Thermowells and Protection Tubes
Thermowells and protection tubes are generally attached into the process three ways, threaded, welded or a flanged connection. For smaller diameters where the well will not be required to be removed on a regular basis and corrosion is not a serious problem, threaded process connections are preferred. By threading into a coupling, thread-o-let or TEE the well is attached directly to the vessel or run pipe.
For installations where the well needs to be removed more frequently due to corrosion or other requirements, a flange connection is used. The flange connection will bolt to a mating flange mounted to the process. Flange connections are more appropriate for high pressure applications and larger pipe sizes.
For applications where access is not required a weld-in or socket well can be used. These provide a high quality connection, but obviously cannot be removed without significant effort. Welded connections are also preferred for high pressure, high temperature steam lines.
Protection tubes or pipe wells are generally less expensive than drilled bar stock styles and are used in applications where pressure and velocity are low enough that the stronger drilled bar stock types aren’t required or where long lengths are needed. A typical application is in stack gas temperature monitoring where a high temperature alloy is used as pipe material. Protection tubes can be welded directly into a vessel or supplied with a threaded bushing or flange welded in place for threaded or flanged process connection.
