regulator freeze up

[buff]

Yooper-
The physics don't lie........
Increasing the pressure DIFFERENCE, wether it from tank to IP to second stage to mouth will increase the adiabatic expansion of the gas and therefore decrease the surrounding temp. as the gas expands and cools the surroundings. Since the pressure difference is greatest as the air moves from the tank, through the first stage, this is where the greatest chance of feeze up can occur with regards to pressure changes

I don't know what the Apeks heat sinks are made out of and I don't understand how they would keep a second stage warm with all that air flow(gas cooling) going on - seems like farting in the wind.

There are two elements to freeze up-the cold and the water vapor expelled from the diver. Each element works in a different part of the reg. For the first stage the problem is created by large amounts of air expanding into the first stage along with the ambient moisture in the tank air. Second stage freeze is probably more of a result of moisture coming from the divers breath being expelled directly onto the second stage mechanical workings-then cool air passes over it and freezes.

That's the best I can come up with.

 

[Lost Yooper]

"For the first stage the problem is created by large amounts of air expanding into the first stage along with the ambient moisture in the tank air. Second stage freeze is probably more of a result of moisture coming from the divers breath being expelled directly onto the second stage mechanical workings-then cool air passes over it and freezes."

Bingo! That's what Netdoc and I were saying. The heat sink retains the heat of the divers breath and prohibits, at least in theory, a second stage freeze up.

I'm working on how to word my arguement that lowering the IP from say 145 to 130 in an Apeks reg will reduce the likelihood of a first stage freeze up.

Mike

 

[buff]

"I'm working on how to word my arguement that lowering the IP from say 145 to 130 in an Apeks reg will reduce the likelihood of a first stage freeze up."



I'll be waiting to see how you violate the laws of physics...HAHAHA

I don't know what that will be but I'll willing to listen.

 

[Ontario Diver]

Hey-O LY;

I'm keen to hear the reason. I've heard that concept from a lot of people but no one has been able to explain it. (which is kinda scary isin't it?)

Mind you, these are mostly the same folks who told me that second stages don't freeze up.

On the path to enlightenment...

 

[The Chairman]

then read this...

Lets get Physics-cal...

The pressure drop is only PART of the process in how cold the first stage will get... the actual VOLUME is the other part, Sherlock. At a reduced IP, the reulting volume of gas vented is also lower... but that is STILL not the entire picture... An hi perf reg will undergo a freeze up far quicker than than a low perf reg... why??? For some of the same reasons that high perf regs free flow more often under benign conditions! The "balance" between the intermediate pressure (IP) and the working pressure of the second stage are extremely fine. If there is more "leeway" for error (ie a detuned first stage or low perf reg) than the likely hood of freeflow is also diminished.

 

[Bob3]

Here's a little writeup I did over at RSD on the topic of regulator freeze:

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 the same set of physical laws 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.
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).

Here's a good post by Norm that gets into more detail:
http://www.scubadiving.com/talk/read.php3?num=3&id=133797&thread=133709
Here's a dandy page to do different conversions on:
http://www.chinaimporters.com/metrical.htm

 

[Lost Yooper]

Ok, the kids are in bed, and I can take the time to write this up. I will comprise this post into two parts: why dropping the IP will reduce the likelihood of first stage freeze up and the easier second stage freeze up discussion.

Intermediate Pressure:

By reducing the intermediate pressure of the first stage, the change of pressure from the first stage to the second (ambient pressure) is reduced. Therefore, when the change of pressure and gas expansion is reduced, less cooling is taking place in the SECOND stage. This is critical, folks, I am not arguing against the laws of physics, but rather the relevance in the system. Yes, the pressure change from tank pressure (3000) to an IP of 145 is less than the change to 130, and therefore, it will cool the first stage with a lower IP (the higher the tank pressure, the colder the first stage). This is irrelevant. Why? First stages don’t freeze up unless there is moisture in the high-pressure chamber (i.e. water vapor in the tank or an unsealed first stage). The relevance is in the second stage where there is water vapor from exhaled breath.

Second Stage Freeze Up:

This is the easy one. You have cold air coming in from the first stage, and when it enters the valve, the increased pressure causes a temperature drop from the expanding air. Ice will form on the valve seat and will not allow the valve spring to close the valve tightly. The ice will build, and the free flow will get worse. The heat exchanger is simply a piece of metal that keeps things warm from your exhaled breath. Also, it is often noted that second stages with metal housings, such as the old US Divers Conshelf, are awesome cold-water regs because the housing is kept warm by the exhaled breath and retains the heat better than plastic housings.
First stage freeze ups occur the same basic way. Cold air and moisture get together and result in ice build up in the first stage. For example, in a piston reg, ice would form around the piston and spring and prevent the piston from closing on the seat. It is critically important that the air you get from the shop has a dew point less than –50 degrees. Anyone who dives really cold water will come out with a huge ball of ice on the first stages yet the reg still works. Why? Because the interior of the first stage is dry from using dry air and having the first staged sealed.
So why doesn’t this occur with the Poseidon second stage? The Odin uses a different valve. With the pilot valve, the air is not expanding within a tightly confined space. The ice forms outside of the mechanism and gets thrown in your throat.

Ok, enough for now.

Mike

 

[buff]

If you tune down your reg. does your body need less air?-No. Less air per breath means more breaths-to keep the minute volume the same. More breathing means more gas and you are were you started. I don't believe that detuning a reg. by a few mm. Hg. would make that much difference, relative to the moisture and the temp of the surrounding water and the large volume of gas inhaled.
Bob3 has good advice and good links. I like the overpressurization of the second stage explanation.

 

[buff]

I am so confused.....must see some of my physics PhD friends for an explanation.

 

[buff]

Someone pull a few strings and get Apeks to explain this....