Hi,

We have an number of open vessels, steam jacketed, with a thermowell with Pt100 at the bottom. There is no "cavity" in the jacket to place a flanged thermowell. The stem of the thermowell is welded on the inside of the vessel and on the outside of the jacket. (for as far as I can see.) length in the vessel is approx 4 inch.

Now when we measure the temperature with a hand probe at the surface of the mixture (being well mixtured), there is always a few centigrades difference with the Pt100 display. Could the reason be this type of thermowell installation or ????

On the www, I can't find any info of proper installment of thermowells in jacketed vessels so if someone could help me.

Thank you

 

I assume your PT100 is reading higher than the hand held probe. Do you think the temperature of the jacket portion is over heating the RTD. Could you possibly insulate the probe through that section with heat shrink, you might need to drill it out a little larger to accommodate the insulation.

Is the probe spring loaded against the end of the thermowell?

Perhaps apply a dab of heat sink compound to the end of the probe.

It might be interesting to do a temperature profile of the well with a tip sensitive thermocouple (The measuring length of older style RTDs was about 1-1/2" long the newer ones are very short).

A 4" projection is not very long, could you extend that further into the vessel?

Make sure there is no moisture inside the thermowell.

>(for as far as I can see.) length in the vessel is approx 4 inch.
>
>Now when we measure the temperature with a hand probe at the
>surface of the mixture (being well mixtured), there is
>always a few centigrades difference with the Pt100 display.
>Could the reason be this type of thermowell installation or
>????
>
>On the www, I can't find any info of proper installment of
>thermowells in jacketed vessels so if someone could help me.