Regulator free flow at 100 feet.

[finnks]

Norway is pretty cold so your comments are due serious consideration. But it's counter to what I know. It's just basic physics. Also, you see it in the reg manufacturers who build "cold water regs" (mostly diaphragms with environmental sealing) but almost never cold water 2nd stages. For second stages, what you can do is put a metal purge cover which facilitates heat conductance w/ the relatively warmer water. That's about it. AL has a cold water 2nd stage in their glacier model but it's just a metal cover w/ an expanded metal hose adaptor to, again, to promote heat conductance w/ warmer water (low 40s/high 30s is cold but obviously not freezing). I have it but use SP S600 and Hollis DC212 which work fine in both cold and warm waters.

Was thinking of commenting on Storker's post as well. I bet diving in Norway and those conditions everyone there has cold water rated 1st stages. For those of us using basic unsealed warm water rated 1st stages, we are more likely to get 1st stage freeze. Sealing the first stage pretty much eliminates water in contact with any moving parts, so pretty much eliminates ice impacting first stage operation.

In effect both of you are right - with sealed first stage diver only needs to worry about second. For the rest of us, 1st stage is the big concern. I suspect that first stage freeze up also releases a much larger air flow - at the very least the same amount from each 2nd, but certainly both 2nds will free flow.

Given OPs story in which it sounds as though only the primary second stage free flowed, I imagine that the 1st stage only partially froze preventing total closure - resulting in IP creep - flow was small enough that primary second stage with lower cracking pressure was the only one leaking.

Still wondering how he was doing on air before the leak started and whether he was monitoring pressure sufficiently before incident.

 

[84CJ7]

My plan for an icing free flow now that I have a 19cf pony is to switch to the pony, shut off the main tank, and and if safety allows it I will just wait a minute before turning the main tank back on to see if I have melted the freeze up. I would do the same breathing buddy air if I had no pony however I like that option less as it doubles the workload on the buddies 1st and risks icing his gear up twice as fast. I have also considered an inline shutoff for my primary LP hose instead since if you stop the air flow you stop the cold and it will thaw out, so you could switch to your octo for a minute while it thaws out, but that's assuming its not a 1st stage ice up.
I can easily operate my tank valve even with 7mm gloves however, YMMV.

Something else to consider is with a cold water kit install, frequently the manufacturers will tell you to drop the IP (mares wants it dropped 15 psi on my MR22) which helps protect the second stage by both lowering the 2nd pressure drop at the 2nd stage by almost 10% to reduce the associated temperature drop and also probably reduces the pressure trying to force the seat open (assuming you don't adjust the orifice to tweak the spring preload and get breathing quality back). My Abyss is a classic downstream second which is metal to help speed up cold dissipation.

After looking at the design of the MR22 and seeing how insulated the area protected by the CWD kit is from the source of the cold air I decided the cwd kit wasn't worth it unless I get into ice diving. The spring itself is insulated by both the diaphragm and the plastic disc between the spring and diaphragm and surrounded by non frozen water. So for an MR22 1st stage to freeze up in that area you would have to have the cold from the LP side of the diaphragm creep up through the outer surrounding metal body itself to cool the water in the ambient chamber, which is almost impossible considering its surrounded by non frozen water on both sides of it and Mares has a 10mm hex shaped hole leading to the ambient chamber allowing substantial water flow, especially since it points forwards while swimming and constantly gets flushed out. A cwd kit on an MR22 would actually reduce its ability to dissipate cold in my opinion by insulating the ambient chamber walls on one side with trapped air (with dry kit) or non exchangeable fluid with the wet kit though at least the silicone doesn't freeze. I would see turning the IP down when cold water diving as the more valuable half of the cwd kit actually, which could be done without the kit in the field in about 10 seconds. Other designs may vary.

 

[bada3003]

Your explanation makes sense. What struck me as odd is that the OP dove in a midwest quarry and experienced a 2nd stage free flow but, implicitly implied, not 1st stage. That should rarely happen for the reasons we discussed. Without an accurate diagnosis of what happened, the recommended actions have limited value. What one should do when a 1st stage free flows from when a 2nd stage does are different. Hopefully the OP will understand the distinctions and not take all the recommendations too closely to heart.

Was thinking of commenting on Storker's post as well. I bet diving in Norway and those conditions everyone there has cold water rated 1st stages. For those of us using basic unsealed warm water rated 1st stages, we are more likely to get 1st stage freeze. Sealing the first stage pretty much eliminates water in contact with any moving parts, so pretty much eliminates ice impacting first stage operation.

In effect both of you are right - with sealed first stage diver only needs to worry about second. For the rest of us, 1st stage is the big concern. I suspect that first stage freeze up also releases a much larger air flow - at the very least the same amount from each 2nd, but certainly both 2nds will free flow.

Given OPs story in which it sounds as though only the primary second stage free flowed, I imagine that the 1st stage only partially froze preventing total closure - resulting in IP creep - flow was small enough that primary second stage with lower cracking pressure was the only one leaking.

Still wondering how he was doing on air before the leak started and whether he was monitoring pressure sufficiently before incident.

 

[Storker]

I bet diving in Norway and those conditions everyone there has cold water rated 1st stages.

Quite likely. In fact, the topic is never mentioned (IME at least) by any LDS I've patronized, so I guess shops up here don't offer reg sets without cold water rated 1st stages.

 

[bada3003]

...
Something else to consider is with a cold water kit install, frequently the manufacturers will tell you to drop the IP (mares wants it dropped 15 psi on my MR22) which helps protect the second stage by both lowering the 2nd pressure drop at the 2nd stage by almost 10% to reduce the associated temperature drop and also probably reduces the pressure trying to force the seat open (assuming you don't adjust the orifice to tweak the spring preload and get breathing quality back). My Abyss is a classic downstream second which is metal to help speed up cold dissipation.

Yes, that's good practice for cold water diving. With a diaphragm design, you can usually adjust it using an outside knob but with pistons you may have to remove shims which entails disassembling the 1st stage which can be a hassle. Although I service my own regs, an "easier" alternative is to adjust the knobs on typical second stages. For example, in the SP S600, it has a venturi knob that I turn off (pre-dive) position and lower the air flow control knob which, overall, increases the breathing effort but decreases the flow rate. Of course, the resultant breathing effort must still be comfortable, otherwise it doesn't make sense.

 

[ciardi23]

Is it possible that your first stage froze up because of the temperatures at that depth? I've read other articles where that has happened.

 

[Tortuga68]

it takes 38 seconds for a AL80 to loose all its gas through a LP Hose and over half an hour with a HP hose

Where did you get those figures? They're certainly in the ballpark but real world tests I've seen say 83 seconds and 22 minutes respectively

I agree with breathing from the free-flowing reg in principal but I don't think it will change the numbers much

 

[mmcdanie]

FYI it takes 38 seconds for a AL80 to loose all its gas through a LP Hose and over half an hour with a HP hose. /QUOTE]

Not to change the subject but is this correct? Does a tank empty faster from the LP hose than HP hose? Why?
Thanks

 

[PfcAJ]

It empties faster through the LP hose. The HP port on regulators is itty bitty teeny tiny and restricts the flow.

 

[hsinhai]

FYI it takes 38 seconds for a AL80 to loose all its gas through a LP Hose and over half an hour with a HP hose.

It empties faster through the LP hose. The HP port on regulators is itty bitty teeny tiny and restricts the flow.

ahh..