Problem at Gilboa 4/21

[diver 85]

Regs can free flow at any temperature, although it is more rare at warmer temps. They can also free flow because of mechanical problems.

My rule of thumb is that free flows are always a possibility below the thermocline. The 38f temp doesn't sound unusually cold for that depth at this time of year.

As far as learning goes- the fact that this is a double fatality in a group of three seems alarming. It sounds like there were simultaneous free flows. Just to put some perspective- I think Curt Bowen did some tests and found that a free flowing reg will drain an AL80 in about 90 seconds. I've had a 2nd stage free flow at 100' and it emptied the AL80 before I made it back to the surface. In my case, I was already sharing air when it ran out.

Even with redundancy and buddies, free flows can be hard to manage- switching to an independant regulator does not alway remove the conditions that cause the first free flow.

(From your free flow problem)...90 seconds-time you have in a freeflow situation with an AL80- AND another 60 secs(or more but lets take a minimal)-time you have with a 3cf Spare Air bottle- to me ='s about 2 and a half minutes.....IMO, plenty of time to make a safe ascent from 100'---heck, maybe even time to hang @ 15' for a while & enjoy a little scenic view of the bottom........

This EXACT reason is why I carry one for 'normal', no overhead obstructive Caribbean diving.......

 

[ianr33]

Do freeflows due to cold water tend to happen all of a sudden or is it a gradual process that gives you some warning?

(I have never dived water below 49 degrees and that suits me just fine ! )

 

[do it easy]

Do freeflows due to cold water tend to happen all of a sudden or is it a gradual process that gives you some warning?

Could be both.

The one that I have experienced personally was a creeping hiss that built up to a bubble shower over about 30 seconds. I've had some near free flows that were stopped simply by slowing down my breathing and flushing the reg with water.

I had a buddy that free flowed a pony reg on the first breath.

 

[pickens_46929]

(From your free flow problem)...90 seconds-time you have in a freeflow situation with an AL80- AND another 60 secs(or more but lets take a minimal)-time you have with a 3cf Spare Air bottle- to me ='s about 2 and a half minutes.....IMO, plenty of time to make a safe ascent from 100'---heck, maybe even time to hang @ 15' for a while & enjoy a little scenic view of the bottom........

This EXACT reason is why I carry one for 'normal', no overhead obstructive Caribbean diving.......

Only 90 seconds if you're at 8 ATA.... if you're within recreational limits its likely to be closer to that 151 seconds... so you should have 5 mins. roughly...

Depends upon how panic'd you are and your SAC rate... I figure if I could safely ascend to 20 ft before pulling out the Spare Air, you could likely do most, if not all of your safety stop too.

 

[ianr33]

.... if you're within recreational limits its likely to be closer to that 151 seconds... so you should have 5 mins. roughly...

If the tank is full,which it wont be.

If it is down to 1000 psi does not give much time at all.Especially after ,say,30 seconds of OMG whats happening?? Wheres my buddy?? What do I do know???

 

[fisherdvm]

Could it be that the first diver had a free flow, then breathed off the second diver's octopus, increasing the demand of the second diver's first stage, then caused a second free flow,...... On and on and on???

 

[Scram Bulleggs]

Good point

 

[do it easy]

Could it be that the first diver had a free flow, then breathed off the second diver's octopus, increasing the demand of the second diver's first stage, then caused a second free flow,...... On and on and on???

Yeah, this is what I am guessing.

Another issue that I see with deep diving is poor buoyancy control during the descent- where a diver will descend quickly and underinflate their drysuit/wing/BC. When they try to stop at their planned depth, they have to kick to maintain depth. This increases breathing. Throw in the additional inflation to become neutral and the reg is overworked and more prone to free flows.

 

[MikeFerrara]

Another issue that I see with deep diving is poor buoyancy control during the descent- where a diver will descend quickly and underinflate their drysuit/wing/BC. When they try to stop at their planned depth, they have to kick to maintain depth. This increases breathing. Throw in the additional inflation to become neutral and the reg is overworked and more prone to free flows.

As long as we're guessing I'll go with your second guess (lost buoyancy control) or just plain panic on the part of one or more of the divers.

 

[fisherdvm]

How about this, first guy reg froze, went for buddies octopus, second guy's reg froze, went for the third, but they had only one octo, then all panicked...

Tell me not to go below 20 ft if it is really cold in the water.