate inside boiler leadingto hard scale formation on tubes. Such scalehas lower conductivity causing increase in metaltemperature, leading to bursting of tubes inextreme conditions.

Therefore, inspire of elaborate external treatment,internal chemical conditioning is alwaysrecommended as additional safety. Followingchemical methods are used for internal treatment.

Phosphate Conditioning

Trisodium phosphate is commonly used.Hardness salts react with trisodium phosphateto form calcium phosphate precipitate. Thisprecipitate above pH of 9.5 colloidal in natureand therefore do not allow for form hard scaleof carbonate and silicates. The precipitatedhardness salts are then removed through blowdown as sludge and boiler tubes are kept scalefree.

Trisodium phosphate, apart from actingas hardness conditioning agent, also is agood corrosion inhibitor. The recommendedconcentration in boiler water is given in Table -1

Note 1 : TSP will act as hardness conditioner,only when boiler pH is above 9.5 . Below 9.5pH TSP may cause hard scale formation of Ca3(PO)2. Therefore, coordinated or congruentphosphate treatment is recommended. The watertreatment experts can advise you right treatmentafter studying your water quality and operationconditions.

Thermax Chemicals can provide services forarriving at right chemical treatment for your boiler.

Chelant- Polymer treatment:

Hardness scales do not precipitate in presence ofchelant like NTA/EDTA The chelant treatment isrecommended when hardness ingress in boiler isexperienced regularly.

Excessive chelant dosing causecorrosion of boilerHence balanced chelant program asrecommended by experts should beused.

Organic polymer conditioners are used toprevent hardness scales. Such organic polymerdisperse scale forming compounds like CaCO3& Ca(PO4)2 in colloidal form facilitating theirremoval through blow down. Polymer andcopolymer of acrylic, methacrylic, styrene maleicacrylics are commonly used. Most of the polymersare proprietary in nature and therefore dosage isbest recommended by manufacturer.

D. Fouling Control

Suspended matter, oil/grease /oxygen & ironsalts commonly cause fouling inside the boiler.Most of the suspended matter and iron salts areremoved by external treatment. However due tomfg. of these equipment, contamination throughcondensate and concentration in boiler causefouling of boiler tubes.

Similar to hardness scales, such foulants arepoor conductor of heat. Thus fouling causesoverheating of tubes.

Fouling can best be avoided by maintaining qualityof feed water as per norms. In case of upsetsor occasional contamination, polymeric disersenthelp to prevent fouling due to turbidity and organicmatter. Iron is picked up mostly in condensatesystem due to corrosion of condensate line. Insuch case, condensate corrosion inhibitor likeammonia cyclohexylamine and filming amine isrecommended.

E. Turbine / Superheater Deposition Control:

The solids in boiler feed water get concentratedin boiler. The concentration of solids in boiler isdecided blowdown and feed water quality. Thecarryover of boiler water with steam depends on;

Mechanical Factors:

• Boiler load - Higher the load, lower is the steampurity

• Water level in boiler - Higher the water level indrum, lower is steam purity.

• Load Variation - Sudden increase in loadreduce steam purity for short time.

Section D 132


• Separation efficiency - Higher efficiency, betteris steam purity.

Chemical Factors:

• TDS - Higher TDS in boiler, lower is steampurity.

• Total Alkalinity - Higher alkalinity as % of TDSlower is steam purity

• Organics - Higher the organic contamination,lower is steam purity.

• Foaming - Higher the foaming character ofwater, Lower is steam purity.

The water carried over with steam due toabove reasons is exactly similar in quality toblow-down or boiler water. In superheater or inturbines, water evaporates, leaving dissolved andsuspended matter as scales or deposits.

Thus severity of scaling and fouling of superheaterand turbine depends on boiler water quality andsteam purity.

Maintaining boiler water quality as per norms andmaximum steam purity is the only way to preventdeposition due to carryover of water with steam.Antifoam agents help to some extend to improvesteam purity in case of excessive in boiler.

F. Silica Deposit Control:

Silica is volatile under high temperatureand pressure inside boiler. In turbines, theevaporated silica precipitates during pressureand temperature reduction and form hard scales.

Maximum allowable concentration of silicadepends on water analysis. Expert’s best decidethe maximum permissible concentration afterstriding the operating parameters.

G. Condensate Corrosion Control:

The carbon dioxide is present in boiler feed waterin dissolved and combined from as carbonate.Under boiler pressure and temperature it isliberated and carried over with steam as CO2gas. This gas re dissolves in steam condensateto form carbonic acid.

CO2 + H2O = H2CO3

H. Maintenance of Peak Efficiency:

Corrosion, scaling, fouling carryover andcondensate corrosion can cause unscheduledshutdown, accidents and deterioration of systemefficiency.Therefore for trouble free operationand maintenance peak operation efficiency,a combination of various internal chemicaltreatments is essential along with a good controlover boiler water quality.

Maintaining boiler water quality by usingcommodity chemicals likes TSP, Hydrazine, andSodium sulfite. However, it is recommendedthat the care and control of water chemistry beentrusted to specialist.

Section D 133


Section E

This section holds the Lubrication Schedule,Spare Part List & Curves for HRSG.

Lubrication Schedule

Lubrication Schedule

Spare Part List

Spare part list

Curves

Cold start up Curve - HP Section.pdf

Hot start up Curve - HP Section.pdf

Warm start up Curve - HP Section.pdf

Section E 134

./O & M Manual.pdf.ditaLinks/Lubrication Schedule (PH 0401_02).pdf

./O & M Manual.pdf.ditaLinks/spare part list.pdf

./O & M Manual.pdf.ditaLinks/Cold start up Curve - HP Section.pdf

./O & M Manual.pdf.ditaLinks/Hot start up Curve - HP Section.pdf

./O & M Manual.pdf.ditaLinks/Warm Start up Curve - HP Section.pdf


Volume 2 — Drawings


♦ List of Drawings

List of Drawings

01. G.A. of HRSG_D11-0HR-10102_3.pdf

02. Pressure Parts Assly Elevation & Sectional Views_D11-0HR-10513_0.pdf

03. Pressure Part Assly Showing Down Comer, HP & RH Attemp._D11-0HR-10514_0.pdf

04. Pressure Parts Assly for IP Economiser_D11-1HR-70558_0.pdf

05. P & ID for HP Section_D12-1HR-7970P_3.pdf

06. P & ID for IP Section_D12-1HR-7971P_4.pdf

07. P & ID for LP & CPH Section_D12-1HR-7972P_4.pdf

08. P & ID for Gas Path_D12-1HR-7973P_3.pdf

09. P & ID for Drain,Vent & Blowdown system_D12-0HR-4496P_5.pdf

10. HP Steam Drum_P21-0HR-10693_3.pdf

11. Steam Purifier Assly_P21-1HR-71575_0.pdf

12. I.P. Steam Drum_P25-0HR-10792_2.pdf

13. Steam Purifier Assly for IP Steam Drum_P25-1HR-72514_0.pdf

14. LP Steam Drum_PF5-0HR-10985_2.pdf

15. Steam Purifier Assly for LP Steam Drum_PF5-1HR-73637_0.pdf

16. LP Superheater Assly_PF1-1HR-69636_1.pdf

17. LP Evaporator Assly_PF2-1HR-69634_1.pdf

18. Condensate Preheater Assly_PF4-0HR-10365_1.pdf

19.HP Superheater -1,2 & 3 Assly_PG1-0HR-10762_1.pdf

20. Assly & Details of HP Evaporator_PG2-0HR-10657_1.pdf

21. Assly & Details of HP Eco-1A, 1B & Eco.2_PG3-0HR-10450_1.pdf

22. H.P. Economiser -3 Assly_PG3-0HR-10449_0.pdf

23. IP Superheater Assly_PH1-1HR-69759_1.pdf

24. Assly & Details of I.P. Economiser_PH3-1HR-67149_0.pdf

25. Assly & Details of IP Evaporator_PH2-1HR-71022_1.pdf

26. Arrangement of Pressure Part Supports_PI1-0HR-11151_1.pdf

27. Assly & Details of Reheater (RH1 & RH2)_PQ1-0HR-11006_1.pdf

28. Assly & Details of CBD Tank_W31-1HR-72751_1.pdf

Volume 2 — Drawings 135

./O & M Manual.pdf.ditaLinks/01. G.A. of HRSG_D11-0HR-10102_3.pdf

./O & M Manual.pdf.ditaLinks/02. Pressure Parts Assly Elevation & Sectional Views_D11-0HR-10513_0.pdf

./O & M Manual.pdf.ditaLinks/03. Pressure Part Assly Showing Down Comer, HP & RH Attemp._D11-0HR-10514_0.pdf

./O & M Manual.pdf.ditaLinks/04. Pressure Parts Assly for IP Economiser_D11-1HR-70558_0.pdf

./O & M Manual.pdf.ditaLinks/05. P & ID for HP Section_D12-1HR-7970P_3.pdf

./O & M Manual.pdf.ditaLinks/06. P & ID for IP Section_D12-1HR-7971P_5.pdf

./O & M Manual.pdf.ditaLinks/07. P & ID for LP & CPH Section_D12-1HR-7972P_5.pdf

./O & M Manual.pdf.ditaLinks/08. P & ID for Gas Path_D12-1HR-7973P_3.pdf

./O & M Manual.pdf.ditaLinks/09. P & ID for Drain,Vent & Blowdown system_D12-0HR-4496P_6.pdf

./O & M Manual.pdf.ditaLinks/10. HP Steam Drum_P21-0HR-10693_3.pdf

./O & M Manual.pdf.ditaLinks/11. Steam Purifier Assly_P21-1HR-71575_0.pdf

./O & M Manual.pdf.ditaLinks/12. I.P. Steam Drum_P25-0HR-10792_2.pdf

./O & M Manual.pdf.ditaLinks/13. Steam Purifier Assly for IP Steam Drum_P25-1HR-72514_0.pdf

./O & M Manual.pdf.ditaLinks/14. LP Steam Drum_PF5-0HR-10985_2.pdf

./O & M Manual.pdf.ditaLinks/15. Steam Purifier Assly for LP Steam Drum_PF5-1HR-73637_0.pdf

./O & M Manual.pdf.ditaLinks/16. LP Superheater Assly_PF1-1HR-69636_1.pdf

./O & M Manual.pdf.ditaLinks/17. LP Evaporator Assly_PF2-1HR-69634_1.pdf

./O & M Manual.pdf.ditaLinks/18. Condensate Preheater Assly_PF4-0HR-10365_1.pdf

./O & M Manual.pdf.ditaLinks/19.HP Superheater -1,2 & 3 Assly_PG1-0HR-10762_1.pdf

./O & M Manual.pdf.ditaLinks/20. Assly & Details of HP Evaporator_PG2-0HR-10657_1.pdf

./O & M Manual.pdf.ditaLinks/21. Assly & Details of HP Eco-1A, 1B & Eco.2_PG3-0HR-10450_1.pdf

./O & M Manual.pdf.ditaLinks/22. H.P. Economiser -3 Assly_PG3-0HR-10449_0.pdf

./O & M Manual.pdf.ditaLinks/23. IP Superheater Assly_PH1-1HR-69759_1.pdf

./O & M Manual.pdf.ditaLinks/24. Assly & Details of I.P. Economiser_PH3-1HR-67149_0.pdf

./O & M Manual.pdf.ditaLinks/25. Assly & Details of IP Evaporator_PH2-1HR-71022_1.pdf

./O & M Manual.pdf.ditaLinks/26. Arrangement of Pressure Part Supports_PI1-0HR-11151_1.pdf

./O & M Manual.pdf.ditaLinks/27. Assly & Details of Reheater (RH1 & RH2)_PQ1-0HR-11006_1.pdf

./O & M Manual.pdf.ditaLinks/28. Assly & Details of CBD Tank_W31-1HR-72751_1.pdf


Volume 3 — E & I Specifications


♦ Section 1♦ Section 2♦ Section 3♦ Section 4♦ Section 5♦ Section 6♦ Section 7♦ Section 8♦ Section 9♦ Section 10♦ Section 11♦ Section 12♦ Section 13

Volume 3 — E & I Specifications 136


Section 1

1. Instrument Hook Up Diagram.pdf

Section 2

2.1 Control Schematic Diagram.pdf

2.2 Control Scheme Narrative.pdf

Section 3

3. DCS IO List.pdf

Section 4

4. Logic Diagram for drives.pdf

Section 5

5.1 EMS1.pdf

5.2 Electrical load list.pdf

Section 6

6. Specification for Motorised Actuator.pdf

Section 7

7. Local Control Station.pdf

Section 8

8. Junction Box and Cable Schedule.pdf

Section 9

9. Instrument canopy.pdf

Section 10

10.1 Transmitter.pdf

10.2 Gauges and Switches.pdf

10.3 Valves and actuators.pdf

10.4 Sensors.pdf

10.5 CEMS.pdf

Section 11

11. EMS2 for recirculation pump.pdf


./O & M Manual.pdf.ditaLinks/1. Instrument Hook Up Diagram.pdf

./O & M Manual.pdf.ditaLinks/2.1 Control Schematic Diagram.pdf

./O & M Manual.pdf.ditaLinks/2.2 Control Scheme Narrative.pdf

./O & M Manual.pdf.ditaLinks/3. DCS IO List.pdf

./O & M Manual.pdf.ditaLinks/4. Logic Diagram for drives.pdf

./O & M Manual.pdf.ditaLinks/5.1 EMS1.pdf

./O & M Manual.pdf.ditaLinks/5.2 Electrical load list.pdf

./O & M Manual.pdf.ditaLinks/6. Specification for Motorised Actuator.pdf

./O & M Manual.pdf.ditaLinks/7. Local Control Station.pdf

./O & M Manual.pdf.ditaLinks/8. Junction Box and Cable Schedule.pdf

./O & M Manual.pdf.ditaLinks/9. Instrument canopy.pdf

./O & M Manual.pdf.ditaLinks/10.1 Transmitter.pdf

./O & M Manual.pdf.ditaLinks/10.2 Gauges and Switches.pdf

./O & M Manual.pdf.ditaLinks/10.3 Valves and actuators.pdf

./O & M Manual.pdf.ditaLinks/10.4 Sensors.pdf

./O & M Manual.pdf.ditaLinks/10.5 CEMS.pdf

./O & M Manual.pdf.ditaLinks/11. EMS2 for recirculation pump.pdf


Section 12

12.1 Motorised valves.pdf

12.2 Valve Schedule.pdf

Section 13

13.1 CBD Valve for LP Drum.pdf

13.2 CBD Valve for IP Drum.pdf

13.3 CBD Valve for HP Drum.pdf


./O & M Manual.pdf.ditaLinks/12.1 Motorised valves.pdf

./O & M Manual.pdf.ditaLinks/12.2 Valve Schedule.pdf

./O & M Manual.pdf.ditaLinks/13.1 CBD Valve for LP Drum.pdf

./O & M Manual.pdf.ditaLinks/13.2 CBD Valve for IP Drum.pdf

./O & M Manual.pdf.ditaLinks/13.3 CBD Valve for HP Drum.pdf


Volume 4 — Vendor Manuals


♦ Section 01♦ Section 02♦ Section 03♦ Section 04♦ Section 05♦ Section 06♦ Section 07♦ Section 08♦ Section 09♦ Section 10

Volume 4 — Vendor Manuals 139


Section 01

Recirculation Pump - Sulzer

O & M Manual

Pump Manual

Datasheet & Curves

Pump Datasheet & Curves

Drawings

Drawings

Section 02

Dosing System - Metapow

O & M Manual

VK Pump Manual_Model PR10

VK Pump Manual_Model PR15–20

Drawings

1. HP Dosing for HP Drum Drawing

2. HP Dosing for IP Drum Drawing

3. LP Dosing for LP Drum Drawing

Test Certificates

1. HP Dosing for HP Drum Certificates

2. HP Dosing for IP Drum Certificates

3. LP Dosing for LP Drum Certificates

Section 03

HP Drum Level Gauge Glass – Hi tech.

O & M Manual

HP Drum Level Gauge Manual

Drawing and Data Sheet

HP Drum Level Gauge Glass Drawing

Section 04

IP & LP Drum Transparent Level Gauge Glass - Chemtrols

O & M Manual

IP & LP Drum Transparent Level Gauge Glass Manual


IP & LP Drum Transparent Level Gauge Glass Drawing


./O & M Manual.pdf.ditaLinks/1. Recirculation Pump - Sulzer_O&M Manual.pdf

./O & M Manual.pdf.ditaLinks/2. Datasheet & Curves.pdf

./O & M Manual.pdf.ditaLinks/3. Drawings.pdf

./O & M Manual.pdf.ditaLinks/1. VK Pump - Model No PR 10.pdf

./O & M Manual.pdf.ditaLinks/2. VK Pump PR15-20.pdf

./O & M Manual.pdf.ditaLinks/3. HP Dosing for HP Drum Drawing.pdf

./O & M Manual.pdf.ditaLinks/4. HP Dosing for IP Drum Drawing.pdf

./O & M Manual.pdf.ditaLinks/5. LP Dosing for LP Drum Drawing.pdf

./O & M Manual.pdf.ditaLinks/6. HP Dosing for HP Drum Certificates.pdf

./O & M Manual.pdf.ditaLinks/7. HP Dosing for IP Drum Certificates.pdf

./O & M Manual.pdf.ditaLinks/8. LP Dosing for LP Drum Certificates.pdf

./O & M Manual.pdf.ditaLinks/1. HP Drum Level Gauge Manual.pdf

./O & M Manual.pdf.ditaLinks/2. HP Drum Level Gauge Drawing.pdf

./O & M Manual.pdf.ditaLinks/1. IP & LP Transparent Level Gauge Manual.pdf

./O & M Manual.pdf.ditaLinks/2. IP & LP Drum Transparent Level Gauge Drawing.pdf


Section 05

Blow Down Tank Reflex Level Gauge Glass - Chemtrols

O & M Manual

Blow Down Tank Reflex Level Gauge Glass Manual


Blow Down Tank Reflex Level Gauge Glass Drawing

Section 06

Stack Damper — Indira Damper

O & M Manual

Stack Damper Manual

Drawing

GA of Damper

Section 07

Spring Hanger – Pipe Support

O & M Manual

Spring Hanger Manual

Data Sheet

Z1E Support Datasheet

Z1B Support Datasheet

Section 08

Flow Nozzle — Micro Precision

Datasheet

Flow Nozzle Datasheet

Section 09

Safety Valve — Tyco Sanmar

O & M Manual

1. Installation Instuctions for SV

2. HCI SV IOM

3. HSJ SV IOM

Drawing & Data sheet

Safety Valve Data Sheet and Drawing


./O & M Manual.pdf.ditaLinks/1. BD Tank Reflex Level Gauge Manual.pdf

./O & M Manual.pdf.ditaLinks/2. BD Tank Reflex Level Gauge Datasheet_Old Lanco.pdf

./O & M Manual.pdf.ditaLinks/1. O&M for stack damper.pdf

./O & M Manual.pdf.ditaLinks/2. GA of Stack Damper.pdf

./O & M Manual.pdf.ditaLinks/1. Spring Hanger - Pipe Support.pdf

./O & M Manual.pdf.ditaLinks/2. Z1 E Support.pdf

./O & M Manual.pdf.ditaLinks/3. Z1 B Support.pdf

./O & M Manual.pdf.ditaLinks/8. Flow Nozzle - Micro Precision_Datasheet.pdf

./O & M Manual.pdf.ditaLinks/1. Installation Instuctions for SV.pdf

./O & M Manual.pdf.ditaLinks/2. HCI SV IOM.pdf

./O & M Manual.pdf.ditaLinks/3. HSJ SV IOM.pdf

./O & M Manual.pdf.ditaLinks/4. SV Datasheet & Drawing.pdf


Section 10

Relief Valve — Tyco Sanmar

O & M Manual

1. JOS_JBS_JLT RV IOM

2. JOS_JBS_JLT RV Product Range

Drawing & Data sheet

Relief Valve Datasheet & Drawing


./O & M Manual.pdf.ditaLinks/1. JOS_JBS_JLT RV IOM.pdf

./O & M Manual.pdf.ditaLinks/2. JOS_JBS_JLT RV Product Range.pdf

./O & M Manual.pdf.ditaLinks/3. RV Datasheet & Drawing.pdf


Volume 5 — Vendor Manuals


♦ Section 01♦ Section 02♦ Section 03♦ Section 04♦ Section 05♦ Section 06♦ Section 07



Section 01

1.1 Differential Pressure Transmitter (EJA) – Yokogawa

O & M Manual

Differential Pressure Transmitter (EJA) – Yokogawa_Manual

Datasheet

Differential Pressure Transmitter (EJA) Datasheet

1.2 Absolute & Gauge Pressure Transmitter (EJA) – Yokogawa

O & M Manual

Absolute & Gauge Pressure Transmitter (EJA) – Yokogawa_Manual

Datasheet

Pressure Transmitter (EJA) Datasheet

1.3 HART Protocol (EJA Series) - Yokogawa

O & M Manual

HART Protocol (EJA Series) - Yokogawa_Manual

Section 02

2.1 Temperature Transmitter (YTA Series) - Yokogawa

O & M Manual

Temperature Transmitter (YTA Series) - Yokogawa_Manual

Datasheet

Temperature Transmitter Datasheet

2.2 HART Protocol (EJA) – Yokogawa

O & M Manual

Temperature Transmitter (YTA Series) - Yokogawa_Manual

Section 03

3.1 O2 Analyser (ZR 402G) — Yokogawa

O & M Manual

O2 Analyser (ZR 402G) — Yokogawa — Manual

3.2 HART Protocol — Yokogawa

O & M Manual

HART Protocol — Yokogawa — Manual


./O & M Manual.pdf.ditaLinks/1.1 Diff. Pressure Transmitter (EJA 110A, 120A, 130A) - Yokogawa.pdf

./O & M Manual.pdf.ditaLinks/1.4 Diff. Pressure Transmitter Datasheet.pdf

./O & M Manual.pdf.ditaLinks/1.2 Pressure Transmitter (EJA 510A_530A) - Yokogawa.pdf

./O & M Manual.pdf.ditaLinks/1.5 Pressure Transmitter Datasheet.pdf

./O & M Manual.pdf.ditaLinks/1.3 HART Protocol (EJA Series) - Yokogawa.pdf

./O & M Manual.pdf.ditaLinks/2.1 Temperature Transmitter (YTA Series) - Yokogawa.pdf

./O & M Manual.pdf.ditaLinks/2.3 Temperature Transmitter Datasheet.pdf

./O & M Manual.pdf.ditaLinks/2.2 HART Protocol (YTA Series) - Yokogawa.pdf

./O & M Manual.pdf.ditaLinks/3.1 O2 Analyser (ZR402G) - Yokogawa.pdf

./O & M Manual.pdf.ditaLinks/3.2 HART Protocol - Yokogawa.pdf


Section 04

Motor for Recirculation Pump - Siemens

O & M Manual

Motor Manual

Datasheet

Motor Datasheet

Section 05

Thermocouple - Pyroelectric

O & M Manual

Thermocouple Manual_100 series



Drawing & Datasheet

Thermocouple Drawing

Section 06

Electronic Level Switch – Levelstate

O & M Manual

Electronic Level Switch Manual

Datasheet

Electronic Level Switch Drawing

Section 07

DO2 Analyser - Emerson

O & M Manual

DO2 Analyser Manual 1

DO2 Analyser Manual 2


./O & M Manual.pdf.ditaLinks/1. Motor for Recirculation Pump - Siemens_Manual.pdf

./O & M Manual.pdf.ditaLinks/2. Motor for Recirculation Pump Datasheet & Curves.pdf

./O & M Manual.pdf.ditaLinks/1. 100 series Manual.pdf



./O & M Manual.pdf.ditaLinks/4. Thermocouple Drawing.pdf

./O & M Manual.pdf.ditaLinks/1. O&M Manual.pdf

./O & M Manual.pdf.ditaLinks/2. Drawing.pdf

./O & M Manual.pdf.ditaLinks/1. DO2 Analyser Liq_Manual_51-1056.pdf

./O & M Manual.pdf.ditaLinks/2. DO2 Analyser Instruction Sheet Liq_Manual_51A-499aTrDO.pdf


Volume 6— Vendor Manuals


♦ Section 01♦ Section 02♦ Section 03♦ Section 04♦ Section 05♦ Section 06♦ Section 07♦ Section 08

Volume 6— Vendor Manuals 146


Section 01

In-Situ Stack Gas Analysers - CODEL

O & M Manual

In-Situ Stack Gas Analysers_Manual

Section 02

Process Valve – Xomox Sanmar

O & M Manual

Process Valve_Manual

Forged Gate, Globe & Check Valves_Manual

LPBB Gate, Globe & Check Valves_Manual

Stem Replacement Process

Datasheet

Process Valve Datasheet

Section 03

Motorised Valve – Xomox Sanmar

O & M Manual

Cast Steel Gate Valve

Cast Steel Globe Valve

Drawings

Forged Motorised Valve Drawings

PS Motorised Valve Drawings

LPBB Motorised Valve Drawings

Section 04

Motorised Actuator - Auma

O & M Manual

Motorised Actuator - Auma_Manual

Wiring Diagram

Section 05

Blow Down Valve - BHEL

O & M Manual

Blow Down Valve_Manual


./O & M Manual.pdf.ditaLinks/1. In-Situ Stack Gas Analysers - CODEL.pdf

./O & M Manual.pdf.ditaLinks/1. Process Valve O&M Manual - Xomox.pdf

./O & M Manual.pdf.ditaLinks/2. Process Valve_Gate, Globe, Check - Xomox.pdf

./O & M Manual.pdf.ditaLinks/3. Process Valve_Low Pressure Bolted Bonnet - Xomox.pdf

./O & M Manual.pdf.ditaLinks/4. Stem Replacement Procdure on Forged valves.pdf

./O & M Manual.pdf.ditaLinks/5. Process Valve Datasheet.pdf

./O & M Manual.pdf.ditaLinks/1. CLS 150,300,600 CAST GATE.pdf

./O & M Manual.pdf.ditaLinks/2. CLS 150,300,600 CAST GLOBE.pdf

./O & M Manual.pdf.ditaLinks/3. GA Annexure - FRG Mot.pdf

./O & M Manual.pdf.ditaLinks/4. GA Annexure - PS Mot.pdf

./O & M Manual.pdf.ditaLinks/5. GA Annexure - LPBB Mot.pdf

./O & M Manual.pdf.ditaLinks/1. Auma E Pac Actuator.pdf

./O & M Manual.pdf.ditaLinks/2. Wiring Diagram.pdf

./O & M Manual.pdf.ditaLinks/5. Blowdown Valve - BHEL.pdf


Section 06

Pressure Gauge - Bourdon

O & M Manual

Pressure Gauge Manual

Section 07

Temperature Gauge – General Instrument

O & M Manual

Temperature Gauge_Manual

Datasheet

Temperature Gauge Datasheet & Drawing

Section 08

Control Valve – Fisher

O & M Manual

HP control valve

ET & EAT CV IOM

EHD & EHT CV IOM

ED CV IOM

EWT CV IOM

YD CV IOM

657 Actuator IOM

667 Actuator IOM

667–6010–6020 Controller IOM

DVC 6000 Series IOM

Datasheet & Drawing

Control valve Datasheet & Drawing


./O & M Manual.pdf.ditaLinks/6. Pressure Gauge Manual.pdf

./O & M Manual.pdf.ditaLinks/1. Temp Gauge Manual - GIC.PDF

./O & M Manual.pdf.ditaLinks/2. Temperature Gauge Datasheet & Drawing.pdf

./O & M Manual.pdf.ditaLinks/1. HP CV.pdf

./O & M Manual.pdf.ditaLinks/2. ET CV.pdf

./O & M Manual.pdf.ditaLinks/3. EHD & EHT CV.pdf

./O & M Manual.pdf.ditaLinks/4. ED CV.pdf

./O & M Manual.pdf.ditaLinks/5. EWT CV.pdf

./O & M Manual.pdf.ditaLinks/6. YD CV.pdf

./O & M Manual.pdf.ditaLinks/7. 657 actuator.pdf

./O & M Manual.pdf.ditaLinks/8. Fisher 667 actuator.pdf

./O & M Manual.pdf.ditaLinks/9. 667-6010-6020 controller.pdf

./O & M Manual.pdf.ditaLinks/10. DVC 6000_6010 .pdf

./O & M Manual.pdf.ditaLinks/12. CV DATASHEET.pdf


Index

AAlarms and Trips .......................................... 95Automatic Controls ....................................... 53

BBOILER ANNUAL MAINTENANCE ANDOVERHAUL ............................................. 105

Boiler Emergency Safety Procedures............. 93Boiler Log Sheet ........................................... 89BOILER PRESERVATIONPROCEDURE........................................... 107

CCBD Drain Temperature Control .................... 59Charging & Operation Of CPH....................... 80Charging HP Steam to Reheater.................... 79Charging IP steam to reheat.......................... 79Chemicals for Dosing...................................... 9Condensate Pre heater (CPH)....................... 33CONTINUOUS BLOWDOWN.......................... 6Cooling of a Shutdown Boiler......................... 87CPH Recirculation Temperature Control ......... 61

DDescription of HRSG Operation ..................... 16Design Code .................................................. 4Design Specifications...................................... 2Dissolved Gases ........................................ 129Dissolved Salts and Minerals....................... 128Do’S and Don’ts For HRSG Operation ........... 87Drain & Dosing System ................................. 45Drum Level Control....................................... 53

EEffects of Impurities .................................... 129Emergency Procedures................................. 93Evaporating Heating Surface Area ................... 6Exhaust Gas Analysis ..................................... 6

FFeed & Boiler Water Conditioning ................ 131Flue Gas System.......................................... 43FORCED COOLING ..................................... 87

GGAUGE GLASS ........................................... 12

GENERAL PRINCIPAL OF WELDREPAIRS ..................................................116

HHot and Warm Start up of HRSG ................... 81HP Attemperator Control ............................... 60HP Boiler Components Description ................ 17HP Boiler Feed water Control Station............. 17HP Drum.................................................20, 28HP Economiser ............................................ 19HP Evaporator.........................................23, 31HP Main Steam line ...................................... 25HP Superheater............................................ 24HP/IP/LP Dosing System .............................. 10HRSG Cold Start Up Curve ........................... 78HRSG Emergency Trips ................................ 86HRSG Operation Walk Down Checks............. 87HRSG Shutdown .......................................... 86HRSG Start Up & Pressurisation.................... 75HRSG Start Up and Shut Down ..................... 63HRSG System Protection .............................. 51

IIP Boiler Feed water Control Station .............. 26IP Economiser.............................................. 26IP Line Back Pressure Control ....................... 61IP Main Steam line........................................ 32IP Section Components Description ............... 26IP Superheater ............................................. 31

LLevels With Respect To Center Line................. 4Log Sheet for HRSG..................................... 89LP Drum / Deaerator..................................... 35LP Drum Pressure Control ............................ 60LP Evaporator .............................................. 38LP Feed Regulating Station........................... 35LP Section Components Description .............. 33LP Superheater ............................................ 38

MMaintaining Quality Of Steam ........................ 42Material Specifications .................................... 4

NNatural Cooling............................................. 87

149


OOPERATION ................................................ 63Operational Control....................................... 39Operational Precautions For Safety ............... 95Other Materials........................................... 129

PParallel HRSG To The Plant SteamMains ......................................................... 80

pH Value of the Water and itsImportance ............................................... 129

Planned Shutdown........................................ 86Pressure Parts ............................................... 4PREVENTIVE MAINTENANCE ................... 100

RRecirculation Pump....................................... 10Recommended Boiler Water Quality ................ 7Recommended HP Feed Water Quality ............ 7RECOMMENDED MAINTENANCEPRACTICES............................................. 100

Reheaters .................................................... 32Relief Valves ................................................ 15RH1 Attemperator Control ............................. 60

SSafety in Boiler House................................... 95Safety Valves ............................................... 13SCHEDULE OF INSPECTIONSFOR CONDITION BASEDMAINTENANCE........................................ 100

SECTION OVERVIEW........................... 63, 100

Site Condition................................................. 9Stack Damper .............................................. 13Stack Temperature (CPH Bypass 3- Way)Control ....................................................... 59

Start up Vent (HP, IP & LP) Control ................ 61Steam & Water System ................................. 17

TTaking Reheater On Line............................... 79Trouble Shooting Chart ................................. 96Tube Failures ............................................... 95TUBE THICKNESS SURVEY ...................... 106

UUndissolved and Suspended SolidMaterials .................................................. 128

Utilities........................................................... 8

VValve Positions Chart For HP, IP & LPSection (Before Light Up) ............................ 66

WWater And Steam Quality Control AndMonitoring .................................................. 40

Water Chemistry......................................... 128WELDING PROCEDURESPECIFICATIONS (WPS).......................... 107

150

o & m manual

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