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Bad union...

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Bad union...

Unread postAuthor: Counterstriker » Sun Mar 09, 2008 2:24 pm

I bought the 2" union and put on my burst disk cannon.. I tried it out today and when I use beer can material and it leaks.. It leaks with aluminum foil after 2 pumps.. I examined the union and it seems perfect... Has this happened to anyone before? Its like an hiss.. And yes its coming from the union.
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Unread postAuthor: DYI » Sun Mar 09, 2008 2:36 pm

When you put it underwater to find the leak, where do the bubbles come from?

What kind of rubber did you use for your gaskets? Butyl rubber seems to work acceptably well for me.

How tight is the union? As in what size of wrench did you use to tighten it? For a 2" union, you'll need an 18" wrench at least. You didn't just hand tighten it, did you?
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Unread postAuthor: hi » Sun Mar 09, 2008 2:37 pm

when i tighten it i use a pipe wrench to seal it. probably not smart on pvc, but it works.
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Unread postAuthor: SpudFarm » Sun Mar 09, 2008 2:39 pm

this was a problem for me the first day of hybriding with aluminium foil so i put some soft plastic behind the disk to act as a gasket...
try it:)
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 2:42 pm

DYI wrote:When you put it underwater to find the leak, where do the bubbles come from?

What kind of rubber did you use for your gaskets? Butyl rubber seems to work acceptably well for me.

How tight is the union? As in what size of wrench did you use to tighten it? For a 2" union, you'll need an 18" wrench at least. You didn't just hand tighten it, did you?


I'll go submerge it in water in a bit. I don't use a wrench because I didn't want to mess up the sides. I tightened it pretty dang tight... But the union had a gasket on it already.. No sure what kind.. i will try to tighten it.. Be right back.
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 2:47 pm

Well back.... Its still not working... I tightened it in a vice until I couldn't any more.. It started to leak after the 3rd pump....I am pissed..
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Unread postAuthor: psycix » Sun Mar 09, 2008 3:13 pm

Counterstriker wrote:Well back.... Its still not working... I tightened it in a vice until I couldn't any more.. It started to leak after the 3rd pump....I am pissed..


pissed cuz your gun hissed? :roll:

I don't use a wrench because I didn't want to mess up the sides.

Maybe you should really start using a wrench
Screw the sides!
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 3:20 pm

psycix wrote:
Counterstriker wrote:Well back.... Its still not working... I tightened it in a vice until I couldn't any more.. It started to leak after the 3rd pump....I am pissed..


pissed cuz your gun hissed? :roll:

I don't use a wrench because I didn't want to mess up the sides.

Maybe you should really start using a wrench
Screw the sides!


I did. I used a vice which I think is better. I am pissed because it doesn't work..
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Unread postAuthor: SpudFarm » Sun Mar 09, 2008 4:01 pm

look what i said and try it...
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 4:18 pm

spudfarm wrote:look what i said and try it...


:D Woops I didn't see it :D
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Unread postAuthor: SpudFarm » Sun Mar 09, 2008 4:21 pm

okey try it out (thick plastic)
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 6:13 pm

spudfarm wrote:okey try it out (thick plastic)


What do you mean by thick plastic? Like plastic bags? I tried them and it didn't leak past 3 layers of aluminum, but then I added four and it leaked.. But thanks!
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Unread postAuthor: koolaidman » Sun Mar 09, 2008 6:53 pm

youre not going crazy tho man, i get the same thing. i cant get past 30 psi, it leaks between the aluminum foil somehow. I did try oiling the union thread and tightening it with a vice. I also oiled the o-ring so that i would seal with the foil better. This all worked pretty well, but it is by no means a solution, it just helped partially. spudfarm, maybe i could try a layer of saran wrap on both sides, thats not a bad idea.
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