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On Nov 23, 10:47am, <MGardens@ao*.co*> wrote: > Subject: Independent vs manifolds > Dr. Ali Lawrie asks for field experience of manifolds vs two independent > cylinders. > > I dive in Lake Superior; water temps are just above freezing to about 50 F. > I, like Dr. Lawrie, could never reach a manifold isolator valve because of a > drysuit and thick underwear. A valve block in front of the diver would help, > if one exists. I don't personally dive with a manafold, but the people I know that do seem to be able to reach the manafold without too much trouble. They also leave the isolation manafold CLOSED, then at points throughout the dive they reach back and crack the valve to equalise the tanks , close and keep going. This means that if they have any failure on either system ie free flow, burst disks, O rings etc they are already in the emergency "mode" ie isolated, that way the max loss is one tank. > > Problem with 2 independent cylinders: A friend of mine nearly died of the > bends in Lake Superior some years back as a result of not opening the valve > on his second cylinder. A small but critical error! He ran out of air at > 140 during an ascent from a 190 for 20 exposure. Lots of permenant damage > resulted. Buddy was below by 20 feet or so and didn't realize the problem in > time to reach him. This is the very reason that I was tought never to breath down one tank and then switch, you have not "managed" your second supply at all. I start with one reg in my mouth, desend, switch to the other tank, now I am sure that both tanks seem to be working. Then I continue to switch at the 1/3 points throughout the dive, I always maintain enough gas in both tanks to complete the dive including deco plus a reserve. I realy don't mean to flame your friend, but he made more than a "small but critical" error. He also must not have been checking his guages to allow the first tank to get down to an out of air situation, he did not maintain a proper reserve in the first tank. I know all this can be dificult at 190 and I haven't been that far yet (160fsw so far), and won't untill all the skills needed to keep me safe are reflex actions learned at relativily shallower depths. I actually prefere Independants, With a manafold I find it hard to belive that a major failure in one system could be dealt with quickly enough at depth and narced etc to save your air supply. Just my $0.02 AUD Terry > > Every equipment configuration has its problems, I guess. > -- > Send mail for the `techdiver' mailing list to `techdiver@opal.com'. > Send subscription/archive requests to `techdiver-request@opal.com'. >-- End of excerpt from <MGardens@ao*.co*> -- Life`s ABYSS, then you dive ******************************************************************** Terry McCracken GEC ALSTHOM Information Technology Software Support Engineer Ph: 61 2 415 0509 terrym@ns*.co*.au* Fax: 61 2 417 8635
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