Aqualung reg problems

[Cdncoldwater]

It is just odd that within about a year we started having the counterbalance cylinder issues and diaphragm problems after so many years with no problems at all. When this started, LDS tech told me he was seeing problems with the cylinders and he wondered if Al had gotten a bad lot from a supplier, but at that point my reg was already several years old, so that seemed unlikely. Part was out of stock for months and I had to substitute with something else for a while.

It baffles me that three have gone south in the course of a year, so I guess I will take RSingler's advice and have the remaining ones replaced. The diaphragms I can see being a poor service skill issue, not that it makes me feel much better. When the first one was torn, LDS said it was so rare I needn't worry about it....it would probably never happen again. Then it did, on another reg.

Since every time I dive it means I am on a trip somewhere, and sometimes a long way from home on an expensive trip, and sometimes with no repair or parts available on the island, having gear fail in a way I cannot repair or work around is a real drag.

I am in Colorado and have primarily used a couple LDSs that are fairly close to me. I suppose I can just switch to the one I have not been using for service over the past several years. Both of those shops are real sticklers on the AL and SP rules, apparently living in fear of losing the "authorized" status if they violate, so I doubt I can get any diaphragms from them.

Annoyingly, one son's Scubapro reg has had no problems. Now I have to hear about that endlessly.

I have specifications if you need them for measurement as well. The lever should sit approximately 4mm (about 3/16) below the body if memory serves correct but I can verify.

 

[jd950]

I'm not sure what the issue is with the 'counterbalance cylinders' (we call them balance chambers) but they don't usually cause a free flow. Usually what happens is there is a little slow dribble of bubbles as the pressurized air leaks into the body of the 2nd stage. Free flows are caused by either a bad seal at the main seat in the 2nd stage or unstable intermediate pressure coming from the 1st stage. If you can be more specific about the issues with what you describe as the counterbalance cylinder, maybe we can help you figure it out more.

In each case, the problem was found when I was checking regs prior to packing for a trip. As a precaution before a trip I setup BCs and regs on a tank and check dump valves, deflator buttons, etc, and also check the regs. Over the course of a few different trips I found three second stages during those checks that would "leak" air when connected. I did not take the regs in a pool or even a tub, so perhaps the leak would have translated in to a dribble and I should not describe it as a freeflow. This occurred in two primaries and one octo, at different times and not all during the same trip prep.

If I recall correctly, the tech described it along the lines of the chamber getting etched or scratched, likely by salt deposits and that being the cause of the problem. He also speculated that some of the parts may have been made of an inappropriate material at some points and not holding up. Frankly, that did not make much sense to me but at the time my primary concern was getting the reg repaired.

In response to the suggestions about measuring the lever, etc., I can probably do that but I have neither the training, tools, nor parts to work on regs. I can do the simple stuff anyone might, but if I am in there and mess up something, I would not be able to fix it. I am reluctant to go beyond my abilities and make the situation worse.

A picture of the part I am talking about, and that was replaced is attached. I am not sure where I picked up the term cylinder for it, but I understand it is called a counter-balance chamber and I will use the correct term in the future.

 

[rsingler]

It is possible that grit or floating sand can migrate into the second stage, into the barrel and settle down in the groove between the poppet stem and the balance chamber. If there's excess lube, the grit will stick in the crack between the o-ring and the side of the balance chamber and possibly begin to scratch as the poppet cycles during breathing. It's more often the case that a grain of sand will prop open the seal between oring and balance chamber, prompting the tiny bubbles that @halocline mentioned above. A scratch sufficient to cause a permanent leak is exceedingly rare.

But at least it's a cheap fix.
One more reason to soak and then thoroughly rinse out your second stages after a dive trip.

Thanks for sharing your story!

 

[halocline]

Over the course of a few different trips I found three second stages during those checks that would "leak" air when connected. I did not take the regs in a pool or even a tub, so perhaps the leak would have translated in to a dribble and I should not describe it as a freeflow.


If I recall correctly, the tech described it along the lines of the chamber getting etched or scratched, likely by salt deposits and that being the cause of the problem.

If you heard a leak coming from the 2nd stage on land, that's far too much leaking air to have anything to do with the balance chamber unless it was cracked or the o-ring was missing. So I'm afraid that doesn't bode well for the tech's expertise. Most of the time, a 2nd stage leak that you can hear on land is because the seat/orifice seal has worn a bit and is letting air through. Those seats will wear in storage; less for balanced 2nd stages, but they will wear. Less common but still not super uncommon is bad enough IP creep to force the 2nd stage open.

 

[Centrals]

Check the IP of the first stage FIRST if there is big leak from the 2nd stage.
A simple IP gauge is dirt cheap but a essential diagnostic tool that any scuba diver should possess.
Compact IP Gauge (PSI and BAR)
Only $10.00

You do need a long nose pliers to loosen the diaphragm retainer though. Other than that there is no special tool required to remove the diaphragm. I really cannot see even an heavy handed tec can pinch two small holes on the diaphragm.

 

[jd950]

When I first had the problem, I assumed it was the seat and that would have been ok. I had no idea or expectation the chamber would be the problem or that it was not a solid explanation for the air leak. I'm finding someone new to service the regs, and I guess I will get everything checked over when I find someone, so I have a clean starting point going forward.

Probably will waste some money but I have no confidence about the true status of the regs at the moment.

 

[Centrals]

I really do not see how a scratch counter-chamber balance would cause the leak! It is sitting at the other end of the barrel from the inlet. A worn shuttle valve, yes but counter-chamber balance? What do I know?
Really appreciate an expert to explain this. Thanks in advance.

 

[halocline]

I really do not see how a scratch counter-chamber balance would cause the leak! It is sitting at the other end of the barrel from the inlet. A worn shuttle valve, yes but counter-chamber balance? What do I know?
Really appreciate an expert to explain this. Thanks in advance.

I'm not really an expert, but I can answer this question, although I don't know what you mean by shuttle valve, unless that's what you call the main seat/orifice valve in the stage.

Anyhow, if a 2nd stage balance chamber leaks, what happens is air slowly bubbles out of the balance chamber. You could have a slight, momentary drop in IP as a result, and of course that would increase, not decrease the ability of the seat to stay sealed against the orifice. This might be a little counter intuitive because we associate a drop in IP with the 2nd stage opening. But it's the valve opening that causes the IP to drop, not the other way around. Anyhow, as soon as a few bubbles escape from the balance chamber, the first stage valve would crack open a tiny smidgeon and allow IP to stabilize. So the leaky balance chamber doesn't have any symptoms at the 2nd stage other than a few slow, tiny bubbles that you could only see by submerging the 2nd stage. If you connect an IP gauge, you'd see a slow, slight drop in IP and then a bump back up, and that cycle would continue.

Not that you asked, but in case you're interested, it's the opposite with a diaphragm 1st stage balance chamber, because that chamber keeps pressure out, not in. So when there's a leak there, which is not that common but does happen from time to time, it causes IP creep as HP air leaks into the balance chamber, through the hole in the poppet, and into the IP chamber.

 

[Centrals]

The 'shuttle valve' is the only moving part of the 2nd stage. It is where the seat and the lever are situated.
The counter-chamber balance does not and should not move at all. There is never any air leak from there because it does not reach there. It all comes out from the opening of the barrel when the lever is depressed.

https://sagc-plongee.fr/wp-content/uploads/2014/08/legendsecond.pdf
Shuttle valve: No 27
Counter-balance chamber: No.30
There is a exploded diagram in P.17

But the counter-balance chamber that the OP posted is different from it.

Interesting read:
Counter Balance Cylinder?

 

[halocline]

The 'shuttle valve' is the only moving part of the 2nd stage. It is where the seat and the lever are situated.
The counter-chamber balance does not and should not move at all. There is never any air leak from there because it does not reach there. It all comes out from the opening of the barrel when the lever is depressed.

No, there are other moving parts. The lever, the spring, the diaphragm, and the exhaust valve all move in use. What aqualung calls the 'shuttle valve' is what SP calls the poppet.

The 'counter balance chamber' does not move, but there is certainly air in it; that's how it works. The air gets there through a hole in the seat and poppet (shuttle valve) and is sealed in the chamber at IP. This IP provides the air balancing by pushing against the end of the poppet.