1st Stage Freeze Up Prevention

[Vin]

For entering the H20 - with no air in your suit or BC. I assume that you can't orally inflate either bc of the condesation / Freeze. Whats the technique for a deep water entry through a cut ice hole? Submerge and inflate to neutrall boyancey quickly?

Vin

Yes. I had one freeze on a 120 ft bottle when I pressurized it at the first stop a few months ago - had to feather the valve all the way up to the 50 ft stop where the thermocline took us from 34F to 38F and the thing finally thawed.

 

[UWSojourner]

Having a "freeze resistant" 1st stage is a good start, that will take care that end of the hose. Then you have to worry about the 2nd stage making mischief.
Here's a little write-up that's probably posted elsewhere on the board:


"Regulator Freeze 101"

There's no set temperature where regulator freezes occur; the colder the water, the more likely it is to happen. Some manufacturers use 40º F (4½º C) as an arbitrary number to define conditions where icing may possibly commence.
Both saltwater AND freshwater can get down to 28º F (-2.2º C) and not turn solid if kept moving, such as in a heavy surge or current.
The most common type of regulator freeze-up is the first stage. Unless you're using an environmentally sealed reg, there is water inside your first stage. That water freezes from the air absorbing heat upon expanding (compliments of a set of physical laws similar to those that make your referigerator work).
The result is overpressurization of the second stage, resulting in a free flow. Most folks THINK their second stage is frozen up, but it's actually the first stage that causes the second to malfunction.

Second stages do freeze up, tho mostly on the surface from breathing in them when air temp, wind chill, etc is below freezing. Simple solution: Don't stick the reg in your mouth until you're underwater. Also, keep the fingers off the BC & drysuit inflator buttons, they will "pre-chill" the 1st stage, setting up conditions for a freezeup when it does hit the water.
The other type of second stage freeze is much more rare, in that the water temp almost always has to be below freezing & you have ice build up inside the regulator from breath condensation.
This can happen to even the BEST freeze-proof regulator if the conditions are right.
Hint... double hose regulators don't have this problem. To date, the most all-around freeze-proof reg is still the double hose.

Tip for folks using a separate bottle for drysuit inflation: Install a pop off (overpressure) valve on an LP port of the regulator. In the event of freezing, you won't have to worry about having a hose blow (or the valve on your suit explode or give you runaway inflation).

Question: Sometimes we have to inflate our BC at least before we descend (since we'll descend if we don't). So, are you advocating manual inflation of BC before descent?

 

[jonnythan]

For entering the H20 - with no air in your suit or BC. I assume that you can't orally inflate either bc of the condesation / Freeze. Whats the technique for a deep water entry through a cut ice hole? Submerge and inflate to neutrall boyancey quickly?

Vin

The problem isn't condensation in the air or breath freezing, it's the extreme cold caused by the expanding air coming from the pressurized hose. Unless the air temp is way, way, way below freezing, I can't imagine a BC inflator freezing because you're orally inflating it.

 

[DA Aquamaster]

I have done a bit of ice diving and lot of cold water diving but not recently and other than ice at the surface have really not seen any freeze-ups. Its really not a concern down here, but I do admit that I dont understand the "enviro kit" as its insulating aspects seem counter productive except for ice external to the dia or piston. Also that would seem to be better served by me by just greasing the housing and dia( or piston) for any ice not to adhere. Has anyone physically seen ice outside of the dia or piston, I realize the cage etc in the way but I just cant imagine it happening although there has been enough written on the boards to elevate it to unresolved problem status. My only thoughts go along with the moisture in the air supply but thats pretty obvious and generally been ruled out on the posts.

In a piston first stage freeze flow what usually happens is that the piston moves up to open the valve and then a bit of ice forms either on the piston stem near the body of the reg or on the first stage body below the piston head. This chunk then prevents the piston from returning to close the valve, the air continues to flow, it gets even colder, more ice forms etc, and you have a really nasty feedback loop that ensures the reg will continue to freeflow until the tank is empty.

Normally a thin film of grease is not enough as a large chunk of ice can still continue to form in the ambient chamber until it has enough volume to interfere with the spring and/or just by its bulk be large enough to block the piston's return. A fully packed silicone filled environmental chamber prevents the problem by keeping the water out.

But small amounts of water in the wrong areas can cause problems and really old environmental silicone can get dirty and clumpy and allow pockets of water to form. So annual replacement of the silicone is normally needed. It makes cleaning the reg harder, is a little messy and ads to the cost of the service (a couple bucks) so it is not real popular with many shops.

Some diaphragm regs use silicone oil or alcohol under a diaphragm to seal the reg and transmit ambient pressure, while other diaphragm regs just use a pad and pin arrangement to transmit ambient pressure in reg designs that allow that arrangement. Again, the silicone or alcohol regs need maintence to ensure the fluid is till there. On some, the liquid will expand in hot weather and seep out.

SP uses a TIS kit which has its good points but also limitations. It is O2 clean freindly and easy to service but can be inadequate in extreme situations on the MK 20 and 25. The most recent AF version of the Mk 25 uses a composite piston with an insulating cover over the piston head and upper portions of the stem, a teflon coated mainspring, and a small rubber sleave on the lower part of the stem that flexes as the piston moves and pops off any ice trying to accumulate. The piston stem is also mirror polished to make it harder for ice to form on it. The strategic placement of a plastic shim between the spring and first stage body also helps to limit heat transfer from the spring to the rest of the reg keeping the spring warmer.

This pretty much prevents ice formation on the piston and spring, but in my experience, it still seems quite possible in very cold water under high airflow situations for ice to form on the sides of the ambient chamber and to potentially block the piston's movement and cause a freeze up. Ice can certainly form outside the reg in this area depite all the water flow around it so it makes sense that it could also form inside the reg where the flow the relatively warm water is much more restricted.

 

[DA Aquamaster]

Question: Sometimes we have to inflate our BC at least before we descend (since we'll descend if we don't). So, are you advocating manual inflation of BC before descent?

I would not use the reg at all for any purpose until you and the reg are completely underwater. So orally inflate if needed and then do not breathe of the reg at all until after you are completely under water.

New cold water divers often have a bad habit of breathing off the reg 2-3 breaths before decending and then very quickly experience a freeze up. The colder the air temp, the bigger the problem will be with doing this. If the outside air temp is 50 degrees you may get away with it with an unprotected reg. If the air temp is colder than this you probably won't. If the air temp is below freezing already, you definitely won't.

 

[Vin]

Good info!
Thanks!
Vin

 

[quimby]

I have to do some playing around with some instrumentation and see what I can reproduce but essentially what problem there is would be eliminated by going back to a trieste (Voit two hose with essentially MR12 guts) and I believe still give a lp and hp ports.

 

[pufferfish]

Lots of good info in the above posts but one also needs to consider moisture in the tank air. Another way of looking at this would be to ask the question, "what is the highest (least negative) dewpoint one should accept for ice diving?"

Attempts have been made to place thermocouples in the walls of a first stage during actual dives in water at the freezing point in order to assess the potential air temps reached inside the reg chambers. Depending on depth and flow rates this wall temperature seemed to bottom out around -5 C. Likely the air temps within the actual flow stream would be even lower. Once this internal temp can be pinned down or estimated the pressure dewpoint is known which can be converted to atmospheric dewpoint. The atmospheric dewpoint is what is reported from the lab when the compressor air is analysed.

If we assume a first stage internal temperature of say -10 C the atmospheric dewpoint converted from a -10 C pressure dewpoint at 3000 psi is about -60 C or -75 F. This would be the dewpoint which should not be exceeded so as to minimize the risk for a freeze failure in these conditions. Of course if you are diving in warmer conditions the acceptable dewpoint would be higher (less negative).

The problem of freeflows while ice diving from excessive moisture does exist as the standards set by the various agencies are set for warmer conditions and not the extremes of temperatures found in ice diving. Consider that NAUI modified Grade E specifies a dewpoint of only -40 F/C. Even in Canada the CSA standard is -53 C which is inadequate for ice diving but probably fine for three season diving. Both of these 'standards' exceed the dewpoint one should accept as a minimum for diving under ice.

So for ice diving I'd make sure your atmospheric dewpoint on the most recent air test was at least -60 C or -75 F. That is about 12 ppm moisture.

 

[Chaos]

I just thought of something after one of you mentioned alcohol-filled 1st stage cold water kits.

Since we're mostly technical divers here, here's something to think about. Sometimes the silicone oil that's used to relay env pressure to the diaphragm leaks past the diaphragm into the interstage pressure chamber of a 1st stage, for whatever reason (worn diaphragm edges, nicks on the sealing surface or whatever). I see it a lot when servicing regs.

It seems logical to avoid easily combustible fluids like alcohol as an insulator in the cold water chamber. Any alcohol (a relatively thin liquid, compared to silicone oil) seeping into the IP chamber of the reg would be evaporated under pressure, somewhat like a carburettor. Add the high oxygen content of a decompression gas and you've got a nice combustion engine .

I don't know if it's ever happened to anyone, but I think it could. Whatcha think?

 

[Chaos]

Ah yes, and another thing. If water temperatures get really low, a diaphragm 1st stage is probably a little better at resisting cold than a piston 1st stage.

One manufacturer of piston 1st stages I know measured temperatures on the piston stem walls of -50 deg C (about 90 deg F?) below ambient. They coated the internals of a reg with a heat sensitive dye to determine the low temperatures and location of heat loss during a typical breathing cycle.