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seems logical but I just want to double check...

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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seems logical but I just want to double check...

Unread postAuthor: pyromanic13 » Tue Aug 28, 2007 9:49 pm

imagine this: cylinder filled with water with water with an inflatable rubber bladder in the center, pressure gauge on side of cylinder. I inflate the bladder to 60 psi (bladder is pushing against the water now). will the gauge read 60 psi?

also what psi are standard "long and skinny" blow torch propane tanks set at?

-thanks
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Unread postAuthor: Novacastrian » Wed Aug 29, 2007 12:49 am

I imagine the gauge would read 60psi (although if placed at the bottom of the cylinder you would have to take into account the weight of the water)

Propane liquifies at 90psi so i would think it would be "set" at around that, maybe a little more. Hope this helps :)
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Unread postAuthor: dongfang » Wed Aug 29, 2007 2:43 am

Hi

Yes, anything flexible or movable will move around until the pressure on both of its sides is the same, or until something prevents them from moving any further. Bladders, pistons, etc...

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Soren
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Unread postAuthor: pyromanic13 » Wed Aug 29, 2007 6:58 am

thanks
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Unread postAuthor: jimmy101 » Wed Aug 29, 2007 11:43 am

pyromanic13, what you describe is a basic water well storage tank. The pressure of the water is the same as the pressure in the bladder.

Propane tanks contain a mixture of gaseous and liquid propane. As long as both phases are present the pressure in the bottle is only dependent on the temperature. (The boling point of propane is -44F)

For propane at 80F the pressure is 128 PSIG.

Code: Select all
Propane Vapor Pressure Chart, PSI
 Temp.   Pressure
   (F)        (PSI)
   –30°        6.8
   –20°      11.5
   –10°      17.5
     0°       24.5
    10°      34
    20°      42
    30°      53
    40°      65
    50°      78
    60°      93
    70°    110
    80°    128
    90°    150
  100°    177
  110°    204
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Unread postAuthor: pyromanic13 » Wed Aug 29, 2007 1:00 pm

do you guys think I should regulate? max psi for 2" sch 40 is 280 psi... plus should the pressure get too high I can turn off the propane via torch valve then dump the pressure via tee valve.

I'd rather not spend the money...regs on mcmaster are 80$
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Unread postAuthor: jimmy101 » Wed Aug 29, 2007 2:22 pm

Pyro: I don't think a regulator is required. It might help, and be a bit safer, if the orifice between the propane tank and the chamber was pretty small. That will make the pressure in the chamber rise slowly. The standard, very tiny, orifice on a benomatic torch puts out something like 10cc/second (~0.6ci/sec) into a syringe. That might be a bit slow for a chamber of a hundred or so cubic inches but it would be a good starting point. If it is too slow you could drill the orifice out a bit.
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Unread postAuthor: pyromanic13 » Wed Aug 29, 2007 4:09 pm

sorry but could you clarify... are you talking about how much propane exits the tank in one sec or how much propane exits the otrch nozzle

the torch head is cut in two...the tiny hole/flame part is at near the blowguns exit. the valve and size of the torch pipe hole is connected to the propane tank.
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