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Jim Cobb wrote: > John- > > On 3/28/98 2:19 PM John Chluski wrote: > > >Jim, > > > >I confess I know little about the engineering issues on much of the > >equipment I dive compared to many on these lists. I suspect, however, that > >ball joints are not used in isolators for the same reason they are not used > >in tank valves. Why I do not know. Ball joints sound like a good idea, but > >I know they are not recommended for use in O2 blending systems, probably due > >to the very rapid acceleration of gas they could cause. > > A ball valve is one which can open or close completely in 1/4 turn. They > are not usually used in high pressure fluid/gas applications and they > offer limited flow rate control. I used the ball valve in my example > because if the goal is to shut off the isolator in as short a time as > possible, that would be the valve to use. But it would have to be a real > catastrophic failure for the time factor to be an issue, as far as I can > see. > > I like to KISS, In my checklist the isolator is OPEN, not "sort of open", > "partially open" or "open-closed-reopend". I run my hand across the > manifold and go OPEN, OPEN, OPEN and then on to the other items. KISS. I > don't think the evidence supports the need for "isolator paranoia". To me > the 1/2-1 system invites clusters. > > But, to each his own! > > >I have not heard of a diver citing confusion as a problem on which way to > >turn the isolator when a shutdown was necessary. I have heard from one > >diver cite two occassions when +ACo-he+ACo- believed that the 1/2-2 turn > >approach > >saved his life. Can we take this to the bank, probably not. But since the > >number of incidences concerning the alternative number zero from everything > >that I have read, I would prefer to dive the same config as other teammates > >for the sake of uniformity. > > > >The issue of 1/2-2 turns or full open in my opinion is not an issue to > >invoke rule +ACM-1. Diving with someone keeping it closed would be on the > >other > >hand. > > Yes the issue is a typical techdiver tempest-in-a-teapot topic, but fun > to discuss, none the less. Esp. if it brings out the independent double > crowd. > > >We do get poor vis on occassion down here, but usually on the shallower > >wrecks and reefs in which case I'm usually in a single 80. We had less than > >10' in Puss Lagoon last week in the Keys. On the other hand many of our > >wrecks do not share the same historical significance as those up in your > >neck of the woods. I will be working out of Cape Hatteras this summer for 6 > >weeks and hope to enjoy some of those good sites, some of which I hear have > >less than great vis. > > > >Do you do any diving with Mike Hillier and the Miss Lindsey? > > Hey, I've been in pus lagoon before, great place to practice stuff. Yes, > The wonderfully rustic Miss Lindsey is my main ride, been out with Mike > on numerous occasions, he's a good man. I go down to Hatteras too, will > be down there for a week in May. Maybe I will see you around here or down > there. > > Jim > > ------------------------------------------------------------------- > Learn About Trimix At http://www.cisatlantic.com/trimix/trimix.html > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. Jim Just a thought but it really wouldn't be difficult with many isolator assemblies to pack the valve stem so that it would only open say 2 or 3 (or whatever) turns. That way the valve could be "fully open" by feel but would be much faster to shut down. One would obviously need to make sure that in the full open position the gas flow would be adequate - say a little over half the requirement for a diver working hard since the diver. Have been kicking this idea around for a while. Any comments? Tony Phillips -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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