PED-LOCK Thermowells can be connected to an RTD, thermistor or thermocouple head by means of several different connection types. Some of the most common are:
Threaded connections are made of materials that can be welded or brazed and provide additional strength. In processes where contaminants from threads must be avoided such as in the food and pharmaceutical industries, weld-in connections are commonly used. O-ring connections use an O-ring to seal inside a sleeve welded to a tank. The double weld construction of the ANSI B16.5 flanged thermowell seals open joints both internally and externally to prevent corrosive substances from entering crevices.
Thermowells are inserted into and connected into a process in a pressure tight manner. The most common process connections for thermowells include threaded, socket weld, and flanged connections.
The most common shank constructions for thermowells are (1) straight, (2) step, and (3) tapered. A straight shank Thermowell is the same size all along the immersion length of the Thermowell. A step shank Thermowell has an outer diameter of at the end of the thermowell immersion length to provide a quicker response time. In a tapered Thermowell the outside diameter of the Thermowell decreases gradually along the immersion length of the Thermowell. A heavy duty tapered thermowell is typically used for high velocity applications due to the specification of a tapered thermowell shank in the old ASME PTC 19.3 (1974) thermowell standard. However, where the nozzle inside diameter is a design constraint the straight shank thermowell design is often the most resistant to velocity induced resonance.
