Cold water regulator question

[froggs]

In looking at the Aqualung Kronos Supreme, it states the following as a feature:

"Specially adjusted at the factory with a lower medium pressure"

Can someone explain the benefit of this for a newb? Will it impact breathing performance of the reg?? Thanx.

 

[DA Aquamaster]

A lower intermnediate pressure does two things.

1. It reduces flow rate, which is a mixed bag as unless the reg has an over abundance of air flow it can increase IP drop and affect performance. At best it just reduces the air flow that could occur during a freeflow as may occur if the reg falls out of your mouth under water.

2. It reduces the adibatic cooling that occurs as the gas flowing through the regulator drops from the intermediate pressure to ambient pressure. The gas will cool proportionately less dropping 120 psi compared to 145 psi. However, this is a moot issue as the air has just dropped from tank pressure to intermediate pressure and the end result either way is the gas dropping from tank pressure to ambient pressure with the same amount of heat being drawn from the regulator, and in turn the surrouding water, to supply the heat energy needed for the gas to expand. The only difference is the percentage of cooling that occurs betwene the tank and first stage versus the first and second stages.

Consequently what counts is the heat transfer traits of the regulator's first and second stages and/or the sealing of the regulator's first stage internal parts to prevent water from freezing on them. Reducing intermediate pressure is just a crutch and in my opinion is either an advertising ploy or symptomatic of a less than perfect cold water regulator that needs all the help it can get in extremely cold water below 40-45 degrees F (like the Scubapro MK 25 S600).

My advice is to get a Scubapro MK 17 X650, Mk 17 G250V or MK 17 S600. All of them are exceptional cold water regulators that will give extremely reliable service even in extremely cold ice diving situations.

 

[Thalassamania]

...

My advice is to get a Scubapro MK 17 X650, Mk 17 G250V or MK 17 S600. All of them are exceptional cold water regulators that will give extremely reliable service even in extremely cold ice diving situations.

as you note, adiabatic cooling is a function of the pressure drop, the greater the drop the greater the cooling. Cold water regulator failure is usually free flow that results from cooling of and ice build up in, the first stage. The greater the drop, the greater the cooling. The second stage does not often play a role in regulator freeze up. Reducing intermediate pressure should make first stage freeze up more likely.

The Scubapro MK 17, despite its diaphragm design, is not approved for cold water use by either the U.S. Navy or the National Science Foundation's Antarctic Diving Program.

 

[SparticleBrane]

Thal -- got a list of regs that are?

 

[Thalassamania]

Thal -- got a list of regs that are?

u.s. navy diving equipment list

I'll have to look for the NSF list that Sherwood Magnum Blizards are what's in the dive locker if memory serves.

Can't find the list, here's an article.

 

[Spratman]

That's pretty amazing stats. However, that report is over ten years old. Do they have anything more up to date?

EDIT: I checked the other link list, and saw the updates....Poseidon, Apeks, Mares and SP

 

[engdiver]

It was interesting that the Sherwood Blizzard had two failures for two dives(100%) but the Maximus had only 1.7% failure from 1341 dives.
What is the difference between the two regulators?

 

[Thalassamania]

It was interesting that the Sherwood Blizzard had two failures for two dives(100%) but the Maximus had only 1.7% failure from 1341 dives.
What is the difference between the two regulators?

Don't know. We got a Sherwood tech out there?

 

[froggs]

Reducing intermediate pressure should make first stage freeze up more likely.

This confuses me and seems to defy the design of the cold water aspect of the Aqualung Supreme model.

 

[froggs]

I'm really looking for a regulator that will mostly be used waters above 50F, but may occassionally be used in waters in the 40s. The Kronos side exhaust intrigues me, but it doesn't have the environmentally sealed dry first stage. Hence the Supreme version being an option, but I'd rather not get the Supreme version if it's going to impact overall performance of the reg, seeing that it'll only be used in cold water a small % of the time. Maybe the Aqualung Legend, since it comes standard with the environmentally sealed dry first stage may be a better option.