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"R_LAROCQUE (418) 775-0792" <r_larocque@AM*.QC*.DF*.CA* writes:
>
> Whenever I get below 130 fsw in cold water (4degC), my Poseidon Odin starts
> blowing bits of ice down my throat. Is it
> due to moisture in the compressed air? or is it condensation from the exhaled
> air? Is it normal? Can something be done about it? Of the regulators I have
> used, the Odin is the only one that does this.
> Walz@la*.ep*.ch* writes:
>So do mine. I don't think there is anything that can be done, you just
>G.Kowalski UHAP010@VM*.RH*.AC*.UK* writes:
>What we have here is a classic case of high performance demand valve dived
>in cold water where large amount of gas (air - and this is important) is
>undergoing what is well known as Joule-Thompson transition. Without going
>into much of physics this is basically an effect of cooling while gas
> pressure is
>dropping from say 200 bar to 10 bar (intermediate). worst) I came across a
> lot
>of those type of problems and even we did some comparatory simulated second
>stage freezing tests on some DV's.
>What to do about it : is not much if you carry on with your ODIN
>- set your DV to be less easy to breath (less gas transported, higher temp at
> second stage)
>- breath slowly
>- avoid using this DV with your BC or Dry suit while you breathing and
> always use it gently for inflation.
>- longer brakes between breaths will allow first and second stage to heat up
>- try to keep water of the second stage while diving.
>- OR buy yourself a DV which is stated to be designed for cold water diving
>(there are some)
> Although none of them is ideal (we have tested them as well)
>- I have seen a simple device at the stage of development which can be mounted
>on any DV and will increase freezing resistance at least 3 times. But this
>is still not at the production stage but maybe at the end of the year it will
>be available.
>There is a lot more to it , like different gases and gas mixtures , materials
>Terho Kaikuranta writes:
>We have been diving in cold waters here in Finland.
>I can tell that there are lot's of other regulators
>which also blow bits of ice
>Although the first stage
>was covered with 1 cm layer of ice
>Nick Simicich <njs@sc*.ma*.co* writes:
>The other problem, of course, is that as good as Poseidon's are, they
>breathe wet because much of the air escapes from an upward pointing flap
>valve. The rim of the diaphragm is the exhaust valve, it opens on the
>top, and some water gets in.
In the dark ages of diving when DV was single stage two hose , large metal box
on your back or when two stage (separated) DV was still in its infancy,
problems with freezing and cold water diving were virtually non existent.
At least for sport divers.
These days all the makers are struggling to produce High performance DV - but
they are only as good as warm is your surrounding water.
So the best bet for cold water diving will be DV :
- Environmentally sealed first stage
- the bigger the first stage the better (heat transfer)
- preferably regulated second stage (like in some of Apeks or Scubapro models)
on some occasions free flow at second stage can be stopped by increasing
spring load (winding in )
- Less plastic bits used for first and second stage construction will give you
better heat exchange properties
- Some of the DV's have got small heat exchangers incorporated in the second
stage those may help but not a lot. (Apeks TX50, Spiro Supra Arctic)
- Use specially designed heat exchange devices to be mounted on any DV to
increase freezing resistance (That in future - although I have been able to
dive preproduction model of such device -- is really good)
Gregory
G.Kowalski -- UHAP010@VM*.RH*.AC*.UK*
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