Normas Texaco GEMS K-8D7 Pressure Measurement

DEC 96 PRESSURE MEASUREMENT GEMS K-8D7

PAGE 1 OF 14©TEXACO GENERAL ENGINEERING DEPARTMENT

TABLE OF CONTENTSPAGE

1. SCOPE .............................................................. 2

2. REFERENCES......................................................... 2

2.1 Purchaser Specifications ..................................... 22.2 Purchaser Drawings ........................................... 22.3 Industry Codes and Standards ................................. 3

3. REQUIREMENTS FOR DESIGN............................................ 3

3.1 Drawings ..................................................... 33.2 Winterproofing ............................................... 33.3 Electrical Requirements ...................................... 33.4 Elements ..................................................... 33.5 Pressure Connections ......................................... 43.6 Pressure Indicators, Recorders, and Controllers .............. 43.7 Auxiliary Devices ............................................ 43.8 Instrument Storage, Checkout, and Calibration ................ 4

4. PRESSURE TRANSMITTERS.............................................. 4

4.1 Application .................................................. 44.2 Design ....................................................... 54.3 Materials and Construction ................................... 54.4 Installation ................................................. 54.5 Safety ....................................................... 7

5. DIFFERENTIAL PRESSURE TRANSMITTERS ................................. 7

5.1 Application .................................................. 75.2 Design ....................................................... 75.3 Materials and Construction ................................... 75.4 Installation ................................................. 8

6. FIELD MOUNTED PRESSURE GAGES....................................... 9

6.1 Application .................................................. 96.2 Design ....................................................... 106.3 Materials and Construction ................................... 116.4 Safety ....................................................... 12

7. PRESSURE SWITCHES.................................................. 12

7.1 Application .................................................. 127.2 Design ....................................................... 127.3 Materials and Construction ................................... 127.4 Installation ................................................. 137.5 Safety ....................................................... 13

TABLESTable 1 Standard Ranges vs. Operating Ranges (Typical)



1. SCOPE

This specification and GEMS K-801M, K-802M, and K-803M define minimumrequirements for selection, materials, construction, and installation ofpressure and differential pressure measuring instruments, includingdirect connected gages, pressure switches, and pneumatic and electronictransmitters.

2. REFERENCES

2.1 Purchase r Specifications

This specification contains references to the following Purchaserspecifications:

1. GEMS G-1D, “Winterproofing and Weather Protection”.

2. GEMS J-1D, “Piping - Design”.

3. GEMS J-8D, “Steam Tracing Systems - Design”.

4. GEMS K-1D, “Instruments and Control Equipment”.

5. GEMS K-6D, “Flow Measurement”.

6. GEMS K-10D, “Field Mounted Pneumatic Controllers, Recorders, andIndicators”.

7. GEMS K-14D, “Control Room Instrumentation - DCS, Electronic, andPneumatic”.

8. GEMS K-17D, “Alarms, Shutdowns, Logic, and Sequential SystemsDesign”.

9. GEMS K-20D, “Instrument Storage, Checkout, and Calibration”.

10. GEMS K-801M, “Process Pressure Gages”.

11. GEMS K-802M, “Pressure Switches”.

12. GEMS K-803M, “Differential Pressure Transmitters”.

2.2 Purchase r Drawings

This specification contains references to the following Purchaserdrawings:

1. 1S-1784, “Utility Instrument Requirements at Unit Limits”.

2. 9S-7590, “Standard Detail of Open Vent for Storage Tanks”.

3. 9S-7691, “Steam Tracer Arrangement for Instrument and PipingItems”.

4. 9S-8262, “Typical Piping - Liquid End of Pumps”.

5. 9S-9170, “Instrument Piping - Differential Pressure Transmitters- Alloy Tubing or C.S. Pipe”.

6. 9S-9191, “Instrument Piping - Differential Pressure Transmitters - C.S. Pipe - Horizontal Orifice Run”.

7. 9S-9243, “Instrument Piping - Line Mounted Pressure Indicators withTake-Off Gage Valves”.



8. 9S-9244, “Instrument Piping - Line and Vessel Mounted PressureIndicators with Piping Specification - Take-Off Valves for ServiceTemperatures up to 200 °F”.

9. 9S-9245, “Instrument Piping - Line and Vessel Mounted PressureIndicators with Piping Specification - Take-Off Valves for ServiceTemperatures Above 200 °F”.

10. 9S-9246, “Instrument Piping - Pressure Instruments Located Above orBelow Line or Vessel Pressure Point”.

11. 9S-9247, “Instrument Piping - Line and Vessel Mounted PressureInstruments for Catalyst or Slurry Service”.

12. 9S-9249, “List of Material - Groups 1 Through 16 - InstrumentPiping -Pressure Instruments”.

13. 9S-9250, “List of Material - Groups 17 Through 32 - InstrumentPiping and Pressure Instruments”.

14. 9S-9251, “List of Material - Groups 33 Through 48 - InstrumentPiping - Pressure Instruments”.

15. 9S-9255, “Instrument Piping - Differential Pressure Transmitters - Alloy Tubing - Horizontal Orifice Run”.

16. 9S-9344, “Typical Piping for Fired Hydrocarbon Heaters - Sheet 1”.

17. 9S-9345, “Typical Piping for Fired Hydrocarbon Heaters - Sheet 2”.

2. 3 Industry Codes and Standards

This specification contains references to the following industry codesand standards:

2. 3 . 1 American Petroleum Institute (API)

1. RP 551, “Process Measurement Instrumentation”.

2. STD 2000, “Venting Atmospheric and Low Pressure StorageTanks: Nonfrigerated and Refrigerated”.

3. REQUIREMENTS FOR DESIGN

3.1 Drawings

1. Piping for pressure instruments shall conform to Drawings 9S-9243,9S-9244, and 9S-9247.

2. Line mounted gages shall have gage valves (per Drawing 9S-9243) orpiping specification valves (per Drawing 9S-9244). Valves shall beselected in accordance with project specifications.

3.2 Winterproofing

Winterproofing shall conform to GEMS G-1D and K-1D.

3.3 Electrica l Requirements

Electrical instruments shall be designed and installed in accordancewith GEMS K-1D.

3.4 Elements

1. Elements shall withstand 1.3 times normal maximum working pressurewithout damage.



2. Elements shall withstand maximum bleed or purge pressure withoutdamage in services which use bleed gas, bleed air, bleed steam, orliquid purge to purge pressure points.

3.5 Pressure Connections

1. Pressure connections shall not be installed in upstream straightruns of flow elements.

2. Pressure connections shall be installed 5 diameters downstream orgreater from an orifice plate or other flow measurement device.

3.6 Pressure Indicators, Recorders, and Controllers

1. Pressure indicators, recorders, and controllers on instrumentcontrol systems shall conform to GEMS K-14D.

2. Field mounted pressure indicators, recorders, and controllers shallconform to GEMS K-1D and K-10D.

3.7 Auxiliary Devices

1. In fluctuating pressure services, such as the discharge ofreciprocating pumps and compressors, pressure lead to element shallhave dampening devices to minimize fluctuating pressures.

2. Pressure elements mounted above pressure point in vapor or steamservice above 200 °F shall have Anderson Greenwood CT-7 condensatetraps or approved equal to protect element from excessive heat.

3. Condensate traps shall conform to Drawings 9S-9243 and 9S-9245.

4. Services with high potential for corrosion and plugging of element(e.g., acid) shall have diaphragm seals.

5. Diaphragm seals may be used for freeze protection in lieu of heattracing.

6. Transmitters in services below 250 °F shall have vent/drain valves.

7. Transmitters in services above 250 °F shall have plugs along withseparate vent and drain valves in impulse lines to keep hot fluidsaway from transmitter.

8. Transmitters and switches shall have manifold valves with specifiedquantity of block, bypass, vent or test, and drain valves.(Drawings 9S-9191 and 9S-9246 contain typical requirements.)

9. Pressure transmitters shall have local indicators.

3.8 Instrument Storage, Checkout, and Calibration

Pressure instruments shall be stored, checked out, and calibrated inaccordance with GEMS K-20D.

4. PRESSURE TRANSMITTERS

4.1 Application

1. If any of the following conditions apply, pressure transmittersshall be mounted at pressure point with minimum connecting pipingto minimize error:

a. Indicating, recording, and controlling instruments are locatedon a control panel.



b. Indicating, recording, and controlling instruments are locatedmore than 50 feet from pressure point.

c. Fluid has high viscosity, typically greater than 300 SUS, atminimum ambient design temperature or contains entrainedsolids.

d. Hydrostatic head is an appreciable part of total pressurerange.

e. Fluid is unstable and hydrostatic head is likely to vary underoperating conditions.

2. Other pressure transmitter applications shall conform to GEMS K-10Dand K-14D.

4.2 Design

1. Transmitter design and ranges shall conform to GEMS K-1D and rangesfor pressure transmitters and gages listed in this specification.

2. Absolute pressure transmitters shall be used for ranges belowatmospheric pressure and fractionating towers with pressure of 20psia or less.

4.3 Materials and Construction

4. 3 .1 Pressure Elements

1. Pressure elements and connections for pressure instrumentsof all ranges shall be type 316 SS except as described inparagraphs 3., 4., and 5.

2. Elements shall be welded at tip, socket, and/or caseconnection.

3. If type 316 SS is not suitable, pressure element shallconsist of other suitable alloy material.

4. If no suitable element material is available, elementprotectors or seals shall be provided.

5. Brass or bronze elements shall be permitted only onpneumatic receiver instruments.

4. 3 .2 Element Protectors or Seals

1. Factory installed diaphragm seal (used to protect pressureelement) shall as a minimum be 316 SS.

2. Liquid fill of suitable characteristics shall be used forelement and void above diaphragm.

3. Filled system seals shall be avoided if process pressuresare below 25 mm Hg absolute.

4.4 Installation

4. 4 .1 General

Pressure transmitters shall be installed in accordance withthis specification and GEMS K-1D.

4. 4 .2 Gas Service

1. Connections to piping in gas service shall be on top orside.

2. Instrument and tubing to instrument shall be above processline.



3. Tubing routed to transmitter shall be:

a. Void of pockets.

b. Not less than 1/2 inch per foot slope.

4. 4 .3 Liquid Service

1. Taps in liquid service shall be on the side.

2. Instrument and tubing to instrument shall be:

a. Below process line.

b. Not less than 1/2 inch per foot slope.

4. 4 .4 Piping at Block Valve

Piping at pressure tap up to and including first block valveshall conform to applicable Piping Material ServiceSpecification (PMSS).

4. 4 .5 Heat Traced Leads

1. Instrument leads shall be heat traced by prefabricatedtubing bundle with heat tracer, insulation, and 316 SSimpulse lines.

2. Heat tracing shall conform to Drawing 9S-7691 and GEMS J-8D.

4. 4 .6 Locations for Pressure Taps, Pressure Gages, and PressureTransmitters

1. Accessibility shall conform to GEMS J-1D and K-1D.

2. Pressure tap on discharge of pumps shall be between pumpand discharge block valve.

3. Pressure tap for pressure control valves shall be locateda minimum of 10 pipe diameters before or after valve.

4. Pressure control tap for fractionator towers shall betaken from same location as temperature control point.

4. 4 .7 Piping Supports

1. Piping type supports may be clamped to existing structuresor pipe.

2. Two or more parallel pressure leads may be clampedtogether.

4. 4 .8 Pressure Element Connections

1. Pressure instruments shall be mounted such that elementconnections are on the bottom, if practical, to permitsediments and solids to settle in piping before reachingpressure element.

2. Pressure instruments in hydrocarbon vapor service shall beself draining back to vessel.

3. Pressure instruments shall have a manifold.

4. Services greater than 250 °F shall have separate block andbleed valves per Drawings 9S-9191 and 9S-9255.



4.5 Safety

Safety requirements for pressure transmitters shall conform to GEMS K-1D.

5. DIFFERENTIAL PRESSURE TRANSMITTERS

5.1 Application

1. Specific applications for differential pressure transmitters shallconform to GEMS K-1D, K-10D, and K-14D.

2. Differential pressure transmitters in level measurement serviceshall conform to GEMS K-7D.

3. Differential pressure transmitters in flow measurement serviceshall conform to GEMS K-6D.

5.2 Design

1. Normal operating range for differential pressure transmitters inservices other than flow shall be within middle one-third of totalrange.

2. Process pre-trip alarms and shutdowns shall have pressuretransmitters. Transmitter output shall be used for “switch”actuation through the instrument control system or safety system.


1. Differential pressure transmitters shall have a minimum rating of1500 psig. Higher ratings shall be used if necessary.

2. Low range meters (10 inch, 2 inch, or lower) shall be suitable forservice conditions.

3. All portions of differential pressure transmitter bodies, includingflanges, in contact with process fluid shall be type 316 SS, exceptif corrosive fluids require other alloy metals, such as Hastelloyor Monel. If suitable metal is not available for internal parts forcorrosive services, seal pots or diaphragm seals shall be used.

4. In hydrogen services, process isolating diaphragm shall be 316 SS.If process conditions warrant or if specified by Purchaser, goldplated capsules shall be used to prevent hydrogen permeation.

5. Hardware used with differential pressure transmitters shall be 316SS or other non-corrosive alloy. Bolts shall not be plated.

6. Seal and Drip Pots

a. Unless fluid being metered is highly corrosive, seal and drippots shall be carbon steel.

b. Stainless steel, Monel, or other alloy shall be furnished forcorrosive fluids.

c. Pot shall be constructed in accordance with pressure,temperature, or corrosion requirements of line to which itconnects.

7. Materials and construction shall conform to GEMS K-803M.



5.4 Installation

5. 4 .1 Heating for Viscosity Control or Freeze Protection

1. Differential pressure transmitters in highly viscousservice or which require heating for freeze protectionshall have heat tracing and insulation.

2. Degree of heating shall conform to GEMS G-1D.

3. Tracing shall conform to GEMS J-8D and Drawing 9S-7691.

5. 4 .2 Piping from First Block Valve to Instrument

1. Except when service conditions require a different alloy,piping material shall be 1/2 inch O.D. x 0.035 inchminimum wall 316 SS tubing.

2. Tube fittings shall be compression type and consist ofsame materials as tubing.

3. Use of tubing unions shall be minimized. If necessary tojoin two or more pieces of stainless steel or other alloytubing, a Swagelok or Gyrolok tubing union shall be used.

4. Except for process piping, manifolds in all services shallbe three-valve, made of 316 SS, suitable for 2 inch pipeclamp mount, such as Anderson Greenwood Model M4AVS.

5. Manifolds shall be capable of being rodded out.

6. Differential pressure transmitters shall have pressurebleed valves in body, piping, or manifold valve inaccordance with Drawings 9S-9255, 9S-9170, and 9S-9191.

5. 4 .3 Seal Pots

1. Services that require seal pots include (type of sealingliquid is oil):

a. Acid flow meters.

b. Differential pressure instruments on acid contactors.

c. Caustic flow meters.

2. Process fluids subject to measurement may be isolated fromdifferential pressure instruments with seal pots locatednear pressure connections.

3. A suitable sealing liquid, such as oil, glycerin, or 100%glycol, shall be used to seal instruments and pots ortees.

5. 4 .4 Drip Pots

1. Services that require drip pots where instrument is belowconnections include:

a. Fuel gas.

b. Natural gas.

c. Plant air.

d. Forced air to boilers or furnaces.

2. If transmitter cannot be line mounted adjacent to primaryflow element and if transmitter body is to be mounted



below pressure tap connections, drip pots shall berequired.

3. Connections to differential pressure transmitter shall befrom top of drip pot in accordance with Drawings 9S-9255,9S-9170, and 9S-9191.

5. 4 .5 Purging of Differential Pressure Leads

1. Purge arrangements shall be subject to Owner approval.

2. Instruments used in catalyst service shall be purged withair or gas using suitable restrictions and pipingarrangement. Purging shall conform to Drawings 9S-9255,9S-9170, and 9S-9191.

3. Instruments used in certain coking, slurry, or dirtyservices shall be purged with a suitable liquid and haveproper restrictions and piping arrangement per Drawings9S-9255, 9S-9170, and 9S-9191.

6. FIELD MOUNTED PRESSURE GAGES

6.1 Application

6. 1 .1 Remote Connected Gages

1. Remote connected gages may be used, provided conditions inparagraphs 2. through 6. are met.

2. Gage shall be within 50 feet of pressure point.

3. Fluid shall not contain entrained solids, wax, or othermaterial that might cause plugging or freezing.

4. Remote connected gages shall not be used in high viscosity(typically greater than 300 SUS) fluids at minimum ambientdesign temperature.

5. Difference in elevation between process point and gageshall not result in a liquid head equivalent pressureamounting to an appreciable part of normal operatingpressure.

6. Gage shall not be located on a control panel.

6. 1 .2 Field Mounted Gages

1. Field mounted gages shall be used to read pressure in thefollowing services:

a. Top of liquid filled towers or vessels.

b. Above liquid level in bottom of vessels, such asfractionating towers, strippers, absorbers,accumulators, K.O. drums, and separators.

c. Discharge of pumps per Drawing 9S-8262. Projectspecification shall include requirement on suctionside of pumps.

d. Discharge of each stage of multistage compressor.

e. Utility lines, such as:

(1) Fuel gas to gas engine.



(2) Fuel gas, fuel oil, pilot gas, and steam to firedheaters in accordance with Drawings 9S-9344 and9S-9345.

(3) Steam supply to vacuum ejectors.

(4) Utilities at process unit limits in accordancewith Drawing 1S-1784.

f. Steam chest on steam heated reboilers.

g. At field mounted pressure controllers, pressuretransmitters, and at least one leg of differentialpressure impulse lines. (Conditions in which both legsrequire monitoring are listed in h.)

h. Points at which it is desirable to read pressure dropacross equipment, such as:

(1) Strainers, separators, dryers, and meters.

(2) Special valves.

(3) Coils of fired process heaters.

(4) Superheater steam coils.

(5) Shell and tube heat exchangers.

(6) Equipment in which coking or clogging may occur.

2. Pressure transmitters with local indicators (instead ofpressure gages) shall be installed in services withdifferential pressure less than 5 psi or differential lessthan 10% of static pressure in psi.

6. 1 .3 Services That Require Pressure Connections Only (No Gage)

1. Top of fractionating towers.

2. Steam to individual vacuum ejector jets.

3. Vacuum developed by individual vacuum ejector jets.

4. Fuel gas pressure at each burner.

5. Fuel oil pressure at each burner.

6. Locations that may require pressure measurements forfuture test runs to determine equipment performance orefficiency.

7. Absorber or fractionating towers in vapor zone at top oftower, in feed section, and below bottom tray for pressuredifferential measurement.

6.2 Design

6. 2 .1 Range

1. Direct connected gage range shall be selected fromstandard ranges in Table 1.

2. Normal operating range shall be approximately withinmiddle one-third of total gage range.

6. 2 .2 Gage Dials

1. Gage dials shall be sized as follows:



a. Field or panel mounted direct connected in generalservice shall be 4 1/2 inches.

b. Auxiliary gages on mechanical equipment shall be1 1/2 inches to 3 1/2 inches.

2. Dials for receiver gages shall conform to GEMS K-10D.

6. 2 .3 Case Protection

1. Cases for indicating pressure gages shall be one of thefollowing:

a. Solid front type with blowout back.

b. Standard type with blowout discs located in lowerside of case.

2. Cases with blowout backs shall have integral bosses ormounting pads on back arranged such that case pressurerelief devices are functional on gages mounted on flatsurfaces.

6. 2 .4 Liquid Filled Gages

1. If increased reliability is required and cost can bejustified, liquid filled gages are recommended.

2. Type of gage to be used shall be included in projectspecifications.


6. 3 .1 Pressure Gages

1. Gages shall be bellows type for pressure ranges less than0 to 15 psi.

2. Draft gages shall be diaphragm type.

3. Materials and construction for pressure gages shallconform to GEMS K-801M.

6. 3 .2 Gage Chemical Seals

1. Factory installed diaphragm seal (used to protect pressureelement) shall as a minimum be 316 SS.

2. Liquid fill of suitable characteristics shall be used forelement and void above diaphragm.

3. Filled system seals shall be avoided if process pressuresare below 25 mm HG absolute.

6. 3 .3 Condensate Traps

Condensate trap shall be Anderson Greenwood Model CT-7 orequal.

6. 3 .4 Pulsating Services

1. Gage cases used in services that have rapidly pulsatingpressures shall be filled with silicone, glycerin, orglycerin and water.

2. Gages shall have a case blowout panel and atmosphericcompensation.

3. If severe pulsations are expected, gage piping may includepulsation damper (in addition to liquid fill).



4. Pressure gages for severe service or high accuracy shallbe Permacall or equal.

6. 3 .5 Installation

1. Field mounted pressure gages shall be installed inaccordance with Drawings 9S-9243 through 9S-9251.

2. If a pressure transmitter tap is already required, gagetap may be tee connected off same vessel connection usedfor transmitter.

6.4 Safety

Field mounted pressure gage safety shall conform to GEMS K-10D and K-1D.

7. PRESSURE SWITCHES

7.1 Application

1. Pressure switches shall be used in accordance with GEMS K-17D.

2. Pressure switches are not be permitted in shutdown service.Transmitters shall be used in such service.

7.2 Design

1. Electrical requirements of pressure switches shall conform toelectrical specifications in GEMS K-1D.

2. Pressure switches shall have adjustable set point with single pole-double throw or double pole-double throw contacts, as required.Dual set point switches, if required, shall be specified on datasheet.

3. Pressure instruments in the field shall have:

a. Top or side taps for gas.

b. Side taps for liquid.

4. Tubing to and on instruments in gas service shall be located aboveprocess line.

5. Routing of tubing to transmitter shall not have pockets.

6. Tubing to and on instruments in liquid service shall be mountedbelow process line.

7. Actuation differential and/or hysteresis of pressure switches usedfor alarm shall not exceed 1.8% of normal operating range.Transmitters shall be required for shutdown service.

8. Current switches shall conform to GEMS K-14D.

9. Process pre-trip alarms and shutdowns shall have a pressuretransmitter. Transmitter's output shall be used for “switch”actuation through the instrument control or safety system.

10. Pressure setting shall be in middle third of switch range.


1. Materials and construction requirements for pressure switches shallconform to Section 4.3 and GEMS K-802M.

2. Unless approved otherwise, switches shall not be bellows type ormercury.



7.4 Installation

1. Pressure instruments shall be installed per Drawings 9S-9244, 9S-9245, 9S-9246, 9S-9247, 9S-9249, 9S-9250, and 9S-9251.

2. Pressure switches shall be mounted in areas free from vibration.

3. If vibration is expected, pressure switches shall not be mounteddirectly to pipe.

4. Pressure switches shall be piped in accordance with details forremote mounted pressure transmitters.

5. Direct mounted pressure switches in hydrocarbon service shall havea mineral insulated (MI) cable seal (preferred) or two conduitseals in series separated by a T-fitting with breather/draininstalled at switch.

6. Pneumatic connected pressure switches shall be mounted inaccordance with GEMS K-14D.

7.5 Safety

Pressure switch safety requirements shall conform to GEMS K-1D.



TABLE 1STANDARD RANGES VS. OPERATING RANGES (TYPICAL)

Standard Range - PSIG Approximate Operating Range - PSIG

0 - 30 10 - 20

0 - 60 20 - 40

0 - 100 30 - 70

0 - 200 65 - 135

0 - 400 135 - 275

0 - 800 260 - 540

0 - 1500 500 - 1000

0 - 3000 1000 - 2000

0 - 5000 1500 - 3500

Note - Compound (pressure-vacuum) ranges of above may be used as needed.

Normas Texaco GEMS K-8D7 Pressure Measurement

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