OP
If I could get the danged valve drill working reliably, maybe I wouldn't worry so much . . .
BTW, the only explanation the shop came up with for my prior freeflow was freezing, as unlikely as that seems.
Prebreathing regs
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If I could get the danged valve drill working reliably, maybe I wouldn't worry so much . . .
BTW, the only explanation the shop came up with for my prior freeflow was freezing, as unlikely as that seems.
Shops are sometimes wrong :11:TSandM:
It wasn't cold enough that day for freezeflowing to be a problem.... and you weren't doing something like breathing off both regs while inflating your wing and drysuit. So it still seems pretty unlikely to me. I still think it was a gradual IP creep problem that would have been fixed with a rebuild.
Green_Manelishi
Contributor
Originally Posted by Green_Manelishi
FWIW ...
Up heeya in (well I won't say where) the air temp drops well below freezing and the water temp will reach low 30s.
I use SP Mk16 1sts on Atomic seconds. I've pre-breathed (inhale only while watching the SPG needle) the regs, with no subsquent problems when the air temp was in the teens and the water temp in upper 30s/low 40s. I also double check the valve just before donning the rig. Most of the problems I've ever encountered have been in that "zone" where all of me is wet but the tank valve/reg is now out of the water because I am talking to the skipper of boat who is hauling the traps I cut free.
Thanks for the kudos but I am not the only hardy (or foolish?) soul braving cold water and air. That particular day was memorable though because I almost called the dive as I walked through the snow down to the boat dock.
FWIW ...
Up heeya in (well I won't say where) the air temp drops well below freezing and the water temp will reach low 30s.
I use SP Mk16 1sts on Atomic seconds. I've pre-breathed (inhale only while watching the SPG needle) the regs, with no subsquent problems when the air temp was in the teens and the water temp in upper 30s/low 40s. I also double check the valve just before donning the rig. Most of the problems I've ever encountered have been in that "zone" where all of me is wet but the tank valve/reg is now out of the water because I am talking to the skipper of boat who is hauling the traps I cut free.
Don Janni:
Thanks for the kudos but I am not the only hardy (or foolish?) soul braving cold water and air. That particular day was memorable though because I almost called the dive as I walked through the snow down to the boat dock.
Peo
Registered
Being a Swede now relocated to the Puget Sound area for the last four years, I second what other people have been saying.
I also dive Mk25 first stages for my back gas, and my trusty old diaphragm ScubaPro first stages on stage and deco bottles.
I prebreath my regs here in the Sound, even if air temperatures are below freezing, but that's about the point where I'd start worrying about keeping my first stages in the water when I do it. However, freezing up a first stage isn't the end of the world unless you're battling a tight slack or have some other time constraints.
Another five degrees colder than what we have here in the winter, and I'd begin to get a bit more concerned. Swedish winter condition with sometimes -30 Fahrenheits on the surface, 30 degrees in the water: no way I'm prebreathing before I'm in the water.
Not exhaling through the second stage while you're doing the prebreath also helps BTW.
Another aspect is to think about why you're prebreathing to begin with.
Taking a couple of breaths shows that the tank valve is open, but if you do it with the second stage out of the water, you won't notice a torn diaphragm or check valve.
I also dive Mk25 first stages for my back gas, and my trusty old diaphragm ScubaPro first stages on stage and deco bottles.
I prebreath my regs here in the Sound, even if air temperatures are below freezing, but that's about the point where I'd start worrying about keeping my first stages in the water when I do it. However, freezing up a first stage isn't the end of the world unless you're battling a tight slack or have some other time constraints.
Another five degrees colder than what we have here in the winter, and I'd begin to get a bit more concerned. Swedish winter condition with sometimes -30 Fahrenheits on the surface, 30 degrees in the water: no way I'm prebreathing before I'm in the water.
Not exhaling through the second stage while you're doing the prebreath also helps BTW.
Another aspect is to think about why you're prebreathing to begin with.
Taking a couple of breaths shows that the tank valve is open, but if you do it with the second stage out of the water, you won't notice a torn diaphragm or check valve.
Peo
Registered
Snowbear:
If you work really hard on it, you can probably get any reg to freeze in any circumstances -- add a bunch of water to your tank before filling and then press the purge button real hard for a couple of minutes.
BUT -- a freeze itself is seldom the root cause of the issue. I'd also first suspect IP creep, second dirt or moisture inside the first stage.
TSandM:
It's a combination of adiabatic cooling from the expanding air, this can form a block of ice on a hard working first stage in above freezing water.
On the second stage it's a combination of the same cooling plus the moisture in your exhaled breath. For this reason some cold water regulators like my Sherwood Blizzard have a heat sink of sorts to capture the exhaled warmth and surface treatments to retard moisture build-up.
Ironicly the cold water is seen as a source of heat compared to the sub freezing air. Also water is a much better thermal conductor. In effect you don't want to breathe from the regulator until it's being "warmed" by the cold water. It's all relative.
42F is the temperature I have read a number of times where you begin to consider wanting a "cold water" capable regulator. I can get very close to than number in mid summer freshwater here in Maine.
Pete
Spectrum has it right. The issue of the air temp being above or below freezing is more or less irrelevent other than that "warmer" air will rewarm the pre-breathed first stage slightly faster. With enough gas flow, you can chill a first stage below freezing even in mid summer.
I think you need to look at it as a checking account. You only have so much money in the account to work with and you only get paid every so often. So if you "spend" your money too fast, you are going to overdraft.
Applying this to a regulator, the reg is going to cool a certain amount during pre-breathing due to adibatic cooling caused by the expanding air needing to draw energy (in the form of heat from the environment) to provide the extra energy needed for expansion. This cooling effect is more or less cumulative above water where transfer of heat from the relatively warm environment is minimal due to the poor heat tranfer traits of air. This is especially true in cold air close to freezing where there is less temperature differential in the first place.
So..if you pre-breathe, the reg will be colder when it enters the water. If it is below freezing, the potential exists for water to freeze inside the ambient chamber where it can impede the movement of the piston or diapgram causing a freeflow. Since you will also breathe off the reg under water it will continue to experience adibatic cooling and even the greater heat transfer traits of the water may not be sufficient (in very cold water) to get the temp back above freezing inside the reg and that small amount of ice in the reg can continue to grow during the dive causing a freeze fllow later in the dive. The colder the water, the less heat available for heat transfer and the greater the risk of this occurring.
So if diving in very cold water and in cold air temps, it's still a bad idea to prebreathe your reg unless it is extremely freeze resistant (ie: a fully sealed ambient chamber). What is worse, some divers not only pre-breathe their regs to test them, but also use the power inflator to fill the BC and inflate their dry suit prior to hopping in - and then blame the reg when it freezes up. Many divers get away with it for a long time, but given enough gas flow prior to the dive, cold enough air temps, and cold enough water temps, a freeze flow is in many cases inevitable.
I also agree exhaling in the second stage is a bad idea in cold weather as the moisture in your exhaled air can freeze inside the air barrel, poppet, etc. and lead to a freeflow. This is especally true with second stages with plastic cases and plastic air barrels as they are essentially insulators that impede heat transfer.
Personally, I feel you should test your reg at home and trust that it will still work an hour or two later at the dive site. I'd also recoomend orally inflating your BC. prior to a very cold water dive in cold air temps or alternatively fill it off another tank and reg that will not be used on the dive.
I think you need to look at it as a checking account. You only have so much money in the account to work with and you only get paid every so often. So if you "spend" your money too fast, you are going to overdraft.
Applying this to a regulator, the reg is going to cool a certain amount during pre-breathing due to adibatic cooling caused by the expanding air needing to draw energy (in the form of heat from the environment) to provide the extra energy needed for expansion. This cooling effect is more or less cumulative above water where transfer of heat from the relatively warm environment is minimal due to the poor heat tranfer traits of air. This is especially true in cold air close to freezing where there is less temperature differential in the first place.
So..if you pre-breathe, the reg will be colder when it enters the water. If it is below freezing, the potential exists for water to freeze inside the ambient chamber where it can impede the movement of the piston or diapgram causing a freeflow. Since you will also breathe off the reg under water it will continue to experience adibatic cooling and even the greater heat transfer traits of the water may not be sufficient (in very cold water) to get the temp back above freezing inside the reg and that small amount of ice in the reg can continue to grow during the dive causing a freeze fllow later in the dive. The colder the water, the less heat available for heat transfer and the greater the risk of this occurring.
So if diving in very cold water and in cold air temps, it's still a bad idea to prebreathe your reg unless it is extremely freeze resistant (ie: a fully sealed ambient chamber). What is worse, some divers not only pre-breathe their regs to test them, but also use the power inflator to fill the BC and inflate their dry suit prior to hopping in - and then blame the reg when it freezes up. Many divers get away with it for a long time, but given enough gas flow prior to the dive, cold enough air temps, and cold enough water temps, a freeze flow is in many cases inevitable.
I also agree exhaling in the second stage is a bad idea in cold weather as the moisture in your exhaled air can freeze inside the air barrel, poppet, etc. and lead to a freeflow. This is especally true with second stages with plastic cases and plastic air barrels as they are essentially insulators that impede heat transfer.
Personally, I feel you should test your reg at home and trust that it will still work an hour or two later at the dive site. I'd also recoomend orally inflating your BC. prior to a very cold water dive in cold air temps or alternatively fill it off another tank and reg that will not be used on the dive.
OP
DA Aquamaster, I don't know why I don't just PM you with my gear questions . . . your answers are always so complete and so good.
The one thing I don't know after reading what you wrote is WHAT is very cold water.
On our cold days, I can definitely use the oral inflation technique for blowing up my BC before I get in the water (and why would anybody inflate their dry suit BEFORE descending?) I would still like to check to make sure at least one reg is working, and the air is on . . . at what combination of air and water temperatures does that become too great a risk? Especially since, according to your explanation, the risk is not just immediate, but later in the dive?
The one thing I don't know after reading what you wrote is WHAT is very cold water.
On our cold days, I can definitely use the oral inflation technique for blowing up my BC before I get in the water (and why would anybody inflate their dry suit BEFORE descending?) I would still like to check to make sure at least one reg is working, and the air is on . . . at what combination of air and water temperatures does that become too great a risk? Especially since, according to your explanation, the risk is not just immediate, but later in the dive?
serambin
Guest
If the water temp is below 45, don't dive, just add a shot of scotch to a half glass of said water and let nature take its course . . .
Kwbyron
Contributor
I was thinking the same thing....TSandM:
Is the potential ice coming from moisture in our breath? I"m in the habbit of taping the purge valve a couple times before breathing off mine...would this be a viable option untill we get in the water if we must make air come out the reg?
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