Hot Days Cause Regulator to "Bubble"

[talonraid]

I've noticed the last few weekends at the lake that my second stage regulators will bubble (not a full blown free flow) for a few minutes when I first get in the lake on very hot days.

More info: I have a Zeagle Envoy 1st and primary second stage. Cressi Sub alternate. They will perform as advertised for the first couple of dives with no "bubbling".
I have noticed the bubbling on the third dive of the day on very hot days. I'm in South Texas and the air temps were in the 95-100 degrees Farenheit range. When the bubbling occurs the tank was hot to the touch (as you can imagine) and registering between 3300-3500 psi when these "bubbling" incidents happen. I tried to purge each reg under water, and given them each a good under water shake to get it to stop. Also, I made sure the tank was below the water line to get it to cool. No luck.
Both times my buddy and I discussed it, formulated contingency plans, and decided to go down to the student platform at about 30 feet to experiment further. Each time the "bubbling completely stopped before we even got to the platform. Then performed flawlessly on the remainder of the dives with no recurrence after ascent to the surface or at the truck with 500-1000 psi left in the tanks.
When I've takent the reg into the pool between lake dives, I've NEVER seen this happen.
So, I have to imagine it has something to do with heat and increased pressure, either affecting the 1st stage or both 2nd stages.

Before these questions are asked: Yes, the regs have been serviced within the last six months by a reputable and authorized technician. The intermediate pressure in the shop has been right at 135 psi (I've checked it personally after the events). The lake temperature at the surface is usually around 78 degrees, low 70s on the platform, and then in the mid to high 50s at the thermocline which is typically BELOW the student platform.

Does anyone have definitive knowledge of what may be causing this?

Thanks in advance.

 

[scubafanatic]

....you might try installing the OEM 'hot-water' kit on the first stage.....

Karl

 

[redacted]

Take an IP gauge with you and check it periodically during the day to see if you can start to isolate the problem.

 

[halocline]

It sure sounds like IP creep. If both of your 2nds are leaking at the same time, it almost has to be. I take it both of these 2nds are unbalanced downstream? That would make them more susceptible to rising IP. The fact that it only happens on the third dive of the day is significant. Either the tanks are much hotter when the reg is pressurized for the third dive or something is happening to mess with the seat by continued cycling on the first two dives.

Try this next time if you haven't already, take the hot tank out of the truck, hook up the reg with the IP gauge, and let it sit for awhile, like at least 30 minutes. If the IP is still fine, carry it into shallow water with the IP gauge still connected (don't let it get wet!) and watch it rise as the tank and reg cool down in the water.

Maybe someone who knows more about diaphragm regs can offer better advice. I do know the IP will tend to rise as supply pressure drops (even though it;s balanced, I doubt if it's 100% stable) so maybe something is happening as it cools, supply pressure drops, less upstream pressure keeping the valve closed, higher IP. WAG.

I guess this must be Medina lake. Not my absolute favorite dive in the world

 

[talonraid]

It sure sounds like IP creep. If both of your 2nds are leaking at the same time, it almost has to be. I take it both of these 2nds are unbalanced downstream? That would make them more susceptible to rising IP. The fact that it only happens on the third dive of the day is significant. Either the tanks are much hotter when the reg is pressurized for the third dive or something is happening to mess with the seat by continued cycling on the first two dives.

Try this next time if you haven't already, take the hot tank out of the truck, hook up the reg with the IP gauge, and let it sit for awhile, like at least 30 minutes. If the IP is still fine, carry it into shallow water with the IP gauge still connected (don't let it get wet!) and watch it rise as the tank and reg cool down in the water.

Maybe someone who knows more about diaphragm regs can offer better advice. I do know the IP will tend to rise as supply pressure drops (even though it;s balanced, I doubt if it's 100% stable) so maybe something is happening as it cools, supply pressure drops, less upstream pressure keeping the valve closed, higher IP. WAG.

I guess this must be Medina lake. Not my absolute favorite dive in the world

What do you mean not your favorite dive in the world? Is there another location where you can find all of your favorite colors in one place? Well, as long as you like green and brown that is.....

Back to the point, the tanks are much hotter by the third dive. It's usually in the low 80s for the first dive. The tanks are cool from sitting in my garage and have not been in direct sunlight. By dive #3 it's in the 90s and they have been sitting in direct sun in the bed of my truck. I try to dive the darkest tank (blue) first, because I imagine that one get's hotter than the others, but they're all hot to the touch by noon.

I'll try your suggestion of hooking up the IP gauge next time. I'm not sure I understand completely. You say that as the temperature increases, the IP will decrease? I would think that the IP would increase with the increased heat and pressure. Is that not the case? I don't know, and I'm not challenging you, it just seems to me that the IP would increase with the temperature. I thought perhaps the tanks or 1st stage were heating up to a point that the 2nd stage diaphrams were being basically "forced" open by increased pressure.....I have absolutely no training in reg repair however.

The Zeagle Envoy is a balanced diaphram regulator in both the 1st and 2nd stage. It does say downstream valve, but I must admit I haven't the slightest idea what that downstream vlave means.

So let's say your suggestion shows IP creep...what next? Should I adjust the IP a bit lower at room temperature, or try harder to keep the tanks out of the sun?

Thanks by the way for the suggestions so far.

P.S. Mattboy, I hope to see you in Roatan in August.

 

[halocline]

"Downstream valve" in a manufacturer's description usually means unbalanced 2nd stage; they're often referred to as "classic downstream" 2nds. There's nothing wrong with them. The reason I'd be really surprised if it were balanced is that both of your 2nds start to bubble at the same time. This indicates that IP is rising, and opening both 2nds at the same time. Balanced 2nds will not open due to rising IP as quickly, because the increased downstream pressure is being matched by an increasing upstream pressure in the balance chamber. If it gets worse, you could expect your LP inflator to eventually start magically inflating your BC as well.

Anyhow, diaphragm 1sts are upstream valves. Unpressurized, they're open. There's a spring pushing on the diaphragm from the outside that does this. When you pressurize them, air pressure pushes on the inside of the diaphragm and builds up until it closes the valve. The amount of air pressure it takes to keep the valve closed is the IP. On the supply (tank) side of the valve is high pressure, and in a diaphragm reg, this air is pushing the seat closed; so when this pressure is really high, you need less IP on the other side to keep it closed. If anything lowers the pressure on the supply side, you then need more IP to keep the valve closed. That's why diaphragm regs will tend to (theoretically) have higher IP with lower tank pressure. There's a balance chamber which is designed to equalize this, but I suspect in your case something is not quite working to do that.

Or, it could simply be that you have a leaky HP seat in the 1st stage and for whatever it gets aggravated by the temperature.

 

[redacted]

I would suspect HP or LP seats that are softening in the heat. IP gauge should be able to eliminate the 1st stage if that is not the problem. The elevated tank pressure from the heat may just be an innocent bystander since your 1st stage is BD. You could leave the reg on the used tank after the 2nd dive and let it heat up during the SI to confirm.

 

[marcienko]

....you might try installing the OEM 'hot-water' kit on the first stage.....

Karl

 

[halocline]

I would suspect HP or LP seats that are softening in the heat.

I was thinking that too, but if it's both 2nds at the same time, it's almost certainly the 1st stage HP seat. The oddball thing is that it doesn't start leaking right away when he connects the reg, unless it's a slow enough leak so that he doesn't notice it until he gets in the water. Maybe what happens is that the hot air and contact from the hot tank takes a few minutes to soften up the seat which then lets a little hp air leak past. But, that air should cool down pretty quickly upon exiting the tank.

 

[talonraid]

I was thinking that too, but if it's both 2nds at the same time, it's almost certainly the 1st stage HP seat. The oddball thing is that it doesn't start leaking right away when he connects the reg, unless it's a slow enough leak so that he doesn't notice it until he gets in the water. Maybe what happens is that the hot air and contact from the hot tank takes a few minutes to soften up the seat which then lets a little hp air leak past. But, that air should cool down pretty quickly upon exiting the tank.

I will listen more closely to the 2nd stages when I connect the reg setup to the hot tanks. I didn't notice any hissing or leaking air, but it's generally noisy enough I wouldn't hear it unless specifically listening with the 2nd stage near my ear.