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Issues with my Vacuum Chamber build

Questions and discussion of tools, materials and techniques.

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Issues with my Vacuum Chamber build

Postby TheMasterTurtle » Sun Sep 18, 2016 10:40 am

So I used a few tutorials to put this thing together and although I think it looks pretty, it doesn't actually work.


I've got a J/B 7cfm vacuum pump. New oil and properly filled. If I hook a gauge right to the pump I can get 26 or so psi

The pot is an old pressure cooker with a flange welded on. On the top we have a piece of polycarbonate. 1 hole with the gauge, 1 with the 2 fitting and 2 ball valves. 1
For the pump, the other to control the suction so my silicone doesn't pour over. On the ball valve going to the pump I've got a 1/4 quick release, 1/4 plug on the hose and a 1/4 to 3/8 adapter connected to the hose. I've made a gasket on the underside of the polycarbonate use RTV automotive gasket maker silicone. I then have bolts going through the flange, gasket and poly with wingnuts on top get a tight seal. Cumbersome but in theory it should work.

I assume I have a leak because when it's all hooked up, the needle on the gauge doesn't even budge a little. It's really frustrating me at this point. Any advice from anyone on what to check and where?
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Joined: Fri Jul 08, 2016 10:18 pm

Re: Issues with my Vacuum Chamber build

Postby johncast » Thu Sep 22, 2016 6:30 pm

Hi master turtle

Tidy set up, all looks pretty new . a Process of elimination as to where the problem is .

Is the top of the metal pot flat to begin with , it may not be, and is just able to prevent the top Perspex from getting the seal on the rubber it needs. Turn the tin pot over and sand it down on a flat surface , not the easiest thing to do , a belt sander would help.
Not too sure about the wind nuts. these shouldn't be needed for a good seal once the pump takes out some of the air from the pot, the outside air should pressure the Perspex to the rubber seal . The other possibility, if you tighten these up there may be a slight distortion put in the Perspex top which unseals the top rather than sealing it.

Is the top Perspex very thick,? it doesn't seem to be in the photo.

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Joined: Thu May 10, 2012 8:19 pm
Location: Sydney Australia

Re: Issues with my Vacuum Chamber build

Postby marctech » Fri Oct 07, 2016 12:54 am

also if the gauge is damaged or even clogged with debris, it won't work.

So pull on that lid, or put a cup of water in there, see if anything is happening.
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Joined: Tue Jul 12, 2016 12:34 am

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