tuning for cold water

[doole]

I once missed a dive due to a fairly dumb mistake on my part: I was wearing a steel tank, which I find it rather difficult to snorkel any distance with because of the top-heaviness. So while swimming on my back a few hundred yards to get to a site, I guess my first stage got quite cold – while my second did not.

I suppose my first breath super-chilled the first. It started freeflowing and wouldn’t stop for love nor money until the tank was nearly completely drained.

I investigated the first fairly closely and did discover some very slight pitting in the HP seat. (The reg was very nearly brand new.) I assume though, that the freeflow was due to my mishandling.

My question is: do any of you specially detune your regs for icy water? How and how much? TIA chris

 

[DA Aquamaster]

Low pressure steel tanks help as the adibatic cooling load is reduced significantly with the lower service pressure.

A lower intermediate pressure also helps as it reduces the overall flow rate of the reg and consequently reduces the amount of cooling occurring. Most regs can tolerate an IP as low as 120 psi and still function well.

Detuning the second stage helps prevent an unintentional freeflow that can cool the first stage, but won't offer much more than that. I prefe to maintain the easy breathing traits of the reg. A pr dive swithc is great to use if you have one. And any venturi adjustment should be left fully closed until you are under water.

The big thing is to never breathe off the reg until you and the first stage are fully submerged. Having the reg in the water during the swim out was probably not the issue. Having cold water in the ambient chamber and breathing off the reg with the first stage out of the water as you got ready to submerge may have been a more likely cause.

You also should not test the reg after you assemble it at the dive site. If worked at home when you packed it in the dive bag, it will most likely still work at the dive site. Some people get real carried away reg testing because they regard the cold water dive they are about to do as kind of extreme and then they freeze up 15 seconds into the dive. You definitely should not inflate your BC using the reg as this will supercool the first stage and create the potential for ice to form.

Pitting on the HP seat, slight or not, is not a normal condition.

 

[doole]

Pitting on the HP seat, slight or not, is not a normal condition.

Yes, I had it replaced.

And thanks - that was good stuff.

 

[hvulin]

just a small advice...

next time close the valve on the tank... (it will stop the freeflow)

oh, and make sure you have another 1st and 2nd or to be on surface when you do it

Yes, I had it replaced.

And thanks - that was good stuff.

 

[Groundhog246]

If you were on your back, was the 1st stage in the water? If so, I think it's more likely that the 2nd stage freeflowed. It was likely quite wet and the first good inhale did it. I've only had one minor freeflow and that was in a similar situation, only after a dive, when I surfaced. Shutting off the air and putting the 2nd stage in the water for a minute then turning on the air was enough to clear it.

 

[doole]

Yes, that's exactly what happened. Problem was, since I was a mere stinking DM, nobody wanted to wait for me, so I just took my sorry self back to shore.

Although I might add that if it were my DM, s/he'd get better treatment.