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John, The freeflow rate is a function of depth, but not as much as you would think. 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. By contrast, your rate of consumption of gas due to breathing on open circuit is 11x higher than at the surface. If you want to see how long a given amount of gas would last in a worst case free flow, just punch the purge button and measure the time it takes to go through say 300 PSI (~20 bar) at the surface. You can then figure out how long it would take to freeflow that amount at any depth. My Scubapro G500 will purge 500PSI from an 80CF tank in ~15 sec. Based on this I'd say that I'd lose 2000 PSI from the same tank in 30 seconds at 330 ft. Your 12litre twins are about double the capacity of a single 80CF tank, so I'd estimate that you'd lose around 1000PSI (68 bar) in 30 seconds at 330 ft from a full up purge. About the only way you could lose more than this would be to have a LP hose break in two. Comments anyone? Later, Don W. (Someone said "the difference between theory and reality is that in theory they are the same") Deep-gasdiver@uk*.ne* wrote: > > How long typically would it take to lose air from a freeflow at depth - say > 60m, tank size 12litre (twins) ? > > Im just interested to know how much time I have got to shutdown a tank, I was > told that a full 15 Litre would empty within 30 seconds at depth. How much > effect does depth have on the rate of loss, is it multiplied by each atmosphere > of depth ie, if I similulate a free flow at the surface, do I then divide the > time by the number of atmospheres ? > > I may have put this question over wrong but Im just interested in what the time > factor would be to losing all my gas in a real situation, I can then judge how > good my shutdown procedures are > > Thanks > > > > > > What's the DIR on pressure gauges one or one on each 1stage for the > > > bottom mix ? > > > > One pg, on left post. > > > > > I know most people will say one but if this is the case ? How i guess > > > from which tank > > > im loosing the air ( in case of rapid air loss ) after the > > > isolation or > > > do i follow the rule the needle doesn't drop > > > that means the leak in on the other tank ? > > > > You've worked the answer out yourself. > > Of course, if you know where the leak is (e.g. freeflowing 2nd stage), you > > can > > shut the post down directly. > > > > > What's the procedure during > > > that crucial moments do i breath from > > > the leaking tank ( if that's possible ) till runs out of air and then > > > switch to the other ? > > > > If you've done your gas planning properly, you shouldn't need to do this. > > Switch to the working tank, and abort the dive. > > > > > Or do i just isolate and > > > take off the gear for a check out from the behind ? > > > > This should not be necessary. Once you've isolated, you have enough gas > > to abort irrespective of where the leak is. If your reg stops delivering > > gas, > > swap regs. If you've really screwed up and don't know what you're doing, > > your buddy can look for the leak and shut it down. If you still can't sort > > it out, > > your buddy has enough gas to get you out. Plenty of options before you start > > with kit removal. > > > > John > > ps: straight question + no attitude = straight answer. > > -- > > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > > > > ---------------------------------------------------------- > This message was sent using http://uk2.net > UK's FREE Domains, FREE Dialup, FREE Webdesign, FREE email > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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