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PVC Burst Pressures

Posted: Fri Aug 03, 2007 12:33 pm
by noname
This topic has beeen debated for quite some time, so I'll try to help settle it.
According to most people, the burst pressure is around 3 times the pressure rating.
So they use it at 100 psi instead of several hundred.
Why?
Because this is air pressure, not water pressure.
So, technically, PVC pipe isn't pressure rated; for air.

Confusing?

Just a bit. I plan on getting a bunch of end caps of various sizes (6 end caps for each size, 1/2"-2"), solvent welding them to short sections of pipe, connecting a long pressure hose, hooking up my shock pump, and pumping until it explodes. I will frag the Sch 40 sizes of 1/2" and 3/4" sometime soon, but I have around $10 (where's all my cash go?), so I won't be able to afford the rest.
If you are unfamiliar, a 2" end cap at Ace Hardware is nearly $2 around here, which is why I won't be doing larger diameters until later.
I may or may not test Sch 80 pipe and fittings, although I do have access to them, sizes 1/2" - 4."

Posted: Fri Aug 03, 2007 12:38 pm
by mopherman
i dont think you will be able to burst 1/2 inch with a shock pump. the rating on my pipe is like 700 psi. If I were you, I would use co2 and sowlycank up the pressure.

Posted: Fri Aug 03, 2007 12:40 pm
by noname
Not to sound rude/mean, but damn, did you read the first section of my post? Doesn't sound like you did. :wink:
I've had 3/4" Sch 40 (rated to 480 psi) explode on me at 140, with nothing wrong with the pipe.

Posted: Fri Aug 03, 2007 1:04 pm
by Gepard
A rating of a pipe has nothing to do with what's in it. A pipe rated at 16bar is for any material at a certain temperature. That said the use of pressuried air in these pipes is not recommended - but the is still a rating.

Wtf your going on about in your second post I don't know - but I agree with mopherman you need to be able to produce pressures in excess of the ratings if your planning on testing it.

Michael

Posted: Fri Aug 03, 2007 1:09 pm
by spanerman
noname....my mom just told me that ''it doesnt matter what exerts the pressure'' and she hasnt even got an o level in science....and you know what shes correct 16bar of water exerts the same force on the pipe as 16 bar of air, the burst caractaristics however are different...but thats not what your testing....

Posted: Fri Aug 03, 2007 2:09 pm
by noname
Gepard wrote: Wtf your going on about in your second post I don't know - but I agree with mopherman you need to be able to produce pressures in excess of the ratings if your planning on testing it.
Not true, or people would have made 6-8x hybrids out of Sch 40 PVC. Ever wonder why pipe and fittings rated to 400 psi have exploded at a mere 200? Stating that I've had 480 psi rated pipe explode at 140 psi is a prime case of this statement.
I've put over 600 psi WATER pressure in PVC; did it blow? No. But when the same stuff blows at 140 psi AIR, you still think there's absolutely nothing different between the two?

Basically, I can test pipe explosion pressure if I can explode it. WHICH I CAN, even if the explosion pressure doesn't exceed the pressure rating (which it usually doesn't).

Posted: Fri Aug 03, 2007 2:13 pm
by mopherman
noname wrote: I've had 3/4" Sch 40 (rated to 480 psi) explode on me at 140, with nothing wrong with the pipe.

I have to dissagree with you on that one. There must have been somthing wrong with that pipe for it to blow at that low pressure. There are members on this site that have used that pipe at more than 200 psi. btw, how did the pipe explosion go? anyone hurt?

Posted: Fri Aug 03, 2007 2:16 pm
by spanerman
how did you know your pipe wasnt defective? there may of been an internal defect in your pipe...''people would have made 6-8x hybrids out of Sch 40 PVC.'' yes but that is a pressure spike which is different to the pressure rating the pvc is subjected to a huge flamefront at those pressures.....and the temperature would also affect the pressure rating...

Posted: Fri Aug 03, 2007 2:28 pm
by SpudBlaster15
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Posted: Fri Aug 03, 2007 2:30 pm
by noname
I can tell when pipe is defective, as I am not an idiot. You may beg to differ, but this was in regular 80 degree weather, under no abnormal conditions, in pressure that the pipe should have held fine.
Honestly, do you people really think that PVC with a wall less than 1/8" thick will hold 400+ psi? There's a reason we don't go over 125 psi, and that's because the pipe will frag out all over.
Mopherman, my friend got a piece about an inch into his leg.
I was standing about 10 feet away, because I thought something like that would happen. I told him to pump it up to maximum 85 psi. Did he listen? Of course not.

Posted: Fri Aug 03, 2007 2:37 pm
by mopherman
noname wrote:I can tell when pipe is defective, as I am not an idiot. You may beg to differ, but this was in regular 80 degree weather, under no abnormal conditions, in pressure that the pipe should have held fine.
Honestly, do you people really think that PVC with a wall less than 1/8" thick will hold 400+ psi? There's a reason we don't go over 125 psi, and that's because the pipe will frag out all over.
Mopherman, my friend got a piece about an inch into his leg.
I was standing about 10 feet away, because I thought something like that would happen. I told him to pump it up to maximum 85 psi. Did he listen? Of course not.
nobodys calling you an idiot. what people are saying is that it can be extremly dificult to detect flaws in pipe. As far as I can tell, there have been no other occurances of pipe failiers in this ize pipe at this pressure.
Sorry dude but i say it was just bad luck.
edit: did you get the peice out of your buddys leg?
edit edit: spelling

Posted: Fri Aug 03, 2007 2:43 pm
by noname
We got it out, though probably not the right way. Just kind of grabbed it and pulled it out, slapped a bandaid on his leg, not a big deal. Luckily for him, most of it was sticking out, and it didn't go through anything important, just some skin and a couple little veins.

I know you guys aren't going to believe that.^

Posted: Fri Aug 03, 2007 2:43 pm
by SpudBlaster15
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Posted: Fri Aug 03, 2007 2:46 pm
by sandman
noname wrote:I can tell when pipe is defective, as I am not an idiot. You may beg to differ, but this was in regular 80 degree weather, under no abnormal conditions, in pressure that the pipe should have held fine.
yes, u may have had the pipe in the right conditions, but you just cant know how everyone before you handled the pipe and if they damaged it

Posted: Fri Aug 03, 2007 2:48 pm
by noname
I didn't see your first post, so I didn't reply to the 600 psi with water thing. My friend's dad is a mechanical engineer. They have the compressors capable of doing that. I asked him, and he said it was fine if I came over and saw him on a day off. He has the clearance to get him into the building whenever he wants, so we went over to the company building and tried it out.
On the note of his job, hopefully sometime this year I'll be able to go see a methane pipe explosion! There's underground pipes that hold around 900 psi in them, and when they burst, the methane gas flows out so fast it actually creates a solid chunk of methane, suspended in midair(midmethane :lol: ). Should be cool.