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Pressure Rated DWV?

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Pressure Rated DWV?

Unread postAuthor: Backyard Pneumatic » Sun Jun 23, 2013 11:24 am

Hey Guys, new member here with a materials question. I'm finally getting started on my first serious pneumatic, a 3" piston valve launcher, and was picking up some PVC when I found this stuff:
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its labeled as both dwv and pressure rated, which doesn't make sense to me, but I assume that it'll be ok to use because its the pressure rating that really matters. I just wanted to check if anyone has experience with this kind of pipe before

Also, how much of a problem is it if you drop your pvc parts? I looked on the failed cannon thread and several people attributed dropped parts to a cannon failure. I accidentally knocked a 3"X 2" bushing reducer (Sch 80) off of my work bench (about 4 feet high) onto the concrete floor. Would that part not be safe to use? I want to be completely safe, but I really don't feel like ordering another one of those

thanks for the help. I hope to have my cannon up and running by mid July
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Unread postAuthor: hawktalk » Sun Jun 23, 2013 12:32 pm

i'm no expert but most combustion cannons produce much more pressure and and sharply than pneumatic . i would look over the fitting for little dents /dings from the drop and look for cracks if you see any id cover then with some PVC cement and DUCK TAPE (hehe have to have duck tape) obviously if there server get a new one and i think if your barrel and ammo fit nice a snug then you wont need such a high pressure. when i built my first ball valve rifle i fired a pencil rapped in duck tape went through my shed panel (accidental miss fire) at only 50psi.
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Re: Pressure Rated DWV?

Unread postAuthor: dewey-1 » Sun Jun 23, 2013 2:22 pm

Backyard Pneumatic wrote: I'm finally getting started on my first serious pneumatic, a 3" piston valve launcher, and was picking up some PVC when I found this stuff:

its labeled as both dwv and pressure rated, which doesn't make sense to me, but I assume that it'll be ok to use because its the pressure rating that really matters.


3 inch SCH40 PVC pressure rated pipe is rated at 260psi @73 degrees F.
Stay with about 100psi maximum and you should be OK.
The reason for the dual rating for DWV is because if it is rated for 260psi it will also work for DWV purposes which a very low pressure.
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Unread postAuthor: jimmy101 » Wed Jun 26, 2013 3:49 pm

All pressure rated pipe is also DWV (like dewey said). It is the converse that is not true, all DWV is not pressure rated.

A typical 1x combustion gun has a working peak pressure of 50-80 PSIG. A low end pneumatic is usually limited by the compressor. A generic shop compressor is typically 100-120 PSIG. So a low end pneumatic is often higher pressure than even an advanced 1x combustion.

A 1x combustion closed chamber (or ammo jammed in the barrel) will hit a peak pressure of perhaps 100-120 PSIG (theoretical peak is IIRC 140 PSI), but that pressure last for only a fraction of a second since the hot gases quickly transfer heat to the chamber walls.

Dropping a loaded and fueled combustion is generally not a problem, unless the trigger is actuated. Dropping a pressurized pneumatic can be a problem even if the pressure is well below the rated pressure of the pipe.
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Unread postAuthor: mattyzip77 » Thu Jun 27, 2013 8:33 pm

the bushing should be fine... Just check for cracks>>>>
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