Lessons My sidemount cylinder valve spun itself completely shut during a dive

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jstotz

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Location
Michigan
# of dives
50 - 99
What happened:
I recently dove a 25-30ft coral reef and cavern area in Isabella, Puerto Rico with 2 friends. I was in sidemount. By about 20 minutes into the first dive, my right cylinder's turnwheel had managed to spin from fully opened to fully closed.

More details:
At the 20 minute mark I noticed that the longhose regulator I was breathing from was starting to feel constricted and out of air. I was about 25 ft down just inside of a small coral cavern opening. A few breaths later the regulator stopped breathing altogether. I had two friends within about 10 feet, a lot of natural light, a surface only 25 ft above me, and lots of training, so I experienced zero anxiety. I calmly switched regulators and peaked at the gauge on the right tank I had just been attempting to breath from: 0 psi. I thought, "well that's impossible." I should have been at no less than 2,000psi. Surely I would have noticed a leak that big. I played with the cylinder's turn wheel and realized it was completely shut off. I turned it all the way back on, my gas came back. I then checked my left cylinder's turn wheel. I can't recall if the left had also spun away from open at all.

I will describe the equipment configuration and environment and perhaps someone with more sidemount experience can give me their ideas about what contributed to or caused the accidental shutoff.

Configuration:
-3mm wetsuit
-left and right Thermo modular DIN valves (I brought them to PR with me)
-2 x rented aluminum 80's
- Diveright Transpac configured for sidemount with loop bungees
-the regulators if you care were Hollis DC3 first stages and 221 second stages.

Environment:

25-30ft Ocean dive in a "blue hole" surrounded by a sheer circular wall of coral that extends to within a few feet from the surface. Lots of small caverns in the coral wall + lots of waves => strong and varying rip currents dragging you in and pushing you out of these coral caverns, with the current changing direction every 3-30 seconds. It's a pretty intense, but very beautiful and rewarding area.

My Theory:
It was my first time diving sidemount with aluminum cylinders, first time in the Transpac rig, and first time experiencing any current. I THINK what might have happened is that the turn wheel was repeatedly rubbed by my tricep/armpit area of the wetsuit while I changed my arm position from in-trim-arms-forward TO reaching back for gear, or bracing inside the caverns to avoid being sucked in.

Yes, I'm positive that I started the dive with both thermo valves all the way open. That's at least 7+ revolutions to fully close.

Has anyone ever heard of this happening before?
 
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I'm positive about a lot of things lately that turn out to be not what I thought originally.

Could be an age thing.
😂

Ok, 99.9% positive. Yes, there's dementia in the family but I'm 35 years old. Leave me alone!

What were we talking about again?
 
The simplest explanation is that the tank was barely open, so a small nudge closed it.
Your theory is plasuble, but not as simple or likely.

How are the tans rotated axially? are the valve knobs up, down, out, in?
It was my first time diving sidemount with aluminum cylinders,
So were the valves on the AL cylinders standard for backmount (looking down on the cylinder, knob to the right if opening is faciing forward), or was one reversed to make it better for sidemount? That is, mirror images?
 
I’ve never heard nor seen anything like this ever happen… and I’ve been teaching Sidemount since 2013 diving it since 2010.

It is nearly impossible for friction motion to fully close a valve. The number of cycles needed to close a valve could not be achieved in any dive within gas limits of two tanks- let alone when 2000 psi remained.

The more likely explanation is that you did NOT open the valve all the way because you were confused about the direction due to the orientation of left and right- and turned the (closed) valve open a half-turn -like we used to teach - which gave you a readable pressure and breathed fine at the surface….
 
The simplest explanation is that the tank was barely open, so a small nudge closed it.
Your theory is plasuble, but not as simple or likely.

How are the tans rotated axially? are the valve knobs up, down, out, in?

So were the valves on the AL cylinders standard for backmount (looking down on the cylinder, knob to the right if opening is faciing forward), or was one reversed to make it better for sidemount? That is, mirror images?
Clarification: My previous sidemount dives(apart from my initial class) had been done with HP100 steel cylinders and mirrored modular valves.

My initial sidemount class was done with identical standard valves (for backmount) and aluminum cylinders. The bungee gets wrapped around the turn wheel itself and one of the valves gets oriented in a cumbersome manner and I recall it being a pain.

I wanted to avoid that scenario in Puerto Rico so I brought my own thermo DIN modular left and right valves with me, I had the shop there bleed down their aluminum tanks, install my mirrored valves, and reVIP.

There are two different conventions when it comes to naming left-hand and right-hand modular valves. So I'll just post this picture of the basic orientation I used. (Ignore the stage mount cylinders in the picture)

Precise Turnwheel Orientation:
I'm not sure how tight my loop bungies were rotatng the cylinders upward. Likely quite a bit since they were calibrated for heavier steel cylinders. I think at least as much rotation as is pictured below, if not more. It's possible they were fully rotated so that each turnwheel rotational axis pointed directly upward (while in trim). I think it's worth getting to the bottom of so I think I'll jump in a pool with a mirror and see exactly what was going on. I do know the backs of my cylinders were sitting way high. Not sure if that contributed.

Photo credit Steve Martin
 

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I’ve never heard nor seen anything like this ever happen… and I’ve been teaching Sidemount since 2013 diving it since 2010.

It is nearly impossible for friction motion to fully close a valve. The number of cycles needed to close a valve could not be achieved in any dive within gas limits of two tanks- let alone when 2000 psi remained.

The more likely explanation is that you did NOT open the valve all the way because you were confused about the direction due to the orientation of left and right- and turned the (closed) valve open a half-turn -like we used to teach - which gave you a readable pressure and breathed fine at the surface….
I don't do the half turn back, and I don't partially open. At the time of the dive and immediately after the dive I was absolutely positive I had them both FULLY open.

The the only reason I have the 0.1% doubt now is because the dive took place a week ago and the memory fades. I'm going to trust my intuition at that time and say I believe they were both fully open.

I'll get in the identical setup in a pool and see if I can recreate the event.
 
Color me dubious, especially after reading your other post. Have full roll offs happened in experienced SM cave divers in a cave? Sure. In open water or large pseudo overheads? Unlikely.
Mate, if you want to comment on something stupid and specific I said in another thread then feel free to comment on it in that thread. I'll either say, "yep, that was pretty stupid of me", or I'll defend it.

This tactic of making implicit arguments from authority and vague allusion to alleged past mistakes is really strange and not pragmatic. It's like when you're having an argument with your girlfriend because she thinks you made eye contact for 0.7 seconds too long at the waitress and she starts bringing up 10 unrelated things from 5 years ago.

Baby, we gotta focus on the problem at hand!
 
Mate, if you want to comment on something stupid and specific I said in another thread then feel free to comment on it in that thread. I'll either say, "yep, that was pretty stupid of me", or I'll defend it.

This tactic of making implicit arguments from authority and vague allusion to alleged past mistakes is really strange and not pragmatic. It's like when you're having an argument with your girlfriend because she thinks you made eye contact for 0.7 seconds too long at the waitress and she starts bringing up 10 unrelated things from 5 years ago.

Baby, we gotta focus on the problem at hand!
The IGNORE button remains available! Use liberally and often for trolls.
 

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