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At 10:44 27/06/00 , RDecker388@ao*.co* wrote: >In a message dated 6/26/00 7:42:41 PM Eastern Daylight Time, >DiverIan@pa*.ne* writes: > > > An H-valve doesn't really provides good redundancy for these (behind the > > head) failures since you can't see what's gone wrong and the 1st stages are > > only a few inches apart. If gas starts spewing out behind your head is it > > the primary 1st-stage's O-ring that has failed, or that of the secondary, >or > > the tank neck O-ring? Which knob do you reach back and turn off? With > > doubles if you're not sure then you can close off the isolator to ensure > > saving half your gas supply, but not with an H-valve. > >Ian, > > While you certainly have a point the fact remains it should take less >than 30 seconds to run through the shut off routine, probably much less than >30 seconds. Shut down the valve for the back-up, if the leak continues, open >it back up, switch second stages and shut-down the primary valve. With a >single outlet valve there is no recourse that may solve the problem. > > Does an H-valve provide a level of redundancy similar to double tanks >with an isolation manifold? Of course not. Does it provide a higher level >of redundancy than a single outlet valve? Obviously. Is the H-valve a better >choice for the single tank diver than a pony bottle? I think so - Failures >are very rare; it weighs less out of the water; it creates less swimming >resistance in the water; it provides a higher level of redundancy than a >single valve; Have any of you guys who rely on H valves for 'redundancy' ever heard a burst disk let go? Helluva scary sound. rgrds billyw -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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