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250 psi

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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250 psi

Unread postAuthor: roughboy » Thu Aug 24, 2006 12:35 am

im planing to make a 250 psi gun, the problem is i don't know what kind of pvc to use and also the SIZES? im talking about only the air chamber.


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Unread postAuthor: rna_duelers » Thu Aug 24, 2006 12:40 am

Well at 250psi i wouldnt trust most PVC pipes but if u do use sch80 and the valve you are using should have a high pressure rating.Personaly i would use steel pipe it has burst pressure psi is into the thousands.And copper pipe has ratings upto 500psi.
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Unread postAuthor: Pete Zaria » Thu Aug 24, 2006 1:43 am

What will your air source be? 250 psi compressors are very expensive, so I assume you're looking into CO2 or another high-pressure source?

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Unread postAuthor: boilingleadbath » Thu Aug 24, 2006 4:27 pm

Most people consider 120 psi in 4" sch 40 pipe quite safe (rating of 220 psi), and (roughly) the same margain of saftey would be afforded by running 250 psi in 1" sch 40 or 2.5" sch 80 or 1.5" sch 80.
(oddly, 2" sch 80 is rated to a lower pressure than 2.5")
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Unread postAuthor: mark.f » Thu Aug 24, 2006 5:28 pm

2" SCH-40 is also rated lower than 2-1/2" SCH-40. I think they just make the walls a little thicker on 2-1/2", for some reason. That might be why it's a little more rare.
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Unread postAuthor: SpudStuff » Thu Aug 24, 2006 5:30 pm

and why it costs so much more then 2"
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Unread postAuthor: jr » Thu Aug 24, 2006 10:34 pm

do we even want to know what you plan to shot with this 250psi cannon :roll: my twin sprink has all the power i could ever use :D

the best way to get 250psi is from a scuba tank :twisted: mine works 10x better than a compressor. :idea:

as for pipe and valve make sure you give yourself plenty of magin between the working psi and your intended psi
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Unread postAuthor: MrCrowley » Thu Aug 24, 2006 10:54 pm

i would use copper/galv steel, how expensive is sch120? if there is sch120.i would stay under 3" as fittings cost too much if you want them to hold 250psi
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Unread postAuthor: GalFisk » Fri Aug 25, 2006 7:15 am

I'd go with copper( and soldered fittings) as well, I'e built several copper guns this way that are run safely at 300 psi.
I hope you're not planning on using one of those 12V compressors to get to 250 psi, they're slow and break easily.
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Unread postAuthor: schmanman » Fri Aug 25, 2006 4:19 pm

will solvent welded bonds even hold up to 250 psi?
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Unread postAuthor: Shrimphead » Fri Aug 25, 2006 6:54 pm

If not, what's the purpose of sch 80 and 120 pvc? I'm pretty sure that it can hold as much as the pipe is rated for, but I'm not positive.
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Unread postAuthor: MrCrowley » Fri Aug 25, 2006 8:31 pm

yeah i think the psi rating is just a saftey margin i recon sch80 could go 30psi-ish higher then its rated
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Unread postAuthor: rna_duelers » Sun Aug 27, 2006 5:37 am

Isnt sch 120 or 160(not sure)availiable in small diameters like 1/2" and 3/4" only.
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Unread postAuthor: dinsdale » Sun Aug 27, 2006 1:33 pm

buy schedule 40 steel; mild steel, galvanized, stainless, it doesn't matter.
have it welded by someone who knows what they're doing and you wont have to worry about pressure, i'm skeptical of soldered copper, or solvent-welded PVC or ABS past 120-140 psi.
you can buy used galvanised steel pipe at a local fence company for a very reasonable price, and if you do the prep work yourself (cutting to size, grinding coating off of weld area, and bevelling edges) a small welding shop (the same fence company is likely to have one) will weld it inexpensively.

BTW i work in the welding shop of a fence company
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Unread postAuthor: LucyInTheSky » Sun Aug 27, 2006 2:08 pm

I cant see why you woulnd like copper?

It bends so it wont shatter. And here http://www.airlines-pneumatics.co.uk/we ... de=S080023 1/2" copper is burst for 316BAR so about 4580PSI so for a safty margin you could easily run copper at 3000psi.
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