Endress+Hauser TM131 iTHERM Thermometer, Welded Thermowell

Endress+Hauser TM131 iTHERM ModuLine thermometer with welded thermowell

The Endress+Hauser TM131 is a metric RTD or thermocouple thermometer with a welded protection tube (thermowell) for general industrial process lines. In the iTHERM ModuLine range it is the all-round model: a thermowell made from tube material, a replaceable insert, an extension neck and a terminal head, all configured to the pipe or vessel. The datasheet states a measuring range of –200 to +1,100 °C and a pressure rating up to 100 bar.

Seven Star LLC supplies the TM131 in Oman and the GCC as an independent supplier in Muscat. The model name identifies the construction, not a single ordering code, so sensor, thermowell, connection and head are set per tag when we quote.

Within the same family, the TM151 (barstock thermowell, higher pressure) and the TM111 (direct contact, no thermowell) cover the other mechanical constructions, and the TM152 is the imperial barstock version.

TM131 technical specifications

How the TM131 builds its measurement

The insert, an iTHERM TS111 (RTD) or TS211 (thermocouple), slides into the thermowell and is spring-loaded against the bottom so heat transfers well. Pt100 inserts measure resistance; thermocouples generate a small voltage proportional to the difference between the hot junction and the cold junction. Thin-film Pt100 elements are small and vibration tolerant. Wire-wound elements are the choice when the process runs hotter than +500 °C or needs the tightest long-term stability.

Thermowell tips follow DIN 43772: Form 2 is straight, Form 3 is tapered, and G or F marks a threaded or flanged connection. A tapered tip is stiffer, which helps at higher flow velocity; a reduced tip speeds the response. The datasheet provides flow-velocity charts for water and superheated steam at 50 bar so you can see how immersion length limits allowable velocity. Always run the thermowell load check for your pressure, temperature and velocity.

Dual Seal and other safety features on the TM131

Process safety is the strongest argument for choosing the TM131 over a basic thermometer. A special extension neck carries a second process seal, called Dual Seal. If the thermowell fails, the process medium stays enclosed and cannot enter the terminal head or the wiring. A pressure switch signals an increase in pressure inside the seal compartment, so maintenance gets a warning while measurement continues for a short period. The datasheet shows two ways to carry that signal: a two-channel iTEMP transmitter on HART, using the second channel for the sensor-break alarm, or a two-channel PROFINET transmitter.

The TM131 also supports tool-free removal through the iTHERM QuickNeck (neck rated –50 to +140 °C), Bluetooth connectivity on the head transmitter, and the explosion-protection approvals named on the datasheet cover: ATEX, IECEx, CSA and NEPSI. Check the approval against the exact configuration quoted.

Process connections and thermowell geometry for TM131

• Threaded male connections: M14x1.5, M18x1.5, M20x1.5, M27x2, M33x2, G 1/2 and G 1 (BSP), supplied with copper seals to DIN 7603 form A
• Flanged and welded variants according to DIN 43772 forms 2G, 2F, 3G and 3F
• Continuous thermowell (lagging kept above the connection), hexagonal-extension thermowell, or a thermowell without lagging for compression fittings
• Version for installation in a separate customer thermowell, which cannot be used for direct immersion

The immersion length U, lagging T and neck length E set the insertion length of the insert. Because the neck length changes by design (fixed, hexagonal or QuickNeck), quote the full geometry so the correct replaceable insert can be delivered.

TM131 compared with sibling iTHERM models

The TM131 is the logical middle point: more option depth than the TM121 and more affordable than the barstock TM151 when pressure stays within 100 bar.

Selection and ordering checklist for the TM131

• Pipe or vessel connection standard and size; flange rating if flanged
• Maximum process temperature and pressure; flow velocity in the pipe
• Thermowell material, diameter and tip shape; immersion length
• Sensor: Pt100 class A or AA, thermocouple K, J or N; single or dual
• Neck type: fixed, hexagonal or QuickNeck; Dual Seal required or not
• Head type and material; M20 or NPT cable entries; display
• Transmitter and protocol (4–20 mA, HART, PROFIBUS PA, FOUNDATION Fieldbus, IO-Link, PROFINET)
• Hazardous-area zone and approval
• Calibration certificate and material test certificates

Installation, commissioning and maintenance of the TM131

Fit the thermowell first and pressure-test the line, then insert the thermometer; this is exactly why the replaceable-insert design pays off. Check the spring travel so that the tip sits on the bottom of the thermowell. Use a new copper seal on cylindrical threads. In terminal heads with a transmitter, the ambient limit is –40 to +85 °C (–30 with display).

Planned maintenance is simple: remove the insert via the QuickNeck or the head, calibrate or swap it, and replace it without opening the process. For spares quote the serial number so the insertion length is calculated for you.

TM131 applications in Oman and the GCC

The TM131 suits the standard temperature points of oil and gas gathering and processing, refinery and petrochemical units, power generation, desalination plants, and utility headers. Typical tags include pump bearing oil lines, exchanger inlets and outlets, steam and condensate lines, and flue and exhaust gas ducts when a thermocouple is chosen. In desert sites, plan for solar heating of the head: a longer neck, a transmitter inside the head, and a suitable cable entry keep electronics within rating, and the IP66 housing resists fine dust and humid coastal air.

Information to send with a TM131 request for quotation

• Tag, service, P&ID reference and quantity
• Process medium, temperature, pressure and flow velocity
• Connection type, size, flange rating or thread
• Thermowell material, tip form, immersion length
• Sensor, accuracy class, Dual Seal requirement
• Head, transmitter, output protocol, hazardous-area details
• Certificates and delivery site in Oman or the GCC

Documents and quotation

The manufacturer technical information for the TM131 is attached to this page. Read it together with your project specification, because the thermowell, sensor, head and transmitter options that apply to your tag are fixed by the order configuration, not by the model name alone. Approvals and ratings should always be checked against the exact configuration that is quoted.

Seven Star LLC quotes against your data sheet or loop drawing and confirms lead time, stock position and the documents that ship with the instrument. Send us the details listed above and we will respond with a priced offer for delivery in Oman and the wider GCC.