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On Sep 21, 11:04am, Marc Dufour wrote: > Subject: Re: Why? - Pony Gauges > ... > > Since the first stage is 'balanced' to ambient pressure by its > >diaphragm or piston, why, isn't the interstage pressure 8-12 bar *above > >ambient*? > > Have you noticed that *BIG*, *HEAVY DUTY* spring in the first stage, > merrily pushing *HARD* against the piston/diaphragm??? > > It makes sure the intermediate pressure is a good number of bars above > the ambient pressure.... Right. 8-12 bar or so, as the first mail presumed. But we're talking about this in the context of ponies, and whether or not they should be turned off or left on. When you turn on your pony at the surface, you pressurize the lp hose to the intermediate pressure of, say, 150 psia. Now turn the pony off. Presumably (no leaks), that *absolute* pressure will remain in the hose. Which means that if you go to a depth which causes ambient pressure to be greater than 150psia, water can begin to enter the system. While I have no immediate plans to hit 300fsw, a "free-flow" in the second stage would probably amount to a half-second's worth of bubbles to depressurize the LP hose, and would likely go unnoticed. Dan Masi (braving his first time on techdiver)
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