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This is a request for anyone to post their experiences with PVC at high pressures, whether it burst or not.
I am most interested in finding the limit of schedule 40, pressure rated PVC in sizes from 1" to 4". I believe this data will be helpful to anyone building a hybrid or high pressure pneumatic from PVC.
hybrids past 2-3x are not recommended for PVC, even if it is sleeved, as it is just too weak. Your standard NSF-PW PVC pipe and fittings are rated from 150psi to 300psi, depending on what they are. That is constant pressure however, and spikes in pressure do a lot more damage. For any serious hybrid, malleable iron or better is required. Especially at 4" I would not trust PVC pipe to hold very well against a hybrid.
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You can safely use the psi rating for each pipe size as a practical limit of usage...no it's not the burst pressure which is significantly higher.
Don't even think about using sched 40 PVC in a hybrid.
I agree with Starman, if the pipe says 280 PSI on it then that is the limit. I, for one, am not going to help you make a bomb.
The problem with PVC hybrids is not necesarly the burst pressure, there is a reason that the pressure rating is below the burst pressure, its for saftey! and i think the PVC would probably degrade anyway from the extreme heat (in larger hybrids) and stress from shock.
The main problem with pressure tests in pvc pipe is that pipe varies in quality and dimensions with different companies. A small defect in one fitting can mean the difference between a successful cannon and a face full of shrapnel when high pressures are involved.
Metal pressure tests are more useful being a small dent or crack won't cause the whole thing to asplode like pvc will.
In my opinion the fatal blow to pvc hybrids came when noname's sch80 one exploded at 2x. There is no way I'd use pvc after such a low pressure failure, even if his pipe did have a defect.
Wow, I guess this is only useful data for normal combustion cannons and pneumatic cannons. I guess it's possible to blow one as low as 250 PSI or so. Wow.
Does anyone have an experience with PVC blowing out in a pneumatic cannon at a pressure that was attained by a gradual (normal) fill?
Just stay under the rating and it wont blow.
Above the rating things will get tricky as one pipe isnt the other: when a 2" sch40 pipe bursts at an X psi pressure, this does not mean that you will be safe when you use 2" sch40 up to that x pressure. The results of going above the rating will be dependent on the difference in brands or stores where you buy it, it may even differ when buying exactly the same PVC, but then from a different production batch. Also environmental things like temperature will affect it, aswell as the age of the pvc, and the way it has been stored (uv light?).
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As this has come up, I'd like to take the opportunity to reiterate my request - any takers?
I'll second that request.
I might just carry out that experiment using an HPA tank. Any suggestions on how to connect a steel pipe to the end caps. I think I would use steel pipe for the pressure hose.
Please, I actually want to know the pressure that pipe fails at. Really, I do. I will stay below the rating of the pipe, but it would be nice to know how much of a safety factor that is.
If I'm not allowed to ask what PVC fails at, that is another thing; I'll stop asking. If no one has tested PVC to failure and no one wants to, the I will.
Just thought I would check to see if the information was available before I did the experiment myself.
The thing is that failure above the rated pressure is a bit hit-and-miss. you might be lucky and have a piece of pipe that will take twice the rated pressure, or be unlucky and have one that fails just above it. Either way, the manufacturer's covered, but you won't be in case of an accident.
Good for you! I'd guess it will be slightly different for each batch of pipe, but on average double the rating. More often than not, it will go below this because of uneven stress on parts of the cannon, such as where the temperature changes, where the recoil is absorbed or even just wherever the weight rests
Just be careful that you're well protected, PVC carries a good bit of mass.
Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety. -Benjamin Franklin
More worrying than that is PVC's ability to fragment into razor sharp fragments that don't need a lot of mass behind them to damage soft tissue
Hence the cuts in my hand when Chappy blew...
The rating on the pipe doesn´t tell you how many times the dumbass clerk dropped the pipe before he sold it to you.
How he left it desintegrating in the sun for a year and a half and why he wears womens panties...
He does you know..
If you want to build a spudgun and go to the limit of PVC, ...switch to metal instead.Keeps you looking purdy and feeling great...
I do, you know...
Until you take a check valve to 10 times its rated pressure and rearrange your face a wee bit:)
Yes. I think it was MrCrowley who had a 45* elbow blow up for no apparent reason. There have been various other failures here and there, but most of them can be attributed to recoil stresses on barrel-to-chamber fittings. This is the only case I can think of where it wasn't the cause.
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