UDT sidemount manifold question.

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Mitchell Teeters

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A good friend of mine took his brand spanning new UDT setup out with me last weekend. We dove it and we noticed that his SPGs were off by about 1100psi. I think that there is something wrong with one of the SPGs. What say the gurus?


Sent from my iPad so please excuse the brevity and typos. 8^)
 
Are both first stages putting out identical Intermediate Pressure? Are they the same model first stage? If not one first stage could be opening earlier and longer than the other and draining that tank faster. But thats just a guess from what I found when I was researching that setup. Im sure some of the UTD Folks have a much clearer troubleshooting guide.
 
I'm failing to see what the spgs (hp) have to do with the manifold (lp)?

Try this. Without anything plugged in, turn on the cylinders and note the pressures. Now depressurise the first stages, swap the spgs, turn on and note the pressures. Then you will have your answer about faulty spg.
 
I am assuming that this 1100 psi difference was noted during the dive after the tanks were used. I am also assuming that the SPGs both seem to be reading normally at the start of the dive both reading full tanks.

This is the Z-Isolatable Manifold http://youtu.be/GeTewlaZsgc right?

The SPG is monitoring the tank pressure HP but without a leak the LP Manifold may not be draining the tanks equally so each breath used more gas from one tank than the other since the UTD manifold is fed by both first stages.
 
Ah. User error the case here. The system is being used incorrectly

I don't know how you are saying that but ok. The manifold is not being used in isolation mode. Everything matches on the system, identical regs. Even if they were mismatched, the concept of transfilling still applies. I think there is an Issue with one of the SPGs.


Sent from my iPad so please excuse the brevity and typos. 8^)
 
there's no issue with one of the SPG's. You can't leave both tanks on while you are breathing, one has to be turned off, which is the main problem with that system. If the IP is not identical, which is essentially impossible, one of the bottles has to be turned off, otherwise the manifold will pull from whichever regulator offers least resistance. It will pull a little from the other side due to the venturi effect inside the manifold/hoses, but it will always pull from that easier side. If you swap the first stages to the other tanks I bet it will read the same pressures. 100% Operator Error
 
As @tbone1004 says, with the manifold you can't just open both valves and go. You still need to switch gas sources as your dive progresses by shutting down one side and opening the other. Typical practice is to breathe the left side down 500PSI (say to 2500 if using an AL80), then switch to the right and breathe it down 1000PSI (i.e. down to 2000) then leap-frog from one side to the other in 1000PSI increments.

If you keep both sides open, the LP system will favor the side with the lower first-stage IP. As you observed, this causes very lopsided gas draw from the tanks.

An example of buying gear without the training. There's little excuse for not knowing this basic info, since AG has made numerous free YouTube videos explaining the Z System and its proper use.
 
Last edited:
Ok I think I see the issue I believe. Since we are talking IP there will need to be a balance struck between the two regs so that they give gas as equally a as possible.


Sent from my iPad so please excuse the brevity and typos. 8^)

---------- Post added December 15th, 2014 at 11:16 AM ----------

there's no issue with one of the SPG's. You can't leave both tanks on while you are breathing, one has to be turned off, which is the main problem with that system. If the IP is not identical, which is essentially impossible, one of the bottles has to be turned off, otherwise the manifold will pull from whichever regulator offers least resistance. It will pull a little from the other side due to the venturi effect inside the manifold/hoses, but it will always pull from that easier side. If you swap the first stages to the other tanks I bet it will read the same pressures. 100% Operator Error

So I guess the UDT video assumes something or it is somewhat limited? Watching the video I didn't see any mention of tank management. I guess we are lucky he didn't DIE.


Sent from my iPad so please excuse the brevity and typos. 8^)
 
Um....yes, so the manifold was used without alternatively shutting down the tanks? In manifolded tanks the switch must be made just like conventional SM and ID BM. If he hasn't had any training or mentoring in SM or specifically UTD SM, have him contact me and I can give him some pointers.


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