1st stage fail into BC?

[Diver0001]

DA Aquamaster once bubbled...
Umm...No. The base of the Schraeder valve lives on the pressurized side of things in an inflator and you have to press the inflator button to open the valve. (essentially the same as pressing the little valve stem in your car tire but with a large button attached.) If it were reversed the inflator button would have to be sealed against the IP as well and would be much harder to press.

In a balanced inflator, the valve stem is o-ring sealed at both ends in a chamber at IP and air is allowed to pass from the IP pressue chamber to the BC side when the inflator button is pressed. The valve it held closed by a return spring. Failure can occur in this situation if the return spring is lost and the inflator button is then pressed as there will be no pressure to return the valve to the closed position. But again, this has nothing to do with failing and inflating due to higher than normal IP.

hmmm..... gotta picture of that? I thought you were talking about the schader valve in the hose. From your description there must be one in the inflator too. Didn't actually know that. Thanks.

R..

 

[neil]

Diver0001,
Of course you are correct, it's the INFLATOR valve that would have to be overcome by pressure, not the one in the hose. That one is open when clipped on.
Not all inflators have Scraeders in them, but even other designs are unlikely to be forced open by pressure.
Neil

 

[CincyBengalsFan]

Diver0001 once bubbled...



hmmm..... gotta picture of that? I thought you were talking about the schader valve in the hose. From your description there must be one in the inflator too. Didn't actually know that. Thanks.

R..

Not all BC's by any means use the shcrader valve in the inflater/deflator assembly. For example, TUSA uses a different type of valve in theirs. I'm about 90% sure it's called a Pilot Vavle but will have to look that one up.

 

[DA Aquamaster]

The Tusa inflator is balanced and is basically a pilot valve where the incoming air enters in the middle and presses more or less equally on the poppet and balance side of the valve until the inflator button is pressed to over come some slight spring pressure and unseat the poppet to allow air to flow into the BC.

In general balanced inflators are very nice to use and allow you to bleed very minute amounts of air into the BC. Unbalanced schraeder valve type inflators are simple and cheaper to produce but tend to offer less control when it comes to making very small adjustments. They tend to be "on" or "off" with much less in bewteen than a balanced inflator.

But again balanced pilot valve type inflators are biased slightly toward the balance side of the valve so that excessive IP will close the valve tighter. This is exactly the opposite from a pilot valve second stage which is normally biased slightly toward the poppet side so that it will open and freeflow with excessive IP like a conventional downstream designed regulator.

 

[nyresq]

the newer poseidon first stages have a OPR valve built into the first stage because a jetstream is an upstream design that if the IP gets to high it will lock it tighter than a frogs butt. if you have a jetstream octo, thats will lock up also, so the pressure has to go some where, so thats why the firsts have a built in OPR valve. BUUUUUT if you put a jetstream second stage on a different first stage with no downstream second for an octo that will blow something if the IP leaks. Normally one of the inflator hoses will bow out and then you have a really bad situation if your not diving with two regs....
If the guy was using a independant fill system for his drysuit (argon) then the first stage should have a OPR valve in one of the LP ports, otherwise your asking for trouble... for $20 its not worth the hassle of a blown hose or runaway ascent.