[labnetwork] Liquid Nitrogen Vacuum Jacketed Line Maintenance Question

[Dennis Schweiger]

Rich,

good morning.  Here at the University of Michigan/LNF, we have about
250-300' of assorted LN2 piping systems delivering LN2 at 50PSI to various
phase separators that are serving MBE tools, and gravity fill stations.
All of our piping, except for about 75', is actively pumped through the
vacuum pumps that support each of the five LN2 phase separators.
Typically, when we have an issue with the piping (frosting over on the
atmosphere jacket) it's because one of the users violated the vacuum
integrity of the jacket at their tool connection.  In those instances,
we'll isolate the section of the system and allow it to warm up while under
vacuum.  That usually fixes the issue.  On occasion, we have had to shut
down the entire delivery system and allow it to warm up to fix the thermal
violation.  We have not noticed any issues with the static vacuum lines,
and they've been installed since 1987.

I will say that our delivery system is designed so that by manipulating
vacuum valves, we can "select" which vacuum pump is "pulling" on the
annular space of the vacuum jacket.  It wasn't always like this.  We made
some changes once we had more than two MBE tools (PI's) on the delivery
system.

If you have any additional questions, just give me a call.

Dennis schweiger
University of Michigan/LNF
Facilities Manager

734.647.2055 Ofc

On Tue, Feb 16, 2021 at 7:48 PM Harlan, Richard D <rharlan at purdue.edu>
wrote:

> 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
>
>
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