There are many industrial applications where insertion of a temperature probe is not possible. Most often, it is because the vessel is pressurized or the process contains dangerous gasses or fluids. Further, there are processes where a thermocouple or RTD, because of their small size, cannot withstand the stresses of the process environment. This may be because of flow issues or the process will eat through the relatively thin walls of a sensor.
To overcome these problems, there are a variety of protection tubes and thermowells available that will protect the thermocouple or RTD. AccuTru custom makes thermowells to your specifications with quick turnaround times. Our catalog contains the drawings for all standard thermowells plus we can make any design, with nearly any material to your exact specifications, even on an emergency basis.
Multiple options available for nearly any application…
In many processes, additional protection is needed for thermocouples and RT Ds. Process environments with very corrosive materials, or applications where there are high velocity particulates are particularly tough on unprotected instruments. Further, processes may be under extreme pressure or contain highly toxic materials, or the process dynamics are such that shutting the process down for sensor replacement is extremely costly. The use of thermowells allows sensors to be replaced “on the fly.”
To address these issues, a variety of protection tubes and thermowells are used .
Protection tubes are available in a wide variety of materials, including ceramics, metals, and metal ceramics.
Thermowells are manufactured in most types of stainless steel, or materials such as Hastelloy X and Inconel 600. Other types of material are also available for applications where standard materials will not withstand the process environment.
Thermowells are available in a wide variety of styles. These include:
- Threaded thermowells with reduced tips
- Tapered threaded thermowells
- Threaded thermowells with lagging extensions
- Flanged thermowells
- Mini-wells designed for use where limited space is available
- VanStone thermowells
- Ground joint thermowells
- Socked weld thermowells
Ceramic protection tubes are available in most standard metals, iron, mullite coated, and alumina
AccuTru’s alumina tubes are made with very high purity, dense alumina and then treated with a proprietary process to provide longer life and improved sensor performance. Alumina is most often used for noble metal thermocouples, Types S, R, and B. The upper temperature limit for alumina is 3452ºF (1900º).
Mulite is an inexpensive alternative to alumina or as a coating on metal protection tubes for letter Type J, K, E, T, and N thermocouples. The upper temperature limit for mullite is 3092ºF (1700ºC).
Metal-ceramic tubes are often the product of choice where abrasive conditions are present. The upper temperature limit of these tubes is 2900ºF (1537ºC).
Metal protection tubes and thermowells are available in 304 stainless, 316 stainless, and Inconel 600. Other exotics are also available upon request. If you have special needs, AccuTru’s sales engineers will assist you in finding the right materials for your application.
The AccuTru 247 material is extremely resistant to environments with rapid process flow and where particulates are present. The upper temperature limit for AccuTru’s 247 material is 3000ºF (1643ºC).
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