Condensation inside pressure vessel

[HenHen]

Hi!

I have a pressure vessel that contains electronics. Recently, I found that water had condensed inside the vessel,
even though the vessel has had all the air vacuumed out of it, and been filled with nitrogen to about 1,5 bar.
What is a good way to ensure that no condensation happens inside a closed compartment, without being able to control the temperature it experiences when in service?
Should I combine the vacuuming and nitrogen filling with some kind of temperature treatment?

 

[MJCronin]

Where did the water come from ?

Was the chamber filled with dry nitrogen after having been repeatedly purged ?

If the water came into the chamber with the eletronics, have you considered a dessicant ?

 

[SnTMan]

HenHen, you can purge to as low a dewpoint as you like, but if you have any kind of gasketed closure I believe you will sooner or later pick up water vapor into the vessel, as that is the way the potential will run. Drop the temp below the dew point and you'll have condensation.

I'd say you need to actively maintain a purge or perhaps dessicant would work.

Regards,

Mike

 

[racookpe1978]

How many times was the vessel opened and closed since you last had "no moisture"? Are you really sure it was dry inside all the time since the pressure vessel was put in service for the previous electronics packages?

What was the outside of the pressure vessel (inside - in a room or actually outdoors?) conditions when it was opened?

How can you control the room when you open it up to put the electronics inside?

Assume you load the pressure vessel with a "new set" of your electronics. Can you then vent (or actually vacuum) the pressure vessel gasses until they dry out if you don't want to put a desiccant inside? (For example, can you apply a vacuum for twenty minutes - let the water evaporate - then put your electronics under the final high pressure?)

 

[HenHen]

Thank you for the replies!
Yes, the vessel was filled with nitrogen. I don't know if dry nitrogen was used. Is there a big difference?
The nitrogen bottle used in the last purge almost ran out of gas. Could this affect the dew point you achieve? Considering the pressure in the nitrogen bottle was getting rather low.
I can't maintain an active purge, but a desiccant could be a viable solution.

 

[racookpe1978]

You are getting your water from somewhere.

if not "perfectly dry" nitrogen, then where did it come from?

 

[HenHen]

racookpe1978
The vessel had not been opened since the last nitrogen fill.
The room is not controlled during installation/removal of electronics.
The vessel is purged through a purging port after the electronics have been installed. We did a 3x vacuum / nitrogen fill.
The vacuum is held for about ten minutes each time. The ambient temperature and unit temperature were the same when it was opened, since it had been laying in the workshop for a few days.

 

[HenHen]

racookpe1978

I'm starting to think that something went wrong during the last nitrogen fill. I'll review the procedure and try again.
Thank you for the replies!

 

[rmw]

If your nitrogen purge system has leaks in it, everywhere there is a leak to atmosphere, moisture (and air) from the atmosphere can difuse back into the nitrogen line and on into your PV.

rmw