Open Thermocouples!

Hey guys ,

Just wondering if there is any refernce to material that suports accepting a validation run performed on a temperatre mapping study that encontered a “open” faulty thermoocuple.

Do all T/Cs need to read good for the entire run or is there a % failure limit that prevents a re-execution of the study ?

  • Hoping so !!:rolleyes:



I saw that some people put in their protocols that Eighty-five percent of thermocouples used must be operational upon completion of the study. In that case, you can have some #open# or #failure# or #under# TCs, but in that case you should write Risk Analysis to explain that missing of the measuring do not have impact on the system or if measuring has impact then repeat testing (if you can not justify missing data)

You did not mention what equipment you are mapping, how many TCs are in the study and how many the protocol requires as minimum needed.

We specify in the mapping procedure description a minimum number of probes required for the mapping [ no rationale or complex calculations here – just say 12] and in the actual execution use 15 probes. Also in the TCs calibration and verification section have a statement to the effect that ‘at least 90% of TCs pass post study verification’.

It is mostly with the autoclaves that we see this OPEN TC issue. How long you had this TC open? Sometimes it will be very very short (20 seconds) then after that all readings were good. With PQ of autoclaves - if that particular TC is used for drain or in one of the load items - the run is as good as rejected and not acceptable.