Why can't this work in an OOA?

[ttew]

So how does it change anything ? Yes there will be a lot more bubbles and they will be moving faster but they will be at the ambient pressure - unless the operator in question will be sticking the valve into the mouth. Then again there is no need to open the valve completely.

Reality is a bit more complex than that. The static pressure of the tank e.g. when no air is flowing out of the than is e.g. 3000 psi, as soon as the tank is open connecting the pressurized tank to the environment through the valve the gas starts flowing. If we neglect gas expansion and we suppose the valve light is big enough to avoid flow perturbation the fluid exchanges pressure for speed so we have a flow of very fast fluid at ambient pressure.
In the real world the pressurized air expands flowing through a very small hole e.g. the volume of the air at ambient pressure is something around 100 times more than in the tank, the expansion reduces the temperature, the flow through the valve is not laminar and produces "vortex" effects, the impact with the surrounding water is unpredictable and we end up with a region around the valve where the models do not apply, i.e. inside the tank we have the nominal pressure e.g. 2000 psi, outside the tank at a certain distance from the valve the air has the ambient pressure, but next to the valve there is a turbulent mix of air and water bubbles at an undefined pressure. The turbulence of this region depends on a number of factors and is strongly influenced by the flow, i.e. how much do you open the tank. If it is slightly opened there is "reduced" turbulence, the air expands slowly and forms nice bubbles that are easy to breath, if we open a bit more it is likely to have some cold foamy fluid that is not so easy to breath and if we open the valve a lot, especially at shallow depth it is likely that the foam will became somehow very cold and creamy, like when a regulator freeze in cold water (a freezing regulator requires cold water and a flow of a few liters/minute, an open tank can deliver a flow of some 1000s liter/minute)


A few months ago I was in the pool when a badly mounted joke went off a full tank a few inches below the surface.
It ended up with a burst of fresh water snow flocks flowing through the sky.

 

[DivemasterDennis]

As the consensus has said, not a good idea and not really a solution to anything. No first stage or second stage to reduce pressure to usable levels? Forget it. The best way to deal with an out of air emergency is to not run out of air. That means planning a safe dive, following the dive plan, monitoring gauges regularly, staying close to your buddy, and aborting if there is an equipment issue. In those cases where entanglement or equipment failure present an emergency, a close at hand buddy to share air and assist with the issue presenting the problem is the best equipment. Solo divers know ( or should know) how to be equipped with redundant gear for contingencies. They will tell you they would never consider a tank of any size with no first or second stage.
DivemasterDennis

 

[elan]

Reality is a bit more complex than that. The static pressure of the tank e.g. when no air is flowing out of the than is e.g. 3000 psi, as soon as the tank is open connecting the pressurized tank to the environment through the valve the gas starts flowing. If we neglect gas expansion and we suppose the valve light is big enough to avoid flow perturbation the fluid exchanges pressure for speed so we have a flow of very fast fluid at ambient pressure.
In the real world the pressurized air expands flowing through a very small hole e.g. the volume of the air at ambient pressure is something around 100 times more than in the tank, the expansion reduces the temperature, the flow through the valve is not laminar and produces "vortex" effects, the impact with the surrounding water is unpredictable and we end up with a region around the valve where the models do not apply, i.e. inside the tank we have the nominal pressure e.g. 2000 psi, outside the tank at a certain distance from the valve the air has the ambient pressure, but next to the valve there is a turbulent mix of air and water bubbles at an undefined pressure. The turbulence of this region depends on a number of factors and is strongly influenced by the flow, i.e. how much do you open the tank. If it is slightly opened there is "reduced" turbulence, the air expands slowly and forms nice bubbles that are easy to breath, if we open a bit more it is likely to have some cold foamy fluid that is not so easy to breath and if we open the valve a lot, especially at shallow depth it is likely that the foam will became somehow very cold and creamy, like when a regulator freeze in cold water (a freezing regulator requires cold water and a flow of a few liters/minute, an open tank can deliver a flow of some 1000s liter/minute)


A few months ago I was in the pool when a badly mounted joke went off a full tank a few inches below the surface.
It ended up with a burst of fresh water snow flocks flowing through the sky.

What you described is correct but again it is not changing anything... We are not discussing breathing from the failed valve fully open. or from a blown burst disk.

When you breath from the tank valve directly you crank it just enough to make the smallest stream of bubbles and catch those bubbles from a distance when their velocity is tolerable. At that moment the pressure inside the bubbles will be equal to ambient or at most close...

We can discuss ad nauseum how much it will be at the tip of the dip tube or when the tank blow up but it's not relevant to the original post, do not you find ? Topic creates a context of discussion and we discuss it in the context.

Unless we want to discuss the obviously idiotic case when the operator in question decides to put the LP hose or the tank valve into their mouth directly...

 

[RJP]

Unless we want to discuss the obviously idiotic case when the operator in question decides to put the LP hose or the tank valve into their mouth directly...

Why not discuss that? I mean, we're already discussing the obviously idiotic case of a diver carrying a cylinder sans regulator as their planned bail-out gas.

 

[muddiver]

I personally like the diver that carries a second regulator setup, without the cylinder, as a bail-out gas so as to save weight and bulk.

 

[elan]

Why not discuss that? I mean, we're already discussing the obviously idiotic case of a diver carrying a cylinder sans regulator as their planned bail-out gas.

Can we go straight to the body recovering procedures then

 

[rhwestfall]

this may actually be the first logical place to say: "You Are Going To Die!!!!!!!!!!!!!!!!!!"

 

[elan]

Only if you wear split fins and a puddle jacket!

 

[nimoh]

carrying a tank with no reg is definitely doing it wrong

edit: since this thread already seems to be going in a downward spiral, I'll run the risk of sending it into the DIR downward spiral

 

[RJP]

I personally like the diver that carries a second regulator setup, without the cylinder, as a bail-out gas so as to save weight and bulk.

That guy's a rookie! I dive with a just an Air2 and no tank as my bail-out. That way I can save weight, bulk, and eliminate one hose!

:d