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sch40 failure

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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sch40 failure

Unread postAuthor: daxspudder » Sun Jul 06, 2008 8:44 pm

Shooting my pneumatic today for the 1000th time, a short piece of 3/4" sch40 blew up as I fired, a piece that connected the chamber to a modded sprinkler valve. It didnt fragment, just split at an angle just in front of a 2"-3/4" reducer at 80psi, which it had been fired today at least 100 times, most of them 80-100psi. Just thought I'd share, and luckily I can still use the valve, just need fittings for a new chamber.
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"<I>For dare to be peace, I have to keep at it everyday, da Man doesn't take days off so neither can I</I>" -<B>Bob Marley</B>, day before a performance, a day after being shot in the chest. "<I>If you are the big, big tree, we are the small axe, ready to cut you down!</I>" -Bob again :brave:
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Unread postAuthor: SEAKING9006 » Sun Jul 06, 2008 8:51 pm

Wow dude, that doesn't really sound right. Did you check the pipe you cut it from? It sounds like you may have gotten a stray piece of DWV in there.
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Unread postAuthor: jr » Sun Jul 06, 2008 9:02 pm

was it the threaded piece?
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Unread postAuthor: Hydra » Sun Jul 06, 2008 9:05 pm

Yipes, looks like you pressurised it too often.
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Unread postAuthor: SEAKING9006 » Sun Jul 06, 2008 9:05 pm

Hydra wrote:Yipes, looks like you pressurised it too often.

That wouldn't do it.
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Unread postAuthor: brogdenlaxmiddie » Sun Jul 06, 2008 9:11 pm

The reason that it broke is just due to it being a stress point. That has happened to me about 3 times and I got really tired of replacing it so I took a bunch of reducers and had it so that I screwed in a steel double male threaded pipe and connected the two that way and it hasn't broken since :D
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Unread postAuthor: jr » Sun Jul 06, 2008 9:13 pm

brogdenlaxmiddie wrote:The reason that it broke is just due to it being a stress point. That has happened to me about 3 times and I got really tired of replacing it so I took a bunch of reducers and had it so that I screwed in a steel double male threaded pipe and connected the two that way and it hasn't broken since :D


Thats exactly where I was headed......Steel male nipples
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Unread postAuthor: koolaidman » Sun Jul 06, 2008 9:17 pm

is it at a stress point? and also, did you leave it unpainted?
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Unread postAuthor: daxspudder » Sun Jul 06, 2008 11:12 pm

Unpainted before it was solvent-welded... I was going to build a new chamber anyway, this just gives me a good excuse... when it blew I had a 5'x2" barrel full of water and it bust as soon as I fired it, not before, but as soon as I fired it the pipe blew, it actually shot the water a good 60', and the chamber went about 3' backwards... Ill add a picture...

It wasn't the threaded piece.

If you have been on this site for more than a week and did more reading than posting, then you would know that I know nsf-pw from pure dwv, so to shoot your lame thought down, it wasnt dwv, it was 280psi rated sch40.... thats why this thread is called SCH40 FAILURE
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IMGA0668.JPG
The blown fitting. And you can see I've already begun scrapping everything usable off the chamber, like the bulk of the chamber, and the schrader valve, but unfortunately I have to dump about 8 fittings
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Unread postAuthor: jr » Sun Jul 06, 2008 11:46 pm

Dax- was the barrel suported? That kind of weight is massive!! And to hit it with that kind of pressure!!!!
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Unread postAuthor: daxspudder » Sun Jul 06, 2008 11:57 pm

yeah, the barrel sat in a mount between the two portions of the chamber. But it didnt always, so its very possible that it had been weakened in the past... good call
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Last edited by daxspudder on Sun Jul 06, 2008 11:59 pm, edited 1 time in total.
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Unread postAuthor: noob of noobs » Sun Jul 06, 2008 11:57 pm

Yeah, if you didn't have a decent barrel support that would happen. Just too much force being exerted on one small joint I guess...
Also, in your picture, it looks like your chamber has a very massive hole in it due to the open elbow. Mind explaining that?

EDIT: Whoops. Foiled again. :cry: But I still suspect the tremendous force of lobbing that much water so far could compromise a 3/4" joint.
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Unread postAuthor: MrCrowley » Mon Jul 07, 2008 12:55 am

daxspudder wrote:If you have been on this site for more than a week and did more reading than posting, then you would know that I know nsf-pw from pure dwv, so to shoot your lame thought down, it wasnt dwv, it was 280psi rated sch40.... thats why this thread is called SCH40 FAILURE

Sch40 is a thickness rating, not pressure. It can be bought either as DWV or NSF-PW. Saying 'Sch40' means almost nothing. Also it's not his fault that he hasn't caught every post by you. He's a new member and there are loads of active members posting, how he is supposed to memorise what every member is like?

IMO, it looks like a stress fracture.

Edit: It appears you've already figured that much :wink:

Yeah the mix of the water and possibly unsupported barrel and small diameter fitting coming from a large one would be enough to make it snap.
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Unread postAuthor: daxspudder » Mon Jul 07, 2008 9:24 pm

noob of noobs wrote:Yeah, if you didn't have a decent barrel support that would happen. Just too much force being exerted on one small joint I guess...
Also, in your picture, it looks like your chamber has a very massive hole in it due to the open elbow. Mind explaining that?

EDIT: Whoops. Foiled again. :cry: But I still suspect the tremendous force of lobbing that much water so far could compromise a 3/4" joint.



After it broke, and before i took the picture, I began stripping all usable parts off of it, I will reuse the portion of chamber cut off of the elbow.

@mrc I'm aware of what sch40 implies, most of that reply is just frustration at someone who Ive seen halfheartedly post whore for the last two weeks, at the rate he posts 1 sentence uselessness he'll soon surpass your post count without adding a significant amount of information/knowledge to this sites users. I definitely only intended to flame the guy :oops: but it is a valid point I didnt cover previously.

It was NSF-pw 280psi@73
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"<I>For dare to be peace, I have to keep at it everyday, da Man doesn't take days off so neither can I</I>" -<B>Bob Marley</B>, day before a performance, a day after being shot in the chest. "<I>If you are the big, big tree, we are the small axe, ready to cut you down!</I>" -Bob again :brave:
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Unread postAuthor: MrCrowley » Mon Jul 07, 2008 10:08 pm

daxspudder wrote:@mrc I'm aware of what sch40 implies, most of that reply is just frustration at someone who Ive seen halfheartedly post whore for the last two weeks, at the rate he posts 1 sentence uselessness he'll soon surpass your post count without adding a significant amount of information/knowledge to this sites users. I definitely only intended to flame the guy :oops: but it is a valid point I didnt cover previously.

It was NSF-pw 280psi@73

No worries :wink:
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