Low pressure manifold?

[victorzamora]

I'm pretty sure the UTD system balances everything. I'm NOT a believer in the utd system. One thing I like about sm is the independance of the two tanks. If one reg leaks, you can feather it easily. If the tank fails, there is ZERO chance of total tank failure

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[nimoh]

the UTD Z system has an isolation manifold for their sidemount setup. From what I can tell it doesn't attach to the tank valve like a typical doubles manifold, but looks to use the LP ports from your 1st stages.

http://www.utdequipment.com/new/pdf/isoconfig.pdf
UTD Equipment Z Side-Mount System


Sounds like what the OP is asking for? I have no experience with the setup, So I'm not 100% as to how it is configured. (pretty sure it doesn't address the balancing issue, so probably best to just ignore me.)

still, this doesn't do anything to solve a free flowing first stage. All you can do is turn off the tank and hope that the problem fixes itself (you don't need a manifold for this approach) and if it doesn't fix itself, you will have to breathe through a free flowing regulator in order to use the gas in that tank.

 

[Doppler]

If the OP wants to sit down with a SM user/instructor and chat about the failings of his/her idea, I'd be happy to oblige. Skype name decodoppler.

And regardless of the failures to second of first stages, proper gas management allows a great margin of safety and exit from an overhead when diving SM. The arguments to and fro on this topic between SM and BM are spurious... in my opinion.

 

[eelnoraa]

With UTD z system, user still need to switch gas supply by switching one tank on at a time during normal operation. Otherwise, gas will always come from first stage with higher LP.Balancing LP exactly between 2 first stages is probably not possible at all.

I'm pretty sure the UTD system balances everything. I'm NOT a believer in the utd system. One thing I like about sm is the independance of the two tanks. If one reg leaks, you can feather it easily. If the tank fails, there is ZERO chance of total tank failure

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[TSandM]

There is no way to "balance" everything. If there is an IP difference, the LP manifold will preferentially draw from the higher IP reg. The Z-system requires that the diver keep one tank shut off at all times, so you have to turn tanks on and off instead of switching regulators. The ONLY advantage of the Z-system is that it permits you always to donate the regulator you are breathing. The disadvantages of the non-isolation system are that any leak anywhere in the system requires that you disconnect both tanks from the manifold block, and attach an auxiliary second stage to one of them (or carry regulators on both bottles, which kind of defeats the streamlining that sidemount is primarily known for). With the isolator, you can solve a leak by isolating and shutting down the tank connected to the offending side, and you are no better off than you would be in plain sidemount with a leaking reg.

 

[victorzamora]

You and Lynne are right. I just got my wires crossed. I knew that one of UTD's big things was not having to switch regs. Honestly, should you be diving sidemount if switching regs is THAT much of a hassle? I get the silt out conditions and not reading gauges and why manifolded doubles is better. However, the UTD system is no better in that regard.

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[MScorpa]

I constructed a setup like this with my Nomad. I used two first stages with gauges and LP commercial bailout whips. These whips connected to a manifold on my back and I had all my hoses pre-routed right where I wanted them (extremely streamlined). All I had to do was plug in the whips and I was ready to dive. The concensus on this thread is correct, the tank that has the first stage with the highest LP output pressure drains first when both tank valves are open. I would just open one valve and leave the other closed, then switch every 500 psi or so to keep the tanks evened out. It worked! The thing is; this is a recreational open water setup only!!! It works the same as if you are diving a single tank with NO REDUNDANCY. A failure of a hose after the manifold means you are SOL unless you have additional second stages attached to the tanks, at that point you might as well just scrap the whole system and breathe those regs (way easier and less crap dangling off you that can fail).

The UTD Z system can isolated failures after the manifold but you still have to open and close each tank valve every 500 psi. It works but adds extra hoses (failure points), weight (bad for travel), and is just as much task loading (if not more) as switching regs. Plus I can see it being extremely difficult trying to close that isolation valve on your back while diving dry in the confined space of a cave/wreck.

So what can you gain from a system like this? Unfortunately...not much. I've since converted back to the standard method of mounting sidemount tanks due to my increase in wreck penetration dives. In this case less is more and more is less!

Hope that helps!!

 

[scubaalblake]

OP here. Thanks for all the great feedback. I posted this one evening in Australia and Wondered whether anyone would reply.....logged on the next morning and there were loads of posts. Thanks all. I must admit I wondered about the differential IP between the tanks but when I saw the utd z-manifold system I thought it might work.....glad someone pointed out that you have to turn the tank valves on and off.....their web site certainly doesn't make that clear....and has been pointed out thats just as much task loading as swapping regs.....so not much point in that......and a long time ago I was told that LP leaks drain faster than HP due to the increased orifice size......but forgot......so thanks for pointing that out.
So two big fails for my idea.....but the discussion has been fun.
Thanks all

 

[OkByMe]

I have thought of the same thing for side mount to eliminate using 2 high pressure gauges and 2 transmitters ($350 each). I designed my config using 2 6000psi stainless steel 1/8" needle valves and thread adapter, one each to the second high pressure port on each first stage regulator. Then installing a high pressure hose disconnect on both and a short flexible HP hose across the chest. I decided to use needle valves as a precaution if the disconnects failed, the air could shut off. Also the needle valves controls the air transfer between tanks to insure I did not "ICE" the regulator being used. If test shows the needle valves are not needed, you could take them off. The female disconnects (if they don't leak) on the HP port would be needed to insure disconnection of the hose does not drain ether tank.

Pushing the tanks ahead should not cause a problem, but I"m thinking of adding a HP swivel to insure not twisting the hose. Just in case though, IF I get to the testing stage, I would carry a 19 pony slung off the belt. Don't have any of this stuff around the shop except for the hose, so I would have to spend a couple hundred to try it out.

I have not had the time to pursue this and I'm not completely sure the tanks would equalize through the high pressure port on the first stage valve body. Looking at the schematics for the Scubapro MK25, the high pressure ports are branched off the inlet before the seat. One of the issues that may be a factor, is insuring no contamination gets into the hose when it is disconnected to get lodged in the seat inlet. I guess one could find a sintered filter to install between the needle valves and disconnects or disconnects and valve body.

 

[Doppler]

I have thought of the same thing for side mount to eliminate using 2 high pressure gauges and 2 transmitters ($350 each). I designed my config using 2 6000psi stainless steel 1/8" needle valves and thread adapter, one each to the second high pressure port on each first stage regulator. Then installing a high pressure hose disconnect on both and a short flexible HP hose across the chest. I decided to use needle valves as a precaution if the disconnects failed, the air could shut off. Also the needle valves controls the air transfer between tanks to insure I did not "ICE" the regulator being used. If test shows the needle valves are not needed, you could take them off. The female disconnects (if they don't leak) on the HP port would be needed to insure disconnection of the hose does not drain ether tank.

Pushing the tanks ahead should not cause a problem, but I"m thinking of adding a HP swivel to insure not twisting the hose. Just in case though, IF I get to the testing stage, I would carry a 19 pony slung off the belt. Don't have any of this stuff around the shop except for the hose, so I would have to spend a couple hundred to try it out.

I have not had the time to pursue this and I'm not completely sure the tanks would equalize through the high pressure port on the first stage valve body. Looking at the schematics for the Scubapro MK25, the high pressure ports are branched off the inlet before the seat. One of the issues that may be a factor, is insuring no contamination gets into the hose when it is disconnected to get lodged in the seat inlet. I guess one could find a sintered filter to install between the needle valves and disconnects or disconnects and valve body.

This is a complex solution to a non-existent problem.

The whole point of SM seems to be lost on the swarms of people who are suddenly rushing towards this kit configuration like moths to a flame.

In the event of a failure, a diver following the gas management guidelines that are taught -- AS PART OF A DECENT SM PROGRAM -- does not need a crossover and certainlyy not a pony bottle slung off his/her belt.

PLEASE... those of you getting into SM, whether you are a cave diver or not, PLEASE sit down and speak to an overhead SM instructor.

Note to self: Perhaps this is the topic for my next dive show presentation...