Issues regarding the sealing surfaces of the primary components of instruments
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As indicated in the title, there are several types of sealing surfaces when connecting thermal resistors, thermocouples, and equipment pipelines. What determines which type to use?
It generally comes in two forms: threaded and flanged, depending on the pressure it is designed to withstand.
I am familiar with many types of threads, such as sleeves. The properties of the medium are primarily taken into consideration, such as temperature, pressure, flow rate (especially with regard to wear and erosion resistance during heat treatment on the surface of thermocouples), etc. Another common example of a sealing requirement is related to threads; for instance, in the case of thermistors used to measure the temperature of turbine bearing shells, it is sufficient to install the wiring enclosure on the turbine’s casing.
Temperature sensors installed on equipment are generally mounted using flanges, while those installed on pipes are usually connected via threads; for high-pressure pipes, flange mounting is also commonly used.
The type of flange sealing surface can be selected based on factors such as pressure and the medium used; options include RF raised face, FMF uneven face, TG tenon groove face, or RJ ring joint face. The specific requirements are outlined in HG20592-97. There’s not much to say about threaded connections; it’s just whether they are NPT, RC, RP, etc.
The answer on the sixth floor was very good. Additionally, at important monitoring points, a sleeve can be installed on the equipment or pipeline to seal it against the equipment and pipeline, allowing for the online replacement of thermocouples or thermal resistors.
For low pressures (PN6.3), threaded connections are generally used; NPT threads are sealed with threads, while metric threads are sealed with gaskets. At higher pressures, welded temperature sleeves are employed, so that the temperature sensing element does not come into direct contact with the process medium. In the ammonia synthesis process at PN32, temperature sleeves in accordance with the H standard are used; see the standard drawings for details.