Ice in my Halt chamber

[BusaJames]

Hi all,
We have a QualMark Halt & Hass chamber here at my work. I can't seem to figure out how all the moisture is getting into it. When we take it down below zero C it ices up bad. We don't have the nitrogen purge hooked up but the other guy figures that after a while the LN2 used to cool the chamber should have driven out the moisture anyway. The website wasn't very much help. Does anybody know if the chamber is sealed on these usually and the LN2 goes through a heat exchanger or is it shot directly into the chamber?

 

[IRstuff]

When you drive the temperature down, the internal air pressure also goes down, which causes external air to enter. Are all your air sources adequately dried?

TTFN

FAQ731-376

 

[RossABQ]

Many of these machines have nitrogen to energize the door seals; do you have that hooked up, if it is so equipped?

 

[BusaJames]

The first thing i suspected was the compressor air entering the chamber to run the drivers on the vibe table. I checked and it has a working water remover. The low pressure thing would cause air to enter anywhere it could though and we've been relatively humid here lately. We are not currently using nitrogen for anything but cooling but the chamber is able to do more, like nitrogen purging. Maybe we need to start there.

 

[NickE]

ou are definately going to have to keep a positive pressure "purge" of completely dry gas (note I didn't say air) as the temp comes down.

Also I doubt your compressor air is anywhere near as dry as you suppose. (is the dryer a dessicant type? Hows the media?)

 

[BusaJames]

I'm trying to convince them to connect the nitrogen gas purge system since our tank and chamber are set up for it. This morning we put new foam in all the ports and it seemed to help quite a bit but we still have a little snow and fog. The drier is not deccicant type. Its the type with a little glass jar. Its not full but does have some fluid in it. I think the purge system is the only way to really get that last little bit out.

 

[IRstuff]

A "little glass jar" is not a dryer, it's to trap LIQUIDs, leaving plenty of room for vapor.

TTFN

FAQ731-376

 

[bvanhiel]

A "little glass jar" is not a dryer, it's to trap LIQUIDs, leaving plenty of room for vapor.

Agreed. Vent the shaker table air outside the chamber.

-b