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PARADIP REFINERY PROJECT

PROJECT SPECIFIC PROCEDURES

PROCESS ENGINEERING

PROCESS ENGINEERINGDESIGN GUIDELINES

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CONTENTS

1.0 INTRODUCTION.................................................................................................................... 32.0 VESSELS............................................................................................................................... 3

2.1 Drum Surge Capacity and Hold-up Volume ....................................................................... 32.2 Tower Bottoms Surge Capacity and Hold-up Volume........................................................ 42.3 Knockout Drum Surge Capacity and Hold-up Volume ....................................................... 42.4 Minimum Auxiliary Nozzle Size .......................................................................................... 52.5 Towers and Columns.......................................................................................................... 5

3.0 HEAT EXCHANGERS ........................................................................................................... 73.1 Fouling Factors................................................................................................................... 73.2 Fluid Allocation................................................................................................................... 73.3 Heat Exchanger Pressure Drops........................................................................................ 8

4.0 PUMPS ................................................................................................................................ 105.0 LINE SIZING ........................................................................................................................ 11

5.1 Liquid Flow ....................................................................................................................... 115.2 Vapour Flow ..................................................................................................................... 14

6.0 CONTROL VALVES............................................................................................................. 157.0 EQUIPMENT DESIGN LIVES.............................................................................................. 15

7.1 Design Life........................................................................................................................ 157.2

Corrosion Allowances....................................................................................................... 15

8.0 EQUIPMENT DESIGN TEMPERATURE AND PRESSURE................................................ 16

8.1 Design Temperature......................................................................................................... 168.2 Design Pressure............................................................................................................... 178.3 Design Pressure and Temperature Example ................................................................... 19

9.0 EQUIPMENT DESIGN MARGINS ....................................................................................... 219.1 Columns ........................................................................................................................... 219.2 Pumps .............................................................................................................................. 219.3 Heat Exchangers.............................................................................................................. 22

10.0 EQUIPMENT SPARING................................................................................................... 2210.1 General ......................................................................................................................... 2210.2 Heat Exchangers .......................................................................................................... 2210.3 Pumps........................................................................................................................... 2210.4 Compressors, Fans and Blowers.................................................................................. 22

11.0 VALVE LEAKAGE CLASSIFICATION.............................................................................. 23

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1.0 INTRODUCTION

The purpose of this document is to ensure consistency of approach to design ofequipment across the Paradip Refinery Project. Where the process design hasdeveloped more than one heat and material balance (eg. multiple cases), all equipmentand piping shall be specified for the most onerous case.

2.0 VESSELS

2.1 Drum Surge Capacity and Hold-up Volume

For drums the surge capacity (hold-up) is defined as the volume between high and lowliquid levels.

If a uniform discharge rate is important, provide the general hold-up timesrecommended below:

Service Hold-up, minutes

Feed to Tower or Furnace

- drum diameter: < 1.2 m 20- drum diameter: 1.2 to 1.8 m incl. 15

- drum diameter: > 1.8 m 10

Reflux to Tower 5

Product to Storage 2

Flow to Heat Exchanger 2

Flow to Sewer or Drain 1

In case hold-up must be provided for both product and reflux, the larger volume isused, not the sum of the two volumes.

When the discharge rate is unimportant, a nominal hold-up time of approximately two(2) minutes is provided.

The normal operating liquid level should be taken as the midpoint between the highand low levels. Level control should span between the high and low levels. Wherehigh and low level trips are required, these should be located at a reasonable elevationabove and below the high and low levels respectively, to allow operator interventionbefore a trip occurs.

Low liquid level shall be at least 200 mm above the bottom (for horizontal vessels) or

bottom tangent line (for vertical vessels).

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For water settling the above applies but this may need to be increased. Where theremay be solids in the drum, which are not to be drawn off, the liquid outlet may beraised and the low liquid level shall be increased accordingly

For horizontal vessels, the highest liquid level shall be at least either 300 mm or 20% ofthe drum diameter below the top, whichever is the greater. Note: if a crinkled wiremesh pad is present then highest liquid level shall be at least 300 mm below thebottom of the pad.

For vertical vessels, if vapour flow is present the highest liquid level shall be at least300mm below the bottom of the inlet arrangement. If little or no vapour is present, the

highest liquid level shall be at least 300 mm or 15% of the drum diameter below the toptangent line, whichever is the greater.

The minimum time between a HHLL alarm and trip and between a LLLL alarm and tripshall be no less than 2 minutes.

2.2 Tower Bottoms Surge Capacity and Hold-up Volume

The liquid residence time (from the low to high levels) for the design of the bottomsection of a column is as follows:

1. Bottoms as feed to a subsequent tower on level control is five (5) minutes. Ingeneral, level control will frequently prove satisfactory to the second of a series of

towers.

2. Bottoms as feed to a subsequent tower on flow control is ten (10) to twenty (20)minutes, when the column is acting as a feed surge drum to another unit. Thissurge capacity may be obtained by swaging to a larger diameter for the hold upsection of the column, in some cases.

3. Bottoms to a heat exchanger and/or tankage is two (2) minutes. This may bereduced in the case of a crude or vacuum tower in order to prevent coking.

4. Feed to a fired coil reboiler is the sum of five (5) minutes on the vaporised portionand two (2) minutes on the bottoms product. It is normally desirable that the five (5)minutes on the vaporised portion be employed to establish the normal low level, withthe subsequent two (2) minutes on bottoms product used to establish the high liquidlevel (normally 300 mm is the minimum allowed distance between these levels).

5. For vacuum towers, a space corresponding to 30 seconds surge on total vacuumbottoms plus quench rate is set between low and high liquid level at tower bottoms.

2.3 Knockout Drum Surge Capacity and Hold-up Volume

For normal accumulation the following liquid hold up applies:

a) At low normal accumulation rate

Liquid drawoff is usually manually controlled. Enough volume should be provided toensure the frequency of emptying is less than once per shift (i.e. eight (8) hours) orpreferably twenty four (24) hours. Generally a nominal height above the lower tangentline (say 200 mm) will be adequate.

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b) At higher normal accumulation rate

Liquid drawoff is usually under level control. The distance between high and low levelis usually made to suit a standard controller range, say 350 mm, (corresponding tocontroller connections and generally providing hold up time far in excess of the normalrequirement of approximately two (2) minutes).

For a spill the following liquid hold up applies:

c) Frequently capacity is required for spill from preceding unit. Provide a volumeequal to the entire production of the unit for ten (10) minutes between the alarm level(see Note * below) and a point 300 mm above the normal high level.

Sometimes spill requirements govern the drum design. That is, an L/D ratio ofapproximately 3:1 results in a large drum diameter relative to the vapour load. Use of acritical wire mesh screen would then be uneconomic.

(Note: * level alarm provided if level rises 300 mm above normal high level)

2.4 Minimum Auxiliary Nozzle Size

The following list is a guide to the minimum auxiliary nozzle sizes to be used forprocess design sizing of nozzles (minimum mechanical nozzle size of 50 mm (2) to bespecified during vessel design).

Vessel Volume, m3 Vent Drain Pumpout Steamout Blowdown

1.5 25 (1) 25 (1) 25 (1) 25 (1) 50 (2)

1.5 5.6 25 (1) 40 (1 ) 40 (1) 25 (1) 80 (3)

5.6 17 50 (2) 50 (2) 50 (2) 25 (1) 80 (3)

17 70 50 (2) 80 (3) 80 (3) 50 (2) 100 (4)

70 and over 50 (2) 80 (3) 80 (3) 80 (3) 100 (4)

2.5 Towers and Columns

2.5.1 Minimum Tray Spacing

Tower IDmm

Max No. of TrayPasses

Min Tray Spacingmm

750 to 1800 1 500

1800 to 2700 2 500

2700 to 3300 2 600

3300 to 4800 4 600

4800 to 6000 4 600

> 6000 4 750

For draw off trays, the spacing is set by the draw off tray design, including hold up.

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2.5.2 L/D Ratio

Towers with L/D greater than 25 shall be avoided, if possible, due to support problems.

2.5.3 Allowable Pressure Drop Guidelines for Trays

Tray Type For: Pressure Servicekg/cm2 per tray

For: Vacuum Servicemm Hg per tray

Sieve 0.007 - 0.014 1.0 2.0Valve 0.007 0.014 3.5 4.5

2.5.4 Preferred Internal Diameters (mm) of Columns/Vessels

300 1100 2000 (3400)

(350) (1200) (2100) 3600

400 (1300) 2200 (3800)

500 1400 (2300) 4000

600 (1500) 2400 4250700 1600 2600 4500

800 (1700) 2800 4750

900 1800 3000 5000

1000 (1900) 3200

NOTE: second preference shown in brackets.

2.5.5 Manholes in Columns and Vessels:

ID 900 mm Use flanged end/top cover if access is required

ID > 900 mm Preferred size: 600 mm (24); Min size: 250 mm (20)

Columns: manholes are to be provided above the top tray and below the bottom tray.The spacing of manholes in trayed columns shall be every 6 m (approx). Theminimum number of manholes for columns is three.Vessels: minimum number of manholes is one. For vessels more than 6 m in lengththe minimum number is two.In case of small vessels, hand holes of 150 mm (6) are to be provided.

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2.5.6 Tower Internals

Where trays are specified, the preferred type is valve trays (stainless steel)

2.5.7 Minimum Corrosion Allowances

Refer to Section 7.0 below

3.0 HEAT EXCHANGERS

3.1 Fouling Factors

Site specific fouling factors will be set as shown below. However, where Licensor hasrequirements, which are more stringent than this, then Licensor values shall beapplied.

i) Cooling water: 0.0005 m.hrC/kcal

ii) For other services, as per TEMA and Licensor standard

3.2 Fluid AllocationTo allocate fluids to shell or tube side of an exchanger, the following general principlesof fluid allocation shall apply:

a) cooling water on tubeside

b) high pressure fluid on tubeside

c) most corrosive fluid on tubeside

d) higher fouling fluid on tubeside

e) most viscous fluid on tubeside

f) large volume of condensing vapours on shellsideg) single phase fluids both sides put smaller flow on shellside

The above principles may conflict in some instances and alternative designs shall beinvestigated. In these cases the most economical design shall be selected.

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3.3 Heat Exchanger Pressure Drops

The pressure drop available shall be specified as below and all hydraulic calculationsshall allow for this specified pressure drop.

3.3.1 Liquids

Total Pressure Drop (kg/cm) for Liquid Flow Through Exchangers in Series

Viscosity @ avg.

temperaturecP

One Shell

Pressure Dropkg/cm

Two Shells

Pressure Dropkg/cm

Three Shells

Pressure Dropkg/cm

< 1.0 0.35 0.70 0.35 0.70 0.70 1.05

1.0 to 5.0 0.70 1.05 1.05 1.41

5.0 to 10.0 1.05 1.05 1.41 1.41

> 10.0 1.41 1.41 2.10 2.10

3.3.2 Gases

Pressure Drop (kg/cm) for Vapour Flow

Operating Pressure (kg/cma) Pressure Drop (kg/cm)

0 1.72 Approx. 0.03 - 0.07

> 1.72 0.14 0.35

3.3.3 Condensers and Reboilers

For partial condensers allow 0.14 to 0.35 kg/cm pressure drop.

For condensers where total isothermal condensation takes place, the pressure drop isusually low or negligible.

For surface condensers allow 3 - 5 mm Hg for operating pressures about 30 mm Hg.

For kettle type reboilers the shell side pressure drop is generally termed negligible.

For thermosyphon type reboilers the exchanger pressure drop must be low and isnormally in the region of 0.017 to 0.035 kg/cm.

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3.3.4 Airfin Cooler Pressure Drops

The pressure drop available for airfin coolers shall be specified as below and allhydraulic calculations shall allow for this specified pressure drop.

Service OperatingPressurekg/cma

Allowable Pressure Dropkg/cm

Liquid Cooling All 0.70 Not valid for viscous fluids

2.06 4.50 0.07

4.50 18.2 0.21

Gas Cooling

18.2 104 0.35

TotalCondensation

Atmospheric &above

0.03 min For multi-pass air coolers, high-pressure drops assure properflow distribution. The higherpressure drop will also assuregood flow distribution at lowerthan design throughput

Partial

Condensation

Atmospheric &

above

0.14 - 0.35 Note as for total condensation

Condensation Vacuum 3 - 5 mm Hg Selection of an allowablepressure drop should be fromthe results of an economicstudy

3.3.5 Viscous fluids

The following typical pressure drops shall be allowed for more viscous fluids.

Service Allowable pressure drop, kg/cm

Light gas oil cooler (airfin) 1.05

Light gas oil cooler (shell and tube) 0.70

Pumparound cooler (airfin) 1.05

Light gas oil cooler (shell and tube) 0.70

Waxy distillate cooler (airfin) 1.41 1.75

Vacuum residue cooler (airfin) 1.75 3.52*

Vacuum residue cooler (shell and tube) 1.75 5.27*

Tempered water cooler (airfin) 2.81 3.52

*Must be estimated by specialist engineers.

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3.3.6 Air Cooling versus Water Cooling

Air-cooling shall be maximised for which the cut-off temperature of process streamsshall be 55 C. Further trim-cooling will be by water as necessary. The dry bulbtemperature specified in the BEDD shall be considered for cooler sizing. However,these guidelines can be relaxed to avoid small trim cooler or air cooler.

3.3.7 Preferred tube sizes

Preferred size for Carbon Steel and low alloy (up to and including 5 Cr. Mo) tubes is20 x 2 and 25 x 2.5 mm.

Preferred sizes for brass tubes and admiralty tubes are 20 x 2 mm and 25 x 2.5 mmrespectively. Standard TEMA tube sizes are an acceptable alternative.

Preferred size for high alloy (above 5 Cr Mo and Austenitic) tube is 20 & 25 x t to suitdesign.

Preferred tube pitch is square pitch in fouling services.

4.0 PUMPS

The available NPSH shall exceed the required NPSH by at least 0.6 m up to design(rated) capacity for boiling liquids, dissolved gases, foaming liquids and other fluids.

For Boiler Feed Water Pumps the available NPSH shall exceed the required NPSH bya minimum 2.0 m margin up to design capacity at the initial calculation stage. Whenaccurate pump suction layouts are known this margin may be reduced to 1.5 mfollowing review of the calculation.

Process engineers shall identify on the process specification turndown flows below50% of the design capacity, when such flows are possible during long-term operatingconditions covered by guarantees of plant performance.

The reference levels for setting NPSHA shall be the bottom tangent line for verticalvessels, the bottom of the vessel for horizontal vessels, the low-low level for tanks, andthe pump impeller centre line for pumps.

The following elevations for pump impeller centreline shall be assumed if no pumpvendor details are available:

Pump Capacitym3/h

Centre Line Elevationm

Up to 45 0.76

45 - 225 0.91

225 - 2270 1.07

2270 - 4540 1.37

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5.0 LINE SIZING

5.1 Liquid Flow

The guidelines shown in the following table should be used to size process piping forliquids. The guidelines cover most normal situations for systems within unit batterylimits, but they may not be applicable for all cases. For critical services and longheaders, the total pressure drop in the system must be checked to ensure the systemmeets the design pressure balance, whether or not individual process lines meet thepressure drop and velocity criteria given here. This standard may not apply to criticalservices, such as slurry lines or high pressure piping, for which reference should bemade to additional standards.

SIZING LIQUID LINES Recommended High Limits

P per 100 m,kg/cm

Velocity (4, 5)m/sec

Pump suction lines (1)

- bubble point liquids 0.10 1.8

- subcooled liquids (< DN 200) [< 8] 0.45 2.4

- subcooled liquids ( DN 200) [ 8] 0.45 3.7

Pump discharge lines

- CS 0.90 6.1

- alloy / SS 0.90 7.6

Reboilers

- trapout lines (3) 0.07 1.5

- return lines 0.07 -

Liquid transfer lines (2) 0.35 3.7

Cooling water lines 0.35 3.7

Steam condensate lines (liquid) - 0.6

Notes

(1)

Pump suction line diameters should normally not be more than two (2) standard linesizes larger than the pump suction nozzle.

(2)

Or as required by system pressure balance.

(3)

For sizing of tower draw-offs, refer to section 5.1.2 below

(4)

If the liquid velocity is too high, swaged up orifice meter runs may be required, hence it isrecommended to restrict velocities in lines containing orifice meters within the followingupper limits:- Line sizes 300 mm (12) : 3.4 m/s max.- Lines sizes 350 mm (14) : 3.1 m/s max.

(5)

For velocity limits in amine systems, refer to section 5.1.3 below

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5.1.1 Pump Discharge Lines

Line sizing is a trade-off between piping installation costs and operating costs. Typicalvalues for allowable pressure drops in pump discharge lines are given below for bothcarbon steel and alloy piping.

Pump Discharge Line Typical Pressure Drops

Flowratem/hr

Carbon Steel PipingP, kg/cm per 100 m

Alloy PipingP, kg/cm per 100 m

0 - 60 0.6 2.0 1.4 3.5

60 - 160 0.3 1.6 0.9 2.5160 + 0.2 0.9 0.5 1.6

5.1.2 Tower Draw-Off Line Sizing

Liquid from a tower tray is aerated to some extent depending on the foaminess of thegas-liquid mixture.

The recommended method for sizing drawoffs employs the following criteria:

i) The depth of the drawoff pan to be 1 1 times the nozzle diameter. The minimumallowable depth is 200 mm.

ii) Allowable velocity may vary from 0.7 m/s to 1.2 m/s depending on the nozzle size(see following tables Capacities of Side-Pan Drawoff Nozzles and Capacities ofBottom-Pan Drawoff Nozzles).

iii) The nozzle is to be swaged down to a line size which will not exceed 0.1 kg/cm2/100m pressure drop. The swage is to occur at a point in elevation 1.2 m below thenozzle drawoff. Only lines 0.2 m and larger are to be swaged down, small lines will bemaintained at nozzle size to the pump or first exchanger (see Table Typical SwagedLines After Side-pan Drawoff Nozzle).

Capacities Of Side-Pan Drawoff Nozzles

Nominal Line Sizemm

Allowable Velocitym/s

Flowratem/hr (BPSD)

80 0.70 12.5 (1,890)

100 0.70 21.6 (3,260)

150 0.70 50.4 (7,610)

200 0.80 88.1 (13,300)

250 0.85 153 (23,100)

300 0.90 237 (35,800)

350 1.00 305 (46,100)

400 1.05 426 (64,300)

450 1.10 567 (85,600)

500 1.15 735 (111,000)

600 1.20 1,027 (155,000)

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Capacities Of Bottom-Pan Drawoff Nozzles

Nominal Line Sizemm

Allowable Velocitym/s

Flowratem/hr (BPSD)

80 0.70 12.5 (1,890)

100 0.70 21.6 (3,260)

150 0.80 52.5 (7,920)

200 0.85 97.4 (14,700)

250 0.90 172 (26,000)

300 1.00 256 (38,700)

350 1.10 344 (52,000)

400 1.15 476 (71,800)

450 1.20 643 (97,000)

500 1.30 838 (126,500)

600 1.40 1,272 (192,000)

Typical Swaged Lines after Side-Pan Drawoff Nozzle

Assumptions are as follows:

1) Capacities of lines as per Capacities of Side-Pan Drawoff Nozzles table (above);

2) Allowable pressure drop limit is approx. 0.1 kg/cm per 100 m.

3) Assumed drawoff fluid properties: hot SG = 0.8; viscosity 3 cSt.

Nominalline size

mm

AssumedFlowrate

m/hr

Swagedline size

mm

Pressure dropin swaged line

kg/cm per 100 m

Velocity inswaged line

m/s

80 12.5 80 0.07 0.7

100 21.6 100 0.06 0.7

150 50.4 150 0.04 0.7

200 88.1 150 0.10 1.3

250 153 200 0.07 1.3

300 237 200 0.12 2.0

350 305 250 0.08 1.7

400 426 300 0.07 1.6

450 567 300 0.10 2.2

500 735 350 0.11 2.3

600 1,027 400 0.11 2.8

Notes: Swaged line size may be slightly different depending on physical propertiesof fluid, static head, physical layout and position of swage in relation to drawoff nozzle.

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5.1.3 Amine Lines

Velocities in equipment and piping shall be limited as follows:

Lean Amine: 2.0 m/s for carbon steel

Rich Amine: 0.9 m/s for carbon steel

4.0 m/s for 300 series Stainless Steel and higher alloys.

5.2 Vapour Flow

The guidelines shown in the following table should be used to size vapour lines. Theguidelines cover most normal situations for systems within unit battery limits, but theymay not be applicable for all cases. For critical services and long headers, the totalpressure drop in the system must be checked to ensure the system meets the designpressure balance, whether or not individual process lines meet the pressure drop andvelocity criteria given here. For long vapour lines, such as flare headers or vacuum

transfer lines, when the P > 10% P, the compressible flow calculation procedureshould be adopted.

SIZING VAPOUR LINES Recommended High Limits

Operating Pressure Range P per 100 mkg/cm

Velocity (1)m/s

HYDROCARBON LINES(< 100 m in length)

Vacuum: 0.07 kg/cma or less 0.014 120 / 0.5

Vacuum: ~ 0.50 kg/cma 0.035 120 / 0.5

0.0 3.5 kg/cmg 0.12 120 / 0.5

3.5 10.5 kg/cmg 0.35 120 / 0.5

10.5 35 kg/cmg - 0.69 120 / 0.5

> 35 kg/cmg 1.15 120 / 0.5

STEAM LINES(< 100 m in length)

Vacuum: 0.07 kg/cma or less 0.014 -

Vacuum: ~ 0.50 kg/cma 0.046 -

0.0 3.5 kg/cmg 0.12 -

3.5 10.5 kg/cmg 0.35 -

10.5 35 kg/cmg - 0.69 -

> 35 kg/cmg 1.15 -

Notes

(1) Vapour density () measured in kg/m

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6.0 CONTROL VALVES

Control valves shall be sized for a normal flow at no more than 70% of the capacity ofthe valve, with no less than 25% of the total system friction drop or 10% of theoperating pressure to 70 kg/cm2, whichever is greater, allotted to the valve. Above 70kg/cm2 a lower percentage of the operating pressure may be used for valve differentialpressure depending on process and control considerations for non flashing services.

(Note that a control valve having a pressure drop of 33% of the total frictional loss,excluding the valve, is approximately equivalent to a valve with a pressure drop of 25%of the total system friction drop)

In all cases the minimum pressure drop allowed for a control valve is 0.7 kg/cm atdesign flow-rate.

Exceptional cases (e.g. gravity flow) where lower pressure drops are required shouldbe evaluated on a case by case basis.

In summary:

i) At normal flowrate,

CV DP > 25% of Total Frictional Pressure Drop or

CV DP > 33% of Frictional Pressure Drop, excluding CV DP.

ii) At normal flowrate,

CV DP > 10% of Discharge Vessel Pressure.

iii) At design flowrate,

CV DP > 0.7 kg/cm2

Control valves in continuous service shall generally be provided with isolation andbypass valves. Hand-wheels shall be provided wherever no bypass valves areenvisaged. Bleeds shall be provided on the upstream side (or both upstream anddownstream side) of the valve as appropriate.

7.0 EQUIPMENT DESIGN LIVES

7.1 Design Life

The required minimum design life for equipment is defined in Basic Engineering DesignData, document no. 3210-8820-SP-0001, section 2.4.

7.2 Corrosion Allowances

If the corrosion allowance calculated to satisfy the required design life is less than thefollowing minimum values, then the minimum values shall be used.

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Vessel/Equipment shells

Carbon Steel and Low Alloys (incl. 0.5 Mo steel) 3 mm minimum

High Alloy steel 0.75 mm minimum

Vessel/Equipment removable internals

Carbon Steel and Low Alloys (incl. 0.5 Mo steel) 50% of corrosion allowance forequipment (shell) i.e. 1.5 mmon each contact surface

High Alloy steel No corrosion allowance

Vessel/Equipment fixed internals*

Carbon Steel and Low Alloys (incl. 0.5 Mo steel) 6mm (total corrosionallowance)

High Alloy steel No corrosion allowance

Cladding Thickness 3.0mm min

*Note: heat exchanger tubes shall not be provided with a corrosion allowance.

8.0 EQUIPMENT DESIGN TEMPERATURE AND PRESSURE

8.1 Design Temperature

8.1.1 Upper Design Temperature

Design temperature shall be set at 25C above the maximum operating temperature.The minimum upper design temperature shall be 65C.

The maximum operating temperature is defined as the highest material balancetemperature. Consideration shall also be given to other conditions such as start-up,shut-down, catalyst regeneration, failure of upstream cooling and steam-out. Such

temperatures should be considered on a case by case basis to establish if they shouldbe taken as the maximum operating temperature.

In the case of coolant failure for process units, the maximum operating temperatureupstream of the cooler shall be taken as the downstream design temperature. Thisshould apply to downstream pipework, only up to the next major item of equipment.For failure of rundown coolers, the higher design temperature shall only be taken to thebattery limit. A high temperature alarm shall be installed downstream of all productrundown coolers.

8.1.2 Lower Design Temperature

The minimum design temperature for which process equipment must be designed willnormally be specified as the minimum operating temperature of the equipment. Thisminimum operating temperature could occur during an abnormal mode of operationsuch as start-up, shut-down or emergency depressuring, but only need be quoted forvalues less than 0C.

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For depressurisation of fluids which have an atmospheric boiling temperature below0C the following should apply:

a) Liquid Filled Systems

Minimum temperature shall be for a near pure component at its atmosphericboiling point

For multicomponent mixtures the minimum temperature shall be determined byflashing the fluid from operating to atmospheric pressure in a series of flashes,removing the vapour after each stage of flashing.

b) Gas Filled Systems

Minimum temperature is to be taken as that resulting from a 40% efficientisentropic expansion from maximum operating pressure to atmosphericpressure.

8.1.3 Multiple Design Temperatures

When different metal temperatures can be predicted to occur for different zones of avessel during operation (as in the case of a large distillation column) then the differenttemperatures zones should be indicated on the vessel sketch in the vesselspecification and these different temperatures should be taken into account for setting

design temperatures for each zone.

8.2 Design Pressure

8.2.1 Pumped Systems

Process piping and equipment which form part of a pumped hydraulic system, andwhich may operate liquid full, will normally be designed for the maximum pressure thatcan be developed by the pump.

For centrifugal pumps for a single consistent case:

Maximum discharge

pressure

= Maximum differential

pressure

+ Maximum suction

pressure

where:

Maximum suctionpressure

= Suction vessel designpressure(or RV set pressure)

+ Vessel static headtaken @ HLL

Pressure drop across trays or vessel internals should be included if it is significant.

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and:

Maximum differentialpressure

= F x Net differential pressure @ rated capacity

where F is:

1.25 for motor driven pumps

1.38 for turbine driven or variable speed pumps

Note: calculation shall be based on maximum operating SG.

For reciprocating pumps, these should be provided with discharge relief valves, the setpressure of which should be specified to avoid the pump over-pressuring any systeminto which it discharges.

8.2.2 Compressor Systems

For centrifugal compressor systems, the design pressure of the suction system shouldbe set considering the settle-out pressure at shut-down. Under these circumstanceshigh pressure gas from the discharge side will pass to the suction side through theanti-surge recycle valve and through the compressor itself.

The settle out pressure will be a function of the relative volumes of the suction anddischarge systems.

Reciprocating compressors shall be fitted with a discharge relief valve set to preventthe compressor over-pressuring any system into which it discharges.

8.2.3 Non-Pumped Systems

The design pressure for equipment in non-pumped systems shall be set as follows:

Max. Operating Pressure (MOP)kg/cmg

Design Pressurekg/cmg

1.8 3.5

1.8 < MOP < 17 MOP + 1.7

17 MOP

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exchanger in the event of a tube rupture. However, the potential for propagation ofhigh pressure into the piping system and other equipment connected to the lowpressure side must also be considered from a design pressure viewpoint.

8.2.5 Steam-Out Conditions

Steam-out conditions are to be 3.0 kg/cmg @175C and Full Vacuum @ 175C.

All process specifications for equipment that is to be steamed-out shall clearly statethis requirement and define the steam-out conditions.

8.2.6 Vessels Subject to Vacuum Conditions

Vessels which may operate under vacuum conditions during normal operation shall bedesigned for full vacuum.

8.3 Design Pressure and Temperature Example

With reference to Fig 1 (below):

1. Vessel design pressure:

Pd1 = Relief valve set pressure, Pr1,

However, for liquid filled systems, Pr1 = Pd1 Ph3

2. Pump suction:

PO2 = PO1 + Ph1 Frictional Losses (based on normal SG)

Pd2 = Pd1 +Ph1 + Ph2 (based on maximum SG)

For pumps in parallel, ie. one operating, one standby, the downstream design pressureis taken back to, and including, the suction block valve.

3. Pump discharge:

PO3 is Net Discharge Pressure

Pd3 is Maximum Discharge PressurePd3 = Maximum Pump Differential Pressure + Pd2

Pd3 should be checked against the design pressure of the downstream equipment. If,for example, a downstream column has a design pressure higher than expected, say tocontain a runaway reaction, this pressure may be taken as the design pressure back toa suitable break point, say the pumps suction block valve.

The method for setting the control valve pressure drop is given in Section 6 above.

4. Exchanger:

In certain circumstances the low pressure side design pressure may be increased to77% of the high pressure side design pressure to allow for the burst tube case asdefined in API 520 & 521. Certain codes dictate the provision of relief protection onheat exchangers.

Above matters must be agreed with FW and/or PMC Contractor prior toimplementation.

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5. Column:

Top: Pd6 = Pr2

Bottom: Pd7 = Pr2 + P across internals

Pd7 does not include the liquid static as this will be added by the vessel design groupbased on the high level.

6. Reboiler:

Pd8 = Pd7 + Ph4 + Ph5

LLL

NLL

HLLP

P

SET @ P

o1

d1

r1

SET @ P r2EXAMPLE PRESSURE PROFILE FOR A PUMPED SYSTEM

H3

H2

H1

P

P

o3

d3

P

P

o2

d2

cL Po4 Po5

P

P

o6

d6

P

P

o7

d7HLLH4

Po = OPERATING PRESSURE

Pd =

=

DESIGN PRESSURE

PRESSURE DUE TO STATIC

H5

P

P

o8

d8

FIGURE 1

Pd6Pd3

DPTDFIG1.DRW

(P )h2

(P )h3

(P )h1

Pd3Pd2

FOR PUMPS INPARALLEL

BREAK POINT

STANDBY

Pd3Pd2

Ph

(P )h4

(P )h5

FOR SINGLE PUMP

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9.0 EQUIPMENT DESIGN MARGINS

The following values shall be incorporated into equipment design to allow for increasedcapacities.

9.1 Columns

Columns shall generally be sized according to vapour/liquid loads specified by the

material balance. Over design on vapour and/or liquid loads must be agreed on a caseto case basis, depending on the service and on whether foaming etc. may occur. Thefactors shall be specified on the equipment data sheets.

The following design criteria shall apply.

Trayed columns

Columns with a diameter under 900 mm shall be designed to a maximum 70% offlooding rate

All other columns shall be designed to a maximum 80% of flooding rate

Packed columnsPacked sections shall be designed to a maximum of 70% of flooding rate and shall bewithin the maximum pressure drop specified for the packing.

9.2 Pumps

Unless otherwise stated, the sizing of pumps shall be in accordance with the materialbalance and the following overcapacity rates on flow rate:

Overcapacity, %

Centrifugal Pumps

- Reflux & pumparound pumps 20

- Offsites product pumps Zero

- All other pumps 10

- Intermittent services Zero

Reciprocating Pumps

- All 10

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9.3 Heat Exchangers

Unless otherwise stated, heat exchangers shall be sized according to the heat andmaterial balance and the following over capacity rates:

10% margin on flow, except for pumparound services where a flow margin of20% shall be used

10% margin on duty

15% margin on reboilers and condensers (duty and flow)

10.0 EQUIPMENT SPARING

10.1 General

Installation of standby spare equipment shall be included where justified for safety,reliability or economic reasons. All refinery units are scheduled for turnaround onceevery five years for planned maintenance. Running equipment requiring more frequentturnarounds shall justify a spare.

Whilst aiming to minimise standby equipment care should however be taken to ensurethat unit operations are not rendered vulnerable to failure of relatively inexpensiveequipment (e.g. lube oil and seal oil pumps for large turbo-compressor units).

10.2 Heat Exchangers

Heat exchangers with a high fouling potential must always be arranged in paralleltrains, such that one train can be taken out of service for cleaning while the train inoperation meets the plants minimum capacity.

10.3 Pumps

All pumps with an immediate influence on the process must have a spare. However,consideration shall be given to the use of common installed stand-by pumpsperforming two duties.

Sparing of pumps with a delayed influence on the process (e.g. inhibitor feedingpumps) will be evaluated on an individual basis.

In general, both the main pump and the spare are to be motor driven. However,consideration is to be given to steam turbine drive for main and/or spare pumps wheresignificant relief load reduction can be achieved.

Consideration is also to be given to having steam turbine drives and motor drives incritical services, such as BFW. For critical services such as firewater, the use of diesel

drives on pumps shall be considered.

10.4 Compressors, Fans and Blowers

Sparing of compressors will be as follows:-

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Centrifugal compressors shall have a spare rotor in the warehouse.

Reciprocating compressors shall have a 100% spare

For fired heaters fans:

ID fans shall have a 100% spare

FD fans shall have a 100% spare

11.0 VALVE LEAKAGE CLASSIFICATIONAll control valves and block & bleed valves connected to a flare system shall be ofleakage Class V or better.

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