PID thermocouple leaking

[Bryan527]

I built a pid last year following what I found on here. It works good. This year, I wanted to mount the K thermocouple through the bottom of the pot, a Lee 4-20. I got what the seller said was a liquid tight thermocouple, but I can't get it to stop leaking. Any of you have any suggestions?

[Tazza]

If it's the screw in type, can you use a bolt and dill and tap it for the thermocouple, just don't drill through the end, so it should be liquid tight.

[bangerjim]

A ferrel-type t/c must be tightened REALLY tight because the metals shrink and swell with the extremes of heat in the pot. They generally always leak and are rarely ever used where there is the concern of leakage.

If you want an industrial solution - - -buy a thermowell to mount a t/c in. The well is a solid piece of brass or sst that is totally sealed and the t/c is inserted into it, normally spring loaded to insure intimate contact with the end. This is the way I design and use t/c's in all my equipment deigns. Never rely on a ferrel to seal against the process liquid and the t/c!

Check out OMEGA.COM for a cheap version. You generally buy the t/c and the thermowell as a matched set. Do not expect prices to be like you have seen on evilbay!!!!!! It only costs a little more to fly 1st class.

bangerjim