What standards does this thermocouple comply with?

The Type K stainless steel tube thermocouple is built to comply with ASTM E608 (the standard specification for metal-sheathed, base-metal thermocouples) and IEC 60584 (the international standard for thermocouples covering tolerance classes and limits of error). Compliance with both standards ensures measurement accuracy, calibration traceability, and interoperability with industrial temperature monitoring and control systems globally.

What thermowell sizes are compatible with this thermocouple?

Three thermowell lengths are available: 2-inch, 4-1/2-inch, and 7-1/2-inch, all in 304 stainless steel construction with a 1/2-inch NPT process connection. Each thermowell is supplied with a standard stainless steel bore-through compression fitting that secures the thermocouple probe at the correct insertion depth. For low-pressure applications, the thermocouple can be installed directly into the process line through a standard 1/4-inch stainless steel tubing compression fitting without the need for a thermowell.

What type of extension wire is used, and how long can it run?

The extension wire is Type K, 20 AWG stranded wire, individually Teflon insulated and housed inside a stainless steel overbraid with drain wire. The outer sleeve uses the industry-standard yellow Teflon jacket, which clearly identifies the cable as a K-type thermocouple extension wire and allows it to be easily separated from high-voltage power wiring during installation. Extension wire is available in lengths of 5 feet, 15 feet, 30 feet, 50 feet, and 100 feet, enabling runs from the measurement point directly to a nearby junction box, conduit entry, or the panel housing the readout instrument. The cable can also be installed in a cable tray.

Can the thermocouple sheath be bent during installation?

Yes. Although thermocouples are shipped in a straight configuration, the 1/4-inch 316 stainless steel sheath can be bent anywhere along its length up to a 90-degree angle using a standard tubing bender. This flexibility is particularly useful in tight installation spaces where a straight probe would require excessive clearance or conflict with adjacent equipment. Bending should be done with care using the correct bender radius for 1/4-inch tubing to avoid kinking or damaging the internal wires.

Type K stainless steel tube thermocouple with 1/4 inch 316 SS sheath, Bell Spring strain relief, 304SS thermowell and yellow Teflon extension wire for industrial temperature measurement

Type K · 1/4" SS Tube Thermocouple

316 SS Sheath | ASTM E608 | IEC 60584

Temperature Sensing · Industrial Thermocouples · Process Instrumentation

Type K Stainless Steel Tube Thermocouple – 1/4 Inch Diameter for Industrial Temperature Measurement

The Type K stainless steel tube thermocouple is a robust, field-proven temperature sensor designed for reliable measurement in demanding industrial environments. Housed in a 1/4-inch diameter 316 stainless steel tubing sheath with a Bell Spring strain relief, it is available in 6-inch and 10-inch probe lengths and can be field-bent to a 90-degree angle for flexible installation. Fully compatible with 304SS thermowells in three insertion lengths and industry-standard Type K yellow Teflon extension wire, this thermocouple is engineered to comply with ASTM E608 and IEC 60584 — making it a dependable choice for engineers specifying temperature sensing on engines, compressors, vessels, and process piping.

Type K Thermocouple

1/4" 316 SS Sheath

ASTM E608 Compliant

90° Bendable Probe

Key Features

The Type K stainless steel tube thermocouple is purpose-built for long-term, accurate temperature measurement in industrial applications where reliable sensing, mechanical strength, and installation flexibility are equally important. Constructed around a 1/4-inch diameter 316 stainless steel tubing sheath, each probe combines a tip-sensitive thermocouple junction with a rugged all-stainless enclosure to deliver consistent readings on engines, compressors, gas processing systems, and general process piping. The complete system — probe, thermowell, and extension wire — is designed to work together as an integrated assembly, minimizing installation complexity and ensuring measurement integrity from the process point all the way to the readout panel.

316 Stainless Steel Tubing Sheath with Bell Spring Strain Relief: Each thermocouple probe is encased in a 1/4-inch diameter 316 stainless steel tubing sheath, providing excellent resistance to oxidation, corrosion, and elevated process temperatures. A stainless steel Bell Spring is integrated at the transition between the probe and the extension wire connection, acting as a strain relief to protect the wiring from repeated mechanical flexing, vibration fatigue, and cable-pull forces during installation and long-term service. This prevents premature wire breakage at what is typically the most vulnerable point of the assembly.
Tip-Sensitive Design for Accurate Process Temperature Reading: The active measuring junction is located at the tip of the probe, making the thermocouple highly responsive to the actual temperature of the process fluid or gas rather than the surrounding pipe wall or vessel structure. For accurate readings, the probe tip should be positioned between 25% and 75% of the internal pipe diameter — deep enough to avoid skin temperature effects, but not so deep as to contact the opposite wall. This design principle ensures the sensor responds to the bulk process temperature and minimizes the influence of ambient or conductive thermal effects from the installation hardware.
Field-Bendable Probe for Flexible Installation: Although each thermocouple is shipped in a straight configuration, the 1/4-inch stainless steel sheath can be bent anywhere along its full length to a 90-degree angle using standard tubing benders. This field-bending capability significantly simplifies installation in confined equipment spaces where a straight probe would obstruct maintenance access or require excessive clearance. Engineers can orient the probe body and extension wire exit point in the most practical direction without requiring specially ordered bent configurations or additional fittings.
Standard Bore-Through Compression Fitting for Thermowell Installation: The thermocouple probe is secured inside a compatible thermowell using a standard stainless steel bore-through compression fitting, which allows precise positioning of the probe tip within the thermowell at the correct insertion depth. The compression fitting provides a reliable, leak-free seal without requiring thread sealants or special tools, simplifying both initial installation and subsequent removal for inspection, recalibration, or replacement — key advantages for equipment that undergoes scheduled maintenance shutdowns.
Direct Low-Pressure Process Connection Without a Thermowell: In lower-pressure installations, the thermocouple probe can be inserted directly into the process stream through a standard 1/4-inch stainless steel bore-through tubing compression fitting, eliminating the need for a thermowell assembly entirely. This direct installation method reduces hardware cost and installation time for applications where process pressures are within the safe working range of the compression fitting and where the process media does not create a corrosion or erosion risk that would necessitate the additional protection a thermowell provides.
ASTM E608 and IEC 60584 Compliance: The thermocouples are manufactured to comply with ASTM E608, the standard specification for metal-sheathed, base-metal thermocouples, and IEC 60584, the international standard governing thermocouple calibration and tolerance classes. Compliance with both standards ensures accurate, repeatable temperature measurement, consistent calibration performance, and straightforward interchangeability with other instrumentation and readout devices specified to the same norms — a critical requirement for systems that are subject to process safety management or instrument calibration audits.
Type K Yellow Teflon Extension Wire for Long Panel Runs: The 20 AWG stranded Type K extension wire uses individually Teflon-insulated conductors enclosed in a stainless steel overbraid with drain wire, with an outer yellow Teflon jacket that meets the industry-standard color code for K-type thermocouple wiring. The yellow identification allows the extension cable to be quickly and correctly separated from power and control wiring in cable trays and conduit during installation and future maintenance work, supporting safe wiring practices. Pre-assembled wire lengths from 5 feet to 100 feet cover runs from the measurement point to nearby junction boxes, conduit entries, or the instrument panel directly.

Applications

Engine Exhaust, Jacket Water, and Lube Oil Temperature Monitoring: Diesel and natural gas engines in power generation, marine propulsion, and compression service require accurate temperature measurement at multiple points including exhaust manifolds, jacket water circuits, and lube oil galleries to ensure safe and efficient operation. The Type K stainless steel tube thermocouple's 316 SS sheath handles the elevated temperatures common in engine exhaust and coolant applications, while the bendable probe body accommodates the tight clearances typical around engine-mounted instrumentation.
Compressor Gas Discharge Temperature Measurement: Monitoring discharge gas temperature is a critical safety and performance parameter on reciprocating and screw compressors. Elevated discharge temperatures indicate valve inefficiency, interstage cooling failure, or approaching process limits that require corrective action. The Type K thermocouple, installed in a thermowell on the discharge line or manifold, provides a reliable temperature signal for compressor monitoring systems, safety shutdown controllers, and process data historians in compression station applications.
Process Piping and Vessel Temperature Sensing: Industrial process systems handling liquids, gases, and vapors require temperature monitoring at reactors, heat exchangers, separators, and pipeline sections for process control, energy management, and safety compliance. The standard 1/2-inch NPT thermowell connection fits common nozzle configurations on process vessels and pipework, while the three available thermowell insertion lengths allow proper tip placement across a range of pipe diameters, ensuring accurate bulk fluid temperature readings rather than wall temperature measurements.
Oil and Gas Production and Processing Facilities: Wellhead production equipment, gas gathering systems, slug catchers, and separation trains all require reliable temperature instrumentation that can withstand the mechanical demands of outdoor installation, the presence of hydrocarbon gases, and the corrosive effects of produced water and sour gas environments. The 316 SS sheath and all-stainless construction of this thermocouple make it well suited for the demanding conditions present at upstream and midstream oil and gas facilities.
Marine and Offshore Engine Room Instrumentation: Marine propulsion and auxiliary engines require continuous temperature monitoring of exhaust gases, cooling water, lubrication oil, and turbocharger components to ensure safe operation and regulatory compliance. The Type K stainless steel tube thermocouple's compact 1/4-inch diameter, field-bendable sheath, and robust construction are well suited for the confined spaces, vibration, and corrosive salt air environments typical of marine engine rooms on vessels operating in coastal and offshore service.
HVAC and Industrial Heating System Temperature Control: Boilers, heat exchangers, furnaces, duct systems, and industrial ovens rely on accurate temperature sensing to maintain process setpoints and protect equipment from thermal overload. The Type K thermocouple covers the temperature ranges relevant to most industrial heating applications, and the availability of direct insertion through a 1/4-inch compression fitting simplifies installation in HVAC duct work and lower-pressure heating systems where a full thermowell assembly is not warranted.

Technical Specifications

Specifications listed below apply to the Type K stainless steel tube thermocouple in 1/4-inch diameter, including thermowell and extension wire accessories.

Parameter	Specification
Thermocouple Type	Type K (Chromel / Alumel)
Sheath Diameter	1/4 inch (6.35 mm)
Sheath Material	316 Stainless Steel
Available Probe Lengths	6-inch and 10-inch
Strain Relief	Stainless steel Bell Spring at transition gland
Probe Configuration	Shipped straight; field-bendable to 90° using standard tubing benders
Measuring Junction	Tip sensitive; grounded or ungrounded junction (design dependent)
Recommended Insertion Depth	25% to 75% of pipe/vessel inside diameter
Compliance Standards	ASTM E608 · IEC 60584
Thermowell Lengths	2 inch · 4-1/2 inch · 7-1/2 inch
Thermowell Material	304 Stainless Steel
Thermowell Process Connection	1/2-inch NPT
Thermowell Bore Fitting	Standard stainless steel bore-through compression fitting with ferrule (supplied)
Thermowell Pressure Rating (304SS)	400°F: 5,600 PSIG · 600°F: 5,400 PSIG · 800°F: 5,200 PSIG · 1,000°F: 4,500 PSIG · 1,200°F: 1,650 PSIG
Direct Process Connection (Low Pressure)	1/4-inch stainless steel bore-through tubing compression fitting
Extension Wire Type	Type K, 20 AWG stranded
Extension Wire Insulation	Individual conductor: Teflon; Outer jacket: yellow Teflon (industry-standard K-type color)
Extension Wire Overbraid	Stainless steel with drain wire
Available Extension Wire Lengths	5 ft · 15 ft · 30 ft · 50 ft · 100 ft
Cable Installation Methods	Conduit, junction box, direct panel run, or cable tray

Technical FAQ

Common Questions Answered

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The Type K stainless steel tube thermocouple is available in two standard 1/4-inch diameter probe lengths: 6-inch and 10-inch. Both are shipped straight from the factory but can be field-bent to a 90-degree angle anywhere along their length using standard tubing benders, allowing flexible routing in confined installation spaces without requiring custom-configured probes.

The Type K stainless steel tube thermocouple is manufactured to comply with ASTM E608, the standard specification for metal-sheathed base-metal thermocouples, and IEC 60584, the international standard that defines thermocouple tolerance classes and limits of error. Compliance with both standards ensures measurement accuracy, calibration traceability, and interoperability with any IEC-compatible readout instrument or control system.

The thermocouple is tip-sensitive, meaning the active junction is at the probe tip. For accurate bulk fluid temperature readings, the probe tip should be positioned between 25% and 75% of the inside diameter of the pipe or vessel. Inserting less than 25% of the pipe ID risks inaccurate readings due to pipe skin temperature effects; inserting beyond 75% risks mechanical damage and excessive thermal loading on the probe tip.

Three thermowell lengths are available: 2-inch, 4-1/2-inch, and 7-1/2-inch, all in 304 stainless steel with a 1/2-inch NPT process connection. Each thermowell is supplied with a bore-through stainless steel compression fitting that secures the probe at the correct depth. For low-pressure applications, the probe can be installed directly into the process using a standard 1/4-inch SS tubing compression fitting without a thermowell.

The extension wire is Type K, 20 AWG stranded with individual Teflon insulation on each conductor, a stainless steel overbraid with drain wire, and an outer yellow Teflon jacket — the industry-standard colour code for K-type thermocouple wiring. Pre-assembled lengths of 5 feet, 15 feet, 30 feet, 50 feet, and 100 feet are available, covering runs to junction boxes, conduit entries, cable trays, or directly to the instrument panel housing the readout device.

Yes. Although thermocouples are shipped straight, the 1/4-inch 316 stainless steel sheath can be bent anywhere along its length up to a 90-degree angle using a standard tubing bender sized for 1/4-inch tubing. This field-bending capability allows the probe to be routed around obstructions and oriented in the most practical direction for both insertion into the process and routing of the extension wire to the nearest conduit entry or junction box.