WIKA TW22 Mode D'emploi page 9

6. Commissioning, operation
In principle, the deflection problem also occurs for metal protection tubes, particularly for
insertion lengths > 500 mm. For process temperatures > 1,200 °C, vertical mounting should
be preferred.
EN
Due to the high thermal, chemical, and mechanical stresses to which ceramic and sapphire
thermowells are subjected during operation, a general indication regarding the service life
can only be given to a limited extent. This is particularly valid for applications in high-load
processes, such as gasification reactors. According to this, the process-related parts of the
thermocouples are wear parts which are not covered by the warranty.
It is recommended to mount the temperature measuring instrument into the thermowell or
protection tube using a suitable sealing material to avoid, for example, humidity ingress.
In general, the tip of the thermowell should be placed in the middle third of the pipe, though
the position may differ in special cases. It must be ensured that the measuring element
(Pt100, thermocouple, bimetal, etc.) is completely exposed to the medium and is not
shielded by the flange stubs. If, as a result of a small pipe diameter, this cannot be ensured,
a pipe expansion can be inserted around the measuring point.
Expansion of the pipe diameter from DN 40 to DN 80
Thermowells are delivered free from oil and grease (exception: carbon steels). Depending
on the application, the end user must check whether additional cleaning prior to assembly
is required.
WIKA operating instructions thermowells 9