Hello group, I am about to buy PT100 sensors for temp measurement on steam, The pipe diameters are 300 and 700 mm. My question is how far in to the pipe the sensor should go. Case 1: DN 300 mm, temp 225 deg C, pressure 12 bar. Case 2: DN 700 mm, temp 160 deg c, pressure 3,5 bar. I have heard different answers, all from measuring near the pipewall from the center of the pipe.
Thanks/ Patrik Johansson
Patrik,
The reason you get so many different answers is that it doesn't matter very much. In any case, neither temperature nor pressure have any bearing on this question. Flow rate does, slightly. While measurement at the center of the pipe is ideal, it is a rather flat optimum. Once you get four times the diameter of the thermowell in from the pipe wall, there are no significant wall effects.
Walter.
If the pipe is insulated over the sensor well enough, all depths will read the same temperature. The only reason to measure with a deep thermowell is to allow for poor pipe insulation.
Just make sure your thermowell doesn't turn into a vortex shedding flow element by accident!
(One of the large international petrochemical companies requires a check on resonant frequencies of thermowells to make sure they are not excited to failure.)
Bruce.
Patrik Johanss>Hello group,
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