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argon piping pressure/leak test

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victorguo

Participant

Posts: 3

Joined: Mon Dec 08, 2014 6:17 pm

Post Wed Jan 09, 2019 4:52 am

argon piping pressure/leak test

Hi Everyone,

What testing protocol would you recommend to verify the integrity/tightness of the argon piping system for Helios/CyTOF?

We recently installed a stainless steel piping system with all Swagelok fittings from the argon tanks (in the hallway) to the instrument (inside lab). Although the system will operate at positive pressure (~80-90 psi), the gas is flowing fast (~8.5 m/s according to my calculation; that is, ~1 second from tank to instrument), so I'm worrying that any potential micro hole in the fittings could create a local turbulence or draft that could suck air in (ie, oxygen).

I'm thinking of doing a cheap pressure test (fill with N2 at ~100 psi) and see if the pressure holds over a few days. Have you done similar or other leak test? What leak rate is typical for your system? And what rate should be acceptable? (Say, <1 psi/day, <10 psi/day, etc?)

Thank you very much for your kind advice and help!

Victor Guo
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed Jan 09, 2019 11:16 pm

Re: argon piping pressure/leak test

Hi Victor,

I have not done formal leak testing of my argon tubing from my argon supply to my two machines. In my situation, I have one feed line from the argon tank, up over the ceiling, and dropping down a few feet from my two machines. At that point, we have a T connector that splits that line into supply lines for each of my instruments. In short, one tank feeds two instruments.

However: my field engineer and I recently discovered a minor leak at the T connector, where a bend in the line for one instrument had caused some fatigue in the plastic tubing at the connection with the brass T connector. This was minor, but still something we could feel with a wet finger. It was also what was causing our line pressure to drop from 100 psi to 0 psi in about 30 seconds once we closed the tank at the end of the day.

After resplicing it and adding an internal brass support plug to strengthen the bend area, it now takes at least 5min for the pressure to drop from 100 to 0 psi.


Since the T connector was installed about 6 years ago when we got a second instrument, who knows how long it had been that way? However, we never had any noticeable oxide issues, so I have to assume the ~90psi positive pressure was sufficient to prevent mixing in of room air.


Mike

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