Freeze- Up & Free Flows

[Thalassamania]

I agree with you, diaphragms are the way to go in general and sealed diaphragms are best for cold. I was just curious so I tried the OCEANIC. My SAC is pretty normal, a bit higher when I plunge into 28 degree water though.

 

[Ayisha]

... As far as using a 1st stage not designed for cold water use, I was curious about that and in the high arctic on a series of blue water dives I used an OCEANIC OMEGA II (piston, unsealed). As long as I was careful not to breathe off the reg before I submerged it preformed fine, but one breath on the surface, or even just BC or suit inflation and then it would freeze up when I started breathing off it underwater.

bold added

What you describe above are cardinal rules for ice diving. In my first deep cold water dives, we were also told that in order to avoid a freeflow, to not inhale and inflate at the same time; to inflate only in tiny, short bursts; to not hold down the inflate button; to avoid purging the reg when doing a reg exchange; and to not overexert oneself or overbreathe the reg - all of which creates more demand on the first stage than it may be able to handle at depth in extremely cold water. Later on, I read and heard that two divers sharing a reg in those conditions makes it more likely for that first stage to freeflow due to the increased demand.

I have never had a freeflow yet, but I have seen many. I observe all of the above guidelines and I use a reg that is known to almost never freeflow (Sherwood Blizzard) - not a high performance reg, but a reliable workhorse.

 

[tstormdiver]

bold added

What you describe above are cardinal rules for ice diving. In my first deep cold water dives, we were also told that in order to avoid a freeflow, to not inhale and inflate at the same time; to inflate only in tiny, short bursts; to not hold down the inflate button; to avoid purging the reg when doing a reg exchange; and to not overexert oneself or overbreathe the reg - all of which creates more demand on the first stage than it may be able to handle at depth in extremely cold water. Later on, I read and heard that two divers sharing a reg in those conditions makes it more likely for that first stage to freeflow due to the increased demand.

I have never had a freeflow yet, but I have seen many. I observe all of the above guidelines and I use a reg that is known to almost never freeflow (Sherwood Blizzard) - not a high performance reg, but a reliable workhorse.

Even though I use MK25/S600's, I follow these same rules. I really watch my breathing & inflation techniques when in deep cold water & also dial back the adjustment knob on the second stage, some. I did have 1 & so far my only free flow/ freeze- up about 2 yrs ago while in my Adv. Nitrox/ deco course at the same quarry. The root cause was that I had accidentally tapped the purge button. To explain- I was wearing double LP85's. My instructor had me do a primary valve shutdown drill. At the time I was really struggling to reach the valves (I didn't have my back plate/ bands set in the most optimal position). I took my secondary & I had to use my other hand, reaching over my head to pull up on the wing to get to the valve. When I shut it down & pulled my hand down, I tapped the purge button which started the whole incident in motion. I began breathing off the reg, holding the mouth piece to the side to let excess air flow out. With that 1 hand tied up, I could not get to my valves. My instructor was right there & tried to give me his reg, but the bubbles were so thick I could not see that he was offering it to me. He was going to do the same thing I had planned on doing Sun., if he could have gotten me on his primary. We made a controlled ascent to the surface where I shut down the offending regulator, thawed it out & turned it back on. We then recalculated gas & went back down to finish the exercises. I have not had any trouble since then, but remain vigilant if my regulator starts acting or sounds different.

The biggest difference was I tried to give my buddy my primary when the bubbles were trickling, not the full free flow. I could plainly see his face, so don't understand why he said he didn't see the regulator I was offering, other than narcosis &/ or perceptual narrowing.

 

[Kevrumbo]

The motivation in any uncontrollable free-flowing second stage scenario is not to waste any more precious breathing gas that can still be used for yourself or your team : shut that tank valve down! If you're on doubles, then go to your back-up regulator and abort the dive, ascending according to your deco plan as necessary. If on single tank, signal out-of-gas and look for your buddy's long hose or octopus donation.

If on single tank and you cannot locate your buddy (or if solo diving), reach back with your right hand and feather/modulate your tank valve open & closed; inhaling on the open/exhaling on the closed valve --breath as normally as you can under the circumstances; and control your wing's exhaust dump with your left hand as you make your CESA.

(This is a skill IMO which all divers should be familiar with and practice regularly . . .)