화학플랜트공정설계기준

CEC (SYSTEM PROCESS DESIGN CRITERIA)

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화학플랜트공정설계기준
(SYSTEM PROCESS DESIGN CRITERIA)

2005. 5. 23

차 순 철 기술사
sc@charstech.com

CEC 기술사사무소 차스텍이앤씨㈜

135.860 서울특별시 강남구 도곡1동 947-30 용호빌딩2층
Tel: 02.573.9795~6 Fax: 02.573.9725
E-mail: cec@charstech.com
www.charstech.com (한글도메인: 차스텍)

All rights reserved.

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TABLE OF CONTENTS

1. GENERAL
1.1 CRITERIA
1.2 RESPONSIBILITIES
1.3 CODES AND STANDARDS

2. SYSTEM PROCESS ENGINEERING

2.1 ENGINEERING UNITS
2.2 LINE SIZING CRITERIA
2.3 PUMP AND COMPRESSOR HEAD CALCULATIONS
2.4 MINIMUM FLOW BYPASS
2.5 PIPE WALL THICKNESS CALCULATIONS
2.6 PROCESS DATA FOR CONTROL VALVES, ORIFICES, AND METER RUNS
2.7 RELIEF EQUIPMENT SIZING CRITERIA
2.8 LINE LIST

3. EQUIPMENT DESIGN
3.1 PRESSURE VESSELS
3.2 TANKS
3.3 EXCHANGERS
3.4 EQUIPMENT IN PUMP DISCHARGE CIRCUIT

4. PIPING DESIGN
4.1 NORMAL OPERATING CONDITIONS
4.2 DESIGN TEMPERATURE AND PRESSURE
4.3 CODE ALLOWANCE

5. P&ID DESIGN PRACTICES

5.1 FORMAT
5.2 TITLE BLOCK, LEGEND, AND FLOWSHEET SYMBOLS
5.3 P&ID REVISIONS
5.4 EQUIPMENT DESCRIPTIONS

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5.5 VENDOR PACKAGE DETAILS

5.6 LINE NUMBER
5.7 INSTRUMENTATION
5.8 VESSEL AND HEAT EXCHANGER NOZZLE SIZES
5.9 CONTROL VALVE MANIFOLD
5.10 PUMP AND COMPRESSOR MANIFOLDS
5.11 VENTS, DRAINS, STEAMOUT AND PURGES
5.12 INSULATION
5.13 TRACING
5.14 SAMPLE CONNECTIONS
5.15 PIPING SPECIFICATION BREAKS
5.16 TIE-IN CONNECTIONS
5.17 BATTERY LIMIT AND HEADER-BLOCK VALVES
5.18 REDUCERS
5.19 DISTRIBUTION DRAWINGS
5.20 LINE CONTINUATION FLAGS
5.21 SPECIALTY ITEMS
5.22 CHEMICAL OR MECHANICAL CLEANING
5.23 RELIEF VALVE ISOLATION
5.24 LOCKING VALVES
5.25 VALVE APPLICATION

6. UTILITIES
6.1 UTILITY STATIONS
6.2 SNUFFING STEAM

APPENDIX 1 BLOCK AND BYPASS VALVE SIZES

APPENDIX 2 LINE NUMBER BLOCKS

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1. GENERAL
1.3 CODES AND STANDARDS
Unless otherwise amended by CEC specifications, System Process Engineering Design
shall be in accordance with the latest edition for the following, unless otherwise
shown below.

Piping
Process Piping ANSI, B31.3
Boiler Piping ANSI, B31.3
Flanges ANSI, B16.5
Pressure Vessels
Unfired ASME, Sect. VIII, Div.1 & ASME, Sect. I
Unfired Steam Boilers ASME, Sect. I
Fired Steam Boilers ASME, Sect. I
Safety Relief Systems
Safety Valves API RP520 and API RP521
Header ASME, Sect. I and VIII
Pumps
Centrifugal API 610
Reciprocating API 674
Compressors
Centrifugal API 617
Reciprocating API 618
Air Compressor (centrifugal) API 672
Steam Turbines API Std 611 & 612
Exchangers ASME Section VIII & TEMA
Flammable and Combustible Liquid Storage NFPA Volume 1
Foam Extinguishing Systems NFPA Volume 7
Storage Tanks
Atmospheric Pressure API Std 620, 650, 2000

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2. SYSTEM PROCESS ENGINEERING

2.2 LINE SIZING CRITERIA
Minimum line size in pipe racks will be 2 inches.
Minimum line size will be 3/4 inch, except for vents, drains, and instrument connections.
The flows shown on the material balances are to be treated as “normal” for line sizing.
Maximum process rates are 110% of normal.
Minimum rates are 50% unless shown otherwise on PFDs or in process specifications.

2.3 PUMP AND COMPRESSOR HEAD CALCULATIONS

Pump head calculations will be in accordance with this design criteria.
Work sheet will be used to summarize the calculated pressure drops for each system.
For gas blanketed vessels, assume saturated fluid conditions.

2.4 MINIMUM FLOW BYPASS

Minimum continuous flow requirements will be specified by the pump vendor.
The rated flow shall not normally be increased for minimum flow requirements.
The minimum flow bypass shall be taken from the pump discharge before the check valve and will
return to the suction vessel.
Manual valves in the minimum flow line shall be locked open.

2.5 PIPE WALL THICKNESS CALCULATIONS

Pipe wall thickness will be determined by CEC’s Piping Material Specification.

2.6 PROCESS DATA FOR CONTROL VALVES, ORIFICES, AND METER RUNS
The System Process Engineer shall provide to the Project Instrument Engineer all the
process data for sizing control valves, orifices, and meter runs.
The control valve data shall be transmitted on Instrument Process Data Sheet.

2.7 RELIEF EQUIPMENT SIZING CRITERIA

The selection and, sizing of relief valves or rupture disks for CEC designed process
units and relieving systems shall be in accordance with API recommended practices
RP520 and RP521, ASME Codes Sections I and VIII, and CEC Design Guides.

2.8 LINE LIST

A line List will be issued with the design issue of the P&ID.
Use CEC PC Computer line summary program.

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3. EQUIPMENT DESIGN
3.1 PRESSURE VESSELS
Complete systems within a process must be checked in addition to the following minimum
design pressure and temperature requirements of vessels :

3.1.1. Operating Pressure - OP Min, Design Press - DP (1)

Vacuum vessels 1.05 kg/cm2g and full vacuum(2)
0 to .35 kg/cm2g 1.05 kg/cm2g (2)
35 to 10.5 kg/cm2g OP + 1.05 kg/cm2 (3)
10.5 to 70.3 kg/cm2g 1.1 x OP
70.3 to 141 kg/cm2g OP + 7.03 kg/cm2
Above 141 kg/cm2g 1.06 x OP
NOTES :
1) Do not include liquid head. Design pressure is for the top of the vessel.
The vessels engineer designs the bottom of the vessel for any liquid head.
2) Maximum DP for vessels without ASME code stamping.
3) or at least the maximum allowable working pressure.

For vessels with a pressure-relieving system to flare, consider 3.5 kg/cm2g minimum design
pressure to reduce flare size requirements.
Suction drums on reciprocating compressors are to be designed for vacuum conditions in
addition to operating conditions.
Mis-operation during steamout of vessels is not to be considered.
For liquified gas controlled under Korea High Pressure Gas Law, design pressure is saturation pressure
at design temperature.
Furnace and reactor sections may be subject to special considerations.

3.1.2. Operating Temperature - OT Design Temperature - DT

Below -28 degrees C Lowest OT

-28 to 537 degrees C OT + 14 degrees C
Above 537 degrees C OT + 12 degrees C
Boiling water service Saturation temperature at design pressure

3.2 TANKS
The following shall be the minimum design pressure and temperature requirements of
tanks :

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3.2.1 Operating Pressure - OP Min. Design Press - DP (1)

Cone roof
up to design pressure .02 kg/cm2g
Dome roof
up to design pressure .035 kg/cm2g
up to design pressure 1.05 kg/cm2g
Notes :
Do not include liquid head. Design pressure is for the top of the tank.
Mis-opertion during steamout is not to be considered.

3.3 EXCHANGERS
Design pressure and temperature of exchangers are as follows :
3.3.1 Operating pressure - OP Min. Design press - DP

Vacuum Exchangers Full vacuum

0 to 3.5 kg/cm2g 5.3 kg/cm2g
3.6 to 17.5 kg/cm2g OP + 1.76 kg/cm2
17.6 to 69.9 kg/cm2g 1.1 x OP
70.0 and above 1.075 x OP

3.3.2 Operating Temperature - OT Design Temperature - DT

-28 to 343 degrees C OT + 28 degrees C

Above 343 degrees C OT + 14 degrees C
Boiling water service Saturation temperature at design pressure

For air-cooled heat exchangers, the design temperature shall be the maximum fluid
temperature specified on the Process Equipment Specification or the Process Flow
Diagram.
If no maximum fluid temperature is specified by Process, the design
temperature shall be the normal operating temperature plus the applicable factor
specified above.
An upset condition may set the design temperature of certain exchanger.

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3.4 EQUIPMENT IN PUMP DISCHARGE CIRCUIT

Equipment in a pump discharge circuit with a downstream block valve and no relief valve
shall have a design pressure at least as high as the shutoff or minimum flow pressure of
the pump at the maximum operating suction pressure.
This is to be checked after equipment design.

For shutoff pressure estimates on motor-driven centrifugal pumps, use the maximum
suction pressure plus 125% of the rated differential pressure of the pump. For steam
turbine-driven pumps, use 1.38 x maximum differential pump pressure at rated flow.
When pump-performance curves are obtained from pump vendors, the maximum pressure for
the purchased impeller shall be compared with the equipment design pressure.

Equipment design pressures must be increased if the pump shutoff discharge head is
greater than estimated.
For turbine-driven pumps, the certified shutoff head must multiplied by the square of
the ratio (turbine trip speed/pump rated speed).

4. PIPING DESIGN
4.1 NORMAL OPERATING CONDITIONS
The process conditions of the greatest severity expected during normal operation.
Conditions such as turndown, startup, dual-cycle, and regeneration shall be included,
when appropriate, as separate entries.

4.2 DESIGN TEMPERATURE AND PRESSURE

The conditions listed shall be set by consideration of the normal operating conditions,
short term variations, and the applicable code requirements. The piping system shall be
designed for the most severe coincident temperature and pressure for the condition
requiring the greatest pipe wall thickness and the highest flange rating. Usually, the
piping
design pressure is equal to the design pressure of the equipment to which the
piping is attached.

4.3 CODE ALLOWANCE

The ANSI B31.3 allowances for variation from normal operating conditions given in
302.2.4 shall not be permitted.

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5. P&ID DESIGN PRACTICES

5.4 EQUIPMENT DESCRIPTIONS
The P&ID shall contain information from the equipment list for each piece of equipment
as shown below :

Tag number
Equipment name as on the equipment list
DP:in kg/cm2g;DT:in Deg C (two values for shell and tube exchangers)
Exchanger of heater absorbed duty in kcal/h
Pump rated capacity in m3/hr or L/hr and differential pressure in kg/cm2
Pump rated power in kW
Vessel dimensions tangent to tangent and diameter
Insulated (when required)
Equipment with spares will be described once unless the spare is on a separate drawing.

5.6 LINE NUMBER

5.6.1 The line number shall be CEC Standard as follows :
Example - 6″-A1A1-100-009-H-SR
Where - 6 = nominal line size (inches)
A1A1 = Piping material specification code
100 = unit number
009 = sequential line number (see appendix III)
H = insulation code
SR = stress relief of piping

5.6.2 Line Size

Line, valve and nozzle sizes shall be in inches. When a single line sequential
number is used for a line which changes sizes, each size shall be listed in the
summary to provide hydrotest pressure and heat tracing requirement.

5.6.3 Unit Number

The unit number shall be the unit from which line originates. Utility lines
originating from the unit battery limit and the branch up to the distribution
header shall be numbered as if originating from the unit.

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5.6.5 Insulation Type

The purpose for insulation, including any external heating requirements, is
designated by a letter symbol as listed below. The holding temperature for external
heating shall be listed in the remarks column of the line summary.
P - Personnel Protection
H - Heat Conservation
C - Cold Insulation
Heat tracing, when required, shall be indicated by a dashed line adjacent to the process line.
The temperature to be maintained shall be shown.
For freeze protection, electric tracing will be used and indicated by (ET) shown
after the temperature in ℃.
For process reasons, steam tracing will be used and indicated by (ST) shown
After the temperature in ℃.

5.7 INSTRUMENTATION
5.7.1 Symbols and identification letters
Instrument symbols and identification letters will be in accordance with the
instrument society of American Standard ISA-S 5.1 “Instrumentation symbols and
Identification”, latest edition.

5.7.2 General instrumentation philosophy

Transmission to or from the control board in the control room is to be via
distributive control system.
Instrumentation and controls are to be compatible with computer control system to be
implemented in the future.
An emergency shutdown system is to be defined.
Safety related interlocks are to be hardwired and fail safe.
Motor status lights will not be shown on P&ID.
Local control loops are to be pneumatic.
Control valves shall have pneumatic operators.

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5.8 VESSEL AND HEAT EXCHANGER NOZZLE SIZES

Vessel nozzle sizes shall be the same as the connecting pipe size except as follows :

5.8.1 Nozzles set by Process

If the nozzle size has been set by process and is larger than the pipe attached to
it, it shall remain larger as per Process requirements.
If the nozzle size set by Process is smaller than the pipe attached to it, the nozzle size
shall be increased to match the pipe size, provided that a special condition does not
exist to justify the smaller nozzle.
(In both cases, the System Process Engineer should review nozzle size with Process)

5.8.2 For liquid drawoff from column, use the following :

Minimum nozzle size in inches for total draws :
dia = 1.36 (L/m)0.4 where L/m is flow in liters/min.
Before reducing diameter or making a horizontal run, a minimum drop of 1500 mm in
elevation is required, after the piping elbow is attached to the drawoff nozzle.
The following detail will be shown on the P&ID. :

5.8.3 Nozzles for Exchangers

Size to limit dv2 = 5965 kg/m sec2 (where “v” is the linear velocity of the fluid in
meters per second and “d” is the density in kg/m3 for single or two phase flows)
Where exchanger shell are connected in series, maintain the larger line size
and bypass valve sizes for performance and capacity.
The line should also be checked to see if it can be reduced in size.

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5.9 CONTROL VALVE MANIFOLD

5.9.1 Manifold sizes
The control Valve Manifold Design Table, Appendix 1, shall be used for selecting
block and bypass valve sizes. Where the control valve is two or more sizes smaller
than the
line size, the project instrument engineer shall carefully analyze the block.

5.9.2 Exceptions
Full-line size block and bypass valves are required for the following :
Vaporization or volume increase requires full-line capacity.
Use downstream line size to size downstream block valve from table.
Gravity flow with small control valve differential.
Requirement for future expansion.
High pressure drop where cavitation could occur.
Expansion will be used immediately at the control valve outlet.

5.9.3 Bleed valves

A 3/4 in. bleed valve shall be shown upstream of the control valve.

5.9.4 Valves without manifolds

A control valve with a handwheel and without block an bypass valves can be used in a
clean, nonabrasive service where a line can be taken out of service without
requiring unit shutdown.

5.10 PUMP AND COMPRESSOR MANIFOLDS

5.10.1 If valve takeoff is made before the pump nozzle sizes are known, both pump suction
and discharge valves shall be line size.

5.10.2 If valve takeoff is made after the pump nozzle sizes are known, valves in suction
and discharge lines shall be sized as follows:

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5.10.2.1 If there is one size difference between pump nozzle and pipe.
pump suction valve shall be line size or suction nozzle size, whichever is greater.
The valves on the discharge of a pump shall be the same size as the pump nozzle or
the piping, whichever is smaller.

5.10.2.2 If pump suction or discharge nozzle differs more than one size from the line size,
valves shall be one size smaller than the line size.
Where pump nozzles are smaller than the line size by two sizes or more, check the
line size for proper sizing and consider, from economic standpoint, a line-size

valve and a single swage versus two swages and a one size smaller valve.
Check line size if pump nozzles are two sizes larger than line size.
Both discharge check and block valves shall be the same size.

5.10.3 Pumps and compressors shall be provided with permanent strainers.

5.10.4 A minimum of three diameters of straight run of pipe shall be shown on compressor
suction piping.
Instrumentation or rotating equipment may have additional requirements.

5.10.5 Install spectacle blinds on suction and discharge of reciprocating compressors.

5.10.6 Install TWs on inlet and outlet of all heat exchangers.

5.10.7 Piping and valving around water cooled heat exchangers shall be shown as in sketch
below :

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5.11 VENTS, DRAINS, STEAMOUT AND PURGES

5.11.1 Vertical vessel drain shall be located in the bottom outlet line.

5.11.2 Steamout connections are located at minimum distance above the bottom head steam of
vertical vessels and the side or head of horizontal drums. If vendor designed
vessels do not have steamout connection and client request the connection, they will
be located on connecting pipeline.

5.11.3 Purge connections follow the same rules as steamout connections, but differ in that
they are used when steam or water could be detrimental to the equipment or process
material. Nitrogen or some other inert gas is therefore used to purge these systems.

5.11.4 Steamout or nitrogen purge shall be permanently piped for sizes 2 inches and larger.
A double block, check, blind, and bleed in the purge piping shall be provided for
the connection to a process line. When piping purges into a vessel, a double block,
removable spool, and vent shall be provided in the purge line.

5.11.5 Vents are located on the top head of towers and vertical vessels. They are located
on the top of horizontal drums at the same end as the drain and at the end opposite
from the steamout or purge connection. All vents are valved and blinded or capped.

5.11.6 Vents, drains, and steamout and purge connection for columns and vessel shall be
sized as follows :

Equipment Volume Vent Size Drain size S.O or Purge Size

Cubic Meters inches inches inches
Up to 5.6 1-1/2 1-1/2 1-1/2
5.6 to 17 1-1/2 2 1-1/2
17 to 71 2 3 1-1/2
over 71 3 4 1-1/2

NOTE : Minimum size vents for vessels having only one personnel access way will be 4
in, for horizontal vessels and 2 in, for vertical vessels.

5.11.7 All drains from towers containing toxic fluid shall have some arrangement for being
double blocked.

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5.11.8 Operating vents and drains for piping systems shall be sized as follows :
Pipe Size, inches Vent size, inches Drain Size, inches
3/4-4 3/4 3/4
6 - 10 3/4 1
12 and over 1 1-1/2
Non-operating and hydrotest vents and drains will not be shown on the P&IDs.

5.11.9 All vents and drains smaller than 3 in. shall be capped. All vents and drains 3 in.
and larger shall be blinded.

5.11.10 Atmospheric tank overpressure protection

Atmospheric tanks shall have vent, overflow, two independent high level alarms or
shutdowns, and API overpressure protection.

5.12 INSULATION
Lines and equipment surfaces normally operating at 65 degrees C and above, not
insulated for heat conservation, shall be insulated for personnel protections.
Insulation thickness shall be as specified in the insulation specifications.

5.13 TRACING
Tracing shall be provided to maintain liquid viscosity at required levels, to keep
lines from freezing, and to prevent condensation. Select temperatures at least 6
degrees C above the liquid pour or freezing points, making sure it is below the
bubble point.

Electric tracing will be used for freeze protection, and steam tracing will be used
for process reasons.
Where operating temperature may exceed 215 ℃, electric tracing shall not be used.

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5.14 SAMPLE CONNECTIONS

Sample connections shall be shown as follows.

5.15 PIPING SPECIFICATION BREAKS

5.15.1 Process pressure greater than steam or utility pressure or hazardous process leakage.

Permanent tie-ins of utility services to process equipment are not allowed. Install
all piping and connect drop-out spool each time.
Snuffing steam, steam out, and nitrogen purge may be excluded. (See above).

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5.15.2 Steam or utility pressure greater than process pressure.

5.15.3 General spec break with or without check valves.

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5.16 TIE-IN CONNECTIONS

Tie-in connections will be denoted by a hexagon containing the tie-in number and the
unit number and will be shown on the P&ID as :

Tie-ins will be shown at plant battery limit.

5.17 BATTERY LIMIT AND HEADER-BLOCK VALVES

5.17.1 Plant battery limit lines will generally require it battery limit block valve with
spectacle blind. A 3/4-in. bleed valve shall be located inside the battery limit.

5.17.2 The following shall be the criteria for header blocks for utilities (other than unit
header blocks) :

5.17.2.1 Steam
Provide block valves at header for all supply and user branches.
A turbine inlet and exhaust valve shall be located at the turbine and not at the
header.

5.17.2.2 Condensate
Provide header blocks.

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5.17.2.3 Cooling Water

No header block valves shall be provided for cooling water.
Block valves shall be provided at each piece of user equipment.

5.17.2.4 Nitrogen
Provide header blocks.

5.17.2.5 Instrument Air, Utility Air

Provide header blocks.

5.17.2.6 Service Water

Provide header blocks.

5.17.2.7 All Services

Provide header blocks for branch lines 2 inches and smaller.

5.18 REDUCERS
Reducers will be shown where it is not obvious where a line has changed size.
Where pump, vessel, control valve or other equipment have sizes other than line size,
the flange or valve sizes shall be shown but the reducers will not.

5.19 DISTRIBUTION DRAWINGS

Drawings for the distribution of utilities including flare and above ground drains will
be grouped showing approximate pipe rack and equipment layout. Drawing will be split
by plant areas as required. Interconnecting process lines and unit blocks will be
shown directly on process P&IDs. Where process lines interface with battery limit
and flare facilities, these lines may be shown on a process interconnecting drawing.

5.20 LINE CONTINUATION FLAGS

Lines continuing from one drawing to another shall be as per relevant legend drawings.

5.21 SPECIALTY ITEMS

If a special type of valve or some other piping item is required that is not included
in the piping material specification, the valve or item shall be shown on the P&ID as
a specialty item.

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The symbol to be used is as follows:

IDENTIFICATION
SP
032

The System Process Engineering Section shall issue to the Piping Material Section all
information necessary for the purchase of these specialty items.

5.22 CHEMICAL OR MECHANICAL CLEANING

Special line treatments such as cleaning, pickling, etc., shall be indicated by notes
on the P&ID. The extent of the cleaning operation and the type of cleaning shall be
indicated by reference to the cleaning specification.

5.23 RELIEF VALVE ISOLATION

Upstream and downstream block valves are required for each relief valve in hydrocarbon
gas service operating above 10 kg/cm2g or in LPG liquid service.
These valves shall be locked open.
3/4-in. capped bleed valves shall be shown between the upstream and downstream block
valves and the relief valve.

All block valves in relief valves service shall be full port, unless the pressure drop
through the inlet piping including the block valve does not exceed 3% of set pressure
and the valve bore is larger than the relief valve inlet nozzle.
The relief valve shall be located at a high point and drain both to the vessel and to
the relief header.

5.24 LOCKING VALVES

Valves that must be open or closed for reasons of safety shall be marked locked open or
closed (not car sealed). Such valve that must be opened or closed in an emergency
shall be car-sealed (not locked).

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5.25 VALVE APPLICATION

The following is a guide for selecting the proper type of block valve for a specific
application. Applications involving special services, such as high pressure drop and
erosive fluids, shall be evaluated individually.

VALVE SELECTION GUIDE

VALVE SYMBOL NOTE
BASIC SELECTION

These are the basic valves to be selected.

GATE

GLOBE Globe Valves normally limited to

1/2 in. to 6 in. size.

CHECK

NEEDLE Needle valves are used at sample

connections, in line classes specified
in piping material specs

BALL Use for air and nitrogen service at

utility stations and for fuel gas
service

BUTTERFLY Use for water service as shown below :

Cooling water 6 in. to 30 in.

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6. UTILITIES
6.1 UTILITY STATIONS
Utility stations for steam, service water, and air shall be provided at convenient
locations throughout the plant. At certain stations, as defined on the utility P&ID,
nitrogen shall be provided.

6.2 SNUFFING STEAM

All snuffing steam shall be taken from the LP steam supply header.

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APPENDIX 1 BLOCK AND BYPASS VALVE SIZES

Valves at control valve manifolds shall be sized in accordance with the following
table, unless otherwise shown on the piping and instrument diagrams : (All
dimensions are in inches)

Control Valve Size Line Size Block valve Size By-Pass Valve Size
3/4 3/4 3/4 3/4
3/4 1 1 1
3/4 1-1/2 1-1/2 1
3/4 2,3,4 2 1
1 1 1 1
1 1-1/2 1-1/2 1-1/2
1 2,3,4 2 1-1/2
1-1/2 1-1/2 1-1/2 1-1/2
1-1/2 2,3,4 2 2
2 2 2 2
2 3,4,6 3 3
2-1/2 3,4,6 3 3
3 3 3 3
3 4,6,8 4 4
4 4 4 4
4 6,8,10 6 6
5(6” flgs) 6,8,10,12 6 6
6 6 6 6
6 8,10,12 8 8
8 8 8 8
8 10,12 10 10
10 10 10 10
10 12,14 12 12

Where piping is expanded after a control valve assembly for flashing conditions,
the block valve downstream of the control valve shall be equal to or one size
smaller than the expanded downstream piping.
Where reducers are used, the maximum reduction shall not be greater than two nominal
line sizes per reducer.

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