Leaky Reg?

[herman]

We are missing a piece of this puzzle. This is not an IP problem, if it were, the computer would not register that unless the loss of gas was considerable, which it was not. Similarly, nothing in a second stage could cause this. The only thing that can cause a SPG/computer to drop pressure on each breath and it stay that way is a blockage of gas coming from the tank. This is the classic description of how a SPG responds when a tank valve is opened, the reg pressurized and the valve closed again. There has to be some blockage between the tank valve and the HP seat area which is where the gauge port taps into the HP gas, what goes on past that point is IP and the HP gauge will not show any proplems past the HP seat.

 

[Bubbletrubble]

The only thing that can cause a SPG/computer to drop pressure on each breath and it stay that way is a blockage of gas coming from the tank.

...or actual loss of that gas from the reg system, right?

 

[LeadTurn_SD]

Herman,

What is confusing me is that there appears to be true loss of tank pressure that does not recover.... An almost-closed valve or blocked filter would cause the SPG to "dip" with each breath or purge of the 2nd stage, but then recover, right?

It should regain pressure, not stay "dipped" (I think...).

This is "Above my pay grade" I'm afraid Since I've never seen it before (almost-closed valve, yes, but other major flow obstructions, no) I just don't know.

If the reg was recently serviced, something might have been "goofed-up" by the tech, but the MR-22 is dirt simple as diaphragm regs go, and the tech would really have to be hamfisted to mess up a rebuild on this reg..... but what assembly error would / could cause an interal obstruction in the first stage between the inlet and the HP port that would cause this symptom?

Could it be at the quick release connection, or inlet of the Atmos computer???

The more I think about, the more I'm puzzled...

To the OP, it is probably quite simple, but I not the sharpest tool in the drawer so I just can't figure it out

Best wishes.

 

[herman]

I agree, this is a good one. If we back off and think about the flow path of the gas and what the SPG/Com is telling us - there is a reduction of HP gas pressure on every breath that does not recover- then we can eliminate most of the possible problems. The reg is filling with HP gas reaching the HP chamber and out to the spg when the tank valve is opened and appears normal but the HP drops with each breath. The only way that this can happen is for the HP gas supply to be totally blocked at some point between the tank dip tube and the reg's HP chamber after the reg is charged. If the reg was simply leaking somewhere, the spg would rebound very quickly, most likely it would not drop at all. Since the tanks were swapped and the problem returned it is very unlikely that the problem is in the tank or valve which leaves us with the reg filter and pretty much nothing else.....unless. Does this reg have one of those "features" that close the reg inlet when it is not on a tank?? I forget what that are called.. That may be something to look at if it does, it would be directly in the gas flow path from the tank valve to the HP chamber.

 

[DevonDiver]

...or actual loss of that gas from the reg system, right?

I think it'd be a fair assumption to think that this volume of gas loss into the water would be very noticeable to the diver and his buddy.

 

[Bubbletrubble]

I think it'd be a fair assumption to think that this volume of gas loss into the water would be very noticeable to the diver and his buddy.

I agree, but the OP never entered the water with the reg. Please re-read his posts. He was doing his pre-dive reg checks on the deck of a boat.
It can be very loud on a boat, and the process of breathing off of a 2nd stage can be noisy in and of itself. I wouldn't be surprised if a leak, that manifested only during/slightly after an inhalation, went unnoticed.

I'd really like to pressurize the 1st stage and do an immersion test while taking a breath off of one of the 2nd stages.

 

[davetowz]

Hope the OP posts what is found to be wrong with the reg. This is an interesting issue.

 

[DevonDiver]

He was doing his pre-dive reg checks on the deck of a boat.....It can be very loud on a boat,

Jeez... WHAT boats do you dive on? Where you couldn't hear 5psi per breath hissing out of a reg?!?

 

[Bubbletrubble]

Jeez... WHAT boats do you dive on? Where you couldn't hear 5psi per breath hissing out of a reg?!?

I use "regular" dive boats -- probably similar to the boats you use.
5 psi in an AL80 ain't much. If I removed 5 psi from your tank, I doubt you'd be able to tell by looking at your analog SPG.
With a moving boat, wind whistling across and subtracting out the volume of the breath being taken, how much "extra" air is really leaking out?
Admittedly, I don't know what ambient noise conditions the OP was subjected to during his reg checks.

 

[LeadTurn_SD]

I agree, this is a good one. If we back off and think about the flow path of the gas and what the SPG/Com is telling us - there is a reduction of HP gas pressure on every breath that does not recover- then we can eliminate most of the possible problems. The reg is filling with HP gas reaching the HP chamber and out to the spg when the tank valve is opened and appears normal but the HP drops with each breath. The only way that this can happen is for the HP gas supply to be totally blocked at some point between the tank dip tube and the reg's HP chamber after the reg is charged. If the reg was simply leaking somewhere, the spg would rebound very quickly, most likely it would not drop at all. Since the tanks were swapped and the problem returned it is very unlikely that the problem is in the tank or valve which leaves us with the reg filter and pretty much nothing else.....unless. Does this reg have one of those "features" that close the reg inlet when it is not on a tank?? I forget what that are called.. That may be something to look at if it does, it would be directly in the gas flow path from the tank valve to the HP chamber.

Hi Herman,

No, no "ACD" or whatever Aqualung calls their wonky-inlet-closer-plug-thingie; the MR-22 is not terribly different (internally) from the MR-12's, or Conshelfs or Titans for that matter. Conical filter versus the flat filter the MR-12 uses; but shares the same HP poppet, same diaphragm. No big surprises inside this first stage.

Best wishes.