Endress+Hauser TM401 iTHERM ModuLine Hygienic RTD Thermometer

TM401 iTHERM ModuLine metric hygienic RTD thermometer

The Endress+Hauser TM401 is a direct-contact Pt100 resistance thermometer for hygienic and aseptic processes. It belongs to the iTHERM ModuLine group, in which the "40x" models use basic technology: a fixed, non-replaceable insert, a standard extension neck and use in non-hazardous areas only. The TM401 is the metric version, with millimetre probe diameters and metric process connections. Seven Star LLC supplies the TM401 in Oman and the GCC as an independent supplier in Muscat.

Because the sensor is in direct contact with the product, there is no thermowell and the response is quick. The wetted parts are 316L stainless steel, the probe is available in 6 mm or 8 mm diameter with a straight or reduced tip, and a long list of sanitary connections allows the thermometer to be matched to existing tank and pipe fittings. The manufacturer positions it as the value option for food, beverage and life-science plants.

TM401 technical specifications

Data come from the manufacturer technical information and product page. The head transmitter, terminal head and cable gland chosen set the electrical limits of the complete assembly.

How the TM401 measures

The TM401 uses a thin-film platinum element: a micron-thin platinum layer on a ceramic substrate, which gives a small, vibration-tolerant sensor with a resistance of 100 Ω at 0 °C. The manufacturer notes that thin-film sensors deviate slightly from the standard curve at higher temperatures, which is why the tight class A tolerance applies only up to roughly 300 °C and, for this basic sensor, up to 200 °C. For the TM401 the practical limit is the 200 °C process range.

A head transmitter can be fitted in the terminal head to convert the sensor resistance into 4–20 mA, HART, PROFINET over Ethernet-APL or IO-Link output, and the transmitter family also includes PROFIBUS PA and FOUNDATION Fieldbus options. Using an iTEMP transmitter reduces wiring and also allows sensor-transmitter matching with Callendar-Van Dusen coefficients, which improves accuracy compared with a bare sensor. Self-heating is negligible when such a transmitter, with its very small measuring current, is connected.

TM401 hygienic design and process connections

A hygienic thermometer is judged by how it cleans as much as by how it measures. The TM401 is offered in versions without gaps and dead space, and the published certifications include 3-A (authorisation no. 1144, Sanitary Standard 74-07), EHEDG type EL Class I for the listed connections, ASME BPE with a certificate of conformity available for designated options, FDA compliance, and a TSE certificate of suitability confirming that no animal-derived materials are used on wetted parts. Materials in contact with product also meet the EU food-contact regulations named in the technical information. The certificates apply to listed connections and options, so confirm them against the configured order code.

Releasable and fixed process connections include:

• Tri-clamp and micro-clamp, and clamp connections to ISO 2852
• Sanitary connection to DIN 11851 (dairy fitting), SMS 1147 and Varivent (including types for VARINLINE housings)
• Ingold connection with a weld-in adapter, and Liquiphant-style G¾″ and G1″ adapters
• Spherical TK40 compression fitting, movable or fixed, for weld-in installation
• Versions without process connection, with M24x1.5 or ½″ NPT thread to the head

The counterpieces, seals and sealing rings are normally not supplied with the thermometer, so these must be ordered separately. Some connections have lower pressure limits, for example 16 bar for many clamp types and 10 bar for certain others.

Terminal heads and electrical options for TM401

All terminal heads follow DIN EN 50446 flat-face geometry with M24x1.5 or ½″ NPT thread to the thermometer. The TA30A is an aluminium head with polyester coating rated IP66/68 (IP66/67 for ATEX) with temperature rating –50 to +150 °C without cable gland. The TA30R is a 316L stainless head with standard IP69K, rated –50 to +130 °C without cable gland, designed for washdown. The TA30S is polypropylene, FDA-compliant, IP65, rated –40 to +85 °C, and white for dairy and clean areas. Cable glands and fieldbus connectors have their own temperature limits, which must be respected, as the manufacturer highlights.

Material resistance of the housing to the cleaning agents P3-topax 66, P3-topactive 200, 500 and OKTO, and to demineralised water, is stated in the technical information, which is helpful when the thermometer is washed down alongside the vessel.

TM401 versus TM402, TM411 and TM412

The TM401 is for plants working to metric piping and fittings. Where inch-based tri-clamp tube dimensions are used, the TM402 is the closer match. The higher-end TM411 and TM412 add a quick-fastening extension neck, vibration-resistant sensors and approvals for hazardous areas, and are chosen when the insert must be replaceable or the area is classified.

TM401 selection and ordering checklist

• Choose the probe diameter (6 mm or 8 mm), tip shape and immersion length, up to 400 mm on request.
• Name the process connection and size exactly, plus its seal, for example clamp size or Varivent type.
• State the surface finish required: standard Ra 0.76 µm, or 0.38 µm, and whether ASME BPE conformity is needed, since the buffed finish is not ASME BPE compliant.
• State which hygiene documents are needed: 3-A, EHEDG, ASME BPE, FDA or TSE.
• Specify the terminal head (aluminium, 316L or polypropylene) and the cable entry thread.
• Choose a head transmitter and its output, or order for direct wiring.
• Check the process pressure and CIP/SIP temperature against the connection limit.
• Request calibration, which covers the insert only, and a certificate if required.

Installing, cleaning and calibrating the TM401

Installation orientation has no restriction as long as the process self-drains, and any leak-detection opening must be at the lowest possible point. The immersion length influences accuracy: the tip must be in the stream and clear of the vessel wall, and in a pipe an angled or elbow installation can give a longer immersion. For EHEDG and 3-A cleanability, the thermometer length in the stub must not exceed the stated ratio to its diameter, so check the installation drawing before welding the adapter.

The manufacturer’s standard calibration is at reference temperatures between –80 and +600 °C on ITS-90, traceable to national standards, and only the insert is calibrated. If a head transmitter is used the minimum immersion length for a valid calibration is 50 mm above 80 °C. Keep a calibration record by serial number, and re-check periodically, especially after CIP/SIP cycles.

TM401 applications in Oman and the GCC

The TM401 belongs wherever product is heated, cooled or sterilised under hygiene rules. In the region this means dairy and juice plants, bottling and beverage lines, bakery and food processing, pharmaceutical and nutraceutical production, and cleanroom utilities such as water-for-injection and clean steam loops. It also suits brewing, cold-room and desalinated-water bottling facilities.

The heat and humidity of the Gulf point to a washdown-rated head, such as the 316L TA30R, in wet process halls, and to a head transmitter if cable runs to the PLC are long. The TM401 is for non-hazardous areas, so for solvent or powder zones a TM411 or other approved model should be considered.

What to send with your TM401 RFQ

• Full order code or nameplate photo of the thermometer being replaced.
• Probe diameter, immersion length, tip shape and surface finish.
• Process connection type, size and seal.
• Required hygiene certificates and material certificates.
• Terminal head, cable entry and head transmitter output.
• Quantity, delivery site and calibration needs.

Documents and quotation

A datasheet (Technical Information) for the TM401 is attached on this page, with the process connection drawings, sensor tolerances, response times and certificate list.

To receive a quotation, send the order code or the requirement from the list above and Seven Star LLC will confirm availability and lead time for Oman and the GCC.