TES-LOK Thermocouple Male Connectors — precision compression fittings with male NPT / BSPT / BSP threads for leak-free connection of thermocouple sheaths and protection tubes to thermowells, process nozzles, and instrumentation manifolds. ISO 9001:2015 certified. Made in India.
TES-LOK Thermocouple Male Connector
Male Connector — Standard Series
Bulkhead Male Connector
Unlike a standard male connector used for instrument tubing, a thermocouple male connector is engineered to accept the smaller OD sizes typical of thermocouple sheaths (1/16" to 1/2") and is rated for the elevated temperatures encountered at thermowell heads. The double-ferrule compression design — front ferrule seals on the tube OD, back ferrule provides grip — ensures the sheath cannot pull out under vibration or thermal cycling.
| Step | Action | Result |
|---|---|---|
| 1. Insert sheath | Thermocouple sheath / protection tube inserted through the nut and ferrule(s) into the fitting body | Sheath reaches its correct depth inside thermowell |
| 2. Hand-tighten nut | Compression nut threaded onto body by hand until snug | Ferrule(s) positioned but not yet swaged |
| 3. Make-up turns | Nut tightened 1¼ turns from finger-tight position | Front ferrule swages onto tube OD; back ferrule grips tube |
| 4. Process connection | Body's male thread screwed into thermowell head or process nozzle with appropriate thread sealant | Leak-free, vibration-resistant connection achieved |
| Type | Thread Configuration | Ferrule System | Best For |
|---|---|---|---|
| Standard Male Connector | Male NPT / BSPT on body end; compression nut on sheath end | Single or double ferrule | General instrumentation, thermowells up to 350°C |
| Heavy-Duty Male Connector | Same as standard; heavier wall body | Double ferrule (SS 316) | High-vibration pipelines, industrial furnaces |
| High-Temperature Male Connector | Male NPT / BSPT; Inconel or Monel body | Double ferrule (Inconel) | Superheated steam, fired heaters, cracker furnaces, 800°C service |
| Reducing Male Connector | Male thread one size larger than sheath OD requires | Double ferrule with reducing bushing | Fitting a 1/4" sheath to a 1/2" NPT thermowell port |
| Straight-Through Male Connector | Male thread both ends (one for process, one for sheath adaptor) | N/A — mechanical union | Panel-mount penetrations, junction head connections |
| Parameter | Details |
|---|---|
| Brand | TES-LOK (Tesco Steel & Engineering) |
| Tube OD Range | 1/16", 1/8", 3/16", 1/4", 5/16", 3/8", 1/2" | Metric: 2 mm, 3 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm |
| Male Thread Sizes | 1/8", 1/4", 3/8", 1/2", 3/4", 1" — NPT / BSPT / BSPP / UNF |
| Pressure Rating | SS 316: up to 6 000 PSI | Brass: 300 / 1 000 / 3 000 PSI depending on size |
| Temperature Range | SS 304 / 316: −196°C to 450°C | Inconel 600: up to 800°C | Brass: −40°C to 150°C |
| End Connection | Tube end: compression (single or double ferrule) | Process end: male tapered thread (NPT / BSPT) or parallel (BSPP) |
| Ferrule Material | Matched to body material (SS 316, Brass, Inconel) |
| Body Material | SS 304, SS 316 / 316L, Brass (CW617N), Inconel 600, Monel 400, Hastelloy C-276 |
| Surface Finish | Bright annealed / passivated (SS); bright zinc or nickel plated (Brass) |
| Certifications | ISO 9001:2015 | Material test certificates (MTC) available per EN 10204 3.1 |
| Standards | Compatible with ASTM E230 / IEC 60584 thermocouple sheath dimensions; threads per ASME B1.20.1 (NPT), BS 21 (BSPT/BSPP) |
| Material | Max Temp | Max Pressure (1/4") | Corrosion Resistance | Typical Application |
|---|---|---|---|---|
| SS 304 | 450°C | 5 000 PSI | Good — general process | Food, pharma, water treatment |
| SS 316 / 316L | 450°C | 6 000 PSI | Excellent — chloride resistant | Chemical plant, offshore, marine |
| Brass (CW617N) | 150°C | 3 000 PSI | Moderate — no ammonia / acids | HVAC, compressed air, water systems |
| Inconel 600 | 800°C | 4 000 PSI | Outstanding — oxidation resistant | Furnace thermocouples, steam superheat |
| Monel 400 | 480°C | 4 500 PSI | Excellent — HF, seawater | Offshore platforms, desalination |
| Hastelloy C-276 | 500°C | 4 000 PSI | Superior — strong acids | Chemical reactors, acid service |
| Thread Form | Profile | Sealing Method | Standard | Common Regions |
|---|---|---|---|---|
| NPT | Tapered 60° | Thread interference + PTFE tape | ASME B1.20.1 | USA, Canada, India, Middle East |
| BSPT (Rc) | Tapered 55° | Thread interference + PTFE tape | BS 21 / ISO 7-1 | UK, Europe, Asia, Australia |
| BSPP (G) | Parallel 55° | Dowty bonded seal or O-ring face seal | BS 2779 / ISO 228 | Europe, OEM instrumentation |
| UNF | Unified fine 60° | Thread + washer/gasket | ASME B1.1 | USA instrumentation panels |
| Tube OD (Inch) | Tube OD (mm) | Male Thread Sizes Available | Max Pressure — SS 316 |
|---|---|---|---|
| 1/16" | 1.6 mm | 1/8" NPT, 1/8" BSPT | 6 000 PSI |
| 1/8" | 3.2 mm | 1/8", 1/4" NPT / BSPT | 6 000 PSI |
| 1/4" | 6.35 mm | 1/4", 3/8", 1/2" NPT / BSPT | 6 000 PSI |
| 3/8" | 9.5 mm | 3/8", 1/2" NPT / BSPT | 5 000 PSI |
| 1/2" | 12.7 mm | 1/2", 3/4", 1" NPT / BSPT | 4 500 PSI |
CNC-turned ferrules hold ±0.01 mm dimensional tolerance, ensuring uniform swage angle and leak-free seal every time — critical when connecting fine-gauge thermocouple sheaths down to 1/16" OD.
Available in Inconel 600 for continuous service at 800°C — suitable for fired heater thermocouples, blast furnace monitoring, and kiln temperature measurement where standard SS grades oxidise.
Full material traceability, EN 10204 3.1 material test certificates, hydro-tested batches, and dimensional inspection reports available on every order — meeting EPC and end-user documentation requirements.
The back ferrule's aggressive bite angle maintains pull-out resistance under thermal shock and vibration — important where thermocouple sheaths experience rapid cycling between hot and cold process conditions.
Single SKU matrix covering NPT, BSPT, BSPP, and UNF threads in every tube size — simplifying procurement across projects with mixed international standards.
Ex-stock availability of SS 316 and Brass connectors in all popular sizes. Custom alloy (Inconel, Monel, Hastelloy) connectors dispatched within 2–4 weeks with full MTC documentation.
| Industry | Typical Use Point | Preferred Material |
|---|---|---|
| Oil & Gas Upstream | Wellhead temperature monitoring, separator vessels | SS 316 / Monel 400 |
| Petrochemical / Refinery | Reactor skin temperature, column profile thermocouples | SS 316 / Hastelloy C-276 |
| Power Generation | Steam turbine inlet / exhaust, boiler tube skin thermocouples | Inconel 600 / SS 316 |
| Cement & Metallurgy | Kiln temperature, molten metal baths, reheating furnaces | Inconel 600 |
| Pharmaceutical | Autoclave sterilisation, CIP/SIP circuits, bioreactor jackets | SS 316L (passivated) |
| Food & Beverage | Pasteuriser, baking ovens, spray dryer outlet temperature | SS 304 / SS 316 |
| HVAC / Building Services | Duct temperature sensing, chiller water temperature | Brass / SS 304 |
| Chemical Processing | Acid reactor temperature, chlorinated solvent service | Hastelloy C-276 / Monel 400 |
Q1. What is the difference between a thermocouple male connector and a standard male connector tube fitting?
A standard male connector is designed for hydraulic or pneumatic instrument tubing (typically 1/4" to 1" OD, heavy wall). A thermocouple male connector is optimised for the smaller OD sizes of thermocouple sheaths (1/16" to 1/2") and is rated for the higher temperatures encountered at thermowell heads. The body wall thickness and ferrule angles are tuned for thin-wall sheath material without crushing it.
Q2. Can I use an NPT thermocouple male connector on a BSPT-threaded thermowell?
No. NPT (60° taper) and BSPT (55° taper) threads are not interchangeable. Mixing them can cause cross-threading, leaks, or breakage. Always match the thread form. TES-LOK supplies both NPT and BSPT versions from stock.
Q3. Can a thermocouple male connector be re-used after the thermocouple sheath is removed?
The body and nut can be re-used, but the ferrule(s) must be replaced. Once swaged, the ferrule cannot reliably reseal on a new tube. TES-LOK supplies spare ferrule kits matched to every body size and material combination.
Q4. What material should I specify for a thermocouple connector used at 650°C in a fired furnace?
Inconel 600 (UNS N06600). It maintains good oxidation resistance and mechanical strength to 800°C. SS 316 begins to lose tensile strength significantly above 500°C and will oxidise in air at 650°C under cyclic conditions. Inconel 600 connectors with matching Inconel ferrules are the correct specification.
Q5. How do I know if my thermocouple sheath is compatible with a TES-LOK compression fitting?
Measure the sheath outer diameter. TES-LOK connectors are sized to imperial inch OD (1/16" to 1/2") and metric OD (2 mm to 12 mm). If the sheath OD falls in those ranges and the wall is at least 0.5 mm thick, the double-ferrule system will grip without collapsing the tube. For very thin-wall sheaths (<0.3 mm), consult our technical team for a support sleeve solution.
Q6. Do you supply material test certificates (MTC) with thermocouple connectors?
Yes. EN 10204 3.1 material test certificates are available for all alloy grades (SS 316, Inconel, Monel, Hastelloy). Brass connectors are supplied with 2.1 compliance certificates as standard. 3.1 MTCs for Brass are available on request.
Q7. What is the minimum order quantity for TES-LOK thermocouple male connectors?
No minimum order quantity (MOQ) for standard SS 316 and Brass sizes — single pieces are accepted. For special alloys (Inconel, Monel, Hastelloy) the minimum is typically 10 pieces per size. Project quantities of 500+ pieces receive priority scheduling and discounted pricing.
Q8. Can TES-LOK supply thermocouple connectors with both imperial and metric markings on the packaging?
Yes. All TES-LOK thermocouple fittings are individually tagged with tube OD (both inch and mm equivalent), thread size, material grade, heat number, and pressure rating. This supports dual-standard documentation requirements for EPC and end-user projects operating under multiple international standards simultaneously.