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Quick disconnect fittings

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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Unread postAuthor: FighterAce » Sat Oct 09, 2010 5:08 am

D_Hall wrote:
FighterAce wrote:Witch quick disconnect can act like a schrader valve?
Umm.... None. Schrader valves act like schrader valves.

I meant witch ones have a check valve built in...

BeaverRat wrote:I simply stated that if you are at pressures above say 300 PSI, where it is nearly impossible to remove a QD female from a QD male, you must first drain the line pressure. Since the check valve is forced open when the male is in the female socket, draining the line before disconnecting will also drain the chamber. Where if there was a true stand alone check valve, the pressure couldn't leave the chamber, even if there was a male QD in the female socket. I stated (very messily) that an alternative to buying a check valve, would be to put a ball valve behind the female (or male) QD on the cannon, and a line drain somewhere else.

Exactly what I was thinking... you cant vent it if its still connected

I just cant afford to have ball valve handles anywhere... so I need to build a check valve but I'm not sure what design I should use.

I have a check valve on my pump that has a piston, on witch is a rubber O ring that seals against a 6mm sealing face with a 3mm hole in the middle to let air past.
It heats up a lot by the time I hit 40 bar. But then I can disconnect the pump and theres no more pressure acting on the check valve.
If I use a similar check valve for the QC, would the heat be a problem?
I'll be depending a lot on that check valve to keep the air in and I dont want the rubber O ring melting, deforming or something.
Would it be better if I used a solid circle of rubber and a spring to push it against the sealing face instead of the piston?
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Unread postAuthor: D_Hall » Sat Oct 09, 2010 10:32 am

Minor nitpick here, but...

While I'm sure they exist, I've never actually seen a QD with a check valve. A check valve is a valve that only allows for unidirectional flow. The valves seen in the low cost pneumatic world (ie, what most folks around here have experience with) are NOT check valves. You could hook them up backwards and the system would still play. What they are is leak prevention valves which are a very different beast.

Which I believe brings us to what the OP meant to ask when he was asking about QDs that "act like Schrader valves." What he should be asking/looking for is "low loss" or "minimal loss" QDs.
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