That Time of Year - Freeflows

[DeepBound]

For those who choose to dive during these cold months, please remember that at this time of year the latent energy or latent heat of the water in the St. Lawrence is getting very low, and freeflows are more likely. The water temperature has been slowly inching its way down towards 32F, and is now at 32.2 or 32.4, and with more cold weather predicted for this week, there will be little latent energy in the water?

What's the big deal of 33.0 vs 32.0? I know it's just one degree, but the heat energy in the surrounding water, when above the freezing point provides heat energy that can counter to some extent the adiabatic cooling that goes on in your regulators. Here's some more information about latent energy of water:

Heat - Latent Heat

I'm not a physicist, but I know from experience that there's a difference with regulator performance in 33F water vs 32F water. Please keep this in mind and keep your diving conservative this time of year.

Perhaps someone with a better physics background can help explain this a bit better... please feel free.

Safe diving,
DeepBound

 

[CaNaDiaNCoLd'N'FrEsh]

What brought this on? did something happen recently?

 

[DeepBound]

What brought this on? did something happen recently?

Well, last year around this time I had all 3 of my regulators freeflow at the same time. (primary, backup and stage) while diving the Connestoga. It was a bit scary, and got me thinking about the physics involved. I haven't heard of any accidents this winter, and I hope it stays that way!

 

[Norberto]

Well, last year around this time I had all 3 of my regulators freeflow at the same time. (primary, backup and stage) while diving the Connestoga. It was a bit scary, and got me thinking about the physics involved. I haven't heard of any accidents this winter, and I hope it stays that way!

What kind of regulators do you have?

 

[jjones9527]

Perhaps your regs need a tune up or adjustment. Your in Ottawa, so you could go to In Depth Scuba Service, located in Kanata. They're awesome at gear service.

InDepth Scuba

 

[DA Aquamaster]

The issue as water gets closer and closer to the freezing point is that the temperture gradient is smaller and heat transfer is reduced.

The air expanding inside the regulator requires heat which is drawn from the regulator. In turn, the regulator has to draw heat from the surrounding water if it is to remain above freezing. If the surfaces of the reg fall below freezing, the water in contact with them can form ice on the surface which then insulates it and further reduces transfer. This rapidly causes an increase in ice and unless the first stage is environmentally sealed, eventually the ice will form in or spread to an area where it impedes the movement of the piston or the diaphragm causing the first stage to fail in an open position.

In the good old days when second stages were metal cased, second stage freeze ups were unheard of. But the current trend toward plastic second stages and air barrels means they have very little heat transfer so the cold air that is both passing through and expanding in the orifice and second stage draws more heat from the metal parts of the second stage poppet and lever than they can draw from the surrounding water with the result that the lever movement can also be impeded causing tthe second stage to fail open or closed.

In general freezing of the regulator can ocur in water below 50 degrees and it becomes common in water colder than 40 degrees. The potential rises faster the closer the temp gets to 32. There is nothing magic about 32 versus 33 degrees except the gradient at that point drops a bit more. It is still not quite zero as the surface of the reg is still attempting to cool below freezing as some heat transfer continues from the surrounding water. More importantly ice requires not only a 32 degree temp but also enough heat loss for the phase change from water to ice to occur and it takes the loss of a lot of heat for this to occur.

In extremely cold water close to 32 degrees, a totally redundant air source is nice to have as if both freeze you can turn the valve feeding the freeflowing one off and use the other while the frozen one thaws. Obviously you need to be able to reach all the valves involved to make this work. A slung pony in the 30-40 cu ft range is nice to have as it is comparatively easy to turn the valve on and off for each breathe if you are in a worst case scenario.

It is a lot easier to just use an environmentally sealed regulator, although at 32-33 degres many sealed regs can still free flow in some situations if ice forms over the exterior diaphragm and increases the intermediate pressure, so good heat transfer and redundancy are still important.

 

[DeepBound]

Perhaps your regs need a tune up or adjustment. Your in Ottawa, so you could go to In Depth Scuba Service, located in Kanata. They're awesome at gear service.

I brought it to Sharky's and they fixed it up right. It's not a regulator problem now, its just the fact than any regulator can freeflow in 32F fresh water.

 

[DeepBound]

What kind of regulators do you have?

They're Apex regulators. Generally they're very good but I think the laws of physics simply indicate that 32F water can't transfer heat to a cold regulator enough to prevent freezing.

 

[lowridersvt]

Yeah i have seen every reg free flow i have had my regs in 30 deg water lol I know it suposed to be frozen but it hard on regs i have only had one free flow that was under the ice about a year ago its not cool

 

[Eric__U]

I get mine serviced there every year and never had any problems. Mine work fine every time, under ice, deep or way back in a cave i trust them.

In freezing cold water it is hard not to have a reg freeflow one in a while, if you found a way to solve this problem let me know please. When i require a working reg without a failure and there is a good chance of a free flow I take enough backups or if its too risky I don't dive at all.

I got all my used parts back everytime so I know they forsure got serviced!