Ice Diving with a Rebreather Article

Louby Lou

Evening Folks!

Alex (AD_ward9) has kindly written and submitted an article to the Rebreatherworld Library on ice diving with a rebreather following a review of a video sent to him of the 1998 - 1999 North Pole Dive Expedition. The article can be found HERE. Images will be added to article shortly.

Please can you use this thread to ask any questions, or leave any comments for feedback for Alex. Please use the article to leave any reputation.

Many thanks Alex!

Cheers

Lou
Rebreather World Admin

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Ekke

Hehe.. I wonder if Alex have ever dived in cold waters..

Here's my friend with his DIY eCCR:

Ice diving in Finland

-Mikko

onetime

Brief yet detailed and to the point. Excellent article and it certainly gets one thinking. It seems to be a little misnamed though I think as it's not just ice diving. If my mental metric conversion is correct 4 degrees C equates to somewhere just shy of 40 degrees F. I have never ice dived but I have been diving in 35 degree water. So perhaps a better name would be cold water diving and rebreathers?

nigelh

But fresh water doesn't get much colder or it stops being water.

The problems are more to do with stopping things freezing up and you tend to use the 'warm' water to do this. ( However I've only ice dived on OC.)

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nigelh

Haapajarvi

Hi!

Nice article, but unfortunately little missleading.
Here in Northern Finland we do Ice diving frequently. Air temperature ranges down to -25C but fortunately water temperature is warmer, near 0 C close to ice and about +4C in bottom.
Its true that repreathers dont like cold, but internal temperature insede scrubber can be high as +25C even water is near icing so scrubber till works. Depending lung and other loop construction temperature in other parts of loops can vary, but is clearly above freezing temperature.
Even diving in cold conditions is not anything special. But some caution shold should be taken. Never start dive with wet or moisture on loop. Get your equipment to water tepperature (its higer than air) before start decent.

Have good dives, have good ice dives!

-Juha

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JonORunde

Most Norwegian CCR-divers should be dead by now then

I have not heard of anyone having problems with the cold water up here. But then, care is been taken to keep the unit reasonable warm before diving, and do a proper/extra long prebreath...

http://www.rebreatherworld.com/megal...ng-norway.html

Jon O

jaap

Someone must have forgotten to tell the rebreathers around here in Sweden that they should freeze and kill us...

I have done icedives with a few different units and when I come to think of it every single rebreatherdiver I know personally around here dive their units during wintertime (under ice or <4 C water, often << 0 C on the surface).

Sure a good prebreath to warm up the scrubber and make sure its working is good practise. I don't challenge that the scrubber and electronics are closer to failing when is very cold.

But having any formation of ice in the loop? On the checkvalves? Hmm, I _think_ the loop is always warmer than 4 celsius. The scrubber and diver generates quite a lot of heat input to the gas.

What do I know maybe we are just incredibly lucky. Last winter I left my unit in the snow by the hole between dives. And sure, the DSV-had a thin layer of ice on it and the ADV was frozen (has happened a few times when its cold). A few minutes of breathing it in the water on the surface and all was well and down we went.

I'm not saying rebreatherdiving is just the same in very cold water. I had a really bad CO2-hit early into a cold water dive on a (partially used scubber, sloppy prebreathing) a few years ago and when I tested it in the nice warm pool (same untouched fill) all was well. So yes cold water is certainly bad news for your scrubber (and electronics). But I'm afraid there are to many divers using their units in cold water to make the case that cold water is "the big Rebreather-killer".

Any facts from tests or users that have had water freeze in the loop while diving the unit? That any water in the loop will freeze if you leave your unit sitting in the snow if of course quite obvious.

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DaveC

ummm interesting article and I'll agree with some of it but some of it I don't think so...

I agree you need to keep the rig warm before and after the dive in sub-freezing temps. At least above freezing, especially for those units that have allot soft material that could expand and crack. Yes batteries that run the electronics well drop in voltage fast in cold conditions which is why, if in doubt, change it out. And that is why certain units have completely separate readouts or secondaries that are independent of the electronics. The risk of dry suits leaks can happen if you're on OC or CCR and that's why you always run the risk factor of if this dive is worth it and where underwear that helps keeps you warm even if the suit floods.

If those of us up here in the frozen north were worried about temps below 40 degrees, we'd never get in the water. In the cold months, and that could be anywhere from late November to May, depending on how fast the water warms up, it could almost always be in the mid 30's. So, Moisture in the loop as long as you're breathing on the loop will stay warm enough so that it doesn't freeze. Anyone that has gone from CC to OC can feel the difference in breathing temps. The exothermic reaction won't stop working just because of the cold. The cells won't stop working as they are in the loop and always are kept warm because of the exothermic action going on. Same as the mushrooms valves. Allot of units use mushroom valves that can be found in regular OC second stages. I've never know one to freeze shut, especially in the water.

Personally, IMO - I feel safer on CC under the ice or in cold water then I would on OC. Warmer, longer, and more gas to work with in the case of a emergency.

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Dave

Any day in the water is better then any day in the office.

Lake_Tahoe_Diver

Well as a diver that dives in water 4C. or colder year around at depth here I have not seen this occuring. During the last weekend I did a very nice 2 hour dive in 4 c water temps, the breathing hoses were warm when you touch them to the face while diving so I do not think the air temp in the loop is anywhere near freezing.
I would agree with many here that if the gas around the senors is cold enough to cause issues you have other problems, such as a scrubber failure since it should be getting hot gas moving over them strait from the scrubber.

As for ice blocking the injector nozzle I guess that could happen depending on where the gas is injected. But I would have to think it would have to freeze really fast an create thick enough layer to hold back the pressure since a thin coating would be blown away during the addition process. Becuase unlike OC where the demand value is open for around 1-5 second during the inhale. On a rebreather it is open for less than 1 second per cycle so tempure drop is not as much from the expanding gas so less chance of icing.

But, again this is my theory and I am open to being corrected if the logic is incorrect.

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PCDiver

<quote>
LCD displays lose contrast in very cold conditions.
Some integrated circuits, particularly Flash memories and DRAM, do not function well in cold conditions.
Batteries will go flat much faster in cold conditions than in warm, and their internal resistance rises even when fully charged. This creates more power supply noise, and will cause equipment malfunction if there is any under performance in the power regulators.

</quote>

Doesn't this apply to OC as well: "dive computers". These also contain LCDs, integrated circuits, etc. I never had a dive computer freeze up because of the cold.