oversea:
I'm not going to tell you not to do it, just as long as you understand the drawbacks. If you can live with it, it's your choice.
Can someone explain freezing
- Thread starter oversea
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I'm not going to tell you not to do it, just as long as you understand the drawbacks. If you can live with it, it's your choice.
AtomicWalrus
Contributor
Warren_L:
I always sling my pony - it's never posed any problems. It's easy to access my gas, turn it on or off, and it's also in a position where I can hand it off to another diver if needed. Once I'm in the water, I haven't encountered any issues with mobility.
Poseidon8118
Contributor
Straight up from Dive Lab! Lots of good info!
This is a small sample of a wonderfully done article:
A first stage regulator, usually attached to the tank valve, reduces the tank pressure to approximately 150 psig O/B (10.3 bar). This lower pressure is fed by means of a hose to a second stage demand regulator that is held in the divers mouth. The reduction in pressure by the first stage causes the compressed gas/air to greatly expand at the first stage flow orifice. This rapid expansion of gas dramatically reduces the temperature of the breathing gas. Dive Lab has found that drops of 50° F (27.8° C) are common. The cooling appears to be linear and predictable. The higher the pressure at which gas is stored, the greater the temperature drop will be when the pressure is reduced to a typical low pressure of about 150 psig O/B (10.3 bar).
When the diver is immersed in relatively warm water of 75° F (23.9º C) and is breathing from a tank of compressed air filled at 3000 psig, the low-pressure air coming out of the first stage regulator can be as low as 25° F or 3.9° C. That is below freezing. Most scuba divers do not sense this cold breathing gas and are not concerned. However, even at these warm water temperatures when using air or NitrOx, it appears that divers have been unknowingly using a great deal of body heat/energy to warm the cold gas inhalations.
The full paper on cold water effects:
http://www.divelab.com/divelab/mainpages/coldgaspaper.htm
You just need one of these setups below...LOL
This is a small sample of a wonderfully done article:
A first stage regulator, usually attached to the tank valve, reduces the tank pressure to approximately 150 psig O/B (10.3 bar). This lower pressure is fed by means of a hose to a second stage demand regulator that is held in the divers mouth. The reduction in pressure by the first stage causes the compressed gas/air to greatly expand at the first stage flow orifice. This rapid expansion of gas dramatically reduces the temperature of the breathing gas. Dive Lab has found that drops of 50° F (27.8° C) are common. The cooling appears to be linear and predictable. The higher the pressure at which gas is stored, the greater the temperature drop will be when the pressure is reduced to a typical low pressure of about 150 psig O/B (10.3 bar).
When the diver is immersed in relatively warm water of 75° F (23.9º C) and is breathing from a tank of compressed air filled at 3000 psig, the low-pressure air coming out of the first stage regulator can be as low as 25° F or 3.9° C. That is below freezing. Most scuba divers do not sense this cold breathing gas and are not concerned. However, even at these warm water temperatures when using air or NitrOx, it appears that divers have been unknowingly using a great deal of body heat/energy to warm the cold gas inhalations.
The full paper on cold water effects:
http://www.divelab.com/divelab/mainpages/coldgaspaper.htm
You just need one of these setups below...LOL
Not all SP regs are prone to freeflow in cold water and saying they SP regs are prone to freeze ups" is an over generalization. The same thing is true when saying all diaphragm regs are less likely to freeze up than piston regs. Not all diaphragm regs are sealed and those that are not can often be very prone to frezeing.
The Scubapro Mk 2 Plus and Mk 16 are actually very freeze resistant and work well for ice diving. Their flow rates are low enough that their TIS systems are more than adequate to handle the adibatic cooling load.
The Mk 25 on the other hand has a reputation for freezing up in very cold water (40 degrees F or less). The S600 second stage seems to be associated with Mk 25 freeze ups more than any other second stage as the S600 has a tendency to develop a slight freeflow in cold water (as does my X650 so far).
Good cold water technique also goes a long way toward preventing a freeze up:
1) don't test (and consequently cool) the reg until the first stage is under water.
2) Don't breathe and inflate BC or drysuit at the same time or in immediate sequence.
3) use several small blasts on the inflator rather than one long one.
Using low presure tanks also helps as with a smaller drop in pressure, 2250 to 2400 psi dropping to 145 psi as opposed to 3000 or 3300 psi dropping to 145 psi, less heat has to be drawn from the reg and surrounding water as the air expands so the chance of ice formation is reduced.
Using good technique, low pressure tanks and D400 second stages I have never frozen up either Mk 20 or Mk 25 first stages in well over 300 dives in water with bottom temps ranging from 35 to 45 degrees. So the Mk 25 can freeze up, but if you do your part, it won't.
In general, due to the reduced effects of adibatic cooling as tank pressure drops, the largest risk of a first stage freeze up is early in the dive with a full tank. Second stage freeze ups on the other hand tend to result from a slow build up of ice in the second stage and they consequently are more likely to occur later in the dive.
Older metal cased second stages and plastic cased second stages with metal air barrels are less likely to freeze as they have much better heat transfer traits. With plastic case/plastic air barrel second stages, getting ice chunks spit at you is better than having the ice stay in the reg and collect until it jams the lever or poppet, but it is still a bad sign. But don't forget that if this starts to occur, you can always give it a break to let it "warm up" for a few minutes by switching to your octo or redundant second stage.
A first stage will always freeze open so that air freeflows, usually in huge amounts. A second stage on the other hand can freeze closed and fail to deliver air. The good news is that again switching to the octo is all that is required until the primary second stage thaws.
If the first or second stage freezes up with a resulting freeflow, turning off the valve to the reg for several seconds will normally allow it to thaw. Obviously a pony or other redundant air source is the way to go to enable you to wait for the primary reg to thaw.
The Scubapro Mk 2 Plus and Mk 16 are actually very freeze resistant and work well for ice diving. Their flow rates are low enough that their TIS systems are more than adequate to handle the adibatic cooling load.
The Mk 25 on the other hand has a reputation for freezing up in very cold water (40 degrees F or less). The S600 second stage seems to be associated with Mk 25 freeze ups more than any other second stage as the S600 has a tendency to develop a slight freeflow in cold water (as does my X650 so far).
Good cold water technique also goes a long way toward preventing a freeze up:
1) don't test (and consequently cool) the reg until the first stage is under water.
2) Don't breathe and inflate BC or drysuit at the same time or in immediate sequence.
3) use several small blasts on the inflator rather than one long one.
Using low presure tanks also helps as with a smaller drop in pressure, 2250 to 2400 psi dropping to 145 psi as opposed to 3000 or 3300 psi dropping to 145 psi, less heat has to be drawn from the reg and surrounding water as the air expands so the chance of ice formation is reduced.
Using good technique, low pressure tanks and D400 second stages I have never frozen up either Mk 20 or Mk 25 first stages in well over 300 dives in water with bottom temps ranging from 35 to 45 degrees. So the Mk 25 can freeze up, but if you do your part, it won't.
In general, due to the reduced effects of adibatic cooling as tank pressure drops, the largest risk of a first stage freeze up is early in the dive with a full tank. Second stage freeze ups on the other hand tend to result from a slow build up of ice in the second stage and they consequently are more likely to occur later in the dive.
Older metal cased second stages and plastic cased second stages with metal air barrels are less likely to freeze as they have much better heat transfer traits. With plastic case/plastic air barrel second stages, getting ice chunks spit at you is better than having the ice stay in the reg and collect until it jams the lever or poppet, but it is still a bad sign. But don't forget that if this starts to occur, you can always give it a break to let it "warm up" for a few minutes by switching to your octo or redundant second stage.
A first stage will always freeze open so that air freeflows, usually in huge amounts. A second stage on the other hand can freeze closed and fail to deliver air. The good news is that again switching to the octo is all that is required until the primary second stage thaws.
If the first or second stage freezes up with a resulting freeflow, turning off the valve to the reg for several seconds will normally allow it to thaw. Obviously a pony or other redundant air source is the way to go to enable you to wait for the primary reg to thaw.
rescuediver009
Contributor
Warren_L:
If you have to try this hard to prevent a freeflow, I think that you need to purchase a regulator more suited to your diving environment.
As for the freeflow, remember the drill in your open water class on how to breathe off a freeflow.... Particularly remember how much air you used in that short time. Your tank will enmpty quite quickly so you have to be able to make a decision fast. Of course it all goes ack to the reg. Dive with something suited to your environment and you will avoid silly problems....
Just my .02 worth. If you have to modify, adjust, or handle your reg in a special way to prevent it from having problems in cold or deep or cold/deep water, you have the wrong reg, period.
I cannot imagine any situation a single person using a reg ever being able to over breath it unless it is an inferior reg.
As my mechanic instructor always told me, the right tool for the job makes all the difference.
I cannot imagine any situation a single person using a reg ever being able to over breath it unless it is an inferior reg.
As my mechanic instructor always told me, the right tool for the job makes all the difference.
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