Thermatel® Model TD1/TD2 Thermal Dispersion Flow/Level/Interface Switch D E S C R I P T I O N Thermatel® Model TD1 and TD2 Thermal Dispersion flow/level/interface switches provide continuous diagnostics with fault indication, temperature compensation, narrow hysteresis and fast response time. TD1 is a basic switch with 24 VDC power and an 8-amp DPDT relay. The TD2 adds LED indication through a glass window, ability to electrically measure the set point, mA output for diagnostics and trending, optional hermetically sealed relay, plus time delay. A universal AC power supply simplifies installation. Model TD2 with spherical probe Thermatel probes are available in 316 Stainless Steel, Hastelloy® C, or Monel® with all welded construction. F E A T U R E S • Temperature compensated to provide repeatable alarm under varying process temperatures • Continuous diagnostics detect sensor fault • Non-linear mA output signal can be used for trending, diagnostics and repeatable flow/level indication (TD2) • Detects minimum flow or presence/absence of flow Model TD1 with twin-tip probe Model TD2 with low flow body • Easy/fast calibration • Excellent low flow sensitivity • Optional hot tap available (see bulletin 41-103) • NACE construction available • Process temperatures from -100 to +400 °F (-73 to +204 °C)—High temp. version to +850 °F (+454 °C) The Thermatel TD1 and TD2 switches utilize the proven thermal dispersion technology. The sensor consists of two RTD elements. One is the reference and the second is heated to a temperature above the process temperature. The electronics detect the temperature difference between the two elements. The temperature difference is greatest in air, then decreases when cooling occurs due to a change in media. An increase in the flow rate further decreases the temperature difference. The set point is adjusted for the switch to alarm at the desired temperature difference. Once the set point is reached, the

The Thermatel flow switch can be ordered factory calibrated to alarm at a specified flow rate. A complete calibration curve can also be provided for the TD2. Using this curve the user can determine the desired set point. Consult factory for calibration options. H O T Hot tap retractable probe assemblies for Thermatel probes are available. See Bulletin 41-103. F A U L T Flow (fps) With Temperature Compensation The TD1/TD2 is equipped with advanced diagnostics which continuously monitor the signal from the sensor and indicate if the signal has gone out of range. In the event of a fault, the alarm...

Current (mA) output The TD2 has a mA output signal can be used for diagnostics, fault detection and trending. While this mA signal is not scalable by the user, it can provide important process information. The mA signal will increase with the sensor cooling – mA will be greater in a wet condition than in a dry condition and will further increase as the flow rate increases. Remote Electronics The TD2 can be provided with remote electronics with up to 500 feet (150 meters) separation between the probe and electronics. Hermetically sealed relay The TD2 provides an optional hermetically sealed relay...

A P P L I C A T I O N S Thermatel has demonstrated reliable performance as a flow or level switch. For use as a flow switch, Thermatel can be used to detect either a high flow or a low flow condition for both gases and liquids. As a level switch, Thermatel can be used to detect difference in thermal conductivity of various media. This includes interface detection between media such as liquid/foam, and oil/water. Level or Interface can be detected due to differences in thermal conductivity. High or low level alarm applications may be installed either vertically or horizontally. In the absence...

Thermatel offers two sensor tip designs—the original twin tip and the unique spherical tip. Both designs have similar operating ranges. The sensors in the twin tip are mounted at the end of each tip. In the spherical tip, the sensors are bonded directly to the wall of the tip, providing protection of the sensors. The spherical tip is recommended for all types of applications—general purpose, high viscosity, full vacuum, and applications where buildup can occur. Spherical Tip For general purpose use, liquid flow applications, and buildup. Suitable for gas flow applications. Maximum temperature...

A P P L I C A T I O N S PUMP PROTECTION Installed on the suction or discharge of a pump, a Thermatel switch provides rapid indication of a low flow or no flow condition to prevent pump damage. No moving parts, excellent low flow sensitivity, and low hysteresis between alarm and reset points are all important features in this application. Enhanced temperature compensation minimizes set point drift due to varying process temperatures. Pump Protection COOLING WATER/COOLING AIR Maintaining the flow of cooling air or water is essential to protect heat generating equipment. A reliable flow switch will...

A P P L I C A T I O N S RELIEF VALVE MONITORING When installed downstream of a relief valve, the switch can detect when flow occurs. The low flow sensitivity of the sensor permits the switches to be calibrated to detect minor valve leakage. LUBRICATION SYSTEMS Relief Valve Monitoring The flow switch with the low flow body can be used to ensure that sufficient quantities of lubrication oil are flowing throughout the entire lubrication system. No moving parts and large openings prevent buildup or plugging which can occur with mechanical switches. OTHER APPLICATIONS • Exhaust Flow Monitoring • Vacuum...

Enclosure Material Cast aluminum A356 containing less than 0.2% copper 316 stainless steel or 304 stainless steel Safe Failure Fraction (SFF) TD1=69.3% TD2=73% Probes: Probe Materials of Construction HTHP Sensor: Mini Sensor: Spherical Tip: Low Flow Body: All wetted parts of 316/316L stainless steel, Hastelloy C, or Monel 316/316L 316/316L 316/316L 316/316L stainless stainless stainless stainless steel, Hastelloy C steel steel steel Process Connection Refer to part number construction Probe Insertion Length: Spherical Tip Probe, TXA, TXB Twin Tip Probe, TXC, TXD Available in lengths from 2 to...