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Thermowells are used in industrial temperature measurement to provide isolation between a temperature sensor (often a thermocouple) and the environment whose temperature is to be measured.
They are intrusive fittings and are subject to static and dynamic fluid forces. These forces govern their design. Vortex shedding is the dominant concern as it is capable of forcing the thermowell into flow-induced resonance and consequent fatigue failure. The latter is particularly significant at high fluid velocities.
Thermowells are among the simplest yet least well publicized accessories used in industrial temperature measurement applications. There are many variations of two basic kinds; low pressure and high pressure. They are used to provide an isolation between a temperature sensor and the environment, either liquid, gas or slurry. A thermowell allows the temperature sensor to be removed and replaced without compromising either the ambient region or the process.
The most expensive, complex thermowells that we have ever seen were made from drilled molybdenum rods with an internal sheath of high purity alumina. The annular space between the alumina and metal had a very slow gas purge of nitrogen+hydrogen to prevent oxidation of the moly surface. The well was inserted into the bottom of an electrically heated glass melting furnace and used to help measure the molten glass temperature. An IR radiation thermometer mounted on an electrically insulating holder was sighted into the tube to read the temperature indicated by the alumina, essentially under blackbody conditions.
Low pressure, moderate to high temperature environments are routinely provided with a thermowell variant called a protection tube that can be made of metal or high temperature glass or ceramic, again according to he conditions. Most high temperature industrial furnaces use ceramic or metal protection tubes, according tho the conditions.
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Thermowells are used to protct thermometers from?
Thermowells are used to protect thermometers from corrosive materials, high pressure, and turbulent flow. They provide a barrier between the process medium and the thermometer, allowing for safe and accurate temperature measurements without exposing the thermometer to harsh conditions.
What is wake frequency in thermowell?
Wake frequency refers to the maximum frequency at which a thermowell can be subjected to a flowing fluid before experiencing damage due to vortex shedding. Operating thermowells at frequencies below the wake frequency helps to prevent fatigue failure and prolong their lifespan. It is important to consider wake frequency when designing and selecting thermowells for industrial applications to ensure their proper functioning and longevity.
What are the properties of Thermic oil for using thermowell?
Thermic oil has high thermal stability, low viscosity for efficient heat transfer, good thermal conductivity, and compatibility with materials commonly used in thermowells like stainless steel or Inconel. Additionally, it should have low volatility to minimize evaporation and a wide operating temperature range to suit various industrial processes.
How many kinds of piping joints?
there are literally hundreds of pipe joints. Dependent on pipe sizes, joining methods, material and strength. sizes range from 1/8" to 48" diameter nominal sizes, methods of joining from glueing, soldering, swaging, threading, grooved end couplers, butt welded, socket welded, flared, compression fitted...etc. materials range from aluminum, copper, brass, pvc, cpvc, .....to specialty stainless steels and inconel. Fittings can be cast or forged, molded, rolled...etc.. Types of fittings can be 45s, ells, tees, couplings, side tees, valves, instrument penetrations, thermowells, reducing fittings, flanges, couplings, unions...etc. Catalogs of hundreds of pages exist just for pipe fittings and pipe, with hundreds of fittings on some pages.
