Endress+Hauser TM121 iTHERM Basic Thermometer, Welded Well

Endress+Hauser TM121 basic iTHERM ModuLine thermometer for non-hazardous areas

The Endress+Hauser TM121 is the economical entry model of the iTHERM ModuLine range with a welded thermowell. The datasheet describes it as a metric RTD or thermocouple basic thermometer with a welded protection tube, for general use in non-hazardous areas. It covers –50 to +650 °C, takes process pressure up to 50 bar (725 psi) and offers ingress protection up to IP68, with Bluetooth communication through the head transmitter for set-up and maintenance.

Seven Star LLC supplies the TM121 in Oman and the GCC as an independent supplier in Muscat. It is meant for the large number of ordinary temperature points in a plant where hazardous-area approval, Dual Seal or very high pressure is not needed and where purchase cost counts.

TM121 technical specifications

How the TM121 works and what the basic label means

The measurement principle is the standard Pt100 resistance element (100 Ω at 0 °C) or a thermocouple that produces a voltage from a junction temperature difference. The insert is replaceable and rests in the welded thermowell. In the basic version the datasheet lists the standard inserts with 3g to 4g vibration resistance, with the higher-end StrongSens (up to 60g) shown as an option; the model is restricted to non-hazardous areas, so Ex approvals are not part of it.

Response time is governed by the thermowell. The datasheet quotes typical values in water at 0.4 m/s with a 10 K step: 90 s to t90 for an RTD in a 9 mm thermowell and 100 s in an 11 mm well. That is adequate for monitoring and slow loops, not for fast control; for faster response look at the TM111 or the TM131 with QuickSens.

Process connections, materials and options for the TM121

• Cylindrical and conical male threads with copper seals to DIN 7603 form A
• Flanged thermowells according to DIN or ASME, in the form of lagging per DIN 43772
• TK40 compression fittings in PEEK or 316L for adjustable immersion; the datasheet states that 316L sets are one-time use and PEEK must never be used below the temperature at which it was tightened
• Thermowell materials include 316L/1.4404, 1.4435 and Alloy 600 (maximum 650 °C and 1,100 °C in air, as reference values)

Terminal heads follow DIN EN 50446 with M24x1.5 or 1/2 NPT thread. Transmitters from the iTEMP family can be mounted in the head for 4–20 mA, HART, PROFIBUS PA or other outputs, with Bluetooth for commissioning from a phone or tablet.

Where the TM121 fits among iTHERM thermometers

Choose the TM121 for utility and general process points in safe areas. If a point is in a classified zone, or needs the second-barrier Dual Seal, step up to the TM131. If pressure exceeds 50 to 100 bar, the TM151 or TM152 with barstock thermowell is the right family. The TM111 is the thermowell-free option when response speed matters, and the TM411 is the hygienic variant.

Remember that the TM121 shares terminal heads, transmitters and many inserts with the others, which makes spares simpler if you standardise on iTHERM ModuLine across a site.

Selection and ordering checklist for the TM121

• Confirm the area is non-hazardous
• Process temperature, pressure (50 bar maximum) and fluid
• Connection: thread type and size or flange standard
• Thermowell diameter (9 or 11 mm style as per datasheet), tip form and immersion length
• Sensor: Pt100 class A or B, or thermocouple J or K
• Head type, cable entries, display; transmitter and protocol
• Bluetooth requirement; ingress rating needed
• Calibration and material certificates

Installation, commissioning and maintenance of the TM121

Mount the thermowell with a suitable seal, keep the tip in the flow, and allow for the extension neck so that the head does not sit on hot insulation. After installation, check that the spring-loaded insert is fully seated in the thermowell; an air gap inside the bore gives a slow or low reading. Wire according to the terminal assignment in the datasheet for 3- or 4-wire RTD or thermocouple connection.

Maintenance is simply removing and calibrating or replacing the insert. Quote the serial number when ordering a spare. The head with transmitter operates from –40 to +85 °C, with display –30 to +85 °C, and humidity up to 95 percent is permitted.

TM121 applications in Oman and the GCC

Typical duties include cooling-water and chilled-water temperatures, lube oil and seal oil return lines, compressed-air aftercoolers, hot-water and low-pressure steam services, HVAC plant rooms, boiler house auxiliaries, and general utility measurements in refineries, power plants and desalination units, provided the location is outside classified areas. Plan for high ambient temperatures by choosing a transmitter in the head only when the head will stay below its limit, and use stainless heads on coastal sites.

Information to send with a TM121 request for quotation

• Tag, service, quantity and P&ID
• Medium, temperature and pressure
• Connection type and size or flange rating
• Thermowell material, diameter, tip and immersion length
• Sensor and accuracy class
• Head, transmitter, protocol, Bluetooth requirement
• Certificates and delivery site in Oman or the GCC

Documents and quotation

The manufacturer technical information for the TM121 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.