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Post by cstmwrks on Aug 16, 2005 14:22:56 GMT -8
OK so a small, and I do mean small amount of effort is going into making either a double or triple tank pack for use with my vintage dry suits. Anyhow I'm not up to spending big bucks on manafolds and the like so the basic rig has the tanks ( 20cuft ) located with the valves down and each one has its own first stage. Two of the first stages just feed into the third via any LP port. The middle tank is what you start with on the dive. the right tank you open for the way back and the one on the left is left for reserve.
I've lost interest in getting a "real" double hose rig off eBay so I'm making my own with a simple adapter that fits the second stage of the regulator. It will feed the double hose assembly and just stay put on ones back. It will all fit in a plastic case/back pack with just the hoses sticking out and cut outs for the valves.
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Post by Ron Hearn on Aug 16, 2005 14:34:41 GMT -8
I got to see this assembly, please post some photos if it gets off the ground.
Ron
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Post by cstmwrks on Aug 16, 2005 14:52:04 GMT -8
No problem. I kinda made a prototype for this years ago when I did "sortatecbutnotrealy" diving. I used a FFM and dived with an 80 and a 13 for bail out. I kinda think of the spare airs as a bit of a joke, though they will work to a degree. Anyhow the 13 was on my lower chest area with a hose that fed to my first stage on my 80. If the 80 went low for unforsean reasons I had another 13 cu ft on my chest. It was not a perfect answer to all issues of your primary air supply failing for things like blown O rings and such. But it worked well for having another 13 cu ft with a valve on it.
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Post by SeaRat on Aug 16, 2005 16:14:55 GMT -8
I've got somewhat the same thing, with my UDS-1 system and the Scubapro AIR-I second stage. I'm running two LP lines from the main manifold to the AIR-1, which can attach the two lines to the regulator. It is a very fine breathing rig.
The AIR-I manual talks about the potential of hooking up the second stage to two first stages. This would work well for doubles, but not get you into the triple rig. For a triple, use two first stages into an AIR-1 second stage, and a completely redundant regulator for the emergency bail-out system. It would accomplish the same thing as discussed above, without the one problem that I see with the above setup.
That problem, which may or may not be real, is that with a third used for reserve, there is a potential (with all three regulators being fed via the LP lines to each other) for air from the tanks to be less than the air in the LP line. You would have to look at each individual first stage to see whether the design could handle pressurization from the opposite side of the regulator (where the normally LP side is higher pressure than the HP side). There could be some issues here, and I'll have to go home and look at my regulator diagrams to see what I think may happen. But with piston regulators, there is a potential for reverse flow into the tanks until they reach the point where the...well, I'm not visualizing this well, and need to see the diagrams to see what would happen.
John
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Post by cstmwrks on Aug 16, 2005 17:24:39 GMT -8
John,
For what its worth I have all diaphram regulators. If your at depth and have sucked dry your first two tanks that are at 145psi + ambiant. and then open up your full tank and make your way to the surface they will always have more pressure on the tank side. Besides, even if you plunged down another 100 feet after going on reserve your only talking 45psi of possable back pressure.
Had an instructor try to convince me that one tank would back fill the empty one with this set up. Not possable. A first or second stage, one way or the other is a vacuum operated valve. a few more psi on one side and they just won't open up.
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Post by SeaRat on Aug 16, 2005 18:16:17 GMT -8
Well, you are almost correct. I have now looked at the diagrams, and if the tank pressure is under the setting for your interstage pressure, there will be some backfilling, up to the interstage pressure. At that point, like you said, the first stage will "lock up" or seal and no more air will enter. This is actually a "safety" mechanism that ensures no tank will have a vacuum, and will potentially get sea water in it when the regulator is removed on the boat or shore. But this is a pretty insignificant amount of air. We are talking about maybe 8 cubic feet of air (for three 80 cf tanks @3000 psi, two empty and one full). It will be much less for your setup, with smaller tanks at lower pressure (the math was easier with 3000 psi and 80 cubic feet of air;)). But these first stages are normally open without much tank pressure.
And I agree that this is no problem for any of the regulators. If it were, there would have been no hookah attachment for the DA Aquamaster and Royal Aquamaster. Having them hooked to tanks eliminates the potential for leaking through the yolk area.
I have thought about picking up three 45 cubic foot tanks, two with the current twin isolation manifold, and one with the regular K valve. I would mount two the normal way, and one upside down on my right side. I'd use the center post for a double hose regulator (when I desired that), and the other post of a single hose regulator. That one would be hooked to a second second stage with the LP ports, and would be my reserve cylinder. This would be the system that Cousteau set up for reserves with his triple sets in the 1950s, but with the modern isolation manifolds. I think this would be a pretty neat system.
But, your system sounds just fine too.
John
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Post by cstmwrks on Aug 16, 2005 18:33:01 GMT -8
I am correct .. as for the back filling I should point out that the guy was saying That if I tied two tanks this way and one had 3000 and the other was emptry they would equlize at 1500 psi each tank. That is not possable.
Anyhow I'm not out to make anything new and improved. Its just being done for the "look" and to function correctly.
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Post by SeaRat on Aug 16, 2005 19:43:48 GMT -8
I agree, the process would only happen until the tank pressure reached interstage pressure, and the valve would then shut. There is no potential for the tanks to "equilize" as they have a valve between them, and the highest pressure the "empty" tank would even see is interstage pressure.
My main concern above was whether having the pressures reversed would cause problems for the balanced valves. I had this weird idea that there could be a problem, and I had a problem picturing what the problem would be (yikes, that sounds like Rumsfield's logic). Anyway, I got over it when I remembered that the Royal Aquamaster was balanced, and had no problems with the hookah arrangement.
The one question I have is where are you getting the LP connector hose with two male fittings?
I mentioned the A.I.R. I above, and wanted to say that I tried the concept with the A.I.R. I on two different second stages with my twin 50s, and it works really well too. The manual states:
John
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Post by cstmwrks on Aug 17, 2005 6:01:12 GMT -8
John,
When I made the first one ( 80 / 13 ) I just machined a SS adapter that fit in the swivel end of a regulator hose and had an L.P. compatable end on it. I still have it and will have to see if I'm smart enough to post an image on this thread if you like. As for the set up with the triple tanks I'll likely use teflon H.P. hoses ( McMaster Carr ) and my own machines L.P. adaptors.
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Post by cstmwrks on Aug 17, 2005 16:36:42 GMT -8
OK so I sent some images to Linda who was willing to insert them to one of my posts. Anyhow the one showes the chest mount bailout tank and you can see a hose from it going under my arm and to a tee adapter to feed my regulator. Image #2 would be the adapter,machines from stainless steel. If you look it over and think: WHY in the world would you do some thing like that? My responce would be: I was in ALASKA, and some times you just make do with what you got!!   |
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