sharing air in cold water

[FoxHound]

Under the ice i always have a redundant back up.

Cold water if im diving single tank, my regs are right tuned down for the cold water. I have been involved in gas sharing at close to max depth on the forest city in tobermory, in 0 C water and no free flow.

I generally dive 2 tanks at all times, and my regs are always tuned for cold water, it always seems to be cold temps here in the great white north so no need to ever tune em for warm.

 

[lowviz]

...//... I've been diving in *very* cold water for many years and I've seen exactly ONE regulator freeze open during a dive due to the cold. ...//...

I'm guessing that you mean a primary reg freeze.

Happens quite often here in the Great Lakes. ...//...

I'm guessing that you mean a secondary reg freeze.

...//... my regs are always tuned for cold water, ...//...

Yes, just set the IP to mid-range and the secondary to "normal breathing", not "anticipates each breath"...

 

[eponym]

Eponym, I think I'll put buddy breathing training on my to-do list. But do you think that drawing air when your Buddy is visibly exhaling (and visa versa) from the octopus might work as an equivalent measure?

I don't know. I'd guess that a freeze-up occurs over maybe a minute's worth of a first stage's cooling (because of the air it's delivering) faster than it can draw warmth from the water. Unless the previous use already cooled it near to freezing. So the timing of the two downstream demands might not be important. I could be wrong.

But trying to time your breaths against your buddy's probably introduces more stress and thus more breathing demand.

-Bryan

 

[TONY CHANEY]

Anyone care to post what Mfg. they have seen free flowed. I have seen HOG's and SP regs free flow but never my Poseidons.

 

[bluephoenix]

A pony for redundancy seems a good option to have available. Is it standard equipment for most diving cold water?

for me it is, I have a 21cuft with EAN28
in comparison to a single tank with two valves an advantage for me is, although I can close my valves by myself perhaps I will have a problem with it one day and then the tank would empty completly - but I still have my pony for a safe ascent

 

[mantajohn]

Andy

My 3 free flows have occurred in a UK quarry (Stoney Cove). I took all the usual precautions to reduce the likelihood of a surface freeflow (not leaving tanks in car o/night, taking great care during buddy checks not to chill first stage etc) but around 25-30m the 1st stage let rip.

I since moved to always carrying a pony with me when diving in cold, poor viz (UK) water. I have only had to use it twice in 300 UK dives, but was very grateful on those 2 occasions! Also, I found my air consumption improved generally - possibly due to the comfort factor.

I have always intended to move on to twins, but haven't got there yet.

FYI my regs are scubapro MK25/650. Allegedly cold water regs, but below 10C, they always 'bleed' a little air & feel as if they are about to let go unless I adjust the sensitivity right down. It does help when getting your regs serviced to specifically state that you will be using them for UK diving.

John

 

[elan]

Anyone care to post what Mfg. they have seen free flowed. I have seen HOG's and SP regs free flow but never my Poseidons.

Apeks (the most) Scubapro, Zeagle, Poseidon, Oceanic, DiveRite
Mostly in lake Ontario/Huron, St lawrence river and some quarries in QC

 

[rhwestfall]

I still really believe that the "higher performance" the regulator, and the "hotter" the tune, the more you risk having a problem. I have dove for years in Erie where the temps below the thermocline are usually 38 degrees or so. My gear was the "terribly archaic" SP MK-10 (without the environmental kit), and either 109 or 156 seconds. It is only the last 3 years that I have aquired my MK-17 & G250v regs. In 25 years of certification, I have not had any free-flow..... in contrast, I have seen others with the "latest & greatest", or other various non-cold water gear have issues. I was taught to use the LP inflator between inhales in quick small shots, do the same with the DS inflator, and just keep your witts. Luck or approach, I know not....

---------- Post added March 14th, 2013 at 09:28 AM ----------

FYI my regs are scubapro MK25/650. Allegedly cold water regs

ummmm, not really..... (the 25). That one has been one that seems to be always on the edge....




edit: I will also add that as I have "matured", and given this all more consideration, a pony has been added to my cold water diving as another option. Gas planning is not inclusive of this extra quantity. H-valves are in consideration, but still not implemented.

 

[GrumpyOldGuy]

I don't know. I'd guess that a freeze-up occurs over maybe a minute's worth of a first stage's cooling (because of the air it's delivering) faster than it can draw warmth from the water. Unless the previous use already cooled it near to freezing. So the timing of the two downstream demands might not be important. I could be wrong.

But trying to time your breaths against your buddy's probably introduces more stress and thus more breathing demand.

-Bryan

I would concur. Buddy breathing tends to cause the divers to suck down more air faster due to stress in anticipation of giving the 2nd back to the other diver. 2 Divers breathing at a more relaxed pace on an octo would be preferable. I was trained to buddy breath, there are multiple reasons why its no longer taught often, the big one being the stress it adds to an emergency in progress.

Better yet, in cold water consider a pony. That gives you a second reg totally isolated from your primary. Even a Y valve requires a quick shut down of the free flowing reg which not all divers can do on a single tank without practice.

 

[rx7diver]

I was taught to use the LP inflator between inhales in quick small shots, do the same with the DS inflator, and just keep youe witts

This is how I was taught as well.

BTW, I've long suspected that cylinder pressure affects the likelihood of first-stage free-flow. The cold water free-flows I have had, or buddies have had while I was diving with them, have all occurred while using either HP cylinders (often over-filled HP cylinders) or over-filled PST 104's. Every one of these free-flows occurred at the beginning of the dive, with full/over-full cylinders. Of course, this might only be coincidental. Still, I suspect that a quick drop from 4,000 or 3,500 psig (say) to an intermediate pressure of 125 psig (say) over ambient is significantly more likely to induce a first-stage freeze-up than a quick drop from 3,000 or 2,640 psig to 125 psig over ambient.

Safe Diving,

rx7diver