Frozen first stage question

[chironomidkraut]

If your first stage froze up while diving would this cause your bcd and dry suit to free flow as well as the regs or just the regs

[Mr Carcharodon]

Your bcd and dry suit have a valve that must be opened to add gas. Most second stages are down stream designs however and will free flow if first stage pressure exceeds intermediate pressure.

[elan]

Any of them , it depends how they are tuned, the easiest one will go first...

[Ayisha]

Yes, any of them can. For the BC, some divers, particularly those who ice dive, use a Tobin's cap to easily disconnect the inflator hose in case of a freeflow.

Just do everything you can to avoid a freeflow in very cold water:
Put a short burst or two of air at a time in the BC rather than hold it down
Avoid using the purge on the reg
If you use an air horn, use a short burst or two
Time the inflation of your BC with your exhaling/in between breaths so that you are not inhaling and inflating at the same time, creating extra demand on the reg
Breathe calmly and slowly - overworking creates more demand on the reg
Try to avoid having to share air in extemely cold water at depth - creates a lot more demand on the reg, increasing the chance that the last remaining reg will freeflow (Many carry a redundant gas source just in case)
Particularly if ice diving, don't pre-breathe the regs on the surface - the moisture created can cause a freeflow.

Hope those help.

[Steve50]

Probably best to research elsewhere when you get answers 180 degrees apart...

[spectrum]

The OP stated "If your first stage froze up while diving". This would likely lead to a jump in IP. In that condition the primary then alternate second stage delivery valves would enter free flow. I'm not sure what it would take or if it's even possible for increased IP to open a BC or Dry suit inflater valve. I now that you never let those pass as over pressure device so they are way down on the list, perhaps after the hoses as relief points.

Yes a a BC or Dry suit inflater valve can freeze if over worked or internally wet in cold water but this has nothing to do with a frozen 1st stage.

On an ice dive (actually 2) I had BC inflater problems traced to a loose QD nipple on the valve. This allowed venturie action to pull water into the valve when activated forming a miniature snow machine inside. I ended both dives with a creeping inflater and burping my BC to maintain buoyancy. That night I identified the problem, tightened the fitting, flushed it with dry air and was fine the next day and going forward.

Pete

[turnerjd]

As spectrum sais, the second stages as they are "fail-safe" (I.e. fail open). Bcd and dry suit valves usually aren't.

So, when the first stage freezes, and IP rises, the second stages free-flow. Usually there is no problem with the Bcd and drysuit valves. However, if the first stage was fully open when it froze, it is possible that the two free-flowing cond stages do not have enough debit to stop the ip rising too high, which can damage the schraeder valves and the hoses as they are not designed for high pressure (only IP).

Whilst all this is what is possible, I have only ever seen second stages free-lowing, and nothing more.

The best way to avoid a first stage freezing is to have an environmentally sealed first stage and a tank full of dry air. If there is no water in the reg, or the air, then it can't freeze.

Jon

[ianr33]

I remember a post where a guy got bent several years ago in California on a deco dive. IP went high , that caused his wing to inflate and a rapid ascent.

IIRC the reg did not freeflow as it was a balanced design that could cope with a very high IP.

Here it is:
http://thedecostop.com/forums/showthread.php?11472-DCS-in-Northern-Cal&highlight=chamber
Conclusion was it IS possible with some regs for a wing/drysuit to auto inflate before the reg releases pressure.

A stuck on inflator is something that scares me. Without the correct,rapid,response it could be really ugly.

[Ayisha]

There was an accident in Ontario a few years ago during an ice dive when the inflator got stuck on all of a sudden. The diver could not disconnect the inflator fast enough, had a rapid ascent and banged his head hard on the ice above, becoming unconscious and then dying. His buddy was beside him but couldn't prevent it. That thread was on Ontario Diving but you need to be registered to view it.

After that accident, many ice divers in and around Ontario started to disconnect their inflator hoses during ice dives or use Tobin's hats.

[elan]

Before any speculation starts on Ayisha's post there were much more on that dive than a stuck inflator AFAIK. The inflator was probably the last in the chain of failures.
But what is true now many people just disconnect the inflator from the wing in very cold water.