The Magnetrol Thermatel TD1 and TD2 are thermal dispersion switches for reliable flow/no‑flow detection in gases and liquids. They can also be used for level and liquid‑liquid interface detection in a single instrument. Both models feature automatic temperature compensation for repeatable alarms under varying process temperatures, continuous diagnostics that detect sensor faults, and fast response time. The spherical tip sensor is popular for pump protection, especially low‑flow detection to prevent dry running.

Model Differences

The TD1 is a basic 24 VDC line‑powered unit with an integral 8‑amp DPDT relay. The TD2 is available in 24 VDC or 120 VAC, with integral or remote electronics and adds LED indication (visible through a glass window), time delay, and a non‑linear mA output for trending, diagnostics and repeatable indication. For SIL‑rated safety loops, both models are suitable for SIL 1 and SIL 2 systems.

Construction and Materials

The sensors are built with 316 stainless steel, Hastelloy C or Monel, all‑welded construction. Process connections include threaded, flanged, compression fittings and optional hot‑tap retractable probes. An optional low‑flow body is available for detecting extremely low flow rates. The TD1/TD2 can be factory‑calibrated to alarm at a specified flow rate; for the TD2 a complete calibration curve can be supplied.

Environmental Ratings

Maximum process temperature reaches +450 °C (+850 °F) and maximum pressure 414 bar (6000 psi). The instrument can be installed at any angle, vertically or horizontally. It is approved for hazardous areas (ATEX, IEC, FM/CSA) and can be used with conductive and non‑conductive media, from light‑density gases to heavy viscous liquids (up to 10,000 cP), ignoring foam, aeration, turbulence and cavitation.

Applications

The Thermatel TD1/TD2 is widely used for pump dry‑run protection, low‑flow alarm in lubrication systems, high‑pressure hydraulic circuits, high‑temperature processes (up to 450°C), and flow/no‑flow detection in both gases and liquids across the chemical, oil & gas, power and general industrial sectors.