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Grenading non rated abs testing possibility.

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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Grenading non rated abs testing possibility.

Unread postAuthor: Sticky_Tape » Sat May 10, 2008 5:36 pm

I am thinking that I am going to do a grenading test for non rated abs 1.5''X2' sch40 pipe this is a possibility because I will be going to the country where shotguns are allowed the noise wouldn't be a problem.
Yes I would be however far away I have about 50' and there would also be a blast sheild over the 2' lenth of pipe. I don't know if I will do this for sure but it is possible. What pressure do you think it would fail at and if it doesn't fail should I a: throw rocks at it or b: shoot it with a pellet gun?
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Unread postAuthor: OuchProgramme » Sat May 10, 2008 5:41 pm

This topic has already been started before, by JSR.
Grenading DWV
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Re: Grenading non rated abs testing possibility.

Unread postAuthor: judgment_arms » Sat May 10, 2008 5:41 pm

Sticky_Tape wrote:...if it doesn't fail should I a: throw rocks at it or b: shoot it with a pellet gun?

C, dump the pressure.

Put a string around the collar on the quick-disconnect and when you need to release the pressure pull the string.
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Unread postAuthor: MrCrowley » Sat May 10, 2008 5:46 pm

For a blast shield I'd recommend something like cardboard as a first layer, to get the chararistics of the explosion, if it does indeed shrapnel or not.

Try and only have one hole in the chamber, and if possible over a fitting as well, for two layers. ABS has failed in combustions before, but only split as a result of cracking from fittings in the chamber. Try and reduce that problem.

Pressure, not sure. Maybe 130-180psi range.

For a backup failure option, try dropping it from a height onto something solid like a rock or concrete. Don't personally drop it, but attach a piece of string or something to pull it off.

This will simulate what happens when you drop it compared to the chamber just splitting open from pressure.

It would be good to get some failure chararistics from this test, and realistic ones at that. You don't usually throw rocks at your cannon :wink:

If it doesn't blow and you do need to drop it, the failure chararistics may be far different, I.E it may shrapnel instead of splitting.

What do you think?
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Unread postAuthor: Sticky_Tape » Sat May 10, 2008 5:46 pm

GEE I was just making a joke I wasn't actually going to shoot it with anything or hit it with anything I forgot to put in jk. Any way I know JSR put somthing in there but I might actually do this doesn't Jsr lives in the burbs I think can't do it there but I will be going to the country so I might actually do that.

MERGED:

MrCrowley wrote:For a blast shield I'd recommend something like cardboard as a first layer, to get the chararistics of the explosion, if it does indeed shrapnel or not.

Try and only have one hole in the chamber, and if possible over a fitting as well, for two layers. ABS has failed in combustions before, but only split as a result of cracking from fittings in the chamber. Try and reduce that problem.

Pressure, not sure. Maybe 130-180psi range.

For a backup failure option, try dropping it from a height onto something solid like a rock or concrete. Don't personally drop it, but attach a piece of string or something to pull it off.

This will simulate what happens when you drop it compared to the chamber just splitting open from pressure.

It would be good to get some failure chararistics from this test, and realistic ones at that. You don't usually throw rocks at your cannon :wink:

If it doesn't blow and you do need to drop it, the failure chararistics may be far different, I.E it may shrapnel instead of splitting.

What do you think?

I like that hopefully it doesn't shrapinalize.
I need to list these things to do.
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Unread postAuthor: D_Hall » Sat May 10, 2008 6:08 pm

Most effective blast shield.... a hole.

Dig a hole in the ground. Doesn't need to be very deep. 12" would probably do it. Place pipe bomb in the hole.

Done.
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Unread postAuthor: MrCrowley » Sat May 10, 2008 6:14 pm

Maybe line the hole with cardboard? It'd be interesting to know how much damage the shrapnel can do.

I've had two PVC explosions but I was only hit once and it was from a piston jamming not pressure, so it was considerably less powerful.
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Unread postAuthor: clide » Sat May 10, 2008 6:23 pm

What do you hope to accomplish with this test? I could tell you that the most probable result is that it will put a big rip in the side of the pipe and fail at a significant pressure (500+ psi assuming you are using solid core).

If you are hoping to show whether or not it is a good idea to use unrated ABS in a pneumatic then you will need a lot more then a few tests to show that with any confidence.
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Unread postAuthor: Sticky_Tape » Sat May 10, 2008 6:36 pm

I think I will dig a hole put in the pipe and cover it with the dirt I dug up that would make it safe to be 20' away and after I would dig it up to see if it split or shatered. or maybe I could dig a hole same but put those square patio blocks over it and line the hole with cardboard or corex you know the coragated plastic I have that stuff. anybody have an idea for a air line I don't think I want to use quik connects maybe hose clamps and a tube to connect to a shrader on the pipe a shrader without the core in it.
What do you hope to accomplish with this test? I could tell you that the most probable result is that it will put a big rip in the side of the pipe and fail at a significant pressure (500+ psi assuming you are using solid core).

If you are hoping to show whether or not it is a good idea to use unrated ABS in a pneumatic then you will need a lot more then a few tests to show that with any confidence.


Well if it would fail at 500+psi what is everybody worried about?
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Last edited by Sticky_Tape on Sat May 10, 2008 6:41 pm, edited 1 time in total.
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Unread postAuthor: DYI » Sat May 10, 2008 6:38 pm

Pressure, not sure. Maybe 130-180psi range.


:laughing5: The theoretical burst pressure of 1.5" SCH 40 ABS pipe is over 800 psi, under static pressure. If you can expose it to repeated high shock loads, it will be less than that. I broke an unmodified SCH 40 2" ABS pipe with a 4x oxy/propane mix, which should have been about 500 psi.

If you're trying to make it fail under static pressure though, you're going to need over 800 psi to do it reliably, so a SCUBA tank could be useful.

You won't get a proper failure if you drop it while pressurised, as it has such high impact resistance. Shooting it with a pellet gun will just make a little hole at best, and I really wouldn't be surprised if it didn't fail at all.

ABS pipe is much tougher stuff than most people give it credit for.

Here's a picture of the unmodified ABS pipe that failed under a very high shock load. The area where the pipe failed is about 10" long.

Image

Image
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Unread postAuthor: Sticky_Tape » Sat May 10, 2008 6:54 pm

Soooooooo it is actually ok to use abs pipe in a pneumatic because it bursts at 800psi I know not all but why are people so worried about non pressure rated abs in a pneumatic?
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Unread postAuthor: DYI » Sat May 10, 2008 7:25 pm

The theoretical burst pressure of 1.5" SCH 40 ABS pipe is over 800 psi


There is very little to no quality control on DWV pipe, as it is not designed for applications that ever exceed 10psi or so. People are worried about non-pressure rated plastics on pneumatic launchers because there are sometimes unnoticeable defects like microfractures that could lead to failure under pressure.

And as I said, you will need over 800 psi to generate reliable failures. Some samples of DWV solid wall ABS might fail at 150 psi, and some might be completely flawless, reaching 900 or so before they fail.

It is a bad idea to use non-pressure rated SCH 40 ABS in a pneumatic because it might fail while you're holding it, scaring the hell out of you and possibly causing a cut or bruise if you were holding the pipe when it ripped. The dangers of using non-pressure rated SCH 40 PVC pipe in a pneumatic are obviously far greater.

EDIT: fixded grammars
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Unread postAuthor: MrCrowley » Sat May 10, 2008 7:28 pm

DYI wrote:
Pressure, not sure. Maybe 130-180psi range.


:laughing5: The theoretical burst pressure of 1.5" SCH 40 ABS pipe is over 800 psi, under static pressure. If you can expose it to repeated high shock loads, it will be less than that. I broke an unmodified SCH 40 2" ABS pipe with a 4x oxy/propane mix, which should have been about 500 psi.

I was referring to when SpudBlaster15 split his chamber in his advanced combustion... as i'm typing this I just realised that we're talking about 1.5" pipe, not 3" or above.

My bad :oops:

Edit: Okay I can't find it but you know what i'm talking about. I just automatically, and idiotically, assumed in my head that this was with 4" ABS pipe, similar to the one SB15 used. I do realise that his failed mainly due to the fittings, but it still failed at low pressures.
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Last edited by MrCrowley on Sat May 10, 2008 7:42 pm, edited 1 time in total.
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Unread postAuthor: clide » Sat May 10, 2008 7:30 pm

Sticky_Tape wrote:Well if it would fail at 500+psi what is everybody worried about?


I said most likely, not always. There are several reasons I would say it is not a good idea to assume all ABS is safe for use in a pneumatic.

a) The pipe may be fine, but what about every fitting from every manufacturer? You would need an idea for what pressure they would fail.

b) Being unrated it is made to a sizing standard, but not necessarily a quality standard. I'm not sure what manufacturing defects are possible, but there are undoubtedly some that are present. Since the manufacture knows the pipes are unrated anyway they probably don't waste any money checking for or preventing defects that don't affect the pipe's dimensions. Just because the pipe will most likely burst at a relatively high pressure doesn't mean you wont get one that bursts at a low pressure.

You can safely use ABS by building a gun and pressure testing it at significantly more pressure than it's working pressure (I would say at least 2x the working pressure), but that doesn't mean that your next ABS gun will be safe for the same pressure or that someone across the country could safely build an ABS gun for that pressure.
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Unread postAuthor: jonnyboy » Fri May 30, 2008 9:51 pm

MrCrowley wrote:For a blast shield I'd recommend something like cardboard as a first layer, to get the chararistics of the explosion, if it does indeed shrapnel or not.

Try and only have one hole in the chamber, and if possible over a fitting as well, for two layers. ABS has failed in combustions before, but only split as a result of cracking from fittings in the chamber. Try and reduce that problem.

Pressure, not sure. Maybe 130-180psi range.

For a backup failure option, try dropping it from a height onto something solid like a rock or concrete. Don't personally drop it, but attach a piece of string or something to pull it off.

This will simulate what happens when you drop it compared to the chamber just splitting open from pressure.

It would be good to get some failure chararistics from this test, and realistic ones at that. You don't usually throw rocks at your cannon :wink:

If it doesn't blow and you do need to drop it, the failure chararistics may be far different, I.E it may shrapnel instead of splitting.

What do you think?

As a matter of fact before every shot I take a lighter and propane and burn the chamber to a crisp. Just to make sure it still holds up.

I would drop it off something as crowley said.
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