Argon--pro and con

[Akimbo]

If workload in diving is changing by a factor of 2-5 in diving you are doing something wrong.

The difference between a photographer’s work output on macro versus open water big animal shots can be more than 2x. Actually, a patient photographer’s rate can be much lower shooting macro than hanging off at a stop. Heck, caloric burn rates can go up 50% just by seeing something new and exciting.

 

[OHIO DIVERS]

Would a 6cuft cylinder be ok for argon?

 

[Rainer]

Works for me (2-3 dives).

 

[Akimbo]

Would a 6cuft cylinder be ok for argon?

Cylinder size depends on how deep you are diving, how many times you want to dive between filling the argon bottle, how much you plan to change depth on a dive, and if you intend to purge the suit after closing the zipper.

I use the displacement to begin estimates. For discussion, let’s say you use 32 Lbs of weight to get neutral. 32 Lbs displacement in sea water equals 0.5 Ft³. People tend to inflate the suit on suit purges, so let’s say 0.75 Ft³/purge. Three purges would be 2.25 Ft³ before leaving the deck.

Let’s say you go to 132’. That is 4 atmospheres or 4x more gas —remember you already have one atmosphere of Argon in the suit so you don’t calculate in Atmospheres Absolute. Four atmospheres would equal 2 Ft³. Let’s say you follow a typical meandering recreational diver profile rather than say a wreck diver profile and go from 80-132’ a number of times. This is a major WAG because the amount of gas you need to add for these depth changes varies tremendously, but let’s say you burn another 2 Ft³. You will USE a minimum of 6¼ Ft³ per dive with no allowance for leaks and no safety margin.

I emphasized “use” because the volume you can get out of your Argon bottle is not the same as how much it holds. You have to figure you can’t get the last 135 PSI out (you can but it may be too slow to meet your needs) due to the IP pressure of the first stage. You also lose the bottom pressure in Absolute Atmospheres of about 73 PSI at 132’. So, off the top, you have to reduce the volume available by about 208 PSI x the floodable volume of the cylinder.

You can save the volume of Argon you have to carry on your back by purging from a larger bottle, which can also be used to cascade fill your small Argon bottle. Probably not worth the trouble for one or two dives, but a good idea if you are on a 3-5 day trip. Also remember that you probably don’t want to top off your Argon bottle between every dive, unless maybe you are talking about 450’. As you can see, the “right” answer has a big range and a lot of individual assumptions about weight versus inconvenience.

 

[Rainer]

Use a separate (larger) bottle for pre-dive flushing.

 

[Jimmer]

Akimbo, you are way over thinking that. There is no way in hell that a single dive to 130 or so feet will use over 6 ft3. I easily get 3 dives out of a 6, and I almost never dive shallower than 100. Most of the tech guys here will make the same claim.

 

[LiteHedded]

It depends on your dive profile. A six cubic foot bottle Doesnt cut it on a lot of dives

 

[Rainer]

It depends on your dive profile. A six cubic foot bottle Doesnt cut it on a lot of dives

Sure it does...if you dive in the ocean.

 

[Akimbo]

Akimbo, you are way over thinking that. There is no way in hell that a single dive to 130 or so feet will use over 6 ft3. I easily get 3 dives out of a 6, and I almost never dive shallower than 100. Most of the tech guys here will make the same claim.

I think you missed my point. Usage changes with all the factors mentioned... my objective was to illustrate what variables were embodied in the question. People will read these posts for many years and dive under a wide variety of conditions. It is important to understand the factors that impact a decision. All you have to do is look at each of the values in the example and you can see that you need to plug in your own numbers to get a good answer.

For starters, 32 Lbs/½ Ft³ is probably a high number to start with — but a really easy example. That number reverberates through most of the rest. Secondly, until you run “your” average depth change profile, you can’t begin to estimate how much gas you may use from changing depth. We have no way of knowing if someone will be wreck diving or chasing seals with a scooter.

You can be conservative when purging or generous. You can unzip between dives and need to purge again or stay zipped on your surface interval. You can also have leaks. Physics is physics. The art is in selecting appropriate numbers to plug into the assumptions.

 

[PfcAJ]

Sure it does...if you dive in the ocean.

Ocean? Wazzat?

For you cave divers out there, think about what happens if you need to share argon. It pays to use a full bottle on those dives, and if you're going deep, consider an al14.