Regulator for waters around freezing

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Suggested models:
- Zeagle (DS V, Z Flathead 7)
- Agualung Legend Glacia
- Scubapro MK 17 1st and G250V
- Sherwood Brut
- Apex
- Sherwood Oasis, Genesis 2000
- Scuba pro MK17/g250
- HOG D1 cold / d1
- Atomic Z2 cold water kit
- Mares Abyss, Proton Metal
- also Poseidon Xstream models

I took a look at what the local dive shops offer. They carry a lot of APEX (XTX50 seems to be very popular) and also Aqualung Legend Glacia. I was told that they are internally the same thing.

Legend Glacia just has a metal second stage and then one inch of metal ribbons in the middle of the hose. Some kind of heat gatherer, but I wonder what difference that one inch of metal could possibly do on a five(?) foot hose. Maybe it is just for product differentiation and marketing? Can't be effective being so small. But maybe a metal first stage is a good thing...

Poseidon Xstreams seem to have some large spring inside the first stage. Probably for heat transfer. I am also wondering what the Poseidons suggested ability to use heat from exhaled air really means. All the regs get exhaled air inside them, right? And isn't that bad, exhaled air beeing moist?

So many names, so little tests and motivations. Difficult to make an informed choise :|

This I already know:
- the bottles should be empty of water
- the air should be as dry as possible
- connect the first stage in warm/dry so no ice or snow gets in between
- good to have an environmentally sealed first stage to keep water out
- some structures may be more resistant to ice forming and/or getting stuck (open or closed), but I don't know what kind of vents are used

- another place that can freeze is the second stage
- metal second stage (or any material that transfers heat well and doesn't become fragile)
- second stage constructions may be different. Don't know what is good and what is bad.

- the usual precautions: first breath of air under water, no fill tests either above surface, keep first stage absolutely dry

Some questions:

- Are there different ways to construct first stages? Sealed, yes, but other modifications?

- Can the second stage be sealed somehow or fitted with an ice resistant valve? Are there multiple ways to route exhaled air and to use it for warming?

 

[=C=]

Good post! Consider this an up vote!

There are cold weather kits you cay buy and have them installed by the shop. Some involve keeping the reg dry while others fill the chamber with an anti-freeze solution. Fins and heat dissipation like you describe are critical. To avoid freezing you have to manage the temp of the erg and this is usually achieved via increased mass/density or improved heat dissipation. Old regs like an SEA 4 weigh twice as much as my MK17. My experience has shown that the large mass does not cool quickly and was efficient at preventing freezing. The 17 accomplished this via fins on the 1st stage as the water will not (usually) be below 0.

So, about your reg design question you have probably discovered piston and diaphragm regs. If not google. Diaphragm are generally favoured for ice diving however there are some notable exceptions. Where I dive ScubaPro are notorious for freezing, even the diaphragm regs, except for the MK2. Many people claim this is an excellent cold water reg and have neve seen one freeze. Piston regs also has fewer moving parts which is nice if you will do your own service but not that big an issue overall. That said the vast majority of cold water rigs are diaphragm like my MK17 (last 4 dives are at or below 6c with an air temp of -8)

And.. I haven't seen a retrofittable second that manages a exhaust air flow.

 

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Hmm, this is interesting:

Diving Under Antarctic Ice
http://peterbrueggeman.com/nsf/diving/robbins.html
http://peterbrueggeman.com/nsf/diving/nedu.html

And also:

"There is simply no way that any single hose regulator (even with backups) can be as safe from freeze-up under ice as an Aquamaster, as the second stage mechanism is always subject to the diver's moist exhalations. They can be made better (Dacor coated their second stages with teflon, and Sherwood has the Blizzard with its heating element). But none of these single hose designs has the first and second stages totally and completely isolated from water like the Royal Aquamaster does." says John C. Ratliff in What is the best regulator for cold water? [Archive] - ScubaBoard

 

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Further research indicates that:

O-RINGS

- o-rings may fail in cold. Actually, I have had several o-rings fail. One failed INSIDE a first stage while pressurizing the system at -10C/14F, and THAT was annoying. External o-rings can always be replaced onsite. So, the quality of the o-ring material may play a role before getting into water. And maybe in water too: it could loose its capability to seal.

FIRST STAGES

- unbalanced first stages rely partly on medium pressure to keep a valve open. Having the first stage free flow, and the resulting drop in medium pressure, must suck then. So balanced is better? Aren't they all balanced nowadays, anyway?

- Wikipedia says this about regulator FIRST stages: "Generally the water that freezes is in the ambient pressure chamber around a spring that keeps the valve open and not in moisture in the dry breathing gas from the cylinder. The modern trend of using more plastics, instead of metals, within the regulators encourages freezing because it insulates the inside of a cold regulator from the warmer surrounding water. Environmental sealing of the ambient pressure chamber and teflon coatings around springs are used to reduce the risk of freezing inside the regulator."

VENTS AND PRESSURE / TEMPERATURE

- due to the venturi effect the air speed is increased and pressure lowered in constricted passages (read: vents). This pressure drop means temperature drop too, volume beeing constant... The bigger the hole, the less cooling, right?

- pressure drop tank --> hose also cools gas; hence lower pressure tank with larger capacity will be beneficial. 200 bar instead of 300 bar. The medium pressure can be adjusted too, but when the initial drop is from hundreds to ten bar or so, the medium pressure doesn't have a huge role here(?).

- when medium pressure gas goes to seconds stage and out, the resulting pressure loss again cools the gas and the second stage. Here a lower medium pressure might be beneficial, if I have now understood all this correctly.

DEPTH

- the deeper the depth the smaller the pressure drop and hence cooling at the second stage? And remember that freezing water is a little lighter than slightly warmer water, so the temperature goes up a degree or two, when one dives deeper. Affects both stages. When taking into account the freezing temps on the surface before the dive (water can be warmer), then the most probable freeflow situation is near the surface, right? I haven't given any thought to the air density aspect yet, so I might be wrong.

SECOND STAGE

- the second stage should be a downstream demand valve, where the medium pressure keeps the valve open (not closed). A downstream valve will remain open when the first stage sticks open.

- when the regulator eventually starts to free flow, it's pretty painfull for the teeth. It would still be nice to breathe that air, and not to waste it. The second stage could maybe be designed to minimize any freeflow, but then again, if the first stage is stuck open and air flow would be restricted, then medium pressure would go up and break something else, such as the BCD. Not fun that either.

- with a free flowing reg it's nice if the bubbles wouldn't obscure vision. It's not fun loosing air in pain while also loosing vision. Obviously, one alternative is to use the octo (to double the bubbles when it fails too) or use buddys regulator until it fails. But the bubbles are really annoying, even at shallow depth. Can't see the depth gauge / ascent rate.

 

[Fishpie]

IP can also be lowered 10-20psi.

 

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This would also be interesting reading:

ScienceDirect - Ocean Engineering : A self-heated second stage regulator for underwater divers

It's a self-heated regulator...

 

[jar546]

Apeks XTX200

 

[gumbo717]

Another vote for APEX.

I routinely dive in 38 degree water and the air temp in the winter is usually colder that the water. I also dive them under the ice while it is on the quarry.

 

[Davidstealey3]

just remember when testing your gear before you dive in cold water and especialy cold atmosphere temps in tyhe air to never exhale through the reg. inhale then remove the reg and blow the air out when on land. this will help prevewnt ice from forming in the second stage. when in the water just keep it submerged and do your test and you will be fine.

you have done some extensive reserch into the subject and should be able to get a well performing reg when you are done. sopme of this was still interesting for me to read and i have been diving for a while

 

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Poseidon jetstream or the cyclone with a full face cresse mask is my first choice for working under the ice just my two cents