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Scuba tank refill

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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Scuba tank refill

Unread postAuthor: ferret_guy » Mon Jul 23, 2012 1:50 pm

I was thinking of using a scuba tank to refill a galvinised steel pressure vessel for my next spud gun to enable quivk high pressure refills my questions are, has anyone tried this before? and how mutch pressure can threded galvinised steel take?
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Unread postAuthor: jsefcik » Mon Jul 23, 2012 3:35 pm

steel can with stand, thousands of psi, extreme high pressure. they why alot of hybrids are made of steel
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Unread postAuthor: ferret_guy » Mon Jul 23, 2012 3:41 pm

Are we talking 1,000-1,500psi or is it high enough to use straight 4,000psi air from the scuba tank
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Unread postAuthor: Goats spudz » Mon Jul 23, 2012 4:19 pm

I wouldn't suggest doing that, use Steel Hydraulic tube or Seamless stainless steel, Jsefcik hybrids only encounter high pressure for a matter or seconds, pre-ignition pressures are usually below 1000psi, 4000psi in galvanised steel tube would probably strip the threads and explode, or rupture.
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Unread postAuthor: ferret_guy » Mon Jul 23, 2012 4:22 pm

What pressure would you recommend? i went with galvanized steel because i wanted to do much higher pressures taking advantage of the scuba tank
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Unread postAuthor: AircannonSweden » Mon Jul 23, 2012 4:45 pm

I have 2 tanks(scuba tanks)that are rated to 1200 bars(17400 PSI)

You could maybe ask your local diving-shop/center or a firestation if they could refill the bottle!
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Unread postAuthor: Fnord » Mon Jul 23, 2012 6:02 pm

I would NOT recommend messing with a scuba tank right off the bat, unless you have suitable machining/engineering knowledge and a work shop to fit your skills. Standard steel pipe does not have a huge safety factor even in small diameters (I remember someone hyrdro-tested some 1/2" fittings and burst a tee at ~5000psi).

When you do decide you're ready, use a high-quality regulator and a high-flow pop off valve as a safety. Use Class-3000 (or higher) pipe and fittings only.


steel can with stand, thousands of psi, extreme high pressure. they why alot of hybrids are made of steel


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Stop giving people advice when you have no idea what you're talking about. I never had any problem with your occasional pointless or redundant questions, but here you're potentially endangering someone else by speaking out your ass.
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Unread postAuthor: Gippeto » Mon Jul 23, 2012 6:04 pm

http://www.engineeringtoolbox.com/wroug ... _1123.html

Would not recommend a safety factor of less than 5 with seamed (erw) pipe.
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Unread postAuthor: ferret_guy » Mon Jul 23, 2012 7:46 pm

I am confident in my machining/engineering knowledge and after talking to an industrial design engineer that I know he suggested the same things you did specifically pop off valve for safety. He could however not tell me if the threaded joints could hold the same as the working pressure of the pipe

[edit]
after looking at McMaster-Carr it appears that they suggest "threaded Schedule 160 extra-thick-wall galvanized steel" for 3,000psi applications and it is rated for "air, water, oil, natural gas, steam"
[/edit]
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Unread postAuthor: jsefcik » Mon Jul 23, 2012 8:04 pm

Fnord wrote:I would NOT recommend messing with a scuba tank right off the bat, unless you have suitable machining/engineering knowledge and a work shop to fit your skills. Standard steel pipe does not have a huge safety factor even in small diameters (I remember someone hyrdro-tested some 1/2" fittings and burst a tee at ~5000psi).

When you do decide you're ready, use a high-quality regulator and a high-flow pop off valve as a safety. Use Class-3000 (or higher) pipe and fittings only.


steel can with stand, thousands of psi, extreme high pressure. they why alot of hybrids are made of steel


Jsefcik
Stop giving people advice when you have no idea what you're talking about. I never had any problem with your occasional pointless or redundant questions, but here you're potentially endangering someone else by speaking out your ass.




i do have an idea on what im talking about if i didnt i wouldnt have said anything, you can kiss my dirt star
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Unread postAuthor: MrCrowley » Mon Jul 23, 2012 8:41 pm

jsefcik wrote:i do have an idea on what im talking about if i didnt i wouldnt have said anything, you can kiss my dirt star

No you don't, jsefcik. I agree with Fnord on this one, you were talking out of your ass. If you did know what you were talking about, you sure as hell wouldn't have said what you posted.
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Unread postAuthor: ferret_guy » Mon Jul 23, 2012 10:22 pm

So I was looking at valves and I can't find any valves except ball valves that are rated for 3,000psi now I am not looking down on ball valves but they are not as awesome as something that can release much faster.

Any suggestions?
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Unread postAuthor: Zeus » Mon Jul 23, 2012 10:37 pm

Machine a piston valve, use a SCH160 tee to house it.

Jesse, steel can withstand into the millions of PSI, but that doesn't mean seamed mild steel can.

I wouldn't trust SCH40 steel under continuous pressure over 1000PSI, but for peak pressures I trust it far more. It's easier to see the ringing at weak spots, whereas high carbon steel just goes bang.

And MrC, you aren't American, so it's arse not a crossbred donkey.
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/sarcasm, /hyperbole
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Unread postAuthor: ferret_guy » Mon Jul 23, 2012 10:52 pm

Could a piston valve switch 3000psi? if so what type to use?
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Unread postAuthor: Crna Legija » Tue Jul 24, 2012 5:10 am

ferret_guy wrote:Could a piston valve switch 3000psi? if so what type to use?


A really strong custom made one, shouldn't be hard since you trust your machining.
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