Complete first stage failure?

[Rick Murchison]

It would be faster and better to ascend to the surface, than to try unscrewing the first stage and breathing out of a tank. Honestly, if you have the presence of mind and ability to take off your BC and tank, unscrew your first stage, and breathe directly off a freeflowing tank valve (???) while maintaining an appropriate rate of ascent then you are way too accomplished a diver to be making a rookie mistake like diving solo with no bailout / redundant gas source.

OK gang, let's unpack this "breathe off the tank valve" thing...
There are two modes of "total first stage failure" - freeflow mode and no flow mode, with freeflow being far more likely. So let's examine that mode first.
(1) First stage failed open - freeflow
There are two basic ways to handle a freeflow.
First, just keep breathing the free flowing regulator until you reach the surface, and
second, shut the air off with the tank valve and then meter it as you need it using the tank valve. No big deal either way, and certainly no need to take the reg off the tank.
(2) First stage failed closed - no flow.
Now, here we are with a reg that ain't flowing, so we just take it off the tank, right?
WRONG!
If it ain't flowing and it ain't delivering, then the hp chamber's full of hp gas, shutting off the tank valve won't release it, and there's little chance you'll be able to get the first stage off there without a pipe wrench!
So whether you can successfully breathe off a tank valve (it takes practice!) or not becomes moot.

Rick

 

[ReefHound]

If it ain't flowing and it ain't delivering, then the hp chamber's full of hp gas, shutting off the tank valve won't release it, and there's little chance you'll be able to get the first stage off there without a pipe wrench!
So whether you can successfully breathe off a tank valve (it takes practice!) or not becomes moot.

Rick

Thanks for going into the detail, this is what I meant when I said "what if you can't remove the reg".

And even if you could, what if your tank really is empty and it was a stuck spg showing more air than you had?

 

[ScubaSteve]

What about if you have no buddy/are solo? What if you are solo and have no redundant air supply?

Well then have a seat at the table next to Darwin and enjoy the show.

Would you quickly screw your 1st stage off the tank and breath from a direct tank free flow?

Have you ever tried to unscrew a DIN valve under pressure?

 

[windapp]

What kind of response is best for a complete first stage failure? What about if you have no buddy/are solo? What if you are solo and have no redundant air supply?

Would you quickly screw your 1st stage off the tank and breath from a direct tank free flow?

"What if your parachute doesn’t open, and you didn’t bother to pack your backup parachute."

In scubu, like many other dangerous sports, we use redundant systems because, if we didn't, the failure of a single component would kill us.

 

[flots am]

What kind of response is best for a complete first stage failure? What about if you have no buddy/are solo? What if you are solo and have no redundant air supply?

The solution is the same as if you ran out of air the "old fashioned" way by not watching your SPG while having lost your buddy: Ascend to the surface.

The reason for being OOA doesn't really matter because the solution is always the same.

flots.

 

[axxel57]

Did somebody of you ever tried breathing directly from a full tank? No? Congratulations!
I did it once to show off and winning a beer for almost seven minutes in 15'feet. If you are very sportive and calm even getting some water in your airways, you might consider that as an option for whatever emergency case. If the valve is just overhauled and opening and closing very smooth, maybe it's practicable.
My valve was not opening and closing smooth, I was very sportive, but that was really a challenge. If you haven't practiced, it's quite dificult to open the valve exact the right way to get just enough air without overdoing it. When the HP first has pumped up your cheeks and flooded your mask you try with less. This is when you swallow water because you didn't open enough and so on.
I drank a lot of water, won my beer and never bet again on that and of course never considered this as an option for an emergency............