Argon Bottles

[jasona111]

Hey guys,
As I mentioned in another thread I'm looking at doing some tech courses next year, so want to start planning and getting some extra required gear... Could someone please tell me what size of tank is usually used as an Argon bottle? I'd assume something fairly small maybe a 20L. and while I'm being nosey why do you fill a drysuit with argon in tech and not your breathing gas? is it just to conserve breathing gas, or some other reason?

 

[JWU42]

Hey guys,
As I mentioned in another thread I'm looking at doing some tech courses next year, so want to start planning and getting some extra required gear... Could someone please tell me what size of tank is usually used as an Argon bottle? I'd assume something fairly small maybe a 20L. and while I'm being nosey why do you fill a drysuit with argon in tech and not your breathing gas? is it just to conserve breathing gas, or some other reason?

Argon is used more when diving Helium mixes. Helium is a fast moving molecule and takes heat away, where as Argon is larger and slow moving - helping to keep heat with you.

// Jeff

===================== From www.gue.com ======================
Argon Bottles

Argon bottles are used to introduce argon into a drysuit for added warmth. Argon has favorable insulative qualities and is used when diving in cold water or when using a gas with high thermal conductivity, such as a helium mix, in one's back tanks. Inflating one's suit with a helium-based mixture can produce a large degree of body cooling due to helium's high thermal conductivity. A dangerous reduction of body temperature can easily result from the use of helium-based mixtures for drysuit inflation and divers should avoid this practice. Additionally there is a limited risk of counter-diffusion when immersed in a gas of lower density than one's breathing medium.

Argon bottles generally range from about 6ft³ to 14ft³ and are most efficient with rated pressures close to 2000psi, as argon is typically supplied at a lower pressure. Divers generally secure the argon bottle to the side of the tanks but occasionally may place smaller bottles on the harness waist strap.

Argon Regulator Choice

An argon drysuit inflation system consists of a first stage, a hose and a pressure relief valve (PRV). The first stage should be "detuned" to lower the intermediate pressure.

A PRV must be installed to protect from a first stage failure. If a diver does not use a PRV and the first stage creeps, this may cause the drysuit to inflate constantly and could even cause a hose to rupture.

The hose is a 24-inch drysuit hose and is run from the first stage under the waist belt of the harness to the chest-mounted inflator.

 

[jasona111]

thanks.

 

[DA Aquamaster]

As indicated above argon demonstrates much less heat transfer efficiency than helium. In general a diver on a helium mix will be colder already through respiration so using a gas other than helium in the dry suit is virtually a neccessity in cold water.

On the other hand, argon is only about 1/3 less efficient in terms of heat transfer than air and that assumes a perfectly purged suit with no air at all left in it. That is difficult to achieve. Consequently given the limited theoretical advantage and the practical limitations of using argon, there is no practical benefit in terms of maintaining core temperature using argon instead of air, something that has been confirmed in double blind studies. This will potentially be an issue of hot debate as many divers believe in argon and I have no doubt that they believe they are warmer as well, regardless of the facts.

So in short if you are diving with helium a separate drysuit inflation system makes a great deal of sense, but save yourself a lot of expense and use air.

This will expand your tank options or capacities as well as you will be able to get an honest 6 cu ft out of a 6 cu ft 3000 psi tank. In my argon believing days, I used a 14 cu ft 2015 psi Luxfer tank that was nearly ideal in that it offerred a nice volume of gas at low pressre in a tank that was still suitably small.

Since no second stage is used and everything else is the same, the OPRV requirement mentioned above is still a neccessity.

 

[jonnythan]

In general a diver on a helium mix will be colder already through respiration

I remember reading in another thread that since helium has a high *thermal conductivity*, its very low *thermal capacity* means that breathing it does not cool you down more than air.. and in fact, breathing it may help you retain more heat than breathing a gas such as air. Think about it... it takes a lot less heat to warm up helium to body temperature in the lungs than it does air or nitrox or whatever. Therefore you're losing less body heat that way. There is no conduction going on in the respiratory system the way there is when the gas is the barrier between your body and a giant heat sink.

 

[jonnythan]

Actually this brings up a good question, especially for DA: do you find you're colder when breathing helium and using air for inflation vs when you're breathing air as well as using it for inflation?

 

[padiscubapro]

As indicated above argon demonstrates much less heat transfer efficiency than helium. In general a diver on a helium mix will be colder already through respiration so using a gas other than helium in the dry suit is virtually a neccessity in cold water.

.

note to jonnythan, you must have made your post while I was composing my answer...

actually through respiration its a big no and misunderstood by many experienced divers. This is taught in my ANDI trimix programs, I am not aware of any other agency teaching it...

All gas we breath is bought up to (or very near) body temperature (in the lungs), Helium requires much less energy (calories) to bring the gas to the same temperature.. This is called specific heat. The energy savings is considerable by breathing helium, however being surrounded by helium is a different story, it will remove more heat from the body as it will not act as much of an insulator as a heavier gas and has a high thermal conductivity..

These are 2 very different things..

From Thermodynamics

This can be sean by the fact that the Cv (molar specific heat and constant volume) of both Ar and He is the same.. 12.5, while oxygen is 21.1 and nitrogen is 20.6 ( the units are joules/mole/deg ) .. that also means that breathing Ar or He would require the same amount of energy to raise the gas temperature (both less than breathing air). The values listed are for 1 atm and 15C. The greater the number the more energy required.. BTW co2 is 28.2


You need about 1.7 times more energy to raise Air to body temp over "pure" helium, so the actual savings would depend on how much helium is part of your breathing mix..

Thermal conductivity, λ, is the quantity of heat transmitted, due to unit temperature gradient, in unit time under steady conditions in a direction normal to a surface of unit area, when the heat transfer is dependent only on the temperature gradient

λ of he is 0.152 W/(m·K)
λ of Ar is 0.01772 W/(m·K)
λ of of O2 is 0.02674 W/(m·K)
λ of of of N2 is 0.02598 W/(m·K)

 

[jerryn]

Question on the Thermodynamics -- given the differential compressability of He vs O2 an N2, how does the energy required to raise the temperature of the inspired gas change with depth?

It my just be an illusion, but I sense that the breathing gas is colder when I am diving with a He mixture than a nitrox mixture. Since there are a lot of other factors, including depth and workload, I'm curious as to the science.

For the original question: I use a 6 cu ft tank attached to my backplate. I fill it with air or argon, depending on what is available. So there is often a mixture of the two. I don't notice much difference, but on a cold dive I can sense the denser Ar whenever I add gas to my suit and it has a slightly warmer feel. I can do two 200' dives on the 6 cu ft tank at 2000 psi with gas to spare.

Jerry

 

[ScubaDadMiami]

I am not aware of any other agency teaching it...

This information is included in NAUI Trimix courses.

 

[padiscubapro]

This information is included in NAUI Trimix courses.

Thanks for that information.. I am fairly familiar what is taught by most of the other agencies, but the Naui programs I am pretty much in the dark with their content..