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Scott, Actually, someone else asked this question in a private email and I should have copied my reply back to the list. The reason that the flow rate in my example is about doubled at 330 feet is that the intermediate pressure is doubled making the gas twice as dense. It is flowing through the same restriction with about the same relative pressure so the "volume" flow rate is about the same. The tricky part is that the volume flow at 330 ft has twice as many gas molecules due to the increased density. Art Greenberg made a good point that the flow may be limited by the first stage being wide open, which would cause less gas to flow than what I calculated. Also, I haven't experienced any freeflows that were as bad as a fully depressed purge button except when the shop had just done the annual on my G500 and put it back together wrong. It breathed normally until I punched the purge button after a reg switch and then it locked up in full purge mode and nothing would make it quit. Don W. ScottBonis@ao*.co* wrote: > > Hi Don, > > I really appreciate your putting out the analysis of how long it might take > to empty a tank due to a free flow at depth and requesting comments. There > is indeed a part of the problem for which I'd appreciate some further words. > > You said << Your 1st stage regulator keeps the intermediate pressure to > your > 2nd stage at ~150 PSI above the surrounding pressure and the freeflow > rate is a function of the intermediate pressure. > > For example if you are at 330 ft (~100M), the pressure increase from the > surface was 147PSI (10 bar) and the intermediate pressure in your hose > is about 150+147 = 297 PSI or roughly double. At this depth, you would > lose gas to a freeflow approximately twice as fast as at the surface. >> > > I certainly agree that the intermediate pressure for most regulators is > around 140 psi above ambient, but (and I may be showing my own ignorance > here,) it is not clear to me why the rate of the freeflow is a (directly > proportional?) function of the [intermediate pressure + hydrostatic pressure > at depth] as you have asserted in your analysis. > > I may be just missing something very simple, so I'd appreciate your > elaborating on where this relationship comes from. It is just not clear to > me how to get it. > > Thanks a bunch for your help. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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