Hi All,
We are doing a loaded chamber temperature mapping of both a dry and liquid cycle. As part of the validation, we need to put a T/C near the controlling probe, which is located in the chamber drain. It was a requirement that the temperature difference between the T/C (let’s call this the drain T/C) and the controlling probe to be within 1 degC . Inspection of the probe showed that it is located at about 60 cm down the chamber drain.
Several runs were performed with the drain T/C in the opening of the drain inside the chamber. Most of the runs failed as the drain T/C was reading temperatures higher than the controlling probe. After some discussions, it was decided to insert the drain T/C into the chamber. This presented a problem as we don’t know how far the T/C was inserted into the drainpipe (as visual confirmation is definitely impossible), nor do we know if the T/C is touching the pipe (which most probably is), or if it’s anywhere near the controlling probe. Runs had varying results on the drain temperature, maybe due to the reasons given above. With some runs, the drain T/C is still reading higher temperatures (>1.6 deg difference) than the controlling probe. Sometimes, if we pushed too far, the T/C will read temperatures lower (>1 degC) than the controlling probe. As a CAPA, validation suggested that the piping on the mechanical side be retrofitted with a port especially made for the drain T/C with its location adjacent to the controlling probe.
May you please give me some thoughts on our approach to this requirement (taking out the requirement from our quality standards is not an option unfortunately)? Is it really possible that the drain T/C is reading higher temperatures than the controlling probe even if it is inserted into the drainpipe?
Your help is very much appreciated. Thank you.
Best regards,
Chris