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dwv....

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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dwv....

Unread postAuthor: nabu92 » Fri Jan 25, 2008 10:50 pm

Hey guys I just finished building my first pneumatic...just waitin for it to dry.I was reading that dmw fittings are dangerous and all of my joints and fittings say dmw on them, they are'nt bell fittings though, they look like http://ecx.images-amazon.com/images/I/3 ... AA280_.jpg . Is it safe for me to go to 80 psi?
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Last edited by nabu92 on Sat Jan 26, 2008 11:06 am, edited 1 time in total.

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Unread postAuthor: DYI » Fri Jan 25, 2008 10:58 pm

Well, I've never even heard of DMW fittings, much less them being dangerous to use.

If they have a little number saying something like "Max WP - xxx psi@73F, and that little number is greater than 80, then you can probably use them at 80 psi. :withstupid:

If, however, you mean DWV, which I strongly suspect you do, it means that your fittings have been deemed acceptable by the NSF for use in Drain, Waste, and Vent systems. Absolutely nothing to do with pressure ratings. If, however, they say PW (potable water) as well, they likely are pressure rated, since drinking water delivery systems are pressurised.
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Unread postAuthor: elitesniper » Fri Jan 25, 2008 11:09 pm

does it say nsf-dwv and nsf-pw?
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Unread postAuthor: nabu92 » Fri Jan 25, 2008 11:35 pm

yes, it is dwv and pw, I guess I misread one of the fittings. Thanks.
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Unread postAuthor: bigbob12345 » Sat Jan 26, 2008 12:26 am

if it is both than they should be fine as long as it has pw on it
edit the title to dwv
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Proofing pipe

Unread postAuthor: dave1 » Sat Jan 26, 2008 10:49 am

I'm wondering if anyone is familiar with proofing and if it applies to various PVC fittnigs and pipe. Proofing is the centuries old practice of overloading a firearm or cannon to pressures that they will never encounter again. The theory has been that if the proof load doesn't blow up the gun then lesser and normal loads will be fine. If this could be done remotely with a pneumatic PVC cannon, I wonder if it would be definitive. In other words, by running that questionable dwv cannon up to 60psi, would it always be safe at 50psi?
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Unread postAuthor: elitesniper » Sat Jan 26, 2008 10:55 am

its never ''safe'' as the manufacture doesn't make it to hold air pressure.
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Unread postAuthor: judgment_arms » Sat Jan 26, 2008 11:21 am

I like the idea of proofing, only thing is if you crack the pipe, but not blow it, you’ve just defeated the purpose.
Plus going to 60 to proof it for 50 isn’t going to work.

By simply increasing the recommended powder charge by 25% you will have assembled a workable proof load.
–black powder guide, George C. Nonte, Jr.

I’d suggest the same principle just think of the compressed air as your powder charge.
The guy also recommends that you tie the gun to be proofed into an old tire to keep it secure and that you stand waaaaaaaayyy back, as do I.
Or dig a deep hole stick the gun in it, put some heavy plywood over the hole then det…charge it with compressed gas.
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