boiler

BOILER

INSTRUMENTATION &

CONTROLS

BOILER

INSTRUMENTATION &

CONTROLS

1. INTRODUCTION:PROCESS INSTRUMENTATION IMPLIES JUDICIOUS APPLICATION

OF CERTAIN DEVICES, WHICH SUBSTITUTE OR SUPPLEMENT THE COGNITIVE HUMAN

CHARACTERISTICS-LIKE

PERCEPTUAL, COMMUNICATIVE, INTELLECTUAL OR MANIPULATIVE-

IN ORDER TO IDENTIFY AND

QUALIFY THE VITAL PROCESS VARIABLES (PHYSICAL OR CHEMICAL)

TO ACCOMPLISH AUTOMATIC CONTROL OF THE PROCESS WITHIN SOME SPECIFIED LIMITATION.

P R I M A R Y O B J E C T I V E S O F P R I M A R Y O B J E C T I V E S O F

INSTRUMENTATIONINSTRUMENTATION TO PROVIDE:TO PROVIDE:

MEASUREMENT & CONTROL.

ONLINE QUALITY & HIGH PRODUCTIVITY.

DOCUMENTATION&REPORT GENERATION. DOCUMENTATION&REPORT GENERATION.

LONGIVITY OF THE PLANT.LONGIVITY OF THE PLANT.

04/12/23 12:51 AM BOILER CONTROLS AT "APOGEE-2002" AT BITS PILANI.

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GOOD INSTRUMENTATION MEANS

QUALITY PRODUCTION, OPTIMISED OPERATION, LONGIVITY

AND SAFETY OF THE PLANT .

WE M E A N :

TOTAL TOTAL ECONOMY ECONOMY OOF F TTHE HE PPLANTLANT.


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"INSTRUMENTATION" CONNOTES

•FACT-FINDING, •DISPLAY OF INFORMATION,•APPLICATION-ENGINEERING AND •AUTOMATIC CONTROL.

THE PROGRESS OF MEASUREMENT IS THE PROGRESS OF SCIENCE.

LIKEWISE ADVANCEMENT IN THE ART AND SCIENCE OF MEASUREMENT

SHOULD LEADADVANCEMENT OF INDUSTRIAL PROGRESS.

“BOILER INSTRUMENTATION &CONTROLS”-TOPIC OF THE DAY

BOILERS PLAY AN IMPORTANT ROLE IN POWER GENERATION

AND IN PROCESSINDUSTRIES AS HEATING MEDIUM, AS COMPARED TO ANY OTHER SOURCE AS

STEAM ENERGY COSTS LESS.STEAM ENERGY COSTS LESS.


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THE PROBLEM OF BOILER CONTROL IS ONE OF THE COORDINATING FIVE FACTORS:

STEAM PRESSURE, FEED WATER SUPPLY.

FUEL QUANTITY, COMBUSTION-AIR QUANTITY AND

REMOVAL OF WASTE GASES.


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BOILER-CONTROLS OVERVIEW

1. DRUM LEVEL 2. STEAM FLOW3. FEED WATER FLOW4. OUTLET STEAM PRESSURE5. FUEL FLOW & COMBUSTION 6. S.H STEAM TEMPERATURE7. FURNACE DRAFT 8. DEAIRATOR LEVAL9. DEAIRATOR ST. PRESSURE10.SOOT BLOW ST.PRESSURE

1. SAFETY INTERLOCKS 2. SOOT BLOW INTERLOCKS


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BOILER WATER&STEAMBOILER AIR & GAS


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AN INCREASE IN FIRING RATE OF THE BOILER, WHEN IT DROPS;

A DECREASE IN FIRING RATE,WHEN

IT INCREASES, INVOLVING

FEED WATER, FUEL & AIR.


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THREE ELEMENT DRUM LEVEL CONTROL: THE AIM OF THIS CONTROL LOOP IS TO

MAINTAIN THE DRUM LEVEL AT THE NORMAL OPERATING LEVEL OF THE BOILER DRUM. THE THREE ELEMENTS IN THIS LOOP ARE

1.DRUM LEVEL

2.STEAM FLOW3.FEED WATER FLOW and

OUTLET STEAM PRESSURE FOR

DENSITY CORRECTION TO DRUM LEVEL


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BOILER F. WATER& STEAM FLOW


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DENSITY ‘D’ CORRECTION:

Head on LP = H * Da ( Da- Water Density @30*C)

Delta p = HP – LP

=Hm (Dw-Ds) – H (Da-Ds)

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

H-Hm

Hm HP

LP

0mm WC

Dw WATER DENSITY

Ds. STEAM DENSITY

H

D elta P

Condensate Pot


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THREE ELEMENT DRUM LEVEL CONTROL: STEAM FLOW SIGNAL IS USED AS A FEED

FORWARD SIGNAL

TO TAKE CARE OF THE SHRINK & SWELL EFFECT

DRUM WATER LEVEL.

F.W. AND STEAM SQ-ROOT SIGNALS ARE LENIARIESED AND FED TO FLOW-COMPUTOR


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COMPUTED FORMULEA:COMPUTED FORMULEA:

DRUM LEVEL CONTROLLER OUTPUT+ STEAM

FLOW SIGNAL- 50 % = REMOTE SET POINT FOR

FEED WATER FLOW CONTROLLER

HENCE FEED WATER FLOW CONTROLLER IS A CASCADE CONTROLLER.

IT’S OUTPUT ACTUATES THE FEED FLOW CONTROL VALVE- F.V. TO FILL DRUM / TO MAKEUP DRUM LEVEL.


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Temperature & Pressure Compensation for any compressible fluid like steam /air.

THE EQUATION FOR COMPENSATION DONE AT FUNCTION BLOCK FX 704 IS AS GIVEN BELOW.

ACTUAL STEAM FLOW:= INDICATED STEAM FLOW X SQRT{[(P1+1.209)*(485.0+273)]/[(66.0+1)*(T1+273)]}

P1- MEASURED STEAM PRESSURE SIGNAL. T1- MEASURED TEMPERATURE SIGNAL

DESIGN PRESSURE (CONSTANT) SAY, 66.0 KG/CM2 &. DESIGN TEMPERATURE (CONSTANT) 485.0 DEG C.


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COMBUSTION CONTROL:

INCLUDES:

1. STEAM FLOW2. OUTLET STEAM PRESSURE3. O2 % IN FLUE GAS AND4. PRIMARY AIR FLOW 5. FUEL CHARGING RATE.

EXCEPTEXCEPT ‘DRUM LEVEL & FEED FLOW


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FUEL FLOW CONTROLLER


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Combustion Control


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STEAM BOILER-AIR & FUEL FLOW


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AN INCREASE IN FIRING RATE OF THE BOILER, WHEN IT DROPS;

A DECREASE IN FIRING RATE,WHEN IT INCREASES,

COMBUSTION CONTROL DOES THIS JOB OF ADJUSTING FIRING RATE BY WAY

CONTROLLING FUEL & AIR .


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THE STEAM HEADER PRESSURE SIGNAL IS FED TO THE MASTER PRESSURE CONTROLLER.

STEAM FLOW SIGNAL IS FED AS A FEED

FORWARD SIGNAL TO THE OUTPUT OF MASTER P.I. C TO COMPUTING BLOCK

WHICH ADJUSTS THE OUTPUT w.r.to STEAM FLOW SIGNAL,

WHICH IS DISTRIBUTED TO INDIVIDUAL RICE HUSK FEEDER#1 & RICE

HUSK FEEDER#2 THROUGH THEIR RESPECTIVE AUTO-MANUAL STATIONS.


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THE OUTPUT OF THESE INDIVIDUAL AUTO/MANUAL STATION ARE CONNECTED TO THE RESPECTIVE VARIABLE FREQUENCY DRIVE OF THE RISE HUSK FEEDERS TO CONTROL THE RISE HUSK FEED.

FURTHER THE OUTPUT OF STEAM ‘P.I.C’ ALSO GOES TO THE AIR-FLOW CONTROLLER AS REMOTE SETPOINT.

ON LINE O2 VALUE IS MEASURED BY ANALYSER AND O2 ‘A.I.C’ OUTPUT CORRECTS THE REMOTE SET POINT VALUE FOR AIR FLOW CONTROLLER IN COMPUTING BLOCK.


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AIR FLOW MEASURED BY USING AEROFOIL WHOSE DIFFERENTIAL PRESSURE IS SENSED BY THE AIR FLOW TRANSMITTER SQ. ROOTED IS COMPENSATED TO THE AIR TEMPERATURE AT FUNCTION BLOCK.

THE COMPENSATED AIR FLOW ACTS AS PROCESS VARIABLE TO. THE OUTPUT OF FIC POSITIONS THE FD FAN DAMPER ACTUATOR


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100%0 150%

02 %

STEAM LOAD

4

50%

2

O2 Vs STEAM FLOW CHART

65.5

4.24

4.7


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3. Steam Temperature Control.

A WELL MAINTAINED STEAM TEMPERATURE HELPS IN ITS EFFICIENT USAGE DOWN STREAM EITHER TO

DRIVE TURBINES OR AS A HEATING MEDIUM.

CONSTANT TEMPERATURE MEANS CONSTANT SPECIFIC VOLUME, THERE BY CONSTANT PRESSURE ON

TRANSMISSION OF STEAM THROUGH PIPE LINES.

THE TEMPERATURE OF STEAM IS CONTROLLED BY ATTEMPERATION I.E. BY SPRAYING FEED WATER INTO

THE STEAM AFTER THE SUPER HEATER.


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HERE S.H I STAGE ‘TIC’ ACTS AS A FEED FORWARD CONTROLLER. ‘TI’ FIRST SENSES ANY VARIATION IN TEMPERATURE AND ‘TIC’ TAKES THE CORRECTIVE ACTION.

WHATEVER DEVIATION IS PASSED ON TO, IS SENSED BY I STAGE & II STAGE ’TE’s AND II STAGE ‘TIC’ WILL TAKE THE CORRECTIVE ACTION BY CHANGING THE OUT PUT,-

- THAT GOES AS REMOTE SETPOINT TO I STAGE S.H.‘TIC’ WHICH FURTHER CORRECTS THE TEMPERATURE.


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THE TRANSFER SWITCH WHEN SELECTED, ENABLES THE OUTPUT OF T.I.C -

-TO TRACK THE SIGNAL WHEN THE S.H. OUT LET TEMP. IS < THAN THE RATED TEMPERATURE, SO AS TO AVOID TIC SIGNAL GOING >100%.

THE FEED WATER FLOW FOR ATTEMPERATION IS MEASURED & INDICATED IN ‘FI’. THE TOTALISER ‘FQ’ INDICATES THE TOTALISED FLOW.


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4. Furnace Pressure Control.

IT IS ESSENTIAL TO MAINTAIN THE BALANCE BETWEEN FURNACE PRESSURE CAUSED BY COMBUSTION AND SUCTIONAL FORCE GENERATED BY ID/ EXHAUST FAN TO TAKE THIS FLUE GAS OUT OF BOILER. THE MEASURED SIGNAL IS FED TO PRESSURE CONTROLLER.

THE OUTPUT OF CONTROLLER GOES TO THE I.D. FAN DAMPER ACTUATOR AND THE OPERATION OF ID FAN FINALLY CONTROLS THE FURNACE DRAFT.

THIS LOOP CONCERNS WITH THE SAFETY OF BOILER& THIS LOOP CONCERNS WITH THE SAFETY OF BOILER& TO PREVENT FURNACE EXPLOSION TO PREVENT FURNACE EXPLOSION OR BUCKLING BUCKLING


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THE CONTENT OF DISSOLVED OXYGEN IN FEED WATER ESCAPES DURING BOILING AND OXEDISES /RUSTS THE INNER WALLS OF BOILER TUBES AND DRUMS.

TO REMOVE THIS ‘O2’, WATER IS BOILED IN THE DEAIRATOR BEFORE FEEDING IN TO BOILER.

Deaerator Pressure & Level Control


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Deaerator Pressure & Level Control


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THE HEATING STEAM PRESSURE IS MAINTAINED BY A CONTROLLER . IT’S OUTPUT ACTS ON THE DEAERATOR PRESSURE CONTROL VALVE . .

TO MAINTAIN A CONSTANT LEVEL OF WATER INSIDE THE DEAERATOR IS A MUST FOR EJECTING OUT THE LIBERATED O2 FULLY.

A LEVEL CONTROL LOOP IS EMPLOYED USING A ‘LT’, ‘LIC’ AND ‘LCV’


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Soot Blower Pressure Control.

SOOT OR CARBON DEPOSITS WASTAGE OF FUEL & COMBUSTION LOSSES AND ESCAPING OF MORE HEAT TO ATMOSPHERE SO, FOR PERIODICAL REMOVAL OF DEPOSITS

ON THE SAID PARTS, STEAM IN A CONTROLLED PRESSURE IS USED TO DE-DUST DRUM, W. TUBES, S.H. TUBES. ETC.


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‘PT’ SIGNAL TO SOOT BLOWER PRESSURE CONTROLLER, MEASURES THE SOOT BLOWER PRESSURE. THE OUTPUT OF ‘PIC’ ACTS ON THE SOOT BLOWER PRESSURE CONTROL VALVE.

ACTION OF SOOT BLOWER PRESSURE CONTROL VALVE IS AIR TO OPEN TYPE. FAIL- SAFE ACTION IS CLOSE.

Good Maintenance Management of Instruments Controls:

IMPORTANT ASPECTS: RECRUITMENT OF PROPER INSTRUMENTPERSONNALS

TRAINING IN MODERN TECHNIQUES,

ON SPECIALISED INSTRUMENTS CALIBRATION & TESTING FELICITIES AND METHODS.

DESIGNING AND EQUIPPING WITH A GOOD INSTRUMENT

CALIBRATION ANDREPAIR SHOP WITH GADGETS KEEPING STOCK OF REQUIRED SPARES,

APART FROM ROUTINE MAINTENANCE,

PREVENTIVE MAINTENANCE TO PREVENT LOSS OF PRODUCTIONS, BREAK DOWN LOSSES AND OTHER WASTAGE.

PREDICTIVE MAINTENANCE SYSTEM, DERIVING THE BENEFIT OUT OF SCADA SYSTEMS AND ITS POTENTIAL TO GENERATE DETAILED ANALYSIS OF

PLANT AND PROCESS RELATED EVENTS ON SCREEN.

ECONOMY AND SAFETY OFA NATION MUCH

DEPENDS UPON GOOD MEASURING AND

MONITORING SYSTEM IT EMPLOYS.

Have a measure 0n every step To have total controlOn our target

REMEMBER:

“COUNTDOWN TO LAUNCH” IS ENSURED BY

SAFE LOGIC CONTROLS!!

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