1st stage of regulator failed in close position - new diver freaking out a bit :)

[Bob DBF]

Of course my tanks have always been on and a quick look in my mirror can confirm that. It's interesting earlier in this thread we had a debate on whether the "visual" bouncing SPG needle check was reliable or not, but some would question an $8 knob that leaves no doubt if the valve is ON or OFF or even partially closed.

I have a Vindicator valve on my boat tank (tanks are refilled on board) for the DM, as I have never had the problem without help.

There are two problems with the bouncing SPG, the first is the training for 1/4 turn, which is part of the "train by catchphrase". The valve is turned back so the valve is not backseated to prevent damage, this only takes a small movement. With old valves a 1/4 turn was OK because it took more turns to open them than the valves I have run across lately, which may not be closed enough, at 1/4 turn, to show any indication until diving. The second problem is that one breath may not show the issue. I was taught to use three fast deep breaths to max the flow so the SPG might be an indicator, at this point you would have to troubleshoot at depth if there were no indication, which we were trained to do. By not understanding the reason for the procedure, and what can happen even if it all tests right, the diver is left with a mystery after an incident, assuming they don't panic.



Bob

 

[2airishuman]

I've taken apart a lot of valves of various eras and have never encountered one that I thought could jam or be damaged by being opened, with reasonable force, all the way. Not sure what the reason for the 1/4 turn thing ever was.

Time will tell whether the Vindicator knobs are a universally good thing. I don't think they would help me. I wouldn't want to encourage any diver to rely upon a mechanism that isn't in widespread use. I am concerned that the product doesn't have any shape or pattern and therefore depends upon the ability to distinguish colors to work, which ability tends to deteriorate at depth, and is weak in some individuals to begin with.

 

[archer1960]

I've taken apart a lot of valves of various eras and have never encountered one that I thought could jam or be damaged by being opened, with reasonable force, all the way. Not sure what the reason for the 1/4 turn thing ever was.

...

Depending on the construction details, temperature changes and the resulting differential expansion of various parts, can cause a valve that is opened against its back seat to be very difficult to close. Of course the same thing can happen in the closed position, but those changes aren't as critical. Closing a valve 1/4 turn after fully opening it is standard practice in high-temperature fluid systems (think steam heating, etc), or you may not be able to budge it after the system heats up.

 

[Diving Dubai]

I haven't looked at the drawings, but would it be possible for a piece of a broken shutter or spring to block the path that the air needs to flow?

For a spring failure, No. the spring is to close the shutter after you remove teh 1st stage. If the shutter sits proud of the O ring, so if the shutter cant be pushed back, the O ring won't seal and you'll get a leak. It really is a very clever design if it isn't 100% you get a gas leak. It cant fail in a partial way either

 

[archer1960]

For a spring failure, No. the spring is to close the shutter after you remove teh 1st stage. If the shutter sits proud of the O ring, so if the shutter cant be pushed back, the O ring won't seal and you'll get a leak. It really is a very clever design if it isn't 100% you get a gas leak. It cant fail in a partial way either

I can't get the drawing to download, so can't check on this stuff myself, but my theory was that if a small piece of the shutter broke off, it might end up blocking the air flow path, held in place by air pressure until something changed enough to knock it loose. However, it sounds like you're saying that if the shutter physically broke, you'd get an obvious air leak.

 

[Diving Dubai]

I can't get the drawing to download, so can't check on this stuff myself, but my theory was that if a small piece of the shutter broke off, it might end up blocking the air flow path, held in place by air pressure until something changed enough to knock it loose. However, it sounds like you're saying that if the shutter physically broke, you'd get an obvious air leak.

View media item 201995
Here's a cutaway. What do you think?

It's not clear, but the shutter (the part supported by the spring) has a sealing face on the underside. If it only opens part way the gas goes around it and you get a leak.

There is an exploded drawing somewhere I'll have a look

The manual is here

 

[archer1960]

View media item 201995
Here's a cutaway. What do you think?

There is an exploded drawing somewhere I'll have a look

The manual is here

Yeah, that's the manual I've been trying and failing to download; I'll try later tonight. From that detail drawing you posted, it's hard to see how a single piece of anything could block the air flow, but I would want to see the surrounding pieces before making a conclusion.

 

[Texas Torpedo]

I thought first stages were designed to fail open. Am I wrong?

All but mine, apparently.. I learned the hard way that Poseidon Xstreme deep 1st stages can fail shut... Mine slammed the door on me at 45 FSW with about 1300 PSI left in the tank. I went for the second reg bungeed to my neck and nodda... Looked at SPG and was like WTH? "Buddy" was about 20' away chasing after Eagle Rays. This was the 4th dive of the day and I'd racked up a few minutes of deco so I decided to make a run for my buddy rather than the surface... I was never really worried but it was definitely surprising, and I probably would have been much more freaked out if I were a new diver at a greater depth.

 

[stuartv]

... you're just spouting an ill informed opinion

I note that I have not espoused any opinion on it whatsoever. I have been asking questions, seeking understanding. The post you quoted was me re-stating what I understood someone else to have told me in order to confirm I had understood them correctly.

Your several posts have made it occur to me that history is littered with failures of designs that were reviewed by numerous "experts" and deemed foolproof - because none of them could think of a way that it could fail.

 

[Diving Dubai]

@stuartv I look forward to your opinion of the way the AL ACD would fail causing the incident described by the OP. Place enlighten us all because it's clear you refuse to believe any of us who actually have this equipment or who have studied it.

I took great interest in the first thread about it, because I have 3 ACD reg sets, if there were an obvious design fault they would have been changed for a different brand right away. As well as looking at the drawings and reading opinions from others far more experienced than I, a very well respected guy in charge of the workshop here has taken me through the workings in detail on the bench.