How cold before a normal regulator is a problem?

I bought an ex-display model regulator (Procean Extreme/Sixth) so I have
no manual with it. I was trying to find out how cold these things are
generally rated for before icing becomes a problem. Anyone know?

"BarryNL" <barry@nospam.nl> wrote in message
news:3F903418.1020700@nospam.nl
> I bought an ex-display model regulator (Procean Extreme/Sixth) so I have
> no manual with it. I was trying to find out how cold these things are
> generally rated for before icing becomes a problem. Anyone know?

NIGEL!!!!!!!!!!!!!!!

I'll have a quick stab at it.

IIRC Cold water is anything below 10 degrees, however I've also
heard the figure 7 degrees bandied about.

Below 4 degrees and you're in seriouly cold territory. Cooler water
will rise so it can actually be colder on the surface than at depth.

Given that water (pure OK!) is densest at 4 degrees this kind of
implies that the surface temp will be below that with the subsequent
risk
of icing.

Nigel will be along in a minute to thke my Physics 'A' level away
from me.

HTH

DaveA





--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

In article <3ba169ad7adadb353c4bd374b9885d1d.122971@mygate.ma ilgate.org>,
Dave Appleby <dave_appleby@yahoo.com> wrote:
>"BarryNL" <barry@nospam.nl> wrote in message
>news:3F903418.1020700@nospam.nl
>> I bought an ex-display model regulator (Procean Extreme/Sixth) so I have
>> no manual with it. I was trying to find out how cold these things are
>> generally rated for before icing becomes a problem. Anyone know?
>
>NIGEL!!!!!!!!!!!!!!!
>
>I'll have a quick stab at it.
>
>IIRC Cold water is anything below 10 degrees, however I've also
>heard the figure 7 degrees bandied about.

The EC regulations define below 7 degrees C as "cold water" and
have a separate set of validations for regulators that are to operate
below this limit.

>Below 4 degrees and you're in seriouly cold territory. Cooler water
>will rise so it can actually be colder on the surface than at depth.

Also, water starts the crystallization process at around 5.5 degrees C.

>Given that water (pure OK!) is densest at 4 degrees this kind of
>implies that the surface temp will be below that with the subsequent
>risk
>of icing.
>
>Nigel will be along in a minute to thke my Physics 'A' level away
>from me.

Regulators are cooled by the expanding compressed air. This can
chill them to -100C or lower; although it usually stops at -92C when
CO2 sublimates out of air. This is extreme, but will happen during a
full free-flow at a high pressure differential. -15 to -30 is pretty
normal though.

The mass of this air is low, fortunatly. A normal SCUBA regulator set
contains betweem 7 and 14 liters of free air, or ( x 1.22) 8 to 16
grams. But this air will still absorb heat. It there is _any_
moisture, be it water, oil or whatever, the heat that needs to
be absorbed goes up a lot. And to stay away from freezing the
parts closest to the gas has to stay above zero degrees C.

If you have a regulator that has 200 grams of active parts; i.e. that
actually participate in this heat exchange; and the gas has a mass of
10 grams; and the gas is 40 degrees colder than the surroundings ; and
we ignore specific heat differences between the materials; we have
ratios of

Reg Gas Ratio
20 C 4000 (20x200) : 200 (20x10) 20
10 C 2000 (10x200) : 300 (30x10) 6 2/3
7 C 1400 : 330 (33x10) 4 1/4
4 C 800 : 360 (36x10) 2 1/5
2 C 400 : 380 1 1/20
1 C 200 : 390 ~ 1/2
(heating side) (chilling side)

(this is only do describe the principle. Actual measurements will vary)

At some point on this gradient the ability to heat the gas to above zero
temperatures goes away, and the regulator has to operate on below-zero
gas. This puts the operation of the regulator into a new domain of
physics. You see that you approach this point in a non-linear fashion
when we appoach zero.

A small amount of moisture that was unproblematic at 10C, because it
was a liquid or a gas is now a solid, and will stick in seats and
sinter-filters; making free-flows, or even sudden OOA. When this
process starts it instantly goes haywire because it is non-linear;
and it spins into a full free-flow within a fraction of a second.

Oil in air is also bad, even if it does not freeze. It increases the mass
on the gas side a lot; and in a wrongly designed regulator things like
silicon lubricant gets to participate on the gas side of the equation.
Some regulators have spaces for seawater to get in where it can jam
if frozen, even if outside of a membrane. When the space is tight,
and the other side of the membrane is chilled gas this can go from
good to free-flow very fast.

Poseidon owners : DO use your cold-water rubbers!

This is why you need DRY air, a good frost-safe regulator and lots
of thermal insulation for yourself to go winter diving.

Happy diving.

-- mrr

Dave Appleby wrote:
> Nigel will be along in a minute to take my Physics 'A' level away
> from me.

Grief no. I looked at the question and thought
"to complicated for me". The physics involved in
gases expanding and compressing give frightening
instantanious temperature changes so the
manufacturers have to use fiendish tricks to
control it. That any reg doesn't ice up when you
purge it anywhere is amazing to me.

To put this in context: many of us use the Buddy
self-inflator DSMB. We are all used to the way
it goes suddenly warm in your hand as it fills.
We take this as proof of full. If just 20grams
of gas hits the inside of a kilogram or so of ali
tank and does that to it how hot was the gas?

Bl**dy hot.

nigelH