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SynC · Historical revision

Pressure Instrumentation

Revision4
EditedOct 8, 2026
StatusSuperseded
Contents

View changes in this revision   Revision history

Historical revision. This is editorial revision 4, kept so citations to it stay resolvable. It is not the current text of this standard — see the current revision.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Remade from scratch to the authoring rules: defaults asserted only where four of five projects would choose them, and scope boundaries matched to the neighboring standards

1 Scope

NOTE This standard covers the pressure measurement point from the instrument side of the manifold or root valve to the signal-output terminals of the transmitter or the contacts of the switch: the pressure, vacuum, and differential pressure transmitter, its sensing element and isolating diaphragm, its process connection and process flanges, its housing and output signal, the diaphragm seal and capillary where one is furnished, the local pressure gauge with its snubber and siphon, and the pressure switch. (1.1)
NOTE A point belongs to this standard when it carries a tag in the project instrument index and its signal is read by a process controller or its reading or contact is used at the equipment, whether the pipe it sits on carries a process fluid, a plant utility, chilled water, or compressed air; a point belongs to HVAC Controls InstrumentationHVAC Instrumentation and Control DevicesResolves to the current adopted revision.sync/hvac-controls-instrumentation when it is wired to a building automation field controller and its range and measurement error are selected under Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system. The same tap on the same pipe is specified under whichever standard owns the controller that reads it, and a gauge that a piping or equipment standard furnishes as part of its own assembly stays with that standard. (1.2)
NOTE The transmitter body, its pressure sensor, its process connection, and its pressure calibration of a multivariable transmitter are specified under this standard; the RTD or thermocouple, its thermowell, and the verification of its temperature reading are specified under Temperature InstrumentationTemperature InstrumentationResolves to the current adopted revision.sync/temperature-instrumentation. (1.3)
NOTE The following are outside this standard and are governed elsewhere. (1.4)
  • The RTD, thermocouple, or thermistor, its thermowell, and the verification of its temperature reading, governed by Temperature InstrumentationTemperature InstrumentationResolves to the current adopted revision.sync/temperature-instrumentation
  • Flow inferred from an orifice, venturi, or nozzle, including the pairing and sizing of the primary element with its transmitter, governed by Flow MeasurementFlow MeasurementResolves to the current adopted revision.sync/flow-measurement
  • Liquid level inferred from hydrostatic head, whether by a submersible sensor or by a transmitter on a tank nozzle, governed by Level SensorsLevel MeasurementResolves to the current adopted revision.sync/level-sensors
  • Loop architecture, tag numbering, the instrument index, and loop diagrams, governed by Process InstrumentationProcess InstrumentationResolves to the current adopted revision.sync/process-instrumentation and Control Systems IntegrationControl Systems Integration and TestingResolves to the current adopted revision.sync/control-systems-integration
  • The root valve, the manifold, the impulse tubing, seal pots, and the heat tracing of the hook-up, governed by Instrument Installation And TubingInstrument Installation and Impulse TubingResolves to the current adopted revision.sync/instrument-installation-and-tubing
  • Pressure sensors furnished inside equipment and wired to the equipment's own controller, such as the discharge sensors of a packaged compressor, a chiller, or a packaged pump station, governed by the standard for that equipment, for example Compressed Air SystemsCompressed Air SystemsResolves to the current adopted revision.sync/compressed-air-systems, ChillersChillersResolves to the current adopted revision.sync/chillers, and Packaged Pump StationsPackaged Pump and Lift StationsResolves to the current adopted revision.sync/packaged-pump-stations
  • Piezometers and total pressure cells in soil and groundwater, governed by Geotechnical Instrumentation And MonitoringGeotechnical Instrumentation and MonitoringResolves to the current adopted revision.sync/geotechnical-instrumentation-and-monitoring
  • Pressure relief, safety, and self-contained regulating valves, governed by the piping or equipment standard for the service they protect, and modulating control valves with their actuators and positioners, governed by Control Valves And ActuatorsControl Valves and ActuatorsResolves to the current adopted revision.sync/control-valves-and-actuators
  • Controllers and input cards, field networks and fieldbus segment design, and operator interfaces, governed by Programmable Logic ControllersProgrammable Logic ControllersResolves to the current adopted revision.sync/programmable-logic-controllers, Process Control NetworksProcess Control NetworksResolves to the current adopted revision.sync/process-control-networks, and SCADA And HMI SystemsSCADA and HMI SystemsResolves to the current adopted revision.sync/scada-and-hmi-systems
  • Control panels and the marshalling of field signals, governed by Industrial Control PanelsIndustrial Control PanelsResolves to the current adopted revision.sync/industrial-control-panels
  • Raceway and cable for instrument wiring, governed by Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit and Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables
  • The calibration laboratory itself; this standard references the laboratory only as the source of the traceable certificate
1.5 Each point's tag, service, process fluid, instrument type (transmitter, local gauge, switch, or a combination), measurement reference, calibrated range, engineering units, process design pressure and temperature including startup and upset conditions, maximum static line pressure for a differential point, switch setpoint and reset direction, and safety instrumented function designation shall be as indicated on the instrument index and instrument data sheets.
1.6 Where a process condition needed to select or verify an instrument is not stated on the instrument data sheet, the Contractor shall request it from the Engineer in writing before procuring the instrument.

2 Referenced Standards

2.1 Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where the contract documents, the adopted building code, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
ASME B40.100 Pressure Gauges and Gauge Attachments
ASME PTC 19.2 Pressure Measurement
ASME B16.5 Pipe Flanges and Flanged Fittings
ASME B1.20.1 Pipe Threads, General Purpose (Inch)
ASME B31.3 Process Piping
ANSI/ISA-5.1 Instrumentation Symbols and Identification
ANSI/ISA-20 Specification Forms for Process Measurement and Control Instruments, Primary Elements, and Control Valves
ANSI/ISA-51.1 Process Instrumentation Terminology
ANSI/ISA-12.27.01 Requirements for Process Sealing Between Electrical Systems and Flammable or Combustible Process Fluids
ANSI/ISA-62382 Automation Systems in the Process Industry - Electrical and Instrumentation Loop Check
IEC 60770-1 Transmitters for Use in Industrial-Process Control Systems - Methods for Performance Evaluation
IEC 61518 Mating Dimensions Between Differential Pressure (Type) Measuring Instruments and Flanged-On Shut-Off Devices up to 413 bar
IEC 61511 (ANSI/ISA-61511) Functional Safety - Safety Instrumented Systems for the Process Industry Sector
API RP 551 Process Measurement
NAMUR NE 43 Standardization of the Signal Level for the Failure Information of Digital Transmitters
NSF/ANSI/CAN 61 Drinking Water System Components - Health Effects
CGA G-4.1 Cleaning of Equipment for Oxygen Service
3-A 74- 3-A Sanitary Standards for Sensors and Sensor Fittings and Connections
NFPA 70 National Electrical Code (Articles 500 through 505, hazardous locations)
NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum)
UL 50E Enclosures for Electrical Equipment, Environmental Considerations
UL 508 Industrial Control Equipment
UL 913 Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous (Classified) Locations
UL 1203 Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for the Engineer's review and return before any pressure instrument is procured:
  • Product data for each transmitter, gauge, switch, and diaphragm seal model, giving the sensing element, the reference accuracy and the method by which it is stated, the rangeability, the overpressure and static pressure limits, the published long-term stability and ambient temperature effect, the process temperature limits, the wetted materials, the fill fluid, the output signal, the enclosure rating, and the hazardous-location certification
  • A completed instrument data sheet in the ANSI/ISA-20 format, or a format accepted by the Engineer, for every tagged point
  • A diaphragm seal assembly drawing for each sealed point giving the seal type, process connection, diaphragm material, fill fluid, capillary length and armor, and the manufacturer's calculation of the temperature effect and the response time of the assembly at the ambient and process temperatures stated on the instrument data sheet
  • Hazardous-location certificates for each instrument in a classified location and, for intrinsically safe loops, the control drawing with the entity parameters of every device in the loop
  • A transmitter configuration sheet for each transmitter giving the calibrated range, the engineering units, the damping, the failure output direction, the transfer function, and the write-protection state
  • A mounting detail for each mounting arrangement furnished, showing the bracket, the stand, and the connection to the manifold or impulse tubing
Required Action Submittalscheckbox
☑ Product data for each instrument model
☑ Instrument data sheet for every tagged point
☑ Diaphragm seal assembly drawings with temperature effect calculations
☐ Hazardous-location certificates and intrinsically safe control drawings
☑ Transmitter configuration sheets
☑ Mounting details
3.1.2 A sealed transmitter shall not be filled or calibrated until its seal assembly drawing has been reviewed and returned without exception.

3.2 Informational Submittals

3.2.1 The Contractor shall submit the following for information before installation begins:
  • Factory calibration certificates for the transmitters, gauges, and switches covered by the certificate scope selected under Calibration
  • Manufacturer's installation instructions for each instrument model
  • The certificate of safety integrity level capability under IEC 61511 and the manufacturer's proof-test procedure for each transmitter or switch serving a safety instrumented function
  • NSF/ANSI/CAN 61 certification for each instrument whose wetted parts contact potable water
  • The cleaning certification under CGA G-4.1 for each instrument in oxygen service
Required Informational Submittalscheckbox
☑ Factory calibration certificates
☑ Manufacturer's installation instructions
☐ Safety integrity level capability certificates and proof-test procedures
☐ Potable water certifications
☐ Oxygen cleaning certifications

3.3 Closeout Submittals

3.3.1 The Contractor shall submit the following before the pressure instruments are accepted:
  • As-left calibration and configuration record for every transmitter, gauge, and switch, including the field verification and the installed zero trim
  • Operation and maintenance data giving the recalibration interval, the proof-test interval where applicable, and the part number of every replaceable sensor module, display, terminal block, gasket, and seal assembly
  • Warranty documentation
Required Closeout Submittalscheckbox
☑ As-left calibration and configuration records
☑ Operation and maintenance data with recalibration intervals
☑ Warranty documentation
3.3.2 Loop check records and as-built loop diagrams shall be submitted as required under Control Systems IntegrationControl Systems Integration and TestingResolves to the current adopted revision.sync/control-systems-integration and shall not be duplicated in this closeout package.

4 Quality Assurance

4.1 Conformance and Certification

4.1.1 Pressure gauges, diaphragm seals, snubbers, siphons, and pressure limiter valves shall conform to ASME B40.100.
4.1.2 Transmitter performance terms shall carry the meanings of ANSI/ISA-51.1, and the reference accuracy of each transmitter shall be published as a percentage of calibrated span including the combined effects of linearity, hysteresis, and repeatability, determined under IEC 60770-1.
NOTE A reference accuracy that leaves out hysteresis or repeatability, or that is stated at a single span rather than across the turndown, reads tighter on paper than the same transmitter reads in service, and two products stated on different bases cannot be compared; holding every submittal to the same method is what makes the accuracy field in this standard a comparison rather than a slogan. (4.1.3)
4.1.4 Pressure switches shall be listed by a Nationally Recognized Testing Laboratory as industrial control equipment under UL 508 for the connected voltage and load.
4.1.5 Instruments installed in a classified hazardous location shall be listed by a Nationally Recognized Testing Laboratory for the class, division or zone, group, and temperature code present, to UL 1203 where an explosion-proof enclosure is the means of protection and to UL 913 where intrinsic safety is the means of protection.
4.1.6 Each transmitter or switch serving a safety instrumented function designated in the instrument index shall carry a certificate of safety integrity level capability under IEC 61511 issued by an accredited assessor, with the failure rates and the proof-test coverage stated.

4.2 Source Limitation

4.2.1 The manufacturer source limitation applying to pressure instruments shall be as indicated in the datasheet.
Pressure Instrument Source Limitationradio
● Single manufacturer for all transmitters and a single manufacturer for all gauges
○ Single manufacturer for all transmitters, gauges, and switches
○ No source limitation
NOTE Transmitters from one manufacturer share a configuration tool, a spare sensor module, and a device description file in the control system, and gauges from one manufacturer share a case, a window, and a fill; requiring one manufacturer for transmitters, gauges, and switches together narrows the bid list to the few suppliers who make all three and buys nothing a two-source limit does not. (4.2.2)

4.3 Identification

4.3.1 Each instrument shall be identified by the tag number assigned under Process InstrumentationProcess InstrumentationResolves to the current adopted revision.sync/process-instrumentation in accordance with ANSI/ISA-5.1.
4.3.2 Each transmitter, gauge, switch, and diaphragm seal assembly shall carry a stainless steel tag plate stamped or engraved with its tag number and attached with stainless steel wire or screws.
4.3.3 Transmitters shall additionally carry the calibrated range and engineering units on the tag plate or on a second stainless steel plate.
NOTE Two transmitters of one model ranged for different services look identical on a pipe rack, and the range on the plate is what lets a technician with a handheld communicator and a work order find the right one without reading the configuration of each. (4.3.4)

5 Environmental and Service Conditions

5.1 Ambient and Process Temperature

5.1.1 Instruments mounted outdoors shall operate within their published accuracy between Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum and Site Ambient Temperature MaximumSite Ambient Temperature MaximumParameterEach project supplies its own value.site-ambient-temperature-maximum, including solar gain on an unshaded housing.
5.1.2 Where the process temperature at a point exceeds the published process temperature limit of the transmitter, gauge, or switch, the instrument shall be connected through impulse tubing, a siphon, or a remote diaphragm seal with capillary so that the fluid at the sensor is within the published limit.
NOTE An isolating diaphragm sits a fraction of an inch from the sensing element and the fill behind it, and a hot fluid against the diaphragm heats the fill and the sensor together; the length of tubing or capillary between the process and the sensor is what lets the fluid cool to the rating before it arrives. (5.1.3)
5.1.4 Where an absolute pressure instrument is ranged to include local atmospheric pressure, the range shall account for the atmospheric pressure at AltitudeAltitudeParameterEach project supplies its own value.altitude.

5.2 Enclosure Rating

5.2.1 Transmitter housings, switch enclosures, and junction boxes furnished under this standard shall carry at least the enclosure rating indicated in the datasheet, rated under NEMA 250 or UL 50E.
Minimum Enclosure Ratingselect
NEMA Type 1
NEMA Type 12
NEMA Type 13
NEMA Type 3R
NEMA Type 4
NEMA Type 4X
NEMA Type 7
NOTE Type 1 is the datasheet default because it is the rating that every location satisfies; the clauses that follow raise it for the locations that need more, whatever the datasheet selects. A project whose points are mostly outdoors or in a process area raises the datasheet value instead so that the few interior points are not the exception. Type 4 excludes hose-directed water and wind-driven rain; Type 4X adds corrosion resistance for salt air, chemical fumes, and washdown chemicals; Type 12 and Type 13 exclude dust and dripping or sprayed non-corrosive liquid indoors; Type 7 is the explosion-proof construction for Class I, Division 1. (5.2.2)
5.2.3 Enclosures mounted outdoors shall be rated NEMA Type 3R, Type 4, or Type 4X.
5.2.4 Enclosures mounted where airborne dust or non-corrosive liquid drips or sprays accumulate shall be rated NEMA Type 12, Type 13, Type 4, or Type 4X.
5.2.5 Enclosures mounted in locations subject to washdown or hose-directed water shall be rated NEMA Type 4 or Type 4X.
5.2.6 Enclosures mounted in locations exposed to corrosive fumes, salt air, or washdown chemicals shall be rated NEMA Type 4X.
5.2.7 Enclosures in a Class I, Division 1 location where an explosion-proof enclosure is the means of protection shall be rated NEMA Type 7 in addition to the rating required for the environment.

5.3 Hazardous Locations

5.3.1 The hazardous-location classification at each instrument shall be as indicated on the electrical area classification drawings.
5.3.2 Instruments in a classified location shall be protected by the method indicated in the datasheet.
Hazardous Location Protection Methodradio
○ Intrinsically safe loop with a barrier or galvanic isolator in the control panel
○ Explosion-proof enclosure with conduit seals
○ Nonincendive equipment and wiring
● Not applicable, no classified locations
NOTE An intrinsically safe loop keeps the field device and its wiring below ignition energy, so the housing can be opened and the transmitter configured with the area live, at the cost of a barrier per loop and an entity-parameter check on every device in it; an explosion-proof enclosure contains an ignition, so it needs conduit seals and a de-energized area before the cover comes off; nonincendive equipment is listed for Division 2 and has no standing in Division 1. The method is a plant-wide convention because it sets the panel design, the wiring practice, and the maintenance procedure for every loop. (5.3.3)
5.3.4 Conduit entries into enclosures in Class I locations shall be sealed in accordance with NFPA 70 Article 501 and the listing of the enclosure.
5.3.5 Where a single isolating diaphragm separates a flammable or combustible process fluid from the electrical system, the instrument shall be certified under ANSI/ISA-12.27.01 for that condition.
5.3.6 The temperature code of each instrument in a classified location shall be lower than the autoignition temperature of the flammable material present, with the housing temperature at the maximum process and ambient temperature included in the determination.
5.3.7 Each intrinsically safe loop shall be documented on a control drawing that lists every device in the loop with its entity parameters and shows that the cable capacitance and inductance are within the barrier's allowed values.

5.4 Safety Instrumented Functions

5.4.1 Transmitters and switches serving a safety instrumented function designated in the instrument index shall be furnished with the diagnostic coverage, the proof-test interval, and the proof-test procedure stated on the instrument data sheet.
5.4.2 Transmitters serving a safety instrumented function shall be configured with write protection enabled after commissioning and shall report the protection state to the logic solver where the protocol supports it.
5.4.3 A mechanical pressure switch shall not initiate a safety instrumented function unless the instrument index designates the switch for that function.
NOTE The determination of the safety integrity level and the design of the safety instrumented system are process safety scope outside this standard; this standard furnishes the field device with the certified capability the instrument index calls for. (5.4.4)

5.5 Process Fluid Compatibility

5.5.1 Every wetted part of an instrument in potable water service, including the isolating diaphragm, the seal diaphragm, the gauge tube and socket, and any fill fluid behind a single diaphragm, shall be certified under NSF/ANSI/CAN 61.
5.5.2 Instruments in oxygen or oxygen-enriched service shall be cleaned and packaged under CGA G-4.1 and filled with a halocarbon or other inert fill fluid, and no hydrocarbon oil or glycerin shall be present in the sensor, the seal, or the gauge case.
NOTE A hydrocarbon fill behind a diaphragm is a fuel, and a diaphragm rupture in oxygen service puts that fuel into an oxidizer at pressure; the inert fill and the clean assembly are what keep a sensor failure from becoming a fire. (5.5.3)
5.5.4 Instruments at points the instrument index designates for hygienic service shall have a sanitary clamp or other crevice-free connection with a flush diaphragm, a surface finish not rougher than 32 µin. Ra on product-contact surfaces, and a food-grade fill fluid, and shall be certified under 3-A 74-.
5.5.5 Instruments at points the instrument index designates for hydrogen service shall have a gold-plated isolating diaphragm or another diaphragm construction the manufacturer rates for hydrogen permeation at the process pressure and temperature.
NOTE Hydrogen atoms pass through a thin stainless steel diaphragm, recombine as gas in the fill behind it, and push the diaphragm outward, so the zero drifts upward over months and the sensor eventually fails; the gold layer closes the path. (5.5.6)

6 Measurement Points

6.1 Measurement Reference and Range

NOTE A gauge pressure instrument reads against the local atmosphere, so a gauge reading of zero is atmospheric; an absolute instrument reads against a sealed vacuum reference, so barometric change does not move it; a differential instrument reads the difference between two connections and sees the static line pressure on both; a compound instrument is a gauge instrument whose scale extends below zero into vacuum; a sealed gauge instrument reads against a sealed reference at atmospheric pressure and is the construction used where a vent to atmosphere is impractical at high ranges. Which reference a point needs is a property of the measurement and is stated in the instrument index for every point. (6.1.1)
6.1.2 Where the instrument data sheet states a calibrated range, that range shall govern; where it states only the operating conditions, the Contractor shall propose a range that places the normal operating pressure between 25 percent and 75 percent of span and shall submit it on the transmitter configuration sheet or the gauge product data for the Engineer's review.
NOTE An instrument ranged far above its operating pressure reads in the bottom of its scale, where a gauge pointer is hardest to read and a transmitter's accuracy as a percentage of span is spread over the least pressure; an instrument ranged too close leaves no room for a transient. Twice the operating pressure puts the normal reading near mid-scale, which is the band ASME B40.100 recommends for gauges and the band in which a transmitter's percentage-of-span error is smallest in engineering units. (6.1.3)
6.1.4 Instruments at points where the pressure can fall below atmospheric under any operating, startup, or upset condition stated on the instrument data sheet shall have a compound or absolute range.
6.1.5 Each instrument shall read in the engineering units stated on the instrument data sheet, with transmitters configured and gauge dials graduated in those units.

6.2 Local Indication Policy

6.2.1 Local pressure gauges shall be furnished at transmitter points as indicated in the datasheet, in addition to the gauges the instrument index designates at points with no transmitter.
Local Gauge at Transmitter Pointsradio
○ A local gauge at every transmitter point
○ A local gauge at every transmitter point whose transmitter has no local display
○ A local gauge only at the transmitter points the instrument index designates
NOTE A gauge beside a transmitter reads with no power, no handheld, and no control system, and it gives the operator at the equipment a second opinion when the two disagree, at the cost of a second tap or a tee, a second wetted part, and a second instrument to calibrate and to leak; a transmitter display shows the same value the control system sees and nothing when the loop is down. Which of the three policies a plant holds depends on how its operators work the equipment, so the field carries no default. (6.2.2)

7 Pressure Transmitters

7.1 Sensing Element

7.1.1 Transmitters shall have the sensing element indicated in the datasheet.
Transmitter Sensing Elementselect
Piezoresistive silicon
Capacitance
Resonant silicon
Metal thin-film strain gauge
Ceramic thick-film
Manufacturer's standard (by default)
NOTE A piezoresistive silicon element is the most common and the least costly, and its output moves with temperature in a way the transmitter electronics have to correct; a capacitance element resolves very small differential pressures with low drift and tolerates high static pressure, and is the element of most differential transmitters; a resonant silicon element gives the highest stability and accuracy of the group and is offered by few manufacturers; a metal thin-film element is welded to its diaphragm with no fill fluid and serves high pressures, hydrogen, and shock and vibration where a filled sensor would not; a ceramic element has no isolating diaphragm and no fill, resists abrasion and most chemicals, and is limited in pressure range. The manufacturer's standard element for the range and service is acceptable because the performance and material fields in this standard hold the result rather than the means. (7.1.2)
7.1.3 Transmitters shall withstand, without damage or a shift in calibration beyond the published reference accuracy, an overpressure of not less than 1.5 times the upper range limit and not less than the maximum pressure stated on the instrument data sheet including startup and upset conditions.
7.1.4 Differential pressure transmitters shall have a published static line pressure rating not less than the maximum static line pressure stated on the instrument data sheet, applied to either side alone and to both sides together.
NOTE A differential sensor that is rated for a few hundred inches of water difference may sit on a line at several hundred pounds per square inch, and a manifold operated in the wrong order puts the full line pressure on one side with the other vented; the static pressure rating is what the sensor survives in that moment, and it is a separate number from the overpressure limit of the differential range. (7.1.5)
7.1.6 The sensor fill fluid of a transmitter shall be silicone oil unless Process Fluid Compatibility requires an inert fill or the instrument data sheet states another fluid.

7.2 Process Connection

7.2.1 Gauge and absolute pressure transmitters shall have the process connection indicated in the datasheet unless the instrument data sheet states another connection at a point.
Gauge and Absolute Transmitter Process Connectionselect
1/2 in. NPT female
1/4 in. NPT female
1/2 in. NPT male
Flanged flush diaphragm, ASME B16.5
Sanitary clamp
NOTE A 1/2 in. female thread accepts the nipple or the manifold outlet that nearly every hook-up ends in and is the connection every transmitter is offered with; a 1/4 in. thread suits small-bore tubing connected without a manifold and seals less reliably at high pressure; a male thread screws into a block manifold or a tee without a nipple; a flanged flush diaphragm puts the sensor at the pipe wall with no dead leg, for slurries and fluids that plug a tap, at the price of a seal and its temperature effect; a sanitary clamp is the crevice-free connection of hygienic piping. (7.2.2)
7.2.3 Differential pressure transmitters shall have the process flange form indicated in the datasheet.
Differential Transmitter Process Flangeradio
○ Coplanar flange
○ Traditional biplanar flange
NOTE A coplanar flange carries both process ports on one face and mounts a compact manifold with the fewest joints; a traditional biplanar flange carries the ports on the two sides of the sensor body, mates to the manifolds and flange adapters that have been made to IEC 61518 dimensions for decades, and is the form offered by the most manufacturers. A plant that already holds spare manifolds of one form holds the field to that form. (7.2.4)
7.2.5 Differential transmitter process flanges shall have 1/4 in. NPT ports on the mating dimensions of IEC 61518 for connection to the manifold furnished under Instrument Installation And TubingInstrument Installation and Impulse TubingResolves to the current adopted revision.sync/instrument-installation-and-tubing, with 1/2 in. NPT flange adapters furnished at the points the instrument data sheet designates for impulse tubing connected without a manifold.
7.2.6 Differential transmitter process flanges shall have a drain and vent valve on each side.
7.2.7 Threaded process connections shall conform to ASME B1.20.1 and flanged connections to ASME B16.5.
7.2.8 Process flanges, flange adapters, and drain and vent valves shall be of Type 316 stainless steel or of the isolating diaphragm material where that material is a higher alloy.

7.3 Wetted Materials

7.3.1 The isolating diaphragm of each transmitter, or the process diaphragm of its seal where one is furnished, shall be of the material indicated in the datasheet at points for which the instrument data sheet does not designate a material.
Wetted Diaphragm Material for Points Not Otherwise Designatedselect
Type 316L stainless steel
UNS N10276 nickel-molybdenum-chromium alloy
UNS N04400 nickel-copper alloy
Tantalum
Titanium
Gold-plated Type 316L stainless steel
Alumina ceramic
NOTE Type 316L serves water, steam, air, and most process fluids and is the diaphragm every manufacturer stocks; the nickel-molybdenum-chromium alloy serves oxidizing and reducing acids, wet chlorine, and high chlorides; the nickel-copper alloy serves hydrofluoric acid, seawater, and caustic; tantalum serves the strongest acids, including hot hydrochloric and sulfuric, at the highest price of the group; titanium serves seawater, wet chlorine, and oxidizing acids; a gold layer on Type 316L closes the hydrogen path; alumina ceramic resists abrasion and nearly every chemical except hydrofluoric acid and strong caustic, with no fill behind it. The data sheet designates another material where the fluid at a point rules the default out. (7.3.2)
7.3.3 A wetted material shall be not less resistant to the process fluid than the piping material at the connection.
7.3.4 Gaskets and O-rings in contact with the process fluid shall be of an elastomer or fluoropolymer the manufacturer rates for the fluid, pressure, and temperature stated on the instrument data sheet.

7.4 Output Signal

7.4.1 Transmitters shall deliver the output signal indicated in the datasheet.
Transmitter Output Signalselect
4-20 mA with HART
4-20 mA without digital communication
FOUNDATION Fieldbus H1
PROFIBUS PA
WirelessHART
Modbus RTU over RS-485
NOTE A 4-20 mA loop with HART runs on two wires, reads on any analog input, and carries configuration and diagnostics over the same pair; without HART the transmitter is configured at its terminals and reports nothing but the value; a fieldbus transmitter puts the value and diagnostics on a segment shared with other devices and needs the segment design, power conditioner, and host integration that go with it; a wireless transmitter needs no field wiring and reports at an interval set by its battery life, which is what decides where it can be used; a Modbus transmitter suits a remote terminal unit or a packaged system with a serial port and has no live zero to show a broken wire. (7.4.2)
7.4.3 Transmitters with a 4-20 mA output shall be two-wire loop-powered devices that deliver their full output into the loop resistance of the installed loop at the minimum supply voltage of the control panel power supply.
7.4.4 HART transmitters shall support HART revision 7 or later.
7.4.5 Transmitters shall drive their output to the failure level under NAMUR NE 43 on a sensor fault or an internal fault, in the direction stated on the instrument data sheet for each point.
7.4.6 A WirelessHART transmitter shall not serve a point used for closed-loop control or a safety instrumented function unless the instrument index designates the point for wireless service.
7.4.7 Fieldbus and wireless transmitters shall join segments and networks designed under Process Control NetworksProcess Control NetworksResolves to the current adopted revision.sync/process-control-networks.
7.4.8 A level transmitter on a fuel storage tank furnished under Fuel Dispensing And Storage TanksFuel Storage TanksResolves to the current adopted revision.sync/fuel-dispensing-and-storage-tanks that provides an analog output to the plant monitoring system shall deliver the output signal selected above and shall meet the hazardous-location requirements of this standard.

7.5 Transmitter Performance

7.5.1 Transmitters shall have a published reference accuracy, stated under Quality Assurance, not exceeding the value indicated in the datasheet at the calibrated span of each point, at points for which the instrument data sheet does not state an accuracy.
Maximum Reference Accuracy for Points Not Otherwise Designatedrange
% of calibrated span
0.0250.040.050.0650.0750.10.150.20.250.5
NOTE The transmitter's error is one term in the loop's error budget beside the installation effects and the input card, so a transmitter tighter than the control system can use buys nothing, and the price step between a utility-grade and a premium transmitter is large; the budget for the loop is set by what the control system does with the value, which is why the field carries no default and the data sheet states a tighter value at the points that need one. (7.5.2)
7.5.3 Transmitters shall have a published rangeability from the upper range limit to the minimum calibrated span of not less than the ratio indicated in the datasheet, with the reference accuracy held over the published turndown at which it applies.
Minimum Rangeability, Upper Range Limit to Minimum Spanrange
to 1
51015203050100150200
NOTE Rangeability is what lets one sensor module serve many points and one spare serve them all, and it is also where the accuracy claim gives way: a transmitter turned down past the ratio at which its reference accuracy is stated carries a larger error that the product data states as a separate formula. A plant that standardizes on a few modules wants a high ratio; a plant that buys each point at its own range needs little. (7.5.4)
7.5.5 Transmitters shall have a published long-term stability and a published ambient temperature effect at the calibrated span, each stated in the product data, and the sum of the reference accuracy, the ambient temperature effect over the installed ambient range, and the stability over the recalibration interval selected under Calibration shall not exceed the total error stated on the instrument data sheet at points where one is stated.
7.5.6 Transmitters shall have adjustable output damping, configurable from the terminals or over the digital protocol, and shall be furnished with the damping stated on the transmitter configuration sheet.
7.5.7 Transmitters shall be configurable for range, engineering units, damping, transfer function, and failure direction without a pressure source connected.

7.6 Housing and Electrical Connection

7.6.1 Transmitter housings shall be of the material indicated in the datasheet.
Transmitter Housing Materialradio
● Coated die-cast aluminum
○ Stainless steel
NOTE A coated aluminum housing is light, inexpensive, and offered in every configuration, and its coating is what stands between it and a salt or chemical atmosphere; a stainless housing resists that atmosphere without a coating at several times the price and weight, and is the housing hygienic plants hold to so that nothing on the line is painted. (7.6.2)
7.6.3 Transmitter housings shall have the conduit entry indicated in the datasheet.
Transmitter Conduit Entryradio
● 1/2 in. NPT
○ 3/4 in. NPT
○ M20 x 1.5
NOTE A 1/2 in. entry fits the conduit size that serves a single loop and is the entry every housing is offered with; a 3/4 in. entry fits a larger conduit or a cable gland for armored cable and takes a reducer when the conduit is smaller; a metric entry suits equipment imported with metric glands and takes a listed adapter to join a conduit system under NFPA 70. (7.6.4)
7.6.5 Transmitter housings shall have a separate terminal compartment isolated from the electronics, threaded covers with a gasket that holds the enclosure rating required under Environmental and Service Conditions, and a housing that rotates on the sensor module for display and conduit orientation.
7.6.6 Transmitters shall be furnished with a local display as indicated in the datasheet.
Transmitter Local Displayradio
○ Display on every transmitter
○ Display on transmitters at points with no local gauge
○ No local display
NOTE A display shows the reading and the diagnostic state at the instrument, which lets a technician check a loop without a handheld communicator, and on a transmitter mounted at eye level it does what a gauge does with the loop live; it adds a windowed cover, a module to stock, and a cost per point, and it shows nothing when the loop is down. The choice pairs with the local gauge policy under Measurement Points. (7.6.7)
7.6.8 Transmitters shall be furnished with integral transient protection as indicated in the datasheet.
Integral Transient Protectionradio
○ Integral transient protection on every transmitter
○ Integral transient protection on outdoor and remotely located transmitters
○ No integral transient protection
NOTE A transient protector in the terminal compartment clamps the surge that lightning or a switching event induces on the loop before it reaches the electronics, and it is the cheapest point at which to protect a transmitter at the end of a long outdoor run; a transmitter inside a building on a short loop from a protected panel sees little, and the protector adds a terminal block to each point and a leakage path to ground that an insulation test has to allow for. (7.6.9)

7.7 Multivariable Transmitters

7.7.1 Where the instrument index designates a multivariable transmitter, the transmitter shall be furnished with the pressure sensor, process connection, output signal, and performance required by this standard, shall accept the temperature element furnished under Temperature InstrumentationTemperature InstrumentationResolves to the current adopted revision.sync/temperature-instrumentation, and shall report the differential pressure, the static pressure, and the process temperature as separate variables over the digital protocol.
7.7.2 Where a multivariable transmitter computes a flow, the computation and the primary element are furnished under Flow MeasurementFlow MeasurementResolves to the current adopted revision.sync/flow-measurement and the transmitter under this standard.

8 Diaphragm Seals and Capillaries

8.1 Seal Provision and Assembly

8.1.1 Diaphragm seals shall be furnished at the points the instrument index designates, of the seal type, process connection, and extension stated on the instrument data sheet.
NOTE A seal puts a flexible diaphragm and a captive fill between the process and the sensor, so a fluid that would plug, corrode, freeze, or overheat the sensor never reaches it, and the transmitter then reads the fill pressure as the process pressure; the fill expands with temperature and sags with its own head in a capillary, so every seal adds a temperature error and a response delay that the assembly drawing has to quantify. (8.1.2)
8.1.3 Each seal, its capillary, and its transmitter shall be furnished as one assembly, filled, evacuated, and calibrated together by the transmitter manufacturer, and shall not be disconnected after filling.
8.1.4 A seal shall be of the flush type where the data sheet states a fluid that is viscous, crystallizing, or solids-bearing, and of the extended type where the process nozzle at the point is longer than the diaphragm's reach.
8.1.5 A flushing ring shall be furnished between the process flange and the seal at the points the instrument data sheet designates for flushing or calibration access.

8.2 Seal Fill Fluid

8.2.1 Seal assemblies shall be filled with the fluid indicated in the datasheet at points for which the instrument data sheet does not designate a fluid.
Seal Fill Fluid for Points Not Otherwise Designatedselect
Silicone oil
High-temperature silicone oil
Halocarbon oil
Glycerin and water
Food-grade white mineral oil
Propylene glycol and water
NOTE Silicone oil holds its viscosity over the widest temperature band and is the fill every manufacturer offers first; a high-temperature silicone extends the band toward 600°F at the cost of a larger temperature effect; halocarbon is inert and is the fill for oxygen and chlorine; glycerin and water and propylene glycol and water are the fills accepted for food contact behind a single diaphragm, with freezing points that rule them out of cold service; food-grade white mineral oil is the hygienic fill with the lowest freezing point. The fluid is a process-contact material the moment the diaphragm fails, so its rating for the fluid matters as much as the diaphragm metal. (8.2.2)
8.2.3 Seal fill fluids shall be rated by the manufacturer for the vapor pressure at the maximum process temperature and for the lowest ambient and process temperature stated on the instrument data sheet, including vacuum service where the data sheet states it.

8.3 Capillaries

8.3.1 Capillaries shall be of Type 316 stainless steel with stainless steel flexible armor over their full length, of the length stated on the instrument data sheet and not longer than the manufacturer's published maximum for the fill and the range.
8.3.2 The two capillaries of a differential pressure seal assembly shall be of equal length and of the same fill, and shall be routed together so that both see the same ambient temperature.
NOTE Two capillaries of different lengths or on different sides of a pipe hold different volumes of fill at different temperatures, and the difference between the two expansions is read as a differential pressure that moves with the sun. (8.3.3)
8.3.4 Capillaries shall not be bent to a radius smaller than the manufacturer's published minimum, and no section of a capillary shall bear the weight of the transmitter or the seal.

9 Local Pressure Gauges

9.1 Gauge Element and Accuracy

9.1.1 Local gauges shall have the pressure element indicated in the datasheet at points for which the instrument data sheet does not designate an element.
Gauge Element for Points Not Otherwise Designatedradio
● Bourdon tube
○ Diaphragm or capsule
○ Bellows
○ Electronic digital gauge
NOTE A Bourdon tube is a flattened tube that straightens with pressure, has no fill and no power, and reads from about 15 psi to the highest ranges made; a diaphragm or capsule element flexes under pressure and resolves ranges in inches of water and ounces per square inch that a Bourdon tube cannot; a bellows element serves low ranges and compound ranges with a larger movement; an electronic digital gauge reads a sensor to a display, resolves to a fraction of a percent with no parallax, and needs a battery or a loop to power it. (9.1.2)
9.1.3 Gauges with a full-scale range in inches of water column or ounces per square inch shall have a diaphragm, capsule, or bellows element regardless of the selection above.
9.1.4 Gauges shall meet the ASME B40.100 accuracy grade indicated in the datasheet at points for which the instrument data sheet does not state a grade.
Gauge Accuracy Grade for Points Not Otherwise Designatedselect
Grade 4A
Grade 3A
Grade 2A
Grade 1A
Grade A
Grade B
Grade C
Grade D
NOTE Grade 2A, accurate to one half of one percent of span across the scale, is the grade of the stainless process gauge that industrial suppliers stock in every range and is the default for that reason; Grade 1A and Grade A cost less and are the commercial gauges of building services, with Grade A accurate to one percent through the middle half of the scale and two percent at the ends; Grade 3A and Grade 4A are test gauges accurate to a quarter and a tenth of one percent, used as references rather than as indicators; Grade B and Grade C are utility gauges whose error grows toward the ends of the scale, and Grade D is a utility gauge accurate to five percent across the scale; their readings serve to show that pressure is present rather than how much. (9.1.5)

9.2 Gauge Case and Dial

9.2.1 Gauges shall have the nominal dial size indicated in the datasheet at points for which the instrument data sheet does not state a size.
Gauge Dial Size for Points Not Otherwise Designatedrange
in.
1.522.53.544.568.512
NOTE A 4-1/2 in. dial is readable from the floor at a pipe rack and is the size in which every process gauge range and grade is stocked; the 2-1/2 in. and 3-1/2 in. dials fit a manifold or a panel and are read close up; the 6 in. and larger dials are read across a room or from grade at an elevated line. (9.2.2)
9.2.3 Gauge cases shall be of the material indicated in the datasheet.
Gauge Case Materialradio
● Type 304 stainless steel
○ Phenolic, solid-front with blowout back
○ Glass-fiber-reinforced thermoplastic
○ Painted steel
NOTE A stainless case resists the weather and the washdown of a process area and is the case on the stocked process gauge; a solid-front phenolic case puts a wall between the element and the dial and vents a tube rupture out the back, away from the reader; a reinforced thermoplastic case is light and resists corrosion at low cost and softens at high ambient temperature; a painted steel case is the lowest-cost commercial case and rusts where its coating is scratched. (9.2.4)
9.2.5 Gauges at points where the fluid is flammable, toxic, or a compressed gas above 1000 psi shall have a solid-front case with a blowout back regardless of the selection above.
9.2.6 Gauge windows shall be laminated safety glass, tempered glass, or a plastic the manufacturer rates for the case fill and the ambient temperature, and plain annealed glass shall not be used.
9.2.7 Gauge dials shall be white with black graduations and numerals, graduated in the engineering units stated on the instrument data sheet, with a pointer that reads to the graduation without parallax.

9.3 Gauge Connection

9.3.1 Gauges shall have the connection size indicated in the datasheet at points for which the instrument data sheet does not state a size, threaded to ASME B1.20.1.
Gauge Connection Size for Points Not Otherwise Designatedradio
○ 1/4 in. NPT
● 1/2 in. NPT
NOTE Gauges with a 4-1/2 in. or larger dial are made with a 1/2 in. connection and gauges with a 2-1/2 in. or smaller dial with a 1/4 in. connection, so the connection follows the dial at the ends of the size range and is a choice only in between; a 1/2 in. socket is stiffer against vibration and matches the manifold and valve ports of a process hook-up. (9.3.2)
9.3.3 Gauges shall have the connection location indicated in the datasheet.
Gauge Connection Locationradio
● Lower
○ Center back
○ Lower back
NOTE A lower connection stands the gauge upright on a nipple or a gauge valve at the pipe and is the location of the stocked process gauge; a center back connection mounts the gauge through a panel or a flush bracket with the dial facing the reader; a lower back connection suits a panel with the piping dropping behind it and a surface-mounted bracket. (9.3.4)
9.3.5 Gauge tubes and sockets shall be of the material indicated in the datasheet at points for which the instrument data sheet does not designate a material.
Gauge Tube and Socket Material for Points Not Otherwise Designatedselect
Type 316 stainless steel
Phosphor bronze tube with brass socket
UNS N04400 nickel-copper alloy
UNS N06600 nickel-chromium-iron alloy
NOTE A stainless tube and socket serve water, steam, air, oils, and most process fluids and are the wetted parts of the stocked process gauge; a bronze tube with a brass socket is the commercial gauge for water, air, and oil at lower cost and is attacked by ammonia, acids, and sulfur compounds; the nickel-copper alloy serves hydrofluoric acid, seawater, and caustic; the nickel-chromium-iron alloy serves high-temperature and high-pressure service and chlorides where a stainless tube would crack. (9.3.6)

9.4 Gauge Case Fill

9.4.1 Gauge cases shall be liquid-filled as indicated in the datasheet.
Gauge Case Fill Policyradio
○ Liquid-filled at every gauge
○ Liquid-filled at the points the instrument index designates for pulsation or vibration
○ Dry at every gauge
NOTE A liquid fill damps pointer flutter, lubricates the movement, and keeps condensation off the inside of the window, so a filled gauge on a pump discharge or a compressor outlives a dry one many times over; a fill adds cost to every gauge, hides a small leak in the case, is read with a vented plug that an installer has to open, and is a contaminant in a few services. Filling every gauge saves the step of deciding per point and is the policy of plants with reciprocating equipment throughout; filling only where designated is the policy of plants with mostly steady service. (9.4.2)
9.4.3 Liquid-filled gauges shall be filled with the fluid indicated in the datasheet.
Gauge Case Fill Fluidradio
● Glycerin
○ Silicone oil
○ Halocarbon oil
NOTE Glycerin is the fill on nearly every liquid-filled gauge sold, is inexpensive, and thickens until the pointer stalls at about -4°F; silicone oil keeps its viscosity to about -40°F and in high ambient heat; halocarbon oil is inert and is the fill for oxygen and chlorine service, where glycerin is a fuel. (9.4.4)
9.4.5 Where Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum is below 0°F, liquid-filled gauges mounted outdoors shall be filled with silicone or halocarbon oil regardless of the selection above.
9.4.6 Liquid-filled gauges shall have a vent plug or a fill plug with a vent position, and the vent shall be opened after installation.
NOTE A filled case that is sealed reads the pressure of the fill's own expansion against the element as a few percent of zero error on a hot afternoon; the vent lets the case breathe. (9.4.7)

9.5 Snubbers, Siphons, and Pressure Limiters

9.5.1 Gauges and switches at the points the instrument index designates for pulsating service shall be furnished with a snubber of the type indicated in the datasheet.
Snubber Typeradio
○ Porous sintered-metal
○ Piston
○ Adjustable needle
NOTE A porous snubber damps through a sintered disc, has no moving part, and plugs in dirty or viscous fluid; a piston snubber damps through the clearance around a loose piston that rises and falls with the pulse, clears itself, and is offered in several piston sizes for different fluids; an adjustable needle snubber is throttled in the field to the damping the gauge needs and can be throttled shut by mistake. Which one a plant stocks depends on the fluids its pulsating lines carry, so the field carries no default. (9.5.2)
9.5.3 Gauges and switches in steam service shall be connected through a siphon of the pigtail or coil type conforming to ASME B40.100, filled with water before the instrument is pressurized.
NOTE A siphon traps a column of condensate between the steam and the element, so the element reads the pressure through a cool liquid rather than through live steam; a dry siphon on first pressurization passes steam straight to the element until condensate forms, which is why it is filled first. (9.5.4)
9.5.5 Gauges at points where the instrument data sheet states pressure excursions above the full-scale range shall be furnished with a pressure limiter valve conforming to ASME B40.100, set to close below the full-scale range of the gauge.

9.6 Differential Pressure Gauges

9.6.1 Differential pressure gauges at the points the instrument index designates for filter, strainer, or pump differential indication shall have the element indicated in the datasheet.
Differential Pressure Gauge Elementradio
○ Piston
○ Diaphragm
○ Bellows
○ Dual Bourdon tube
NOTE A piston element is a magnet-coupled piston against a spring, tolerates the full static pressure on either side and a reversal, and is the low-cost gauge for a filter whose differential matters only as it approaches the changeout point; a diaphragm element resolves a few inches of water with the static pressure on both sides and is the gauge for low differentials in liquid service; a bellows element serves low differentials in gas and compound ranges; a dual Bourdon gauge reads two separate elements against one dial and shows both pressures and their difference, at the cost of the accuracy of two elements combined. (9.6.2)
9.6.3 Differential pressure gauges shall have a published static pressure rating not less than the maximum static line pressure stated on the instrument data sheet, and shall withstand that pressure applied to either side alone without damage or a shift in calibration.

10 Pressure Switches

10.1 Switch Construction

10.1.1 Pressure switches shall be of the type indicated in the datasheet.
Pressure Switch Typeradio
● Electromechanical snap-action switch
○ Electronic pressure switch with programmable setpoint
NOTE An electromechanical switch moves a snap-action contact with a diaphragm, piston, or Bourdon element against a spring, needs no power, and holds its setpoint for years with a deadband fixed by the mechanism; an electronic switch reads a sensor, sets its setpoint and deadband from a keypad or over a protocol, shows the pressure on a display, and reports its own faults, and it needs a supply and costs several times as much. (10.1.2)
10.1.3 Pressure switches shall have the contact arrangement indicated in the datasheet at points for which the instrument data sheet does not state an arrangement.
Pressure Switch Contact Arrangementradio
● Single-pole double-throw
○ Double-pole double-throw
○ Two independent single-pole double-throw contacts
NOTE A single-pole double-throw contact gives one circuit a closing and an opening path and is what a controller input or an alarm needs; a double-pole arrangement switches two circuits together, for a control circuit and a status indication from one setpoint; two independent contacts can be set at two pressures within one switch, for an alarm and a trip, with the deadband of each set separately. (10.1.4)
10.1.5 Switch setpoints shall be adjustable over the published adjustable range without disassembly, and the switch shall be furnished set to the setpoint and the reset direction stated on the instrument data sheet with the setpoint falling within the middle half of the adjustable range.
10.1.6 Switch deadband shall be adjustable where the instrument data sheet states a reset pressure, and shall not exceed the deadband stated there.
10.1.7 Switch contacts shall be rated for the voltage and the connected load stated on the loop diagram, and contacts switching a controller input at less than 100 mA shall be gold-flashed or hermetically sealed.
NOTE A silver contact relies on the arc of a few hundred milliamperes to burn off the film that forms on it, and switched into a dry circuit it builds that film until the input stops reading the contact; a gold flash or a sealed contact has no film to burn. (10.1.8)
10.1.9 Switch sensing elements shall withstand the overpressure and static pressure required of transmitters under Pressure Transmitters, with wetted parts of the material selected under Wetted Materials at points for which the instrument data sheet does not designate a material.
10.1.10 Switches shall have a published repeatability of the setpoint not worse than 1 percent of the adjustable range.

11 Calibration

11.1 Factory Calibration

11.1.1 Individual calibration certificates traceable to a national metrology institute shall be furnished for the scope indicated in the datasheet.
Individual Calibration Certificate Scoperadio
○ Every transmitter, every gauge, and every switch
○ Every transmitter, with a lot conformance certificate for gauges and switches
○ Transmitters, gauges, and switches at the points designated in the instrument index, with lot conformance certificates elsewhere
NOTE An individual certificate records the instrument's measured error at stated pressures and is what a loop error budget and a recalibration trend are built on; a lot certificate states that the lot met its grade or its reference accuracy, which is all a Grade A gauge or a general-purpose transmitter on an indication-only loop needs. The cost is a bench test per device, so the scope follows how many points carry an error budget the published accuracy alone does not satisfy. (11.1.2)
11.1.3 Every transmitter and switch serving a safety instrumented function, and every gauge of Grade 3A or Grade 4A, shall carry an individual calibration certificate regardless of the scope selected above.
11.1.4 Transmitter certificates shall report the as-shipped error at 0, 25, 50, 75, and 100 percent of the calibrated span, rising and falling, against a reference standard whose uncertainty is not more than one quarter of the transmitter's reference accuracy at that span.
11.1.5 Gauge certificates shall report the error at not fewer than five points across the scale, rising and falling, in accordance with ASME B40.100.
11.1.6 Switch certificates shall report the actuation and reset pressures at the set point, rising and falling, over not fewer than three cycles.
11.1.7 Sealed transmitter assemblies shall be calibrated with the seal and capillary attached and mounted in the orientation of the installation stated on the assembly drawing.

11.2 Field Verification

11.2.1 Before installation, each transmitter shall be verified at zero and at not fewer than one point above 50 percent of span with a portable reference whose uncertainty is not more than one quarter of the transmitter's reference accuracy, and the reading recorded on the as-left calibration record.
11.2.2 A device whose field verification disagrees with its factory certificate by more than its combined published error shall be returned and replaced rather than adjusted.
11.2.3 After installation and before loop check, each transmitter shall be zero-trimmed in its installed orientation with the process isolated and the sensor vented, and a differential transmitter equalized, and the trim recorded on the as-left calibration record.
NOTE The fill behind the diaphragm has weight, and a transmitter mounted with its diaphragm vertical reads that head as a zero offset of a fraction of an inch of water that a bench calibration with the diaphragm horizontal never saw; a sealed assembly with a capillary carries a larger head, and a wet leg on a differential point a larger one still. The trim at the installed orientation is what removes them, and it cannot be done on the bench. (11.2.4)
11.2.5 Each transmitter's as-left configuration, including the range, engineering units, damping, transfer function, failure direction, and write-protection state, shall be recorded on the as-left calibration record.
11.2.6 Each switch shall be verified at its setpoint and reset pressure with a portable reference after installation, and the actuation and reset pressures recorded on the as-left calibration record.
11.2.7 Loop checks from the instrument to the controller shall be performed and recorded under Control Systems IntegrationControl Systems Integration and TestingResolves to the current adopted revision.sync/control-systems-integration in accordance with ANSI/ISA-62382.
11.2.8 The recalibration interval stated in the operation and maintenance data shall be not longer than the interval indicated in the datasheet.
Maximum Recalibration Intervalrange
months
612243660
NOTE A transmitter drifts with thermal cycling, overpressure events, and the hydrogen or chemical attack its diaphragm sees, and a gauge movement wears with every pulse, so the interval is a judgment about the service rather than the device; the published stability over the interval is one term in the total error under Transmitter Performance, so a longer interval and a tight total error cannot both be held on a utility-grade transmitter; a point feeding a safety instrumented function follows its proof-test interval where that is shorter. (11.2.9)

11.3 Repeat Testing

11.3.1 The cost of repeating a factory calibration or a field verification after a failure shall be borne by the Contractor.

12 Installation

12.1 Transmitter and Switch Mounting

12.1.1 Transmitters shall be mounted as indicated in the datasheet at points for which the instrument index does not designate a mounting.
Transmitter Mounting for Points Not Otherwise Designatedradio
○ Direct-mounted on the manifold at the process tap
○ Bracket-mounted on a 2 in. pipe stand or wall near the tap
○ Rack-mounted with other transmitters at a common location
NOTE A direct-mounted transmitter has no impulse tubing to slope, freeze, or leak and the fewest joints, and it sits at the height and in the heat and vibration of the tap; a transmitter on a stand near the tap is read and serviced at eye level away from the line, at the cost of a short tubing run and a stand; a rack gathers many transmitters where a technician can reach them all and runs long tubing from each tap, with the lag, the freeze protection, and the leak points that length brings. The process fluid and the layout of the lines decide which a plant holds as its norm, so the field carries no default. (12.1.2)
12.1.3 Mounting brackets shall be of the material indicated in the datasheet.
Mounting Bracket Materialradio
○ Type 304 stainless steel
○ Carbon steel, zinc-plated or painted
NOTE A stainless bracket with stainless bolting outlasts the transmitter in a wet or corrosive area; a plated or painted carbon steel bracket costs less and serves indoors, and streaks rust down the stand where its coating is cut by the U-bolt. (12.1.4)
12.1.5 Bracket-mounted transmitters shall be mounted on a pipe stand or wall bracket at a height between 4 ft and 5 ft above grade or platform, within the tubing length the instrument data sheet states for the point.
12.1.6 Transmitters and switches shall not be supported by their impulse tubing or capillary, and a transmitter connected directly to a manifold shall be supported by the manifold's own mounting bracket or by the process connection where the manufacturer rates the connection to carry it.
12.1.7 Transmitters shall be mounted with the housing oriented so that the display faces the operator position and the conduit entry faces down or to the side, with a drip loop in any cable entering the housing and an unused entry closed with a listed plug.
12.1.8 Differential transmitters in liquid service shall be mounted below the taps, and in gas service above the taps, unless the hook-up drawing under Instrument Installation And TubingInstrument Installation and Impulse TubingResolves to the current adopted revision.sync/instrument-installation-and-tubing shows another arrangement with the seal pots or vents that make it read correctly.
12.1.9 Transmitters and switches shall be accessible for configuration, zero trim, and removal from grade or a permanent platform without removing insulation, scaffolding, or another device.

12.2 Gauge Installation

12.2.1 Gauges shall be installed upright on a gauge valve or on the manifold outlet furnished under Instrument Installation And TubingInstrument Installation and Impulse TubingResolves to the current adopted revision.sync/instrument-installation-and-tubing, with the dial facing the operator position and readable from grade or a permanent platform.
12.2.2 Gauges on vibrating equipment, where the instrument index does not designate a liquid fill, shall be remote-mounted on a bracket connected by flexible tubing or hose rather than mounted on the equipment.
12.2.3 Gauge threads shall be made up with a sealant rated for the fluid and temperature, applied to the male thread only, and tightened with a wrench on the socket and never on the case.
12.2.4 Snubbers, siphons, and pressure limiter valves shall be installed between the gauge valve and the gauge, in the orientation the manufacturer publishes, with a siphon filled with water before the valve is opened.

12.3 Sealed Assembly and Capillary Installation

12.3.1 Seal assemblies shall be installed in the orientation shown on the reviewed assembly drawing, with the transmitter at the elevation relative to the seal that the drawing states.
12.3.2 Capillaries shall be routed along the pipe or structure, supported at intervals not exceeding 3 ft, protected from traffic and from contact with hot surfaces, and coiled without kinks where excess length is stored.
12.3.3 Insulation shall be finished around the seal and the capillary at the pipe and the transmitter left clear, coordinated with Mechanical InsulationMechanical InsulationResolves to the current adopted revision.sync/mechanical-insulation.

12.4 Grounding and Electrical

12.4.1 Metal housings, brackets, and the raceway serving transmitters and switches shall be bonded to the equipment grounding system under Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding.
12.4.2 Signal pair shields shall be continuous through junction boxes and grounded at the control panel end only, with the shield at the instrument insulated from the housing.
12.4.3 Signal pairs shall be installed in raceway under Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit, separated from power conductors in accordance with the manufacturer's instructions and Industrial Control PanelsIndustrial Control PanelsResolves to the current adopted revision.sync/industrial-control-panels.

13 Delivery, Storage, and Handling

13.1 Instruments shall be delivered in the manufacturer's original packaging with tag numbers, calibration certificates, and installation instructions enclosed, and with process connections capped and conduit entries plugged.
13.2 Transmitters, gauges, and switches shall be stored indoors in a clean, dry location within the storage temperature range published by the manufacturer until installation.
13.3 Sealed assemblies shall be shipped and stored with the seal and transmitter connected, the diaphragm covered by its protective plate, and the capillary coiled to not less than the manufacturer's published minimum radius.
NOTE A seal diaphragm is a few thousandths of an inch thick and set flush to its flange, and a fingernail or a dropped tool dents it into a permanent zero shift; the protective plate stays on until the flange is bolted up. (13.4)
13.5 Liquid-filled gauges shall be stored and shipped upright with the vent closed.

14 Warranty

14.1 Pressure instruments and seal assemblies shall be warranted against defects in materials and workmanship for the period indicated in the datasheet, measured from the date of substantial completion.
Pressure Instrument Warranty Periodrange
years
1235
14.2 The warranty shall cover repair or replacement of the failed transmitter, gauge, switch, or seal assembly and the calibration, field verification, and zero trim of the replacement.
14.3 Where a device is repaired or replaced under warranty, the repaired or replaced device shall carry a new warranty of the same term from the date of the repair, or the remainder of the original term, whichever ends later.

15 Spare Parts

15.1 The Contractor shall deliver the spare parts indicated in the datasheet at substantial completion.
Spare Parts Delivered at Substantial Completioncheckbox
☑ Transmitters of each model and sensor range installed
☑ Gauges of each range, grade, and connection installed
☐ Pressure switches of each model installed
☐ Seal assemblies of each type and material installed
☐ Transmitter display modules and terminal blocks of each model installed
☐ Snubbers and siphons of each type installed
15.2 Spare parts of each selected class shall be furnished in the quantity indicated in the datasheet for every ten installed, with not fewer than one of each.
Spare Part Quantity per Ten Installedrange
units
1235
15.3 Spare parts shall match the installed devices in model, range, wetted material, output signal, and firmware, and shall be turned over against a written inventory signed by the Owner's representative.

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