Detuning regulators for cold water

[Joris Vd]

Dear scubaboarders,

There's alot of anecdotal evidence and info to be found about detuning your regs for really cold water diving. Usually it consists of both detuning thé first and second stage.
However I can't really find any real literature on the use of detuning your first stage for cold water diving.is this solely so they drop from 8-10 bar to ambient would be less? If so is the drop from tank pressure to 9 bar less significant then?

Wouldn't the temperature drop be even greater from tank pressure to first stage pressure when detuning a first stage?

How does this work exactly, and is there any significant proof that detuning a first actually helps with cold water reliability?

I'm not trying to stir up a debate wether or not this is useful, but i'm more looking for reliable info on the why and if.

Kind regards,

Joris

 

[tbone1004]

most freezing occurs in the second stage where you are exhaling 100% relative humidity gas, plus spit, plus any moisture in the body itself, then blasting freezing gas over it. The first stages if properly sealed can turn into ice blocks and function properly.

Don't detune your regs, if they're certified for ice temperatures, it's at the manufacturers recommended adjustment. If your reg freezes, it's operator error

 

[runsongas]

detuning the IP decreases the adiabatic expansion cooling at the 2nd stage a bit. jury is out whether it makes a significant difference or not.

 

[Bigbella]

detuning the IP decreases the adiabatic expansion cooling at the 2nd stage a bit. jury is out whether it makes a significant difference or not.

De-tuning regulators is much the fool's errand and makes such an infinitesimal change in adiabatic cooling rates (really only appreciated by lonely physics and engineering wonks, on paper) -- also trumped, in a big way, by any aforementioned user error. That initial cooling drop of pressure, from, say 200 bar to 8.5 at the second stage can scarcely be avoided or mitigated in any real mechanical way, save for keeping your gear warm in colder climes; not Bogarting it on the surface for any damn fool reason; and using only the driest of air. It's not the cold water that's the biggest concern; it's the air supply.

I have used the very same sets of gear at freezing temperatures, as well as in tropical waters, with little alteration -- aside from the cold water use of a vodka-filled rubber cap on one of the older regs.

My incidence of regulator free-flow, even under very icy conditions: nulla, cero, zero, nulls, μηδέν . . .

Just don't buy crap; that will always cover a multitude of sins . . .

 

[rob.mwpropane]

Everyone in this thread has more experience than me, so take what I have been told with a grain of salt.

I was told in my reg rebuild class set ip to 125psi for ice, 135psi for cold, and 145psi for tropical. I set mine at 135, and if I ever get the opportunity to dive ice hopefully by then I'll have learned enough to know weather or not to drop to 125..

You can commence the firing squad

 

[Bigbella]

Everyone in this thread has more experience than me, so take what I have been told with a grain of salt.

I was told in my reg rebuild class set ip to 125psi for ice, 135psi for cold, and 145psi for tropical. I set mine at 135, and if I ever get the opportunity to dive ice hopefully by then I'll have learned enough to know weather or not to drop to 125..

You can commence the firing squad

No firing squad. A lot of modern myths go into the regulator trade, including that advice that you've received. You'll notice little more than sub-par breathing, more or less dependent upon the specific brand.

Just for scheiß and giggles, I once attempted various "cold water" settings with a Poseidon Cyklon 5000 and its earlier model, 300, years ago; and the breathing at 9.6 -10 bar (145-152 psi, the older Jetstream IP) was noticeably more of an effort; and at 8.5 bar (123 psi, the current XStream IP) was like sucking the tastiest of beverages through one of those collapsed paper straws -- you know, the ones which are set to save the world; that, or at least, contribute to the greater welfare of coke snorting turtles.

The Cyklon still possesses the highest standard IP setting of any regulator, of which I am aware, at 11.5 bar (about 167 psi); the seconds, actually meant to be tuned just short of free-flow -- and yet remain fully functional -- effortless breathing -- even at freezing temperatures.

What does that tell you?

 

[rob.mwpropane]

What does that tell you?

Black voodoo magic?

In all seriousness, I don't know.

 

[Bigbella]

Black voodoo magic?

In all seriousness, I don't know.

A combination of Black voodoo magic, yes, and decent tuning, heh, heh, heh . . .

 

[axxel57]

Dear scubaboarders,

There's alot of anecdotal evidence and info to be found about detuning your regs for really cold water diving. Usually it consists of both detuning thé first and second stage.
However I can't really find any real literature on the use of detuning your first stage for cold water diving.is this solely so they drop from 8-10 bar to ambient would be less? If so is the drop from tank pressure to 9 bar less significant then?

Wouldn't the temperature drop be even greater from tank pressure to first stage pressure when detuning a first stage?

How does this work exactly, and is there any significant proof that detuning a first actually helps with cold water reliability?

I'm not trying to stir up a debate wether or not this is useful, but i'm more looking for reliable info on the why and if.

Kind regards,

Joris

For me this article was a good orientation, even when it is de-tuning not really discussing as far as I remember.......

 

[halocline]

The idea of lowering IP for cold water is not about lessening adiabatic cooling. It actually increases it at the 1st stage. Lowering the IP was done to lower flow rates through the regulator, and it does do that. It's really noticeable with unbalanced 2nd stages. But, divers can easily control flow rate as well simply by not purging or allowing any free flow, using good technique on the surface, etc.

The two things that seem to be the most effective in preventing freeze ups are sealing the 1st stage ambient chamber and using 2nd stages with plenty of heat transfer from the water to the cooling air. Since metal is a much better heat conductor than plastic, using a metal 2nd stage or at least one with a big metal jamb nut and air barrel would be a good strategy.

Now that I'm a full time resident of upstate NY, I suspect I'll be learning more about cold water diving than I ever wanted to! My first cold dives up here will be with my sealed MK10s and balanced/adjustables.