Temperature Instrumentation
Remade for neutrality: every choice explained, project facts as parameters, scope boundaries linked both ways
Showing changes from Rev 2
to Rev 3
in Temperature Instrumentation.
---
−title: Temperature Measurement
+title: Temperature Instrumentation
category: Instrumentation & Controls / Field Instrumentation
−toc_depth: 3
description: >
− When to use: selection, specification, procurement, installation, and commissioning of
− field-mounted temperature sensing and transmitting assemblies for process control and
− HVAC/mechanical systems — RTDs (Pt100/Pt1000), thermocouples (Types J, K, E, N, T),
− bimetallic dial and filled-system thermometers, integral- and remote-mount temperature
− transmitters, thermowells (flanged, threaded, socket-weld), connection heads, and
− extension/compensating cable. Covers water/wastewater, industrial process, power,
− pharma, food and beverage, commercial HVAC, and building automation, from cryogenic
− (-200°C) through high-temperature process service (up to ~1260°C), with 4-20 mA,
− HART, WirelessHART, FOUNDATION Fieldbus, and Modbus RTU outputs.
− Not intended for: pressure/DP instruments ([[sync/pressure-instrumentation]]); flow
− devices even when temperature-compensated ([[sync/flow-measurement]]); level sensors
− ([[sync/level-sensors]]); loop architecture, P&ID conventions, and the instrument index
− ([[sync/process-instrumentation]]); sensors integrated within packaged HVAC equipment
− ([[sync/variable-air-volume-terminals]], [[sync/makeup-air-units]]); geotechnical
− temperature arrays ([[sync/geotechnical-instrumentation-and-monitoring]]); heat-trace
− control sensors wired to the heat-trace system; and laboratory-grade precision
− thermometry or NIST-traceable calibration facilities.
+ When to use: Instrument-tagged temperature measurement points on industrial, process, power, and water and wastewater projects: the sensing element (platinum RTD, thermocouple, or thermistor), its insert and sheath, the thermowell, the connection head, the temperature transmitter and its output signal, thermocouple extension wire, the local dial thermometer, hazardous-location protection, calibration, installation, and acceptance. Applies to every point that carries a tag in the project instrument index and is read by a process controller, including the temperature element of a multivariable transmitter and temperature elements on storage tanks and plant piping that are not building automation points.
+
+ Not intended for: Building automation temperature points, meaning the space, duct, pipe, and outdoor air sensors wired to building automation field controllers, which are governed by [[sync/hvac-controls-instrumentation]] with the element and measurement error selected under [[sync/building-automation-system]]; pressure instruments and the pressure side of a multivariable transmitter ([[sync/pressure-instrumentation]]); flow and level instruments ([[sync/flow-measurement]], [[sync/level-sensors]]); loop architecture, instrument tagging, the instrument index, and loop diagrams ([[sync/process-instrumentation]], [[sync/control-systems-integration]]); temperature sensors furnished inside equipment, such as transformer winding sensors, chiller motor sensors, and the sensors of packaged air handling units ([[sync/medium-voltage-transformers]], [[sync/chillers]], [[sync/air-handling-units]]); heat-tracing control sensors and thermostats ([[sync/electric-heat-tracing]]); ground temperature arrays ([[sync/geotechnical-instrumentation-and-monitoring]]); and the controllers, networks, and operator interfaces that receive the signal ([[sync/programmable-logic-controllers]], [[sync/process-control-networks]], [[sync/scada-and-hmi-systems]]).
---
# Scope {toc}
−## This standard governs field-mounted temperature sensing and transmitting assemblies used to measure, indicate, and transmit process and ambient temperature in process control and HVAC/mechanical systems.
+## This standard covers the temperature measurement point from the thermowell at the pipe or vessel to the signal-output terminals of the transmitter or, where no transmitter is furnished, to the terminals of the connection head: the sensing element, its insert and sheath, the thermowell, the connection head, the transmitter, the thermocouple extension wire, and the local dial thermometer. {note}
−## The standard covers resistance temperature detectors, thermocouples, bimetallic and filled-system thermometers, integral- and remote-mount transmitters, thermowell assemblies, connection heads, and associated extension and compensating cable. {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, whether the pipe it sits in carries a process fluid, a plant utility, or chilled water; a point belongs to [[sync/hvac-controls-instrumentation]] when it is wired to a building automation field controller and its element and measurement error are selected under [[sync/building-automation-system]]. The same thermowell in the same pipe is specified under whichever standard owns the controller that reads it. {note}
−## It applies to temperature elements in pipe, vessel, duct, and ambient air service from cryogenic (-200°C) through high-temperature process service (approximately 1260°C thermocouple range), with 4-20 mA analog, HART, WirelessHART, FOUNDATION Fieldbus, and Modbus RTU output configurations. {note}
+## The temperature element, its thermowell, and the temperature calibration of a multivariable transmitter are specified under this standard; the transmitter body, its pressure sensor, its process connection, and its pressure calibration are specified under [[sync/pressure-instrumentation]]. {note}
−## The standard addresses both process/industrial use cases (IEC/ISA-centric, thermowell-focused) and HVAC/building-automation use cases (duct sensors, room sensors, pipe-immersion sensors), because both fall within the Instrumentation and Controls discipline. {note}
+## The following are outside this standard and are governed elsewhere. {note}
−## The following are outside the scope of this standard and are governed elsewhere. {note}
−- Pressure and differential-pressure transmitters and gauges — see [[sync/pressure-instrumentation]].
−- Flow measurement devices (orifice plates, vortex meters, magnetic flowmeters), even when temperature-compensated — see [[sync/flow-measurement]].
−- Level sensors and level transmitters — see [[sync/level-sensors]].
−- Loop architecture, P&ID conventions, and the instrument index — see [[sync/process-instrumentation]].
−- Temperature sensors integrated within and shipped as part of packaged HVAC equipment (VAV box controllers, AHU discharge sensors) — see the relevant equipment standard such as [[sync/variable-air-volume-terminals]] or [[sync/makeup-air-units]].
−- Geotechnical temperature monitoring (ground temperature arrays, thermal conductivity testing) — see [[sync/geotechnical-instrumentation-and-monitoring]].
−- Electrical heat-tracing temperature sensors wired as part of the heat-trace control system.
−- Laboratory-grade precision thermometry and NIST-traceable calibration facilities.
+- Pressure, differential pressure, flow, and level instruments, governed by [[sync/pressure-instrumentation]], [[sync/flow-measurement]], and [[sync/level-sensors]]
+- Loop architecture, instrument tag numbering, the instrument index, and loop diagrams, governed by [[sync/process-instrumentation]] and [[sync/control-systems-integration]]
+- Temperature sensors furnished inside equipment and wired to the equipment's own controller, such as transformer winding sensors, chiller motor sensors, and the sensors shipped in packaged air handling units, governed by the standard for that equipment, for example [[sync/medium-voltage-transformers]], [[sync/chillers]], and [[sync/air-handling-units]]
+- Heat-tracing control sensors and thermostats furnished with the heat-tracing controls, governed by [[sync/electric-heat-tracing]]
+- Ground temperature arrays and thermal conductivity testing, governed by [[sync/geotechnical-instrumentation-and-monitoring]]
+- Controllers and input cards, field networks and fieldbus segment design, and operator interfaces, governed by [[sync/programmable-logic-controllers]], [[sync/process-control-networks]], and [[sync/scada-and-hmi-systems]]
+- Control panels and the marshalling of field signals, governed by [[sync/industrial-control-panels]]
+- Raceway for instrument wiring, governed by [[sync/raceways-and-conduit]]
+- Laboratory thermometry and the calibration laboratory itself; this standard references the laboratory only as the source of the traceable certificate
+## Each point's tag, service, process fluid, calibrated range, process design pressure and temperature, maximum fluid velocity including startup and upset conditions, line size, and insertion length shall be as indicated on [[drawing: the instrument index and instrument data sheets]].
+
+## 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.
+
# Referenced Standards {toc}
## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
−## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+## 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.
−## ISA-MC96.1 has been withdrawn as a standalone standard and its technical content folded into ASTM E230 and IEC 60584; this standard references ASTM E230 as the primary US thermocouple authority and retains ISA-MC96.1 only for extension-wire color coding. {note}
−
| Standard | Title |
|----------|-------|
−| IEC 60751:2022 | Industrial Platinum Resistance Thermometers and Platinum Temperature Sensors |
−| ASTM E230/E230M-17 | Specification and Temperature-EMF Tables for Standardized Thermocouples |
−| IEC 60584-1:2013 | Thermocouples — Part 1: EMF Specifications and Tolerances |
−| ASME PTC 19.3 TW-2016 | Thermowells — Performance Test Codes |
−| ASME B40.200-2008 (R2013) | Thermometers, Direct Reading and Remote Reading |
−| ISA-MC96.1-1982 (R2018) | Temperature Measurement Thermocouples |
−| ISA-51.1-1979 (R1993) | Process Instrumentation Terminology |
−| NFPA 70 (NEC) | National Electrical Code (Article 250 Grounding, Article 500 Hazardous Locations) |
−| ANSI/ISA-12.27.01-2003 (R2019) | Requirements for Process Sealing Between Electrical Systems and Flammable or Combustible Process Fluids |
−| IEC 61511 / ISA-84.00.01-2004 | Functional Safety — Safety Instrumented Systems for the Process Industry Sector |
+| IEC 60751 | Industrial Platinum Resistance Thermometers and Platinum Temperature Sensors |
+| ASTM E1137/E1137M | Standard Specification for Industrial Platinum Resistance Thermometers |
+| ASTM E230/E230M | Standard Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples |
+| ASTM E585/E585M | Standard Specification for Compacted Mineral-Insulated, Metal-Sheathed, Base Metal Thermocouple Cable |
+| ASTM E608/E608M | Standard Specification for Mineral-Insulated, Metal-Sheathed Base Metal Thermocouples |
+| ASTM E220 | Standard Test Method for Calibration of Thermocouples by Comparison Techniques |
+| ASTM E644 | Standard Test Methods for Testing Industrial Resistance Thermometers |
+| ASME PTC 19.3 TW | Thermowells |
+| ASME B40.200 | Thermometers, Direct Reading and Remote Reading |
+| 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-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 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 |
+| 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 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 |
# Submittals {toc}
−## The Contractor shall submit the following action submittals for each temperature instrument or assembly type prior to fabrication or procurement:
−- Product data sheets identifying sensor technology, range, accuracy class, output, and enclosure rating.
−- Completed instrument data sheets (ISA-20 format or Engineer-approved equivalent) for every tag.
−- Thermowell dimensional drawings with insertion length, bore, root and tip diameters, and process connection.
−- ASME PTC 19.3 TW-2016 wake-frequency calculations for every thermowell in flowing process service.
−- Hazardous-area certification (intrinsic safety, explosion-proof, or non-incendive) for instruments in classified areas.
−- Material certifications and, where wetted, mill test reports for thermowell stock.
+## Action Submittals {toc}
+### The Contractor shall submit the following for the Engineer's review and return before any temperature instrument or thermowell is procured:
+
+- Product data for each element, insert, connection head, transmitter, and dial thermometer model, giving the sensing element, tolerance class or limits of error, the transmitter reference accuracy and ambient rating, 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 dimensional drawing for each thermowell giving the process connection, stem profile, root and tip diameters, bore, insertion length, lagging extension, and material
+- A wake-frequency calculation under ASME PTC 19.3 TW for each thermowell in flowing service, at the maximum velocity stated on the instrument data sheet
+- Material certificates and mill test reports for thermowell stock
+- 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 sensor type and connection, the failure output direction, the damping, and the sensor matching coefficients where sensor matching is furnished
+
```datasheet
−label: Action Submittals
+label: Required Action Submittals
type: checkbox
options:
− - Product data sheets
− - Instrument data sheets (ISA-20)
− - Thermowell dimensional drawings
− - ASME PTC 19.3 TW wake-frequency calculations
− - Hazardous-area certification
− - Material certifications / mill test reports
+ - "Product data for each instrument model"
+ - "Instrument data sheet for every tagged point"
+ - "Thermowell dimensional drawings"
+ - "Thermowell wake-frequency calculations"
+ - "Thermowell material certificates and mill test reports"
+ - "Hazardous-location certificates and intrinsically safe control drawings"
+ - "Transmitter configuration sheets"
default:
− - Product data sheets
− - Instrument data sheets (ISA-20)
− - Thermowell dimensional drawings
− - ASME PTC 19.3 TW wake-frequency calculations
+ - "Product data for each instrument model"
+ - "Instrument data sheet for every tagged point"
+ - "Thermowell dimensional drawings"
+ - "Thermowell wake-frequency calculations"
+ - "Thermowell material certificates and mill test reports"
+ - "Transmitter configuration sheets"
```
−## The Contractor shall submit the following informational submittals:
−- Factory calibration certificates, NIST-traceable where required by this standard.
−- Manufacturer installation, operation, and maintenance instructions.
−- Loop diagrams showing element, transmitter, cable type, and DCS/PLC termination.
−- For safety-instrumented applications, the IEC 61511 SIL capability statement and proof-test procedure.
+### The thermowell drawings and the wake-frequency calculations shall be submitted together, and a thermowell shall not be fabricated until its calculation has been reviewed and returned without exception.
+## Informational Submittals {toc}
+
+### The Contractor shall submit the following for information before installation begins:
+
+- Factory calibration certificates for the elements and transmitters 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 element and transmitter serving a safety instrumented function
+- Positive material identification reports for alloy thermowells where required under Testing
+
```datasheet
−label: Informational Submittals
+label: Required Informational Submittals
type: checkbox
options:
− - Factory calibration certificates
− - Installation/operation/maintenance instructions
− - Loop diagrams
− - SIL capability statement and proof-test procedure
+ - "Factory calibration certificates"
+ - "Manufacturer's installation instructions"
+ - "Safety integrity level capability certificates and proof-test procedures"
+ - "Positive material identification reports"
default:
− - Factory calibration certificates
− - Installation/operation/maintenance instructions
− - Loop diagrams
+ - "Factory calibration certificates"
+ - "Manufacturer's installation instructions"
```
−## The Contractor shall submit the following closeout submittals at project completion:
−- As-installed loop diagrams and instrument index.
−- Field calibration and loop-check records.
−- Warranty documentation.
+## Closeout Submittals {toc}
+### The Contractor shall submit the following before the temperature instruments are accepted:
+
+- As-left calibration and configuration record for every element and transmitter, including the field verification results
+- Thermowell test records
+- Operation and maintenance data giving the recalibration interval, the proof-test interval where applicable, and the part number of every replaceable insert, transmitter, and gasket
+- Warranty documentation
+
```datasheet
−label: Closeout Submittals
+label: Required Closeout Submittals
type: checkbox
options:
− - As-installed loop diagrams and instrument index
− - Field calibration and loop-check records
− - Warranty documentation
+ - "As-left calibration and configuration records"
+ - "Thermowell test records"
+ - "Operation and maintenance data with recalibration intervals"
+ - "Warranty documentation"
default:
− - As-installed loop diagrams and instrument index
− - Field calibration and loop-check records
− - Warranty documentation
+ - "As-left calibration and configuration records"
+ - "Thermowell test records"
+ - "Operation and maintenance data with recalibration intervals"
+ - "Warranty documentation"
```
+### Loop check records and as-built loop diagrams shall be submitted as required under [[sync/control-systems-integration]] and shall not be duplicated in this closeout package.
+
# Quality Assurance {toc}
−## Temperature instruments and assemblies shall be the product of a manufacturer regularly engaged in the production of industrial temperature instrumentation.
+## Conformance and Certification {toc}
−## All instruments of a given type and service shall be the product of a single manufacturer to maintain interchangeability of spare elements and transmitters.
+### Platinum RTD elements shall conform to IEC 60751 or ASTM E1137/E1137M for resistance-versus-temperature relationship and tolerance.
−## Factory calibration shall be NIST-traceable for all RTD Class A and Class AA elements and for all instruments used in safety-instrumented functions.
+### Thermocouple elements and extension wire shall conform to ASTM E230/E230M for electromotive force tables, limits of error, and color code, and mineral-insulated thermocouples to ASTM E608/E608M.
−## Calibration shall be performed at the ice point (0°C) plus two span points bracketing the operating range.
+### Thermowells shall be designed and evaluated under ASME PTC 19.3 TW.
−## Instruments installed in classified hazardous locations shall carry third-party certification (UL, FM, CSA, or ATEX/IECEx) appropriate to the area classification.
+### Dial thermometers shall conform to ASME B40.200.
−## For safety-instrumented functions, the element and transmitter shall be certified to the required Safety Integrity Level per IEC 61511, with the proof-test interval and proof-test procedure stated on the instrument data sheet.
+### 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.
−# Environmental and Service Conditions {toc}
+### Each element and transmitter 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.
−## The Contractor shall verify that each instrument's published ambient and process temperature ratings envelope the site service conditions before procurement.
+## Source Limitation {toc}
−## Head-mount transmitter electronics shall be rated for the connection-head ambient temperature, which for high-process-temperature service is elevated by conduction from the thermowell.
+### The manufacturer source limitation applying to temperature instruments shall be as indicated in the datasheet.
−## For high-process-temperature service, the connection-head ambient is elevated by conduction from the thermowell and may exceed the transmitter electronics rating; verify the ambient derating before specifying a head-mount transmitter. {note}
+```datasheet
+label: Temperature Instrument Source Limitation
+type: radio
+options:
+ - "Single manufacturer for all transmitters and a single manufacturer for all elements and thermowells"
+ - "Single manufacturer for all temperature instruments"
+ - "No source limitation"
+default: "Single manufacturer for all transmitters and a single manufacturer for all elements and thermowells"
+```
−## Where the process temperature would drive the connection-head ambient above 70°C, a remote-mount transmitter shall be used in lieu of a head-mount transmitter.
+### Transmitters from one manufacturer share a configuration tool, a spare, and a device description file in the control system, and elements and thermowells from one manufacturer share an insert length convention and a spare insert. Requiring one manufacturer for both narrows the bid list to the suppliers who make both, which few do, and buys nothing a two-source limit does not. {note}
−## Enclosures and connection heads installed outdoors or in wash-down areas shall be rated NEMA 4X (IP66) minimum.
+## Data Sheets and Identification {toc}
−## Instruments in Class I Division 1 locations shall be explosion-proof (NEMA 7) or protected by an approved intrinsically safe barrier.
+### Each instrument shall be identified by the tag number assigned under [[sync/process-instrumentation]] in accordance with ANSI/ISA-5.1.
−## Instruments in Class I Division 2 locations shall be intrinsically safe, non-incendive, or otherwise approved for the classification.
+### Each element, transmitter, thermowell, and dial thermometer shall carry a stainless steel tag plate stamped or engraved with its tag number and attached with stainless steel wire or screws.
−## Process seals shall be provided at conduit entries on instruments in hazardous locations in accordance with ANSI/ISA-12.27.01 where a single seal is relied upon.
+### A thermowell installed before its element arrives is identified only by its tag plate, and a plate that reads the same as the one on the element is what lets the element reach the right well on a pipe rack of identical connections. {note}
−```datasheet
−label: Hazardous Area Classification
−type: radio
−options:
− - Non-hazardous (general purpose)
− - Class I Division 2 (intrinsically safe / non-incendive)
− - Class I Division 1 (explosion-proof or intrinsically safe)
− - Zone 1 (Ex d or Ex ia)
− - Zone 2 (Ex nA or Ex ic)
−default: Non-hazardous (general purpose)
−```
+# Environmental and Service Conditions {toc}
+## Ambient Conditions {toc}
+
+### Instruments mounted outdoors shall operate within their published accuracy between [[parameter: site-ambient-temperature-minimum]] and [[parameter: site-ambient-temperature-maximum]], including solar gain on an unshaded housing.
+
+### A head-mounted transmitter shall be rated for the temperature reached inside the connection head at the maximum process temperature, with the head conducting heat from the thermowell through the extension.
+
+### Where the temperature inside the connection head at the maximum process temperature would exceed the transmitter's rated ambient, the transmitter shall be field-mounted away from the head regardless of the mounting selected under Transmitters.
+
+### Heat travels up the thermowell and the extension into the head at a rate set by the extension length and the ambient air around it, and a transmitter that drifts on hot afternoons and reads correctly at night is one that sits in a head hotter than its rating. {note}
+
+## Enclosure Rating {toc}
+
+### Connection heads, transmitter housings, 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.
+
```datasheet
−label: Enclosure / Connection Head Rating
−type: radio
+label: Minimum Enclosure Rating
+type: select
options:
− - NEMA 4X (IP66)
− - NEMA 4 (IP65)
− - NEMA 7 (explosion-proof)
− - NEMA 4X stainless steel
−default: NEMA 4X (IP66)
+ - "NEMA Type 1"
+ - "NEMA Type 12"
+ - "NEMA Type 13"
+ - "NEMA Type 3R"
+ - "NEMA Type 4"
+ - "NEMA Type 4X"
+ - "NEMA Type 7"
+default: "NEMA Type 1"
```
−```datasheet
−label: Ambient Temperature Range
−type: range
−unit: °C
−min: -40
−max: 85
−step: 5
−```
+### 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. {note}
−# Sensor Technology Selection {toc}
+### Enclosures mounted outdoors shall be rated NEMA Type 3R, Type 4, or Type 4X.
−## Sensor technology shall be selected on the basis of required accuracy, temperature range, and output type.
+### 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.
−## An RTD shall be specified where the service requires high accuracy and long-term stability within the -200°C to +850°C range; a thermocouple shall be specified where the service exceeds the RTD range, requires fast response, or requires a rugged sheathed element in severe environments.
+### Enclosures mounted in locations subject to washdown or hose-directed water shall be rated NEMA Type 4 or Type 4X.
−## A bimetallic dial thermometer or filled-system remote thermometer shall be specified only for local indication where no electrical output to the control system is required.
+### Enclosures mounted in locations exposed to corrosive fumes, salt air, or washdown chemicals shall be rated NEMA Type 4X.
+### 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.
+
+## Hazardous Locations {toc}
+
+### The hazardous-location classification at each instrument shall be as indicated on [[drawing: the electrical area classification drawings]].
+
+### Instruments in a classified location shall be protected by the method indicated in the datasheet.
+
```datasheet
−label: Sensor Technology
+label: Hazardous Location Protection Method
type: radio
options:
− - RTD (Pt100, platinum)
− - RTD (Pt1000, platinum)
− - Thermocouple
− - Bimetallic dial thermometer
− - Filled-system remote thermometer
−default: RTD (Pt100, platinum)
+ - "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"
+default: "Not applicable, no classified locations"
```
−## Resistance Temperature Detectors {toc}
+### An intrinsically safe loop keeps the field device and its wiring below ignition energy, so the head 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. {note}
−### RTD elements shall be platinum, conforming to IEC 60751:2022 resistance-versus-temperature tables and tolerance classes.
+### Conduit entries into enclosures in Class I locations shall be sealed in accordance with NFPA 70 Article 501 and the listing of the enclosure.
−### RTD elements in field installations shall be three-wire minimum to compensate for lead resistance; two-wire RTDs shall not be used for lead runs exceeding 3 m.
+### Where a single process seal separates the process fluid from the electrical system, the instrument shall be certified under ANSI/ISA-12.27.01 for that condition.
−### RTD elements in precision and safety-instrumented service shall be four-wire to eliminate lead-resistance error entirely.
+### The temperature code of each instrument in a classified location shall be lower than the autoignition temperature of the flammable material present, with the connection head temperature at the maximum process temperature included in the determination.
−### Two-wire RTD connection on field runs is a common source of uncompensated lead-resistance error and is prohibited here for that reason except for short factory-internal leads. {note}
+### 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.
−### RTD accuracy class shall be IEC 60751 Class A for industrial process control and Class B for general HVAC and building automation; Class AA shall be reserved for precision and safety-instrumented service. {note}
+## Safety Instrumented Functions {toc}
−### Class B tolerance is ±(0.30 + 0.005|t|)°C, Class A is ±(0.15 + 0.002|t|)°C, and Class AA is ±(0.10 + 0.0017|t|)°C, each evaluated at the measured temperature t in °C. {note}
+### Elements and transmitters 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.
−### RTDs used in IEC 61511 SIL 2 loops shall be Class A or better with an individual calibration certificate; Class B shall not be used for SIL-rated temperature measurement.
+### 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.
+### 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. {note}
+
+# Sensing Elements {toc}
+
+## Element Technology {toc}
+
+### The sensing element at each point shall be the technology designated in the instrument index or, where the index does not designate one, the technology indicated in the datasheet.
+
```datasheet
−label: RTD Element Type
+label: Element Technology for Points Not Otherwise Designated
type: radio
options:
− - Pt100, 3-wire
− - Pt100, 4-wire
− - Pt100, 2-wire (factory-internal leads only)
− - Pt1000, 3-wire
−default: Pt100, 3-wire
+ - "Platinum RTD"
+ - "Thermocouple"
+ - "Thermistor"
+default: "Platinum RTD"
```
+### A platinum RTD holds its calibration for years and resolves tenths of a degree, within a range that ends near 600°C and with a response slowed by its mass; a thermocouple reaches furnace and exhaust temperatures, responds faster in a thin sheath, and drifts with exposure, so it needs a periodic check against a reference; a thermistor resolves hundredths of a degree over a narrow range below about 150°C with no lead-resistance error and a nonlinear curve the transmitter or input card has to hold. The index designates another technology where the process temperature or response time at a point rules the default out. {note}
+
+### An element shall not be applied outside the temperature range the manufacturer publishes for its tolerance class or limits of error.
+
+## Platinum RTD Elements {toc}
+
+### Platinum RTD elements shall have the nominal resistance at 0°C indicated in the datasheet.
+
```datasheet
−label: RTD Accuracy Class (IEC 60751)
+label: RTD Nominal Resistance at 0°C
type: radio
options:
− - Class B (±0.30°C at 0°C) — HVAC/building automation
− - Class A (±0.15°C at 0°C) — industrial process
− - Class AA (±0.10°C at 0°C) — precision/SIL
−default: Class A (±0.15°C at 0°C) — industrial process
+ - "Pt100"
+ - "Pt1000"
+default: "Pt100"
```
+### A Pt1000 element produces ten times the resistance change of a Pt100 for the same temperature change, so the same lead resistance is a tenth of the error, which matters on a two-wire connection; nearly every process transmitter and input card accepts Pt100 and a smaller number accept Pt1000. {note}
+
+### RTD elements shall be furnished with the lead configuration indicated in the datasheet.
+
```datasheet
−label: RTD Operating Range
−type: range
−unit: °C
−min: -50
−max: 200
−step: 10
+label: RTD Lead Configuration
+type: radio
+options:
+ - "Two-wire"
+ - "Three-wire"
+ - "Four-wire"
+default: "Three-wire"
```
−## Thermocouples {toc}
+### Two leads add their own resistance to the element's and read it as temperature; three leads let the transmitter subtract the resistance of one lead on the assumption that the other matches it; four leads let the transmitter measure the element with no lead error at all, at the cost of a fourth conductor and an input that supports it. The length of the lead between the element and the transmitter is what decides how much the configuration is worth. {note}
−### Thermocouple elements shall conform to ASTM E230/E230M for EMF tables and limits of error; IEC 60584-1 shall apply for export or global projects.
+### Where two-wire leads are selected, the leads shall terminate at a head-mounted transmitter in the same connection head as the element.
−### Thermocouple type shall be selected for the process temperature range and atmosphere.
+### RTD elements shall meet the tolerance class indicated in the datasheet over the calibrated range of the point.
−### Type K (-200°C to 1260°C) shall be the default for general oxidizing process service; Type J (-40°C to 750°C) for reducing atmospheres; Type E (-200°C to 900°C) where the highest sensitivity is required; Type T (-200°C to 350°C) for cryogenic and food service; Type N for high-temperature oxidizing service; and noble-metal Types R and S for furnace service.
+```datasheet
+label: RTD Tolerance Class
+type: radio
+options:
+ - "Class AA"
+ - "Class A"
+ - "Class B"
+ - "Class C"
+default: "Class A"
+```
−### Type K standard limits of error are ±2.2°C or ±0.75% of reading, whichever is greater; special limits are ±1.1°C or ±0.4%. {note}
+### Each IEC 60751 class halves the allowed error of the one below it, and each tighter class is available over a narrower temperature range, so a Class AA element is offered to roughly 250°C and a Class A element to roughly 500°C, with Class B covering the full range of the technology. A tighter class costs more per element and buys nothing where the transmitter and the control system are not held to a matching error. {note}
−### Thermocouple extension or compensating cable shall be type-matched to the thermocouple per ISA-MC96.1; copper extension wire shall not be used with a thermocouple element.
+### Elements procured to ASTM E1137/E1137M shall meet a grade whose tolerance is equal to or tighter than the selected class over the calibrated range of the point.
−### Using copper extension wire with a thermocouple introduces a parasitic EMF error that varies with ambient temperature and corrupts the measurement; type-matched cable carries the thermoelectric reference unbroken to the cold junction. {note}
+### RTD sensing elements shall be of the construction indicated in the datasheet.
−### Cold-junction compensation shall be provided at a single defined location; thermocouple extension cable shall not be spliced to copper at intermediate terminal blocks ahead of the transmitter or DCS cold junction.
−
−### Where a thermocouple home run from a junction box to the marshalling cabinet would otherwise use copper, a head-mount transmitter shall be specified to convert to a 4-20 mA copper loop at the instrument.
−
```datasheet
−label: Thermocouple Type
+label: RTD Sensing Element Construction
type: radio
options:
− - Type K (-200 to 1260°C, general oxidizing)
− - Type J (-40 to 750°C, reducing)
− - Type E (-200 to 900°C, high sensitivity)
− - Type T (-200 to 350°C, cryogenic/food)
− - Type N (high-temperature oxidizing)
− - Type R/S (noble metal, furnace)
−default: Type K (-200 to 1260°C, general oxidizing)
+ - "Thin-film"
+ - "Wire-wound"
```
+### A thin-film element is a platinum layer on a ceramic substrate, small enough to respond quickly and robust against vibration, with a usable range that ends near 500°C; a wire-wound element is a platinum coil that reaches 600°C and holds the tightest tolerance over a wide range, and whose coil can shift under sustained vibration. {note}
+
+## Thermocouple Elements {toc}
+
+### Thermocouples shall be of the type designated in the instrument index or, where the index does not designate one, the type indicated in the datasheet.
+
```datasheet
−label: Thermocouple Limits of Error
−type: radio
+label: Thermocouple Type for Points Not Otherwise Designated
+type: select
options:
− - Standard (±2.2°C or ±0.75%)
− - Special (±1.1°C or ±0.4%)
−default: Standard (±2.2°C or ±0.75%)
+ - "Type J"
+ - "Type K"
+ - "Type E"
+ - "Type T"
+ - "Type N"
+ - "Type R"
+ - "Type S"
+ - "Type B"
+default: "Type K"
```
+### Type K covers the widest range of the base-metal types in oxidizing and inert atmospheres and drifts at a known rate above 800°C; Type N holds its calibration better than Type K at the same temperatures and costs more; Type J suits reducing atmospheres and rusts in moist ones; Type T is the most accurate base-metal type below 350°C and the one used at cryogenic temperatures; Type E produces the largest signal per degree. Types R, S, and B are platinum alloys for furnace service above the base-metal range, with Type B usable to the highest temperatures and insensitive below about 50°C. {note}
+
+### Thermocouples shall meet the limits of error indicated in the datasheet under ASTM E230/E230M.
+
```datasheet
−label: Extension / Compensating Cable
−type: select
+label: Thermocouple Limits of Error
+type: radio
options:
− - Type KX (for Type K)
− - Type JX (for Type J)
− - Type EX (for Type E)
− - Type TX (for Type T)
− - Type NX (for Type N)
− - Copper (RTD / transmitter output only)
−default: Copper (RTD / transmitter output only)
+ - "Standard limits of error"
+ - "Special limits of error"
+default: "Standard limits of error"
```
−## Number of Sensing Elements {toc}
+### Special limits of error are met by selecting wire from tighter lots, which roughly halves the allowed error at a modest premium on the element and leaves the drift rate of the type unchanged. {note}
−### Single-element assemblies shall be used for general indication and control service.
+### Thermocouple measuring junctions shall be of the type indicated in the datasheet.
−### Dual-element assemblies shall be specified where redundancy is required for safety-instrumented functions, or where independent control and monitoring measurements are taken from one penetration.
−
```datasheet
−label: Number of Sensing Elements
+label: Thermocouple Junction Type
type: radio
options:
− - Single element
− - Dual element (redundant)
−default: Single element
+ - "Ungrounded"
+ - "Grounded"
+ - "Exposed"
+default: "Ungrounded"
```
−### Dual-element construction lets a control loop and a safety loop share one thermowell penetration without sharing a common element failure, and supports averaging or hot-standby schemes. {note}
+### An ungrounded junction is isolated from the sheath, so a transmitter wired to it sees no ground loop through the thermowell and the control system; a grounded junction is welded to the sheath and responds faster at the cost of that isolation, so it suits an isolated transmitter input and a loop with no other ground; an exposed junction responds fastest and has no protection from the medium, so it suits dry gas and short-term measurement. {note}
−# Output and Transmitter {toc}
+### Noble-metal thermocouples shall be furnished with high-purity alumina insulators and a protection tube rated for the process atmosphere and temperature.
−## Output and protocol shall be selected to match the control system interface and the accuracy budget.
+## Thermistor Elements {toc}
−## New field temperature transmitters shall provide a 4-20 mA analog output with superimposed HART revision 7 digital signal as the minimum, unless a fieldbus or wireless architecture is specified for the project.
+### Requirements in this article apply where a thermistor is selected under Element Technology or designated in the instrument index.
−## WirelessHART output shall be limited to monitoring-only or retrofit service where wiring a new loop is impractical and the measurement is not used for closed-loop control or safety.
+### Thermistor elements shall be negative-temperature-coefficient devices furnished with the manufacturer's published resistance-temperature curve, and the transmitter or input card reading them shall hold that curve.
−## Local-indication-only service (bimetallic or filled-system) shall be specified where no electrical signal to the control system is required.
+### Thermistor elements shall be interchangeable to within ±0.2°C over the calibrated range of the point without individual calibration of the transmitter to the element.
−## Transmitter total loop accuracy shall be within ±1.0°C for process control and within ±0.5°C for precision applications, including element, transmitter, and reference uncertainty.
+### Thermistors shall not be applied at points where the process temperature can exceed the manufacturer's published upper limit for the element under any operating or upset condition stated on the instrument data sheet.
−## Transmitter accuracy is typically ±0.1°C to ±0.5°C and is span-dependent; the loop accuracy budget shall account for the element tolerance class in addition to the transmitter.
+## Insert and Sheath Construction {toc}
−```datasheet
−label: Output / Protocol
−type: radio
−options:
− - 4-20 mA + HART rev 7
− - 4-20 mA analog only
− - WirelessHART (monitoring/retrofit)
− - FOUNDATION Fieldbus
− - Modbus RTU
− - Local indication only (no electrical output)
−default: 4-20 mA + HART rev 7
−```
+### Elements shall be furnished as inserts of the construction indicated in the datasheet.
```datasheet
−label: Transmitter Mount
+label: Element Insert Construction
type: radio
options:
− - Integral / head-mount (on element connection head)
− - Remote-mount (DIN-rail or panel)
−default: Integral / head-mount (on element connection head)
+ - "Mineral-insulated metal-sheathed insert"
+ - "Sheathed insert with ceramic-insulated conductors"
+ - "Ceramic protection tube with insulated conductors"
+default: "Mineral-insulated metal-sheathed insert"
```
+### A mineral-insulated insert packs the conductors in compacted magnesium oxide inside a drawn metal sheath, so it bends, resists vibration, and keeps moisture out of the insulation; a sheathed insert with ceramic insulators is rigid and serves where the element must be rebuilt in the field or the mineral insulation would be exceeded by the temperature; a ceramic protection tube is the construction for noble-metal thermocouples in furnace gas, where a metal sheath would contaminate the wire. {note}
+
+### Sheaths shall be of the material indicated in the datasheet.
+
```datasheet
−label: Total Loop Accuracy
−type: radio
+label: Element Sheath Material
+type: select
options:
− - ±1.0°C (process control)
− - ±0.5°C (precision)
−default: ±1.0°C (process control)
+ - "Type 304 stainless steel"
+ - "Type 316 stainless steel"
+ - "Type 310 stainless steel"
+ - "UNS N06600 nickel-chromium-iron alloy"
+ - "UNS N06625 nickel-chromium-molybdenum alloy"
+default: "Type 316 stainless steel"
```
−## Transmitter Mounting {toc}
+### Inside a thermowell the sheath sees the air in the bore and not the process, so a stainless sheath serves to about 870°C and the choice above that is driven by temperature: Type 310 and UNS N06600 hold up in oxidizing gas to about 1150°C, and UNS N06625 adds resistance to chlorides and sulfur compounds where the sheath is directly immersed. {note}
−### Integral head-mount transmitters shall be used where the connection-head ambient remains within the transmitter electronics rating, typically -40°C to +85°C.
+### Inserts shall have the sheath outside diameter indicated in the datasheet.
−### Remote-mount transmitters shall be used where the process temperature would raise the connection-head ambient above the electronics rating, or where the element location is inaccessible for configuration and maintenance.
+```datasheet
+label: Insert Sheath Outside Diameter
+type: range
+unit: in.
+min: 0.125
+max: 0.375
+setpoints: [0.125, 0.188, 0.25, 0.375]
+default: 0.25
+```
−### Ordering a head-mount transmitter for high-process-temperature service without checking the ambient derating is a recurring field failure: a 300°C process can heat the connection head above the 85°C electronics limit and cause drift or failure. {note}
+### A thinner sheath responds faster and bends more easily; a thicker sheath holds a larger wire-wound element and survives rougher handling. The thermowell bore follows the sheath diameter, so a project that holds one diameter can carry one spare insert for every well. {note}
−# Thermowells {toc}
+### Each insert shall be spring-loaded so that the tip is held against the bottom of the thermowell bore, and shall be replaceable from the connection head without removing the thermowell from the process.
−## A thermowell shall be provided for every temperature element installed in pressurized piping, process vessels, or any service where element removal under pressure or process leakage is a safety concern.
+### Each point shall be furnished with the number of sensing elements indicated in the datasheet.
```datasheet
−label: Thermowell Requirement
+label: Sensing Elements per Point
type: radio
options:
− - Thermowell required (pressurized piping/vessel)
− - Bare element (duct / non-pressurized)
−default: Thermowell required (pressurized piping/vessel)
+ - "Single element"
+ - "Dual element"
+default: "Single element"
```
−## Specifying a bare RTD or thermocouple element in pressurized piping creates a personnel-safety and process-leak hazard and is prohibited; the thermowell isolates the element from the process and permits removal without breaching containment. {note}
+### A dual-element insert carries two independent elements in one sheath, so a control loop and a monitoring loop can share one thermowell, a transmitter can switch to the second element when the first fails, and the two readings can be compared for drift; both elements share the sheath, so a sheath failure takes both. {note}
−## Bare elements (no thermowell) shall be limited to duct service and other non-pressurized service such as HVAC air measurement.
+# Thermowells {toc}
−## Thermowell material shall be compatible with the process fluid.
+## Thermowell Provision {toc}
−## 316 stainless steel shall be the default thermowell material; nickel-chromium-molybdenum alloy (UNS N10276), nickel-copper alloy (UNS N04400), nickel-chromium alloy (UNS N06600/N06625), or alumina ceramic shall be specified for corrosive or high-temperature service.
+### Every element in a pipe or a closed vessel shall be installed in a thermowell unless the instrument index designates the point for direct immersion.
+### Direct immersion shall be limited to open tanks, channels, ducts, and ambient air, and to closed systems that operate at atmospheric pressure with a fluid that is neither flammable, toxic, nor hot enough to injure on contact.
+
+### The thermowell separates the element from the process, so the element is replaced without draining, depressurizing, or opening the line, and a sheath failure does not become a leak. {note}
+
+### The thermowell connection on the pipe or vessel, whether a threaded coupling, a weld boss, a nozzle, or a flanged branch, shall be furnished and installed under the piping or vessel specification at the locations indicated on [[drawing: the piping drawings]].
+
+### Thermowells shall be delivered to the piping installer before the section of pipe or the vessel they serve is closed and pressure tested.
+
+## Thermowell Construction {toc}
+
+### Thermowells shall be of the construction indicated in the datasheet.
+
```datasheet
−label: Thermowell Material
−type: select
+label: Thermowell Construction
+type: radio
options:
− - 316 stainless steel
− - 304 stainless steel
− - Nickel-chromium-molybdenum alloy (UNS N10276)
− - Nickel-copper alloy (UNS N04400)
− - Nickel-chromium alloy (UNS N06600)
− - Alumina ceramic
−default: 316 stainless steel
+ - "Machined from solid bar stock"
+ - "Fabricated from tube and bar"
+default: "Machined from solid bar stock"
```
−## Thermowell process connection rating shall match the pipe specification.
+### A thermowell machined from bar has no weld in the pressure boundary and is the construction ASME PTC 19.3 TW evaluates; a fabricated well is a tube welded to a connection and a tip, which is cheaper in long lengths and large diameters and carries welds that have to be examined and a geometry the performance test code does not cover. {note}
−## Specifying a thermowell with a lower pressure rating than the piping class (e.g., 150# flange on a 600# line) is a common RFI generator; cross-check the piping class before procurement to avoid this error. {note}
+### Thermowell stems shall have the profile indicated in the datasheet.
−## The thermowell style shall be specified, selected for compatibility with the process connection, pressure rating, and immersion requirements of the installation.
−
```datasheet
−label: Thermowell Style
+label: Thermowell Stem Profile
type: radio
options:
− - Tapered (stepped)
− - Straight
− - Flanged
− - Threaded (NPT)
− - Socket-weld
−default: Tapered (stepped)
+ - "Tapered"
+ - "Stepped"
+ - "Straight"
+default: "Tapered"
```
−## The thermowell process connection shall be specified, and its pressure rating shall be cross-checked against the piping class before procurement.
+### A tapered stem has the highest natural frequency for a given length and the largest root, so it passes the wake-frequency calculation at higher velocities and longer insertions than the other profiles; a stepped stem keeps a thin tip for fast response on a stiff root and is the usual answer where a tapered stem is too slow; a straight stem is the cheapest to machine and the first to fail the calculation at any velocity. {note}
+### Thermowells shall have the process connection indicated in the datasheet.
+
```datasheet
−label: Process Connection
+label: Thermowell Process Connection
type: select
options:
− - 1/2" NPT male
− - 3/4" NPT male
− - 1" NPT male
− - ANSI 150# flange
− - ANSI 300# flange
− - ANSI 600# flange
− - Socket-weld
−default: 1/2" NPT male
+ - "Threaded NPT"
+ - "Flanged"
+ - "Socket weld"
+ - "Weld-in"
+ - "Lap-joint Van Stone"
+ - "Sanitary clamp"
```
+### A threaded well installs in a coupling and is removed with a wrench, and its thread is the one path through which a leak can develop; a flanged well matches the piping class, removes without disturbing the pipe, and is the connection a wake-frequency calculation favors for its stiff root; a socket-weld or weld-in well is a permanent part of the pressure boundary with no joint to leak and no way out except cutting; a lap-joint well is a flanged well whose flange rotates for bolt alignment; a sanitary clamp well suits hygienic piping with no thread or crevice at the product. The piping class at each point decides which of these the piping specification provides. {note}
+
+### The connection size, thread form, flange class, and facing of each thermowell shall match the connection furnished under the piping or vessel specification at that point, with flanges to ASME B16.5 and threads to ASME B1.20.1.
+
+### The thermowell bore shall be sized to the selected insert sheath diameter with the diametral clearance the thermowell manufacturer publishes for a spring-loaded insert.
+
+### Thermowells in insulated lines shall have a lagging extension of a length not less than the insulation thickness specified under [[sync/mechanical-insulation]] at that line.
+
+## Thermowell Material {toc}
+
+### Thermowells shall be of the material indicated in the datasheet.
+
```datasheet
−label: Process Connection Size and Rating
−type: radio
+label: Thermowell Material
+type: select
options:
− - 1/2" NPT (pipe ≤4", ≤600 psig)
− - 3/4" NPT (larger pipe)
− - Flanged ANSI 150#
− - Flanged ANSI 300#
−default: 1/2" NPT (pipe ≤4", ≤600 psig)
+ - "Type 316/316L stainless steel"
+ - "Type 304/304L stainless steel"
+ - "Carbon steel"
+ - "Duplex stainless steel UNS S31803"
+ - "UNS N04400 nickel-copper alloy"
+ - "UNS N06600 nickel-chromium-iron alloy"
+ - "UNS N06625 nickel-chromium-molybdenum alloy"
+ - "UNS N10276 nickel-molybdenum-chromium alloy"
+ - "Titanium Grade 2"
+ - "Brass"
```
−## Wake-Frequency and Insertion Length {toc}
+### Type 316/316L serves water, steam, and most process fluids and is the material every supplier stocks; Type 304/304L is cheaper and gives up chloride resistance; carbon steel matches carbon steel piping in non-corrosive utility service and rusts in the bore; duplex stainless resists chloride pitting and stress cracking in brine and seawater; nickel-copper alloy serves seawater and hydrofluoric acid; the nickel-chromium alloys serve high-temperature and high-chloride service and the nickel-molybdenum-chromium alloy serves oxidizing and reducing acids; titanium serves seawater and chlorine solutions; brass serves low-pressure water at low cost. Which one a project holds as its default depends on the fluid in most of its lines, so the field carries no default. {note}
−### An ASME PTC 19.3 TW-2016 wake-frequency (Strouhal) calculation shall be submitted for every thermowell in flowing process service to confirm structural adequacy against vortex-induced resonance.
+### Thermowell material shall be not less resistant to the process fluid than the piping material at the connection, and shall be the piping material where the piping specification requires alloy or lined pipe at that point.
−### A wake-frequency calculation shall be required for all thermowells where fluid velocity exceeds 1 m/s for liquids or 10 m/s for gases.
+### Thermowell stock shall be furnished with a mill test report traceable to the heat.
−### Thermowell resonance failure in high-velocity service is a documented field failure mode in which vortex shedding excites the thermowell at its natural frequency and fatigues the root; the PTC 19.3 TW calculation governs L/D limits and the fatigue assessment. {note}
+## Wake Frequency and Immersion {toc}
−### The frequency ratio of natural to shedding frequency shall be at least 1.3 for an unsupported thermowell per ASME PTC 19.3 TW; stepped or tapered thermowells shall be preferred for high-velocity service.
+### Each thermowell in flowing service shall be evaluated under ASME PTC 19.3 TW for the stem profile, insertion length, bore, material, and process connection furnished, at the maximum fluid velocity, density, and temperature stated on the instrument data sheet, including startup and upset conditions.
−### Thermowell insertion length shall place the tip at a minimum of 60% of the pipe inside diameter into the flow stream to limit conduction error.
+### A thermowell that does not pass the evaluation shall be redesigned by shortening the insertion, changing the profile, adding a velocity collar or support, or changing the process connection, and resubmitted at no additional cost to the Owner.
−### The insertion-length-to-bore ratio shall satisfy L/D greater than 5 to limit conduction error along the well.
+### Vortices shed from a stem in flowing fluid push it at a frequency that rises with velocity, and when that frequency approaches the stem's natural frequency the stem resonates and fatigues at the root until the tip breaks off into the line; the calculation finds the margin between the two frequencies and the stress at the root, and both have to clear before the well is cut. {note}
−### Insertion length shall be verified against the pipe inside diameter on the instrument data sheet so the well neither bottoms out nor falls short of the 60%-immersion target.
+### Where a thermowell falls outside the geometry the performance test code covers, the Contractor shall submit an alternative analysis, prepared by the thermowell manufacturer and accepted by the Engineer, before the thermowell is fabricated.
−### A standard 6-inch-insertion thermowell bottoms out in a 2-inch pipe; insertion length versus pipe size is the single most common RFI generator in this category and shall always be checked against the pipe ID.
+### The insertion length of each thermowell shall be the length stated on the instrument data sheet.
−### Use the following guidance for nominal insertion length versus pipe size, subject to the wake-frequency calculation. {note}
+### The thermowell tip shall lie within the central one-third of the pipe inside diameter or, where the wake-frequency evaluation does not permit that length, not less than 2.5 in. beyond the inside wall of the pipe.
−| Pipe size (NPS) | Nominal pipe ID | Target tip immersion (60% ID) | Typical insertion length (U) |
−|-----------------|-----------------|-------------------------------|------------------------------|
−| 2" | ~52 mm | ~31 mm | 2.5" (63 mm) |
−| 3" | ~78 mm | ~47 mm | 4.5" (114 mm) |
−| 4" | ~102 mm | ~61 mm | 6.0" (150 mm) |
−| 6" | ~154 mm | ~92 mm | 7.5" (190 mm) |
−| 8" | ~203 mm | ~122 mm | 10.5" (267 mm) |
−| ≥10" | per drawing | 60% of ID | per wake-frequency calculation |
+### Where the pipe is too small for the required immersion, the thermowell shall be installed in an elbow with the tip pointing upstream, in a tee, or in an enlarged section of pipe furnished under the piping specification.
−### For pipe smaller than 3 inches, a tapered thermowell in an elbow or a pipe expansion (tee with a larger-bore run) shall be used where straight-run immersion cannot meet the 60% target.
+### A tip that stops short of the flowing core reads the wall, and the wall is cooled by the ambient and the insulation around it, so the error grows with the difference between process and ambient and is largest on the hot and cold lines where the measurement matters most. {note}
+# Connection Heads {toc}
+
+## Connection Head Construction {toc}
+
+### Connection heads shall be of the material indicated in the datasheet.
+
```datasheet
−label: Wake-Frequency Calculation Required
+label: Connection Head Material
type: radio
options:
− - Required (flowing process service)
− - Not required (static / non-pressurized)
−default: Required (flowing process service)
+ - "Coated die-cast aluminum"
+ - "Stainless steel"
+ - "Glass-fiber-reinforced polymer"
+default: "Coated die-cast aluminum"
```
+### A coated aluminum head is light, inexpensive, and offered in every configuration, and its coating is what stands between it and a salt or chemical atmosphere; a stainless head resists that atmosphere without a coating at several times the price and weight; a polymer head is immune to corrosion and to galvanic contact with the thermowell, is not offered in explosion-proof form, and loses strength at the temperatures a hot process can conduct into the head. {note}
+
+### Connection heads shall have the conduit entry indicated in the datasheet.
+
```datasheet
−label: Thermowell Insertion Length (U)
−type: range
−unit: mm
−min: 50
−max: 600
−step: 10
−drawing_ref: "thermowell schedule"
+label: Connection Head Conduit Entry
+type: radio
+options:
+ - "1/2 in. NPT"
+ - "3/4 in. NPT"
+ - "M20 x 1.5"
+default: "1/2 in. NPT"
```
−# Element Construction and Connection Head {toc}
+### A 1/2 in. entry fits the conduit size that serves a single loop and is the entry every head 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. {note}
−## Element construction shall be selected for the protection-tube environment and required response time.
+### Connection heads shall have a threaded screw cover with a captive chain or a hinged cover, with a gasket that holds the enclosure rating required under Environmental and Service Conditions.
−## Bare elements shall be used inside thermowells in clean, non-severe service; mineral-insulated metal-sheathed (MIMS) elements shall be used where vibration, moisture ingress, or bending is a concern; ceramic protection tubes shall be used for high-temperature furnace service.
+### Connection heads for head-mounted transmitters with a local display shall have a cover with a window.
−## Sheath or protection-tube material shall be 316 stainless steel for general service, nickel-chromium alloy (UNS N06600 or UNS N06625) for high-temperature oxidizing service, and alumina ceramic for furnace service.
+### Terminal blocks in connection heads shall be ceramic or glass-filled thermoplastic rated for the head temperature at the maximum process temperature, with the terminals of a thermocouple head made of the thermocouple alloy or the matching extension alloy.
−## The connection head shall be cast aluminum for general service and stainless steel for corrosive or wash-down service.
+### Each connection head shall be mounted to its thermowell through an extension of nipple, union, and nipple of the length needed to clear the pipe insulation and to hold the temperature inside the head within the rating of the transmitter and terminal block.
−## The conduit entry shall be sized 1/2" or 3/4" NPT to match the project wiring method.
+# Transmitters {toc}
−## The connection head enclosure rating shall be NEMA 4X (IP67) minimum for general process service.
+## Transmitter Provision {toc}
−## The connection head enclosure rating shall be NEMA 7 for Class I Division 1 hazardous locations.
+### Temperature transmitters shall be furnished as indicated in the datasheet.
```datasheet
−label: Element Construction
+label: Transmitter Provision
type: radio
options:
− - Bare element (in thermowell)
− - Mineral-insulated metal-sheathed (MIMS)
− - Ceramic protection tube
−default: Bare element (in thermowell)
+ - "Transmitter at every point"
+ - "Transmitter where designated in the instrument index, element wired to the controller input elsewhere"
+ - "Element wired to the controller input at every point, no transmitters"
+default: "Transmitter at every point"
```
−```datasheet
−label: Sheath / Protection Tube Material
−type: select
−options:
− - 316 stainless steel
− - Nickel-chromium alloy (UNS N06600)
− - Nickel-chromium alloy (UNS N06625)
− - Alumina ceramic
−default: 316 stainless steel
−```
+### A transmitter converts the element's resistance or millivolt signal to a standard signal at the point of measurement, so lead resistance, noise pickup, and thermocouple extension wire end at the head and the control system needs one kind of input card; wiring the element directly removes a powered device from every point and puts the conversion in the input card, which then needs the lead compensation, the cold-junction reference, and the linearization for each element type it reads, and holds every lead run to the error its length produces. {note}
+## Transmitter Mounting {toc}
+
+### Transmitters shall be mounted as indicated in the datasheet.
+
```datasheet
−label: Connection Head Material
+label: Transmitter Mounting
type: radio
options:
− - Cast aluminum (epoxy-coated)
− - Stainless steel
−default: Cast aluminum (epoxy-coated)
+ - "Head-mounted in the connection head"
+ - "Field-mounted in a housing on a pipe stand or wall near the element"
+ - "DIN-rail-mounted in a junction box or control panel"
+default: "Head-mounted in the connection head"
```
+### A head-mounted transmitter has the shortest element leads and no separate housing, and lives in the temperature the head reaches; a field-mounted transmitter sits in its own housing with a display at eye level, away from the heat and vibration of the line, at the cost of a stand and a short element lead run; a DIN-rail transmitter collects many points into one panel and runs raw element signals back to it, which saves field housings and puts the conversion where the leads are longest. {note}
+
+### Where the element is not accessible from grade or a platform for configuration and maintenance, the transmitter shall be field-mounted at an accessible location regardless of the mounting selected above.
+
+## Output Signal {toc}
+
+### Transmitters shall deliver the output signal indicated in the datasheet.
+
```datasheet
−label: Conduit Entry
−type: radio
+label: Transmitter Output Signal
+type: select
options:
− - 1/2" NPT
− - 3/4" NPT
− - M20
−default: 1/2" NPT
+ - "4-20 mA with HART"
+ - "4-20 mA without digital communication"
+ - "FOUNDATION Fieldbus H1"
+ - "PROFIBUS PA"
+ - "WirelessHART"
+ - "Modbus RTU over RS-485"
+default: "4-20 mA with HART"
```
−# Local Indicating Thermometers {toc}
+### 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. {note}
−## Bimetallic dial thermometers shall conform to ASME B40.200 and shall be provided with an every-angle adjustable stem and a thermowell where installed in pressurized service.
+### Transmitters with a 4-20 mA output shall be two-wire loop-powered devices.
−## Filled-system remote thermometers (capillary bulb and dial) shall be used where a local reading is required at a distance from the process connection that a rigid-stem dial cannot reach.
+### Transmitters shall drive their output to the failure level under NAMUR NE 43 on a sensor open circuit, a sensor short circuit, or an internal fault, in the direction stated on the instrument data sheet for each point.
−## Dial size shall be selected for the required reading distance; a 3-inch dial is typical at arm's length and a 5-inch dial where the gauge must be read from a walkway or grade.
+### 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.
−## Bimetallic and filled-system thermometers provide local indication only and shall not be relied upon for control or alarm functions, which require an electrical-output element and transmitter.
+### Fieldbus and wireless transmitters shall join segments and networks designed under [[sync/process-control-networks]].
+### Temperature elements on fuel storage tanks furnished under [[sync/fuel-dispensing-and-storage-tanks]] shall deliver the output signal selected above and shall meet the hazardous-location requirements of this standard.
+
+## Transmitter Performance {toc}
+
+### Transmitters shall have a published reference accuracy for a Pt100 input not exceeding the value indicated in the datasheet.
+
```datasheet
−label: Local Thermometer Type
+label: Maximum Transmitter Reference Accuracy, Pt100 Input
+type: range
+unit: °C
+min: 0.05
+max: 0.5
+setpoints: [0.05, 0.1, 0.15, 0.2, 0.3, 0.5]
+```
+
+### The transmitter's error adds to the element's, so a transmitter tighter than the element's tolerance class buys little, and one looser than it wastes the class; the budget for the loop is set by what the control system does with the value, which is why the field carries no default. {note}
+
+### Transmitters shall provide galvanic isolation between the sensor input and the output.
+
+### Transmitters shall accept the element types and lead configurations selected under Sensing Elements and shall be configurable for range, sensor type, damping, and failure direction without a reference source connected.
+
+### Transmitters shall be matched to their RTD elements as indicated in the datasheet.
+
+```datasheet
+label: Transmitter-to-Element Sensor Matching
type: radio
options:
− - Bimetallic dial (every-angle adjustable)
− - Filled-system remote (capillary)
− - None (no local indication)
−default: None (no local indication)
+ - "Sensor matching for every RTD transmitter and element pair"
+ - "Sensor matching for the points designated in the instrument index"
+ - "No sensor matching"
```
+### Sensor matching loads the element's individually measured resistance-temperature coefficients into the transmitter, so the pair reads to the element's calibration rather than to the class tolerance; it needs an individually calibrated element, a transmitter that accepts the coefficients, and a re-entry of the coefficients whenever either is replaced, which is a maintenance step a plant either builds into its procedures or does not. {note}
+
+### Transmitters shall be furnished with a local display as indicated in the datasheet.
+
```datasheet
−label: Dial Size
+label: Transmitter Local Display
type: radio
options:
− - 3 inch
− - 5 inch
−default: 3 inch
+ - "Display on every transmitter"
+ - "Display on field-mounted transmitters, none on head-mounted transmitters"
+ - "No local display"
```
−# HVAC and Building Automation Sensors {toc}
+### A display shows the reading and the diagnostic state at the instrument, which lets a technician check a loop without a handheld communicator; on a head-mounted transmitter it needs a windowed cover and is read at the head's elevation, which on a pipe rack is from a ladder. {note}
−## Duct-mounted air-temperature elements shall be bare Pt100 RTDs without thermowells, with a remote-mount or transmitter output suitable for the building automation system.
+# Thermocouple Extension Wire and Element Leads {toc}
−## Averaging elements shall be specified for supply, return, and mixed-air measurement in ducts where a single-point sensor would not represent the bulk air temperature across the duct cross-section.
+## Thermocouple Extension Wire {toc}
−## A single-point sensor in a large or stratified duct cross-section can misrepresent mixed-air temperature; averaging-element length or multiple point locations shall follow ASHRAE duct-measurement guidance. {note}
+### Thermocouple signals between the measuring junction and the cold-junction reference shall be carried on extension or compensating wire of the grade matched to the thermocouple type under ASTM E230/E230M, color-coded to that standard.
−## Pipe-immersion RTDs for hydronic heating and chilled-water service shall be installed in thermowells in accordance with the pressurized-service requirements of this standard.
+### Extension wire shall run unbroken from the connection head to the transmitter or input card that provides the cold-junction reference, with every intermediate terminal made of the matching alloy.
−## Room and space temperature sensors shall be Pt100 or Pt1000 RTDs with an enclosure and aesthetic suited to the occupied space and the building automation system interface.
+### A copper splice in a thermocouple circuit forms a second pair of junctions whose voltage follows the temperature of the splice, and the measurement then wanders with the weather in the junction box. {note}
+### Where a head-mounted transmitter is furnished at a thermocouple point, the cold-junction reference shall be in the transmitter and no extension wire shall be run beyond the connection head.
+
+### Thermocouple extension wire shall be twisted and shielded, with the shield grounded at the control panel end only.
+
+## Element Leads {toc}
+
+### RTD and thermistor leads between the element and a transmitter or input card outside the connection head shall be copper, twisted, shielded, and furnished with the conductor count of the lead configuration selected under Sensing Elements.
+
+### Element leads and transmitter signal pairs shall be installed in raceway under [[sync/raceways-and-conduit]], separated from power conductors in accordance with the manufacturer's instructions and [[sync/industrial-control-panels]].
+
+### 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.
+
+# Local Dial Thermometers {toc}
+
+## Dial Thermometer Construction {toc}
+
+### Local dial thermometers at the points designated in the instrument index shall be of the type indicated in the datasheet.
+
```datasheet
−label: HVAC Sensor Service
+label: Dial Thermometer Type
type: radio
options:
− - Duct air (single-point)
− - Duct air (averaging)
− - Pipe immersion (thermowell)
− - Room / space
−default: Duct air (averaging)
+ - "Bimetal dial thermometer"
+ - "Gas-actuated dial thermometer"
+ - "Loop-powered digital indicator"
+default: "Bimetal dial thermometer"
```
+### A bimetal thermometer has no fill and no electronics, reads at the well, and is the lowest-cost local indication; a gas-actuated thermometer reads through a capillary at a distance from the well and holds its accuracy at low temperatures where a bimetal coil loses sensitivity; a loop-powered indicator reads the transmitter output, so it shows the same value the control system sees and nothing when the loop is down. {note}
+
+### Dial thermometers shall have the dial size indicated in the datasheet.
+
```datasheet
−label: Averaging Element Length
+label: Dial Thermometer Dial Size
type: range
−unit: m
−min: 0.5
−max: 7.5
−step: 0.5
−drawing_ref: "duct sensor schedule"
+unit: in.
+min: 3
+max: 5
+setpoints: [3, 5]
+default: 5
```
−# Extension and Field Cable {toc}
+### Dial thermometers shall meet ASME B40.200 Grade A accuracy.
−## RTD field wiring shall be copper, with a dedicated three-conductor (three-wire RTD) or four-conductor (four-wire RTD) twisted, shielded cable per loop.
+### Bimetal thermometers shall have an every-angle adjustable stem and a hermetically sealed case.
−## Thermocouple field wiring ahead of any transmitter shall be type-matched compensating or extension cable per ISA-MC96.1, color-coded to the thermocouple type, twisted, shielded, and 20 AWG minimum for runs exceeding 15 m.
+### Dial thermometers shall be ranged so that the normal operating temperature of the point falls within the middle half of the scale.
−## Cable shields shall be continuous and grounded at one end only, at the control-system end, to avoid ground loops.
+### Dial thermometers in pipes and closed vessels shall be installed in thermowells meeting the requirements of this standard.
−## Armored or jacketed cable shall be provided where the field route requires mechanical protection; armor and conduit shall be bonded and grounded per NEC Article 250.
+### Gas-actuated thermometers shall have a capillary of the length stated on the instrument data sheet, armored over its full length.
−```datasheet
−label: Field Cable Type
−type: radio
−options:
− - Copper, 3-conductor twisted shielded (3-wire RTD)
− - Copper, 4-conductor twisted shielded (4-wire RTD)
− - Thermocouple extension/compensating, twisted shielded
− - Copper, 2-conductor twisted shielded (transmitter output)
−default: Copper, 3-conductor twisted shielded (3-wire RTD)
−```
+# Calibration {toc}
+## Factory Calibration {toc}
+
+### Individual calibration certificates traceable to a national metrology institute shall be furnished for the scope indicated in the datasheet.
+
```datasheet
−label: Cable Armor / Mechanical Protection
+label: Individual Calibration Certificate Scope
type: radio
options:
− - Unarmored (in conduit)
− - Interlocked armor
− - Continuously welded armor
−default: Unarmored (in conduit)
+ - "Every element and every transmitter"
+ - "Every transmitter, with a lot conformance certificate for elements"
+ - "Elements and transmitters at the points designated in the instrument index, with lot conformance certificates elsewhere"
```
−# Testing {toc}
+### An individual certificate records the element's measured error at stated temperatures and is what sensor matching and a tight loop budget are built on; a lot certificate states that the lot met its class, which is all a Class B element wired to a general-purpose input needs. The cost is a bench test per device, so the scope follows how many points carry an error budget the class tolerance alone does not satisfy. {note}
−## Every instrument shall be bench-calibrated and tagged before installation, with the calibration record retained for the closeout submittal.
+### Elements of Class AA tolerance and every element and transmitter serving a safety instrumented function shall carry an individual calibration certificate regardless of the scope selected above.
−## Each loop shall be field loop-checked end to end, verifying 4 mA at the lower range value (LRV) and 20 mA at the upper range value (URV).
+### Individual element certificates shall report the measured error at not fewer than three temperatures spanning the calibrated range of the point, with RTD elements tested under ASTM E644 and thermocouples under ASTM E220.
−## Thermocouple loops shall be verified for correct cold-junction compensation at ambient conditions during the loop check.
+### Transmitter certificates shall report the as-shipped error at 0%, 50%, and 100% of the calibrated range with a precision resistance or voltage source at the input.
−## Insulation resistance of RTD elements and field cable shall be tested and recorded prior to energization.
+## Field Verification {toc}
−## Safety-instrumented loops shall be proof-tested per the IEC 61511 procedure stated on the instrument data sheet before the safety function is placed in service.
+### Before installation, each element and transmitter pair shall be verified together at one temperature within the calibrated range using a dry-block calibrator or an ice bath, and the reading recorded on the as-left calibration record.
−## A loop is not accepted until the measured value at the control system agrees with a traceable reference at two points spanning the operating range within the loop accuracy budget.
+### 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.
+### Each transmitter's as-left configuration, including the range, sensor type, lead configuration, damping, failure direction, and matching coefficients, shall be recorded on the as-left calibration record.
+
+### Each thermocouple loop shall be verified for correct cold-junction compensation by comparing the reading at the control system with a reference at the measuring junction.
+
+### The insulation resistance between the element circuit and the sheath of each RTD insert shall be verified at not less than 100 MΩ at 100 V DC before installation.
+
+### Loop checks from the instrument to the controller shall be performed and recorded under [[sync/control-systems-integration]] in accordance with ANSI/ISA-62382.
+
+### The recalibration interval stated in the operation and maintenance data shall be not longer than the interval indicated in the datasheet.
+
```datasheet
−label: Field Test Scope
+label: Maximum Recalibration Interval
+type: range
+unit: months
+min: 6
+max: 36
+setpoints: [6, 12, 24, 36]
+default: 12
+```
+
+### A thermocouple drifts with exposure and an RTD drifts with thermal cycling and vibration, so the interval is a judgment about the service rather than the device; a point feeding a safety instrumented function follows its proof-test interval where that is shorter. {note}
+
+# Testing {toc}
+
+## Thermowell Testing {toc}
+
+### Each thermowell shall be tested and examined by the manufacturer as indicated in the datasheet before shipment.
+
+```datasheet
+label: Thermowell Testing and Examination
type: checkbox
options:
− - Bench calibration and tagging
− - End-to-end loop check (LRV/URV)
− - Cold-junction compensation verification (TC)
− - Insulation resistance test
− - SIL proof test (safety loops)
+ - "Hydrostatic test of the bore and stem"
+ - "Liquid penetrant examination of welds"
+ - "Positive material identification of alloy stock"
+ - "Dimensional inspection against the reviewed drawing"
default:
− - Bench calibration and tagging
− - End-to-end loop check (LRV/URV)
− - Insulation resistance test
+ - "Hydrostatic test of the bore and stem"
+ - "Dimensional inspection against the reviewed drawing"
```
+### Where a hydrostatic test is selected, the thermowell shall be tested externally at not less than 1.5 times the design pressure of the piping class at the connection with no leakage into the bore.
+
+### Positive material identification shall be performed on every thermowell of a material other than carbon steel or Type 304 or Type 316 stainless steel, regardless of the selection above.
+
+### Welds in fabricated thermowells shall be examined by liquid penetrant regardless of the selection above.
+
+### Thermowell test and examination records shall identify the thermowell by tag number and shall be included in the closeout submittal.
+
+## Repeat Testing {toc}
+
+### The cost of repeating a factory calibration, a field verification, or a thermowell test after a failure shall be borne by the Contractor.
+
# Installation {toc}
−## Thermowells shall be installed so that the tip reaches the required immersion depth into the flow stream and, where practical, points slightly into the flow in elbows for fastest response.
+## Thermowell and Element Installation {toc}
−## Elements shall be spring-loaded against the bottom of the thermowell to ensure thermal contact, and the annular gap shall be filled with thermal compound where the manufacturer requires it.
+### Thermowells shall be installed perpendicular to the pipe axis, or in an elbow with the tip pointing upstream.
−## Connection heads shall be installed so the cover and conduit entry permit drainage and prevent moisture accumulation in the head.
+### Thermowells shall be installed at a distance downstream of a mixing point, an injection point, or a heat exchanger sufficient for the stream to be mixed, as stated on the instrument data sheet.
−## Transmitters shall be installed accessible for configuration and calibration without removing the element from the thermowell.
+### Thermowells on vertical lines and vessels shall be installed with the connection head above the thermowell unless the thermowell is in a bottom or side nozzle.
−## Instruments shall be installed to permit removal of the element from the thermowell without breaking into the pressurized process.
+### Inserts shall be installed with the spring compressed so that the tip bears on the bottom of the bore.
−## Conduit and cable entries into connection heads in classified areas shall be sealed in accordance with NEC Article 500 and the certification of the instrument.
+### Where the process temperature does not exceed 200°C, the thermowell bore shall be filled with a thermally conductive compound before the insert is installed; above that temperature the bore shall be left dry.
−## Metal thermowells, connection heads, and conduit systems shall be grounded and bonded in accordance with NEC Article 250.
+### A conductive compound fills the air gap between the sheath and the bore and cuts the response time by a large fraction; the compounds dry out and bake hard above a few hundred degrees and then bind the insert in the well. {note}
−## Instrument locations, routing, and field-device arrangements shall be installed as shown. [[drawing: instrument location plan]]
+### Thermowell threads shall be made up with a sealant rated for the process temperature, and flanged thermowells shall be installed with the gasket and bolting of the piping class.
+## Connection Head and Transmitter Installation {toc}
+
+### Connection heads shall be oriented so that the conduit entry faces down or to the side, with a drip loop in any cable entering the head.
+
+### Field-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 10 ft of the element unless the instrument data sheet states a longer lead run.
+
+### Transmitters and connection heads shall be accessible for configuration and insert replacement without removing insulation, scaffolding, or another device.
+
+### Metal thermowells, connection heads, transmitter housings, and the raceway serving them shall be bonded to the equipment grounding system under [[sync/grounding-and-bonding]].
+
+### Pipe insulation shall be finished around the lagging extension and the connection head left clear, coordinated with [[sync/mechanical-insulation]].
+
# Delivery, Storage, and Handling {toc}
−## Instruments shall be delivered in the manufacturer's original packaging with tags, calibration certificates, and protective thread or flange covers intact.
+## Instruments shall be delivered in the manufacturer's original packaging with tag numbers, calibration certificates, and installation instructions enclosed.
−## Instruments shall be stored indoors in a clean, dry, temperature-controlled environment until installation.
+## Thermowell bores and process threads shall be capped until the element is installed.
−## Thermowell bores and process threads shall be kept capped until the element is installed to prevent contamination and thread damage.
+## Elements and transmitters shall be stored indoors in a clean, dry location within the storage temperature range published by the manufacturer until installation.
−## Electronic transmitters shall be protected from moisture, impact, and electrostatic discharge during storage and handling.
+## Mineral-insulated inserts and thermocouple cable shall be stored with their ends sealed.
+## Compacted mineral insulation absorbs moisture through an open end, and the insulation resistance falls until the end is dried and resealed. {note}
+
# Warranty {toc}
−## The manufacturer shall warrant each instrument against defects in materials and workmanship for a minimum of 24 months from startup or 30 months from shipment, whichever occurs first.
+## Temperature instruments and thermowells shall be warranted against defects in materials and workmanship for the period indicated in the datasheet, measured from the date of substantial completion.
−## The warranty shall cover repair or replacement of failed elements, transmitters, and thermowells, including the cost of recalibration of replacement units.
−
```datasheet
−label: Warranty Period
−type: radio
−options:
− - 12 months
− - 24 months
− - 36 months
−default: 24 months
+label: Temperature Instrument Warranty Period
+type: range
+unit: years
+min: 1
+max: 5
+setpoints: [1, 2, 3, 5]
+default: 1
```
−# Spare Parts {toc}
+## The warranty shall cover repair or replacement of the failed element, transmitter, or thermowell and the calibration and field verification of the replacement.
−## The Contractor shall furnish spare sensing elements and transmitters sufficient to maintain the installed instruments without procurement delay.
+## 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.
−## Spare parts shall be furnished as follows:
−- One spare element of each type, range, and accuracy class for every ten installed, minimum one of each.
−- One spare transmitter of each model and configuration for every ten installed, minimum one of each.
−- Spare thermowells for any non-standard material or process connection that is not stock.
+# Spare Parts {toc}
+## The Contractor shall deliver the spare parts indicated in the datasheet at substantial completion.
+
```datasheet
−label: Spare Elements (per 10 installed, min 1)
−type: range
−unit: each
−min: 0
−max: 10
−step: 1
+label: Spare Parts Delivered at Substantial Completion
+type: checkbox
+options:
+ - "Inserts of each type, length, and tolerance class installed"
+ - "Transmitters of each model installed"
+ - "Thermowells of each material and connection not stocked by the manufacturer"
+ - "Dial thermometers of each range installed"
+ - "Connection head gaskets and covers of each model installed"
+default:
+ - "Inserts of each type, length, and tolerance class installed"
+ - "Transmitters of each model installed"
```
+## 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.
+
```datasheet
−label: Spare Transmitters (per 10 installed, min 1)
+label: Spare Part Quantity per Ten Installed
type: range
−unit: each
−min: 0
−max: 10
−step: 1
+unit: units
+min: 1
+max: 5
+setpoints: [1, 2, 3, 5]
+default: 1
```
+
+## Spare parts shall match the installed devices in model, range, tolerance class, and firmware, and shall be turned over against a written inventory signed by the Owner's representative.