Dear Sir
I am new to Cryogenic tank repair currently doing cryogenic tank leak checking.
I have already conducted a mass spec with helium test for outer tank and found no sign of any leaking from my leak detector, the unsolve puzzle arise since then. I've pumped down the vacuum to 37 micron and started doing cold shock test by pumping liquid nitrogen into the inner tank, the vacuum reading which i recorded when the liquid nitrogen pumping was about at a rate of 8seconds/micron increased, until it climb steadily to 102 micron and halted. Then started to goes down steadily about at a rate of 13seconds/micron until 19micron, then i come back the other day and check the vacuum reading, it was recorded at 5micron. The liquid level was about 5 to 10 inch height for the first day. I am not sure what makes the result to be like this and hope you guys can assist in this problem. If you are feeling lacking of information to this scenario please do tell me. Your help most appreciate
update* i just got the latest vacuum reading for third day which is 5micron
Many thanks
Isaac Wong
Edited by isaacwong, 12 August 2014 - 09:47 AM.