[labnetwork] Liquid Nitrogen Vacuum Jacketed Line Maintenance Question

[Nicholas Menounos]

Hi Rich,

I don't know the type of system you have (dynamic - always pumped, static sections "factory sealed", custom static or flexible), but the industry standard for "good" vacuum on VJ is ~10 micron cold and 40 micron warm. If you have a vacuum pump port, you should be able to measure and/or pump down. If you are unable to maintain vacuum, you can identify leaks with He leak checker. If you have some form of getter in the interstitial, it may need to be regenerated (unlikely)...Flexible stuff is generally replaced.

Also worth noting on a system that age: Thermal safety reliefs in the piping should be replaced every 10 years and every 5 years on the ASME pressure vessels.

Nicholas Menounos, PE, LEED AP (he/him/his)
Assistant Director of Infrastructure

MIT.nano
Massachusetts Institute of Technology
77 Massachusetts Ave, Bldg 12-4003
Cambridge, MA 02139
Cell: (508) 932-0938
Office: (617) 253-7234
Email: Menounos at mit.edu

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Harlan, Richard D
Sent: Tuesday, February 16, 2021 4:30 PM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Liquid Nitrogen Vacuum Jacketed Line Maintenance Question

Greetings All,
Our facility is now 15 years old and starting to require more preventative maintenance. The vacuum jacketed liquid nitrogen line was showing an increased leak rate for a short period of time. It has since stabilized, but has raised questions about potential leaks in the system.
Have any of your facilities experienced this type of problem and what PM's have you put in place to address the LN2 and vacuum jacketed line integrity?
Thank you in advance for the feedback.

Thanks,
Rich Harlan
Research Engineering
Birck Nanotechnology Center | Room 2287C
Office: 765.494.6697 | Email: rharlan at purdue.edu<mailto:rharlan at purdue.edu>
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