Cold Water Reg

[Firebrand]

Do you only need to have a cold water regulator environmentally sealed for diving where the water temp is around (or possibly below) the freezing point?

 

[dirthead]

No, I believe cold water is defined as being below 45°-50° or so. When the compressed air in your tank flows through the 1st stage and is stepped down to 130ish psi, the expansion of the air cools the regulator. So that cooling effect can cause ice to form even if the water temp is not at the freezing point. When air is compressed it creates heat, when it expands it removes heat.

Maybe someone else can explain that a little better than I did.

 

[do it easy]

That pretty much sums it up. I think it is theoretically possible to freeze a reg at any temp, but as the water temp drops, the chance of freeflow/freezing increases.

Not all regs need the environmental seal (excluding contaminated environments). It's my understanding that the seal does more good on a piston reg. On a diaphragm reg, it basically prevents the main spring from icing over when you're getting in and out repeatedly.

Preventing cold water free flows is largely technique- deep, slow breathing, not purging on the surface, sacrificing the right kind of goat, etc. There are already several threads about this, but I'll bet we start another one here.

 

[Firebrand]

Thanks! That pretty much summed up my question. I didn't realize that the slow expansion from the low PSI to breathable levels could cause the temperature to drop that much. (My air never felt "cold" when diving).

 

[do it easy]

I just wanted to add that I dive with a Mares Abyss with out the seal. I've had it in water that was in the upper 30's and it was fine. One dive, it did start to creep, but that was towards the end of 2 dives, 38f water, 1hr+ total bottom time. My buddy's reg was creeping during the first dive, but he is a bit of a hoover.

I also had an MR12 free flow (a lot more than a creep) at 70', but it stopped around 50'. Again, this was 44f water and I was breathing hard. Once my breathing slowed down, the reg was fine.

 

[do it easy]

(My air never felt "cold" when diving).

It depends on how much air/gas you are releasing. I had a buddy that had a raging free flow at 65' and he said after half a minute, his teeth were freezing. He didn't have a seal, but his reg was also tuned wrong- IP pressure was way high. His backup reg did the same thing as soon as he switched to it. I guess it wasn't his best day diving.

 

[WarmWaterDiver]

Thanks! That pretty much summed up my question. I didn't realize that the slow expansion from the low PSI to breathable levels could cause the temperature to drop that much. (My air never felt "cold" when diving).

The temperature drop from 130 PSI above ambient to ambient pressure is 3 degrees F maximum in a 'perfect' adiabatic system. It's the pressure difference between full tank pressure, such as 1800 to 3500 PSIG, or even 4350 PSIG - 300 BAR, and the intermediate pressure of 130 PSIG above ambient that can experience as much as a 67 dgree F temperature drop in a 'perfect' adiabatic system. See my post #32 on this thread.

http://www.scubaboard.com/showthread.php?t=47081&page=4&pp=10

Obviously, this is not a 'perfect' adiabatic system in actual practice. During a freeflow event, approach to adiabatic behavior will be greater than in the normal breathing cycle however.

The water content of your breathing gas fills are a factor here, as well as ambient water and/or air temperature, techniques, etc. as mentioned by others.