1 Scope
NOTE This specification covers field-mounted process instrumentation — the measurement elements, transmitters, and local indicators that sense pressure, level, and temperature and convert them to a standardized signal for monitoring and control. (1.1)
NOTE Equipment covered includes pressure transmitters and gauges; level transmitters and switches; temperature elements (RTDs and thermocouples), thermowells, and temperature transmitters; the integral or remote transmitter electronics; local displays; mounting hardware and manifolds; and the process and wetted-part materials that contact the measured medium. (1.2)
NOTE Both 4-20 mA analog instruments (with and without superimposed HART digital communication) and digital fieldbus instruments are addressed. (1.3)
NOTE The boundary of work under this standard is the field instrument itself, from the process connection (the tap, thermowell, or nozzle at the pipe or vessel) through the transmitter signal-output terminals. (1.4)
NOTE The measured process variable, its range, and the instrument location are determined by the contract drawings and the instrument index. (1.6)
1.7Each instrument shall be tagged and identified in accordance with ANSI/ISA-5.1.
1.8The signal and identification conventions established here shall be coordinated with the loop diagrams and instrument index under Control Systems Integration. 2 Referenced Standards
2.1Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2Where conflicts exist between referenced standards, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
| Standard |
Title |
| ANSI/ISA-5.1 |
Instrumentation Symbols and Identification |
| ANSI/ISA-50.00.01 |
Compatibility of Analog Signals for Electronic Industrial Process Instruments (4-20 mA) |
| ANSI/ISA-50.02 / IEC 61158 |
Fieldbus Standard for Use in Industrial Control Systems |
| ANSI/ISA-60079-11 (12.02.01) / ANSI/UL 60079-11 |
Explosive Atmospheres — Equipment Protection by Intrinsic Safety "i" |
| ANSI/UL 60079-0 |
Explosive Atmospheres — Equipment — General Requirements |
| UL 913 |
Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1 Hazardous (Classified) Locations |
| ANSI/ISA-RP12.06.01 |
Recommended Practice for Wiring Methods for Hazardous (Classified) Locations Instrumentation — Intrinsic Safety |
| ANSI/ISA-12.27.01 |
Requirements for Process Sealing Between Electrical Systems and Flammable or Combustible Process Fluids |
| NFPA 70 (NEC) |
National Electrical Code — Articles 500, 501, 504, and 505 (hazardous locations and intrinsically safe systems) |
| IEC 60751 |
Industrial Platinum Resistance Thermometers and Platinum Temperature Sensors (Pt100 RTD tolerance classes) |
| ASTM E1137 |
Standard Specification for Industrial Platinum Resistance Thermometers |
| IEC 60584-1 / IEC 60584-2 |
Thermocouples — Reference Tables and Tolerances |
| ASTM E230 / ANSI MC96.1 |
Standard Specification and Temperature-Electromotive Force Tables for Standardized Thermocouples |
| ASME PTC 19.3 TW |
Thermowells — Performance Test Codes (mechanical design, wake-frequency calculation) |
| IEC 60529 |
Degrees of Protection Provided by Enclosures (IP Code) |
| NEMA 250 |
Enclosures for Electrical Equipment (1000 Volts Maximum) |
| ASME B16.5 |
Pipe Flanges and Flanged Fittings (process-connection flanges) |
| ASME B1.20.1 |
Pipe Threads, General Purpose (NPT process connections) |
| IEC 61508 / IEC 61511 |
Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems / Safety Instrumented Systems for the Process Industry (SIL) |
| ASME B40.100 |
Pressure Gauges and Gauge Attachments |
| NFPA 70 |
National Electrical Code (NEC) |
3 Submittals
3.1 Action Submittals
3.1.1The Contractor shall submit the following for the Engineer's review and approval prior to procurement.
- Instrument index correlating each tag number to the service, measured variable, range, location, signal type, and the drawing on which the instrument appears
- Manufacturer's product data for each instrument type, including measurement principle, accuracy, turndown/rangeability, ambient and process temperature and pressure limits, wetted materials, and process-connection type and size
- Calibrated measuring range and span for each instrument, with the units of measure stated
- Output and signal type for each instrument (4-20 mA, 4-20 mA with HART, or the specific digital fieldbus protocol)
- Hazardous-area certification documentation: the protection method (intrinsic safety, explosionproof/flameproof, nonincendive), the certified Class/Division or Zone, gas/dust group, and temperature class (T-code), with the control-drawing or entity parameters for intrinsically safe instruments
- Enclosure rating (NEMA type and/or IEC IP code) for each instrument
- Thermowell data and the ASME PTC 19.3 wake-frequency (flow-induced vibration) calculation for each thermowell in flowing service, including insertion length, bore, root and tip diameters, and material
- Dimensional drawings showing process connection, mounting provisions, conduit/cable entries, and overall envelope
- Installation, mounting, and impulse-piping/manifold details for each instrument type
- Instrument loop diagrams cross-referenced to Control Systems Integration (may be furnished jointly with that work)
☐ Instrument index (tag, service, range, location, signal)
☐ Product data with accuracy, turndown, materials, limits
☐ Calibrated range and span for each instrument
☐ Output/signal type (4-20 mA / HART / fieldbus)
☐ Hazardous-area certification (method, Class/Div or Zone, T-code)
☐ Enclosure rating (NEMA / IP)
☐ Thermowell data with ASME PTC 19.3 wake-frequency calculation
☐ Dimensional and mounting drawings
☐ Installation / impulse-piping / manifold details
☐ Instrument loop diagrams
3.1.2Fabrication and procurement shall not proceed until action submittals have been reviewed and returned.
3.2 Closeout Submittals
3.2.1At substantial completion, the Contractor shall provide the following before instruments are accepted.
- Operation and maintenance manuals for each instrument type, organized with a table of contents
- As-calibrated certificates for each instrument showing the as-found and as-left calibration at the verification points, the reference standard used, and the reference standard's traceability to NIST
- Completed loop check and calibration records correlating each tag to its verified range, signal, and control-system point
- Final instrument index reflecting as-installed tags, ranges, locations, and serial numbers
- Hazardous-area certification records and, for intrinsically safe loops, the as-installed entity-parameter verification
- Configuration record for each smart (HART or fieldbus) instrument, including the saved device configuration and damping settings
- Warranty documentation
- Spare parts inventory list with manufacturer part numbers
☐ Operation and maintenance manuals
☐ As-calibrated certificates with NIST traceability
☐ Loop check and calibration records
☐ Final as-installed instrument index
☐ Hazardous-area certification and entity-parameter verification
☐ Smart-instrument configuration records
☐ Warranty documentation
☐ Spare parts inventory list with part numbers
4 Quality Assurance
4.1 Manufacturer Qualifications
4.1.1Instruments shall be the products of a manufacturer regularly engaged in producing process instrumentation of the type specified for a minimum of ten years.
4.1.2The manufacturer shall maintain an ISO 9001 certified quality management system.
4.1.3Replacement parts and factory service support for each instrument model line shall be available for a minimum of ten years from the date of manufacture.
4.2 Calibration Traceability
4.2.1Each instrument shall be factory-calibrated, and the calibration shall be traceable to the National Institute of Standards and Technology (NIST).
4.2.2The as-found and as-left calibration data shall be furnished with each instrument.
NOTE NIST traceability establishes that the instrument's accuracy claim is anchored to a recognized reference, which is the basis on which the loop's overall measurement uncertainty is later evaluated. (4.2.3)
4.3 Hazardous-Area Certification
4.3.1Instruments installed in a hazardous (classified) location shall be certified for that location by a Nationally Recognized Testing Laboratory (NRTL) and shall bear the certification mark, the protection method, the area classification, the gas/dust group, and the temperature class.
4.3.2Instruments protected by intrinsic safety shall carry the entity parameters (or the FISCO designation) required to verify the loop against the associated apparatus (barrier or isolator).
NOTE A hazardous-area certification is specific to a protection method and a defined classification; an instrument certified explosionproof for Class I Division 1 Group D is not automatically suitable for a Group B atmosphere or a dust location, and the mismatch is a common and dangerous specification error. (4.3.3)
4.4 SIL Capability
4.4.1Where an instrument serves a safety instrumented function, it shall be certified for the required Safety Integrity Level (SIL) per IEC 61508, and the loop shall be designed and verified per IEC 61511.
Not a safety function — no SIL requirement (basic process control)
SIL 1 capable per IEC 61508
SIL 2 capable per IEC 61508
SIL 3 capable per IEC 61508
NOTE A basic-process-control measurement and a safety-instrumented measurement have different reliability requirements; specifying SIL capability where there is no safety function adds cost, while overlooking it on a true safety loop defeats the protection layer. (4.4.2)
5 Environmental and Service Conditions
NOTE Instruments shall be selected and rated for the ambient and process conditions at the installation point. (5.1)
5.3 Ambient Conditions
Indoor — heated/conditioned process building
Indoor — unheated process building or pump room
Outdoor — sheltered (under canopy)
Outdoor — fully exposed (rooftop, tank farm, headworks)
Wet well / below grade / high-humidity (WWTP)
5.3.1Instruments shall be rated for the ambient temperature range at the installation point, including solar gain on outdoor instruments and the minimum winter design temperature.
5.3.2Outdoor and wet-location instruments shall be provided with an enclosure rated for the exposure and, where the process medium or ambient can freeze, with freeze protection of the impulse lines and wetted parts.
NOTE Water and wastewater installations frequently combine high humidity, washdown, corrosive (H2S) atmospheres, and submergence risk; the enclosure rating and wetted/external materials shall be selected for these conditions. (5.3.3)
5.4 Enclosure Rating
NEMA 4X / IP66 — washdown, corrosion-resistant (default for outdoor and WWTP)
NEMA 4 / IP66 — weatherproof, painted/coated
NEMA 7 / explosionproof — Class I Division 1
NEMA 6P / IP68 — prolonged submersion (submersible level)
NEMA 12 / IP54 — indoor industrial, dust-tight
5.4.1The instrument enclosure shall meet the selected NEMA type or IEC 60529 IP code for the installation environment.
NOTE NEMA 4X (IP66) is the default for outdoor, washdown, and water/wastewater service because it adds corrosion resistance over plain NEMA 4; submersible level sensors require an IP68 / NEMA 6P rating for prolonged immersion. (5.4.2)
5.5 Hazardous-Area Classification
Unclassified (general purpose)
Class I, Division 1 — flammable gas/vapor, normally present
Class I, Division 2 — flammable gas/vapor, abnormal only
Class I, Zone 0 / Zone 1 / Zone 2 (NEC 505)
Class II, Division 1 or 2 — combustible dust
Class I, Division 1 — digester gas / methane (WWTP)
○ Intrinsic safety (IS) — Ex i, with certified barrier/isolator
○ Explosionproof / flameproof — Ex d enclosure
○ Nonincendive — Class I Division 2 only
○ Not applicable — unclassified location
5.5.2Instruments in classified locations shall use a protection method certified for the classification and listed by an NRTL.
NOTE Intrinsic safety limits the electrical energy in the field circuit below the level that can ignite the atmosphere, which permits live work and simpler maintenance; it requires a certified barrier or isolator and an entity-parameter match between the field instrument and the associated apparatus per ANSI/ISA-RP12.06.01 and NEC Article 504. (5.5.3)
NOTE Digester-gas and methane atmospheres at wastewater plants are routinely Class I Division 1, Group D, and instruments there shall be certified accordingly. (5.5.4)
6 Signal and Output
6.1 Analog and Digital Output
NOTE The 4-20 mA analog current loop per ANSI/ISA-50.00.01 remains the dominant output for process transmitters because it is simple, immune to voltage-drop error over distance, and able to power a two-wire instrument over the same pair. (6.1.1)
NOTE HART superimposes a low-level frequency-shift-keyed digital signal on the 4-20 mA loop, carrying the primary variable, additional variables, diagnostics, and configuration without disturbing the analog signal, and is the default for new smart instruments because it adds digital value while remaining backward-compatible. (6.1.2)
NOTE Digital fieldbus (FOUNDATION Fieldbus H1 or PROFIBUS PA per IEC 61158) multidrops multiple instruments on one pair with both power and data, reducing wiring on large multi-instrument installations, but requires fieldbus-capable I/O and segment engineering. (6.1.3)
○ 4-20 mA with HART (two-wire, smart) — default
○ 4-20 mA analog only (two-wire)
○ FOUNDATION Fieldbus H1 (IEC 61158)
○ PROFIBUS PA (IEC 61158)
○ Discrete (switch) output — dry contact or solid-state
6.1.4Transmitters shall provide the selected output, and 4-20 mA instruments shall be two-wire (loop-powered) unless the measurement principle requires four-wire power.
6.1.5The output type shall be coordinated with the control-system I/O type and the loop power supply under Control Systems Integration. 6.2 Failure Mode
○ Upscale (≥ 21 mA) on failure — default
○ Downscale (≤ 3.6 mA) on failure
6.2.1Smart transmitters shall drive the analog output to a defined failure value (upscale or downscale) on detection of an internal fault, and the failure direction shall be configured consistently with the control-system alarm logic.
NOTE A consistent, agreed failure direction lets the control system distinguish an instrument fault from a real process excursion; an upscale default is common, but the choice must match the safe state of the controlled process. (6.2.2)
6.3 Damping
6.3.1Output damping (signal time constant) shall be set to the minimum value that gives a stable indication for the service, and shall be recorded in the configuration submittal.
NOTE Excessive damping hides real process dynamics and slows control response, while too little damping passes process noise to the controller; the setting is a service-specific tuning decision, not a fixed default. (6.3.2)
7 Pressure Measurement
7.1 Pressure Measurement Type
NOTE A gauge-pressure transmitter measures process pressure relative to local atmospheric pressure and is the general-purpose choice for most pressure and pump-discharge measurements. (7.1.1)
NOTE An absolute-pressure transmitter measures relative to a sealed vacuum reference and is used where the reading must be independent of barometric variation (vacuum service, distillation, vapor pressure). (7.1.2)
NOTE A differential-pressure (DP) transmitter measures the difference between two connections and is the workhorse for DP-based level, filter and strainer differential, and pump differential — and for DP flow, which is covered separately in
Flow Measurement.
(7.1.3) ○ Gauge pressure (relative to atmosphere) — general purpose
○ Absolute pressure (sealed reference)
○ Differential pressure (DP)
○ Compound (vacuum and positive gauge)
7.1.4The pressure transmitter shall measure the selected type of pressure for the service.
7.2 Calibrated Range
16000
1510301003005001000200030006000
Default: 100 psi
7.2.1The calibrated range shall be as indicated on the instrument index and shall be selected so that the normal operating pressure falls between approximately 25% and 75% of span. NOTE Selecting a transmitter URL far above the operating pressure wastes the device's turndown and degrades accuracy; the range should be set near the actual process, within the device's rangeability. (7.2.2)
7.3 Accuracy and Turndown
±0.025% of span (high-accuracy custody/critical)
±0.04% of span
±0.075% of span (standard process)
±0.1% of span
±0.25% of span (utility/general)
7.3.1Reference accuracy shall be stated as a percent of calibrated span and shall meet or exceed the value selected for the service.
NOTE Accuracy is meaningful only together with the turndown at which it is held; a transmitter rated ±0.075% at 10:1 turndown may degrade beyond that span ratio, so the accuracy and the calibrated range must be evaluated together. (7.3.2)
7.4 Diaphragm Seals
NOTE A diaphragm seal (remote or direct) isolates the transmitter from the process where the medium is corrosive, viscous, slurry-laden, fouling, or at a temperature that would damage the transmitter. (7.4.1)
Direct process connection — clean, compatible fluids
Direct diaphragm seal (flush-mount) — viscous/fouling/slurry
Remote diaphragm seal with capillary — high temperature or remote mounting
Chemical seal with NACE materials — sour service
7.4.2Where the process fluid is incompatible with direct connection, the transmitter shall be furnished with a diaphragm (chemical) seal of materials compatible with the process.
7.5 Pressure Wetted Materials
316/316L stainless steel — default
Hastelloy C — corrosive/chloride service
Monel — fluoride/seawater service
Tantalum — highly corrosive acids
PTFE/PFA-lined or ceramic — abrasive/aggressive
7.5.1Wetted parts (diaphragm, fill, and process flanges or connections) shall be of materials compatible with the process fluid for the service life.
7.6 Pressure Process Connection
1/2 in. NPT (ASME B1.20.1) — default
1/4 in. NPT
Flanged per ASME B16.5 (with diaphragm seal)
Sanitary clamp (tri-clamp) — hygienic service
7.6.1The process connection shall match the impulse-piping or seal connection for the service.
7.7 Pressure Manifold
7.7.1Each pressure or DP transmitter shall be provided with an instrument valve manifold (two-valve for gauge/absolute, three- or five-valve for DP) to permit isolation, equalization, and calibration without breaking the process connection.
NOTE A five-valve DP manifold allows the transmitter to be zeroed and removed without disturbing the process taps, which is essential for DP-level and DP-flow service where blocking and equalizing must be done in sequence to avoid over-ranging the cell. (7.7.2)
8 Level Measurement
8.1 Level Measurement Technology
NOTE Level technology shall be selected for the medium, the vessel, and the process conditions. (8.1.1)
NOTE Hydrostatic (submersible or DP) level infers level from the head pressure of the liquid column; it is simple and inexpensive, well suited to open tanks, wet wells, and clarifiers, but reads true level only at a known, constant specific gravity. (8.1.2)
NOTE Non-contact radar measures the time of flight of a microwave pulse to the surface; it is unaffected by density, vapor, and temperature, tolerates agitation and coating better than ultrasonic, and is the default for new closed-vessel and many open-channel applications. (8.1.3)
NOTE Guided-wave radar (TDR) sends the pulse along a probe, giving a strong, focused echo for low-dielectric, turbulent, or foaming media and for interface measurement, at the cost of a process-wetted probe. (8.1.4)
NOTE Ultrasonic measures time of flight of a sound pulse through the vapor space; it is non-contact and economical for open tanks and channels but is degraded by heavy vapor, foam, temperature gradients, and turbulence. (8.1.5)
NOTE Float and displacer devices give simple, reliable point or continuous level on clean liquids and are common for sump and tank switching. (8.1.6)
○ Non-contact radar (microwave TOF) — default continuous
○ Guided-wave radar (TDR) — low dielectric, turbulent, interface
○ Hydrostatic — submersible/DP pressure (open tanks, wet wells)
○ Ultrasonic (non-contact) — open tanks and channels
○ Float / displacer — point or continuous (clean liquids)
○ Capacitance / admittance — interface or coating-tolerant
8.1.7The level instrument shall employ the selected measurement technology for the service.
8.2 Continuous or Point Level
○ Continuous (transmitter) — analog level over full range
○ Point (switch) — high/low alarm or pump control
8.2.1Continuous level instruments shall provide an analog (or digital) signal proportional to level over the measured range; point-level switches shall provide a discrete output at the set point.
8.3 Level Measured Range
1100
135101520305075100
Default: 15 ft
NOTE Radar and ultrasonic instruments have a near-field blocking distance below the sensor in which they cannot measure; the usable measuring range must account for it so the high-level set point does not fall in the blind zone. (8.3.2)
8.4 Hydrostatic Specific-Gravity Basis
8.4.1Where hydrostatic level is used, the design specific gravity of the medium shall be stated, and the instrument shall be configured for it.
NOTE Hydrostatic level reads head pressure; a change in specific gravity (from temperature, concentration, or solids) shifts the indicated level, so the SG basis must be documented and stable for the reading to be valid. (8.4.2)
8.5 Level Wetted Materials and Connection
316/316L stainless steel — default
PVDF / PTFE — corrosive or hygienic
Hastelloy C — aggressive chemical
Polyurethane / coated — abrasive (sludge, grit)
Flanged per ASME B16.5 — vessel nozzle
Threaded NPT (ASME B1.20.1)
Bracket / cantilever mount (open tank, channel)
Submersible (suspended by cable) — wet well
8.5.1Wetted parts and the process connection shall be compatible with the medium and shall match the vessel nozzle or mounting provision.
9 Temperature Measurement
9.1 Sensor Type
NOTE An RTD (resistance temperature detector) varies a precise resistance with temperature; the Pt100 platinum element per IEC 60751 / ASTM E1137 is the default for process temperature because it is accurate, stable, and repeatable over the common process range (roughly -200°C to 600°C). (9.1.1)
NOTE A thermocouple generates a small temperature-dependent voltage at the junction of two dissimilar metals per IEC 60584 / ASTM E230 (ANSI MC96.1); it is rugged and reaches much higher temperatures than an RTD, but is less accurate and stable and requires cold-junction compensation. (9.1.2)
NOTE Choose an RTD for accuracy and stability at moderate temperature, and a thermocouple where the temperature exceeds the RTD range or rugged high-temperature service is required. (9.1.3)
○ RTD — Pt100, 3-wire (IEC 60751 Class A) — default
○ RTD — Pt100, 4-wire (highest accuracy)
○ Thermocouple — Type J (iron-constantan)
○ Thermocouple — Type K (chromel-alumel, high temperature)
○ Thermocouple — Type T (copper-constantan, low temperature)
○ Thermocouple — Type E or N (per service)
9.1.4The temperature element shall be the selected sensor type for the service.
9.1.5RTDs shall be wired three-wire as a minimum to compensate for lead resistance, and four-wire where the specified accuracy requires it.
9.2 RTD Tolerance Class
○ Class A — ±(0.15 + 0.002|t|)°C — default process
○ Class B — ±(0.30 + 0.005|t|)°C — general purpose
○ Class AA (1/3 DIN) — high accuracy
9.2.1Pt100 RTDs shall meet the selected IEC 60751 tolerance class over the measured range.
9.3 Thermocouple Tolerance Class
○ Standard grade (ASTM) / Class 2 (IEC) — general purpose
○ Special grade (ASTM) / Class 1 (IEC) — higher accuracy
9.3.1Where thermocouples are used, they shall meet the selected ASTM E230 / IEC 60584 tolerance grade.
9.4 Thermowell
9.4.1A thermowell shall be provided for every temperature element in a pressurized, flowing, or otherwise inaccessible process, so the element can be removed without breaching the process.
9.4.2Each thermowell in flowing service shall pass an ASME PTC 19.3 TW wake-frequency (flow-induced vibration) calculation for the actual insertion length, bore, and process velocity.
NOTE A thermowell that fails the wake-frequency check can resonate and fracture at the root under flow-induced vibration, dropping the broken tip into the process and opening a leak path; the ASME PTC 19.3 calculation is a mandatory check, not a formality. (9.4.3)
Tapered, flanged (ASME B16.5) — default process
Tapered, threaded NPT (ASME B1.20.1)
Tapered, weld-in (socket weld)
Straight / stepped shank
None — direct immersion (low-pressure open tank only)
316/316L stainless steel — default
Hastelloy C — corrosive service
Monel — seawater/fluoride
Inconel — high temperature
Carbon steel — non-corrosive utility
9.5 Temperature Transmitter
○ Head-mounted transmitter (in connection head) — default
○ Rail/field-mounted transmitter (remote)
○ Direct sensor wiring to control system (no transmitter)
9.5.1Where a transmitter is provided, it shall convert the sensor signal to the selected output (4-20 mA with HART or fieldbus) and shall provide sensor-fault and open-circuit detection.
NOTE A head-mounted transmitter converts the low-level RTD or thermocouple signal to a robust 4-20 mA signal at the sensor, avoiding the lead-wire error and noise pickup of running raw millivolt or resistance signals long distances back to the control system. (9.5.2)
10 Local Indication
10.1 Integral Display
○ Integral digital display (LCD/LED) on transmitter — default
○ Local gauge in addition to transmitter
○ None — remote indication only
10.1.1Transmitters should be furnished with an integral digital display in engineering units where operators or maintenance personnel access the instrument locally.
NOTE A local display lets a technician verify the reading and commission the loop at the instrument without a handheld communicator or a trip to the control room; it is inexpensive and almost always worth specifying on field transmitters. (10.1.2)
10.2 Pressure Gauges
10.2.1Where a local pressure gauge is provided independent of a transmitter, it shall conform to ASME B40.100, with the accuracy grade and dial size suited to the service.
11 Instrument Tagging and Loop Identification
11.1 Tag Numbering
11.1.1Each instrument shall bear a unique tag number assigned per the ANSI/ISA-5.1 identification scheme, in which the first-letter set identifies the measured variable and the succeeding letters identify the function (for example PT for a pressure transmitter, LT for a level transmitter, TT for a temperature transmitter, and TW for a thermowell).
11.1.2The instrument tag number shall match the P&ID, the instrument index, and the loop diagram for that loop.
NOTE Consistent ISA-5.1 tagging across the P&ID, the index, and the physical nameplate is what lets any party trace a field device to its function and loop without ambiguity; a mismatch between the drawing tag and the field tag is a frequent source of commissioning errors. (11.1.3)
11.2 Loop Numbering
11.2.1Instruments that act together on one measured variable shall share a common loop number per ANSI/ISA-5.1, so the measurement, any controller, and any final element are identifiable as one loop.
Stainless steel tag, wired to instrument — default
Engraved laminated phenolic nameplate, fastened
Adhesive label (indoor, non-washdown only)
11.3.1Each instrument shall be permanently identified in the field with a durable tag bearing the ISA-5.1 tag number.
NOTE Stainless steel wired tags are the default in outdoor and washdown environments because adhesive labels fail in the weather, sun, and washdown typical of process and water/wastewater sites. (11.3.2)
12 Testing and Calibration
12.1 Factory Calibration
12.1.1Each instrument shall be factory-calibrated to its specified range against NIST-traceable standards, and the calibration certificate shall be furnished.
12.2 Field Calibration
12.2.1Each instrument shall be field-verified against a NIST-traceable reference at a minimum of three points across the range (typically 0%, 50%, and 100%), with as-found and as-left values recorded.
NOTE Field verification confirms the instrument survived shipping and installation and reads correctly as mounted, including any effect of mounting position or static head on a DP cell. (12.2.2)
12.3 Loop Check
12.3.1Each loop shall be checked end-to-end, confirming that a known input at the instrument produces the correct value at the control system, and that the signal scaling, engineering units, and failure direction are correct.
☐ Three-point as-found / as-left calibration per instrument
☐ End-to-end loop check (field to control-system point)
☐ Signal scaling and engineering-unit verification
☐ Failure-direction verification
☐ Smart-instrument configuration saved and recorded
☐ Intrinsically safe loop entity-parameter verification
12.3.2Loop check records shall be included in the closeout documentation and correlated to the instrument index.
13 Installation
13.1 Mounting and Accessibility
13.1.2Transmitters shall be mounted to minimize vibration, shielded from direct process heat, and oriented so the display is readable and conduit/cable entries drain away from the enclosure.
NOTE Crowding an instrument against piping or structure so its manifold cannot be operated or its element cannot be withdrawn makes routine calibration and replacement impossible without a shutdown. (13.1.3)
13.2 Impulse Piping
13.2.1Impulse (sensing) lines for pressure, DP, and hydrostatic-level transmitters shall be sloped continuously to drain or vent per the service: pitched down toward the transmitter on liquid service to shed gas, and up toward the transmitter on gas service to shed liquid.
13.2.2Impulse lines shall be as short as practical, supported, and provided with isolation and blowdown/vent valves.
NOTE An improperly sloped impulse line traps gas in a liquid leg (or condensate in a gas leg), which puts a false head on the transmitter and is one of the most common causes of a stable but wrong pressure or level reading. (13.2.3)
13.3 Process Sealing
13.3.1In Class I hazardous locations, process-connected instruments shall be provided with process sealing per ANSI/ISA-12.27.01 and NEC Article 501 to prevent process fluid from migrating through the conduit system on failure of the primary seal.
13.4 Electrical Connection and Grounding
13.4.1Signal wiring shall be installed per Conductors And Cables, using twisted shielded pair for analog and fieldbus signals, with the shield grounded at one end only (typically at the control system) to prevent ground-loop current. 13.4.3Intrinsically safe wiring shall be separated and identified per ANSI/ISA-RP12.06.01 and NEC Article 504, and shall not share a raceway or wireway with non-IS circuits unless separated as the code permits.
NOTE Grounding a signal-cable shield at both ends creates a ground loop that injects noise into the measurement; single-point shield grounding is required for clean analog signals. (13.4.4)
14 Delivery, Storage, and Handling
14.1Instruments shall be delivered in the manufacturer's original packaging with the calibration certificate and the protective covers on process connections and conduit entries.
14.2Instruments shall be stored indoors, dry, and within the manufacturer's storage temperature range until installed.
14.3Process-connection protectors and diaphragm-seal covers shall remain in place until the instrument is connected; a scratched or dented isolating diaphragm permanently shifts the calibration.
14.4Radar and ultrasonic sensor faces shall be protected from impact and contamination during storage and construction.
15 Warranty
15.1 Warranty Terms
1 year from substantial completion (standard)
2 years
3 years
5 years (extended, where offered)
15.1.1The manufacturer shall warrant each instrument against defects in materials and workmanship for a minimum of one year from substantial completion.
15.1.2The warranty shall cover the transmitter electronics, the sensing element, and the wetted parts under the specified service conditions.
16 Spare Parts
16.1 Spare Parts Package
16.1.1The Contractor shall furnish the manufacturer's recommended spare parts for commissioning and the first year of operation.
- Spare transmitter of each major type and range for critical loops
- Spare RTD/thermocouple elements for each thermowell type and length used
- Replacement diaphragm seals or seal assemblies for instruments so equipped
- O-rings, gaskets, and process-connection seals
- Spare display modules where used
☐ Spare transmitter (each major type/range) for critical loops
☐ Spare temperature elements (each thermowell type/length)
☐ Replacement diaphragm seals / seal assemblies
☐ O-rings, gaskets, and process-connection seals
☐ Spare display modules
☐ Recommended fieldbus/HART configuration spares
16.1.2The spare-parts list with manufacturer part numbers shall be included in the closeout documentation.