Magnetrol Thermatel TD1/TD2 Thermal Dispersion Flow and Level Switch

Overview

The Magnetrol Thermatel TD1/TD2 is a family of thermal dispersion switches that detect flow, level or interface without any moving parts. Magnetrol designed the TD1 as a basic switch and the TD2 as an advanced version with more diagnostics and indication, and both provide continuous diagnostics with fault indication, temperature compensation, narrow hysteresis and fast response. The same switch can be used for liquid flow, gas flow, high or low level and interface detection, which makes the Magnetrol Thermatel TD1/TD2 one of the most versatile point instruments in a plant.

Seven Star LLC supplies the Magnetrol Thermatel TD1/TD2 to refineries, power stations, chemical plants and water utilities across the Sultanate of Oman and the GCC. Our Muscat engineers help customers choose the probe tip, material and insertion length, and confirm whether a TD1 or a TD2 suits the duty and the control room requirements.

Operating Principle

The Magnetrol Thermatel TD1/TD2 relies on thermal dispersion. The sensor has two RTD elements: one measures the process temperature and acts as a reference, while the other is heated to a temperature above it. The electronics compare the two. The temperature difference is greatest in dry air and falls when the heated element is cooled by a liquid, and it falls further as the flow velocity rises. The set point is adjusted for the switch to alarm at the chosen temperature difference, and the relay changes state when that value is reached.

Because the switch is self-heated, it can use the same principle for flow and level. In flow service it sees heat carried away by moving media, and in level or interface service it sees the difference in thermal conductivity between air, foam, oil and water. Temperature compensation prevents the set point from drifting when the process temperature changes, and a factory calibration can be ordered at a specified flow rate. Fault detection monitors the sensor signal continuously and de-energises the relay if the signal goes out of range.

Engineering Design of the Magnetrol Thermatel TD1/TD2

The Magnetrol Thermatel TD1/TD2 is built with probes in all-welded construction using 316/316L stainless steel, Hastelloy C or Monel. Two tip designs are offered: the twin tip, preferred for higher pressures up to 3000 psig, corrosion-resistant materials and gas flow, and the spherical tip, recommended for high viscosity, full vacuum and applications where build-up can occur. A high temperature/high pressure sensor reaches +850 °F (+454 °C) and 6000 psi, a mini sensor fits tees of 1/2, 3/4 and 1 inch, and a low flow body handles very small flows.

The electronics are housed in cast aluminium (A356 with less than 0.2 percent copper) or stainless steel. The TD2 can be supplied with remote electronics up to 500 feet (150 m) from the probe, and the TD1 and TD2 are offered with hot tap retractable assemblies and NACE construction. Probe insertion lengths run from 2 to 130 inches for spherical and twin-tip probes, and the process connection is defined in the part number.

Key Features

The Magnetrol Thermatel TD1/TD2 switches combine simplicity with strong diagnostics. Key features of the Magnetrol Thermatel TD1/TD2 include:

• No moving parts, with excellent low flow sensitivity and low hysteresis between alarm and reset points.
• Temperature compensation for a repeatable alarm under varying process temperatures, with repeatability better than 1 percent.
• Continuous diagnostics that detect sensor faults and de-energise the relay, with the TD2 also driving the mA output to 3.6 or 22 mA.
• Non-linear mA output on the TD2 for trending, diagnostics and flow or level indication.
• Set point ranges of 0.01 to 5 feet per second for water and 0.1 to 500 standard feet per second for air.
• Adjustable time delay of 0 to 100 seconds on the TD2, with a hermetically sealed relay option.
• Process temperature range of -100 to +400 °F, with a high-temperature version to +850 °F.
• Safe failure fraction of 69.3 percent for the TD1 and 73 percent for the TD2.

Industrial Applications

The Magnetrol Thermatel TD1/TD2 is widely used for pump protection, where a no-flow or low-flow condition must trip a pump before damage occurs, for cooling air or water flow monitoring on heat-generating equipment, for relief valve leakage detection and for lubrication systems. In Oman, cooling-water loops in power and desalination plants, seal-water lines on pumps and compressors, and chemical feed pumps in water treatment all call for a robust flow alarm. The switch is also used for oil and water interface detection and liquid and foam detection, where its adjustable sensitivity is useful. Alternative technologies for level duty include the VEGASWING 61 and the ABB RS85 vibrating fork switch.

Seven Star LLC supplies the Magnetrol Thermatel TD1/TD2 on request, with engineering support in Muscat, to contractors and operators in the Sohar and Salalah economic zones. For clean level applications where thermal sensing is unnecessary, we can also supply the ABB A75 RF capacitance switch, and our team will advise which technology gives the best reliability for your fluid.

Technical Specifications

The table lists the main data of the Magnetrol Thermatel TD1/TD2 from the Magnetrol datasheet. Probe style and process connection are defined by the part number.

Request a Quote for Magnetrol Thermatel TD1/TD2

Send your RFQ for the Magnetrol Thermatel TD1/TD2 to Seven Star LLC with the medium, pipe or vessel size, flow set point or level duty, temperature, pressure, power supply and the TD1 or TD2 preference. Our instrumentation division in Muscat will select the probe and electronics, confirm calibration options and provide the Magnetrol datasheet with the quotation. Seven Star LLC supplies Magnetrol equipment with manufacturer documentation and local engineering support across Oman and the GCC, so contact us today for the Magnetrol Thermatel TD1/TD2.