Avoiding cold water Free Flow - best practices

[grf88]

I think the Apeks first stages have something similar. I thought I remembered reading something about a heat trap or something before I bought my singles set.

Apeks second stages have heat exchangers on them that help mitigate the issue but not prevent them.

 

[EireDiver606]

Apeks second stages have heat exchangers on them that help mitigate the issue but not prevent them.

I thought that the top of the new Apeks first stages were heat exchangers, not challenging you, just wondering

 

[grf88]

I thought that the top of the new Apeks first stages were heat exchangers, not challenging you, just wondering

Quite possible, all mine are a few years old but I did see a photo that had something similar on a newer version. Not sure how effective it would be as the entire first stage is already effectively a heat exchanger.

 

[electric_diver]

Would like to get insights from experienced cold water divers (32-45 degree water) on best practices we as divers can follow to diminish the probability of a free flow when diving cold water.

1. Buy high quality cold water regs.
2. Get them serviced by someone who knows what they are doing. This is the hard part in that the average dive store reg tech doesn't really know what they are doing. Some do. Find one that does.

Most cold water free flows that I have witnessed have been the result of poor quality servicing. Its the #1 cause of free flows IMO.

Also salt water can be colder than 32F.

 

[Diver0001]

Would like to get insights from experienced cold water divers (32-45 degree water) on best practices we as divers can follow to diminish the probability of a free flow when diving cold water. The assumption of this question is we are diving with cold water rated regs that are properly serviced. Does lowering IP pressure at lower end of scales help? avoiding excess work at depth to ensure slow breathing..etc etc. What factors do we have control of as divers?

1) In my experience the air temperature makes a big difference. In diving under ice in -15C air and +2C water temperatures the water was actually quite a bit warmer than the air. We discovered that when you put the 2nd stage inside a knitted cap while top side and spent the first 5 min of the dive near the entrance letting the gear "warm up" to the temperature of the water that the number of free flows decreased greatly.

Having had that experience I apply the same idea even if the air isn't as cold as -15C. I keep the 2nd stage inside a tuque until just before we hit the water.

2) Entry is the other time where a lot of free flows happen. If your reg freeflows as you enter the water, even for a moment, then there is a good chance that it will freeze. Lowering the IP doesn't help because it's the flow rate of the air through the 2nd stage valve (ie. how much gas is expanding) that causes ice to form on the valve. At a intermediate pressure of 10 bar the flow rate through the valve is still virtually the same as when the ip is set to 8 bar.

What you need to do here is to make sure that the venturi flaps are set to the minus setting in order to reduce the chance of the regulator free flowing during entry. De-tuning the 2nd stage slightly (not uncomfortably, just slightly) will help in this regard a lot more than setting the IP to a lower setting. Having decent regs fitted with 2nd stage heat sinks helps a lot too.

3) Finally, in my ice diving experience the regulator is far less likely to free flow than your inflator(s). During one dive we had 4 divers in the water all with drysuits (8 inflators) and 7 of them free flowed during the dive. Not massively, but enough to be irritating and require being uncoupled. For this you need to make adjustments on your inflator(s) with small bursts giving enough time in between for the water to warm the valve back up again.

Hope this helps.

R..

 

[Landlocked123]

Great information. Thanks for sharing.