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Vacuum chamber leakage

Vacuum chamber leakage

Vacuum chamber leakage

(OP)
I have built a homemade vacuum chamber with the intention of developing a reliable vacuum of 1 Pa to 5 Pa, however when I isolate the pump the pressure rises by 100 Pa in 5-10 minutes and then the rate tapers off to insignificant rise after 24 hrs approx; between 900 Pa to 2,400 Pa (similar to mass damper system cure). At first, I thought that this was due to degassing, but I get the same result when I restart the pump hence the difference in the final pressure. The vacuum pump I am using can only develop 500 Pa and that is another issue, but I don’t think that should change this problem. I am looking for tips/advice on what I am doing wrong and how to improve it. Details of the construction are below.

Vacuum chamber from 8” PVC pipe, with stub flanges fixed with a PVC cement. The ends are 20mm acrylic, with a 3mm thick solid rubber C40 rubber seal. There is currently a single port in one of the acrylic ends, made from 15 mm dia copper pipe (standard central heating pipe) which is fix in place with super glue and with a twin pack epoxy forming a boss on both sides. The port is connected to the vacuum pump via a double ball valve cross with mechanical gauge from a commercially available vacuum chamber set. The two are connected by John Guest Speedfit style elbow, but 3D resin printed with space for 2 and 3 o-rings. Pressure measured by a Adafruit pressure sensor over Bluetooth.

RE: Vacuum chamber leakage

I imagine The components were glued and assembled atmospheric pressure.
Applying vacuum distorts things a bit, especially flat panels .
Lots of joints to potentially leak.
How sure are you the isolation valve is up to the task?

Supposedly Loctite wicking 290 may good to e -8. It may not be compatible with some of your materials though.
A few drops of 290 on each joint with the chamber at fill vacuum might seal things up, almost permanently.

I'd probably apply the 290 to one joint at a time while watching the vacuum gage. The info about particular joins would be helpful building chamber 2.0.

https://en.wikipedia.org/wiki/Materials_for_use_in...

RE: Vacuum chamber leakage

(OP)
Thanks Tmoose the wiki page very use and it looks like I've used all the wrong materials.

RE: Vacuum chamber leakage

I wonder if there "paints" that that can reduce material outgassing?

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