Regs do not always free flow when they fail

Steve_C · Oct 26, 2014

I thought I would relay an incident I observed on a boat within the last couple years. I found it interesting.

DM got ready to set the hook in 100 ft of water, second dive of the day. Tested his reg and it free flowed and would not stop. So he removed the reg and dove with the one reg that seemed to be working well. That reg stopped at 60 fsw. He thought his tank might not be on all the way but quickly discovered it was and made an emergency CESA to the surface. Other than being very winded he seemed ok but was told not to dive anymore that day.

The reg was examined but seemed to be working. Second DM dove with the REG but carrying back up air. The reg again stopped completely at 60 ft on a full tank of air but it did not matter since he had plenty of redundant air with him.

Later they took apart the faulty reg and found that it would stick in the off position.

What I take from this.

1. It is very rare but Regs can fail in the off position

2. That is not a problem IF you have a second functioning reg.

3. In my experience, some instructors/DM are more casual about routine maintenance than regular rec divers. This I do not know for sure, but my impression from the comments was that this DM had not been super conscientous about servicing.

undrwater · Oct 26, 2014

Can you get a determination what made it "stick in the off position"?

Steve_C · Oct 26, 2014

I can check. I watched while they took it apart on the boat and the part that was supposed to pop open clearly would stick sometimes in the off position. I heard the word spring so maybe that had become corroded or damaged.

redacted · Oct 26, 2014

Steve_C:
I can check. I watched while they took it apart on the boat and the part that was supposed to pop open clearly would stick sometimes in the off position. I heard the word spring so maybe that had become corroded or damaged.

It might help just to know what type regulator we are talking about. Downstream valve 2nds have springs that help close the valve so a broken spring opens the valve. Contamination interfering with the spring operation would make it harder to operate but that should not be depth dependent. While very uncommon, probably any reg can fail in a valve closed position. But I'm having a hard time thinking of such a failure that would also be depth dependent.

knotical · Oct 26, 2014

As you say, the fail-safe of delivering too much air is not 100%. I know of a couple of cases, and both were in the first stage. The part you saw that was stuck, was it in the first or second stage?

eelnoraa · Oct 27, 2014

knotical:
... The part you saw that was stuck, was it in the first or second stage?

I have the same questions too. I am no reg expert, but I have taken apart my reg, first stage is balanced piston (atomic), 2nd stage is down stream balanced (atomic).

For 2nd stage, I don't see how it would stuck close with the faulty spring. The spring only help the valve close here. I can see it stop delivery air if the level fall off or some how not able to open the valve when depress.

For the 1st stage, the spring actually help to open the HP valve and and once medium pressure is reached, the MP will close the valve. So I guess if the spring broke, it may or may not deliver air. I don't how will the reg behave. If the spring stuck firm when pushing the piston into the HP seat, then it will sure stop delivering air.

I would like to hear from reg expert too.

Pinecube · Oct 27, 2014

Is it possible that something was clogging the reg's port in the first stage?

tech_diver · Oct 27, 2014

I'm not sure what 'stuck in the off position' means. If the regulator is stuck in a closed position and won't open, that's a just a symptom and doesn't really say anything about the problem it's having. The question in my mind is why and how is it stuck.

It may not be possible now, but I'm sure a lot of us would like to know the model regulator that was involved. If a reg tech tells me that my regulator just got 'stuck closed', I'm am going to have many questions.

Even as rare as reg failures are, this is still a message that needs to be be heard by all the single-tank, deep air, bounce dive daredevils out there.

tbone1004 · Oct 27, 2014

let's think ladies and gentleman. Dive boat, dive master, not super concerned about PM's. So, what can we say about this instance? Likely the reg set in question was not subjected to proper soaks and rinses in fresh water, this leads to an accumulation of salt inside the regulator itself, salt is very sticky and nasty and if it got into the balancing mechanism, it could certainly cause the orifice to stay closed under what is still minimal pressure, but still pressure. Very likely that proper soaks and rinses in fresh water would fix this, and it just needs some TLC and a nice bath in the ultrasonic. There is a spring that pushes against the orifice and it is balanced so if the salt was causing added resistance to the pin inside the regulator, the extra 30psi of pressure at 60ft would have been enough to where the tanks IP wasn't enough to push the spring back.

The reason we say the 2nd stages fail open isn't actually due to the second stages themselves failure, which is fairly uncommon. First stage IP creep is by far the most common failure in regulators, this is why the first stage service is infinitely more important than the second stage servicing, when the IP gets above the spring pressure in the second stage, it freeflows. Basic physics. The second stages don't have high pressure parts inside them, so the seats inside the barrels are much less prone to damage than the first stages, 150psi is a lot nicer than 3500psi. When salt gets into the metal bits, it can cause all sorts of problems. In the first stages it can mean that the HP spring is caked in salt causing an increase in spring pressure which can jack the IP up a bit, this is why environmentally sealed regs are much nicer overall and worth the slight cost increase over non sealed. In the second stages it can lead to the internals sticking causing this phenomena to occur.

If the guy had soaked his regs in fresh water regularly this wouldn't have happened to him. 100% operator error.

redacted · Oct 27, 2014

tbone1004:
let's think ladies and gentleman. Dive boat, dive master, not super concerned about PM's. So, what can we say about this instance? Likely the reg set in question was not subjected to proper soaks and rinses in fresh water, this leads to an accumulation of salt inside the regulator itself, salt is very sticky and nasty and if it got into the balancing mechanism, it could certainly cause the orifice to stay closed under what is still minimal pressure, but still pressure. Very likely that proper soaks and rinses in fresh water would fix this, and it just needs some TLC and a nice bath in the ultrasonic. There is a spring that pushes against the orifice and it is balanced so if the salt was causing added resistance to the pin inside the regulator, the extra 30psi of pressure at 60ft would have been enough to where the tanks IP wasn't enough to push the spring back.

The reason we say the 2nd stages fail open isn't actually due to the second stages themselves failure, which is fairly uncommon. First stage IP creep is by far the most common failure in regulators, this is why the first stage service is infinitely more important than the second stage servicing, when the IP gets above the spring pressure in the second stage, it freeflows. Basic physics. The second stages don't have high pressure parts inside them, so the seats inside the barrels are much less prone to damage than the first stages, 150psi is a lot nicer than 3500psi. When salt gets into the metal bits, it can cause all sorts of problems. In the first stages it can mean that the HP spring is caked in salt causing an increase in spring pressure which can jack the IP up a bit, this is why environmentally sealed regs are much nicer overall and worth the slight cost increase over non sealed. In the second stages it can lead to the internals sticking causing this phenomena to occur.

If the guy had soaked his regs in fresh water regularly this wouldn't have happened to him. 100% operator error.

Compromising the "pneumatic spring" in a balanced 2nd would reduce the valve closure total spring force and result in the valve failing open.

Regs do not always free flow when they fail

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Steve_C

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undrwater

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knotical

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tbone1004

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