Air Volume

[spectrum]

I was on the rowing machine the other morning counting ceiling tiles in the gym. All of a sudden I was doing mental math visualizing the actual air volume in a 100cf air cylinder, I had never looked at it that way. The whole thing at 1 ATM is only a 56.7 inch cube, and again that is at 1 atm. Somehow that was a much smaller volume that I had thought.

I took the exercise a step further this morning and wrote a little spread sheet and learned 100 CF became:
at 2 ATM (33 FSW) =became a 42.2 inch cube
at 3 ATM (66FSW) =became a 36.6 inch cube
at 4 ATM (99 FSW) =became a 35 inch cube
at 5 ATM (132 FSW) =became a 32.5 inch cube

This gave me a fresh perspective on diminishing percent change as you go deeper, importance of breathing control, leak control and anything else that has to do with the use of or conservation of air. It's even more striking when I consider that a chunk of this fiinite volume has been used during descent and a good portion should be held in reserve.

Time to go rake the lawn.
Pete

 

[Gary D.]

I was on the rowing machine the other morning counting ceiling tiles in the gym. All of a sudden I was doing mental math visualizing the actual air volume in a 100cf air cylinder, I had never looked at it that way. The whole thing at 1 ATM is only a 56.7 inch cube, and again that is at 1 atm. Somehow that was a much smaller volume that I had thought.

I took the exercise a step further this morning and wrote a little spread sheet and learned 100 CF became:
at 2 ATM (33 FSW) =became a 42.2 inch cube
at 3 ATM (66FSW) =became a 36.6 inch cube
at 4 ATM (99 FSW) =became a 35 inch cube
at 5 ATM (132 FSW) =became a 32.5 inch cube

This gave me a fresh perspective on diminishing percent change as you go deeper, importance of breathing control, leak control and anything else that has to do with the use of or conservation of air. It's even more striking when I consider that a chunk of this fiinite volume has been used during descent and a good portion should be held in reserve.

Time to go rake the lawn.
Pete

The volume of the tank doesn’t change at those depths but the rate you use air does. Your idea works with a collapsible container or just figuring volume but not when the air is contained in a rigid tank. At extreme depths the tank will get slightly smaller.

Then there is Partial or Absolute Pressure.

An easy rule of thumb is:
ATM Depth Volume
1 ------ 0 ---- 100%
2 ----- 33' ---- 1/2
3 ----- 66' ---- 1/3
4 ----- 99' ---- 1/4
5 ---- 132' ---- 1/5
6 ---- 165' ---- 1/6
7 ---- 198' ---- 1/7

Gets people thinking.

Gary D.

 

[spectrum]

The volume of the tank doesn’t change at those depths but the rate you use air does. Your idea works with a collapsible container or just figuring volume but not when the air is contained in a rigid tank. At extreme depths the tank will get slightly smaller.

Then there is Partial or Absolute Pressure.

An easy rule of thumb is:
ATM Depth Volume
1 ------ 0 ---- 100%
2 ----- 33' ---- 1/2
3 ----- 66' ---- 1/3
4 ----- 99' ---- 1/4
5 ---- 132' ---- 1/5
6 ---- 165' ---- 1/6
7 ---- 198' ---- 1/7

Gets people thinking.

Gary D.

I realize that. I think we're saying the same thing from different directions. The diminishing volumes I listed illustrate the volume as it would be consumed at the depening depths. Your numbers are part of my formula, I just took it out represent effective (lung filling) volume at each depth.

Pete

 

[mxracer19]

Discover Scuba in Daytona Beach, Fl has a tank in their shop that is cut in half vertically. Its an AL80, and although you would think that high pressures would dictate a very thick wall, the wall thickness on an aluminum tank is only around an inch or so thick.

 

[Gary D.]

I realize that. I think we're saying the same thing from different directions. The diminishing volumes I listed illustrate the volume as it would be consumed at the depening depths. Your numbers are part of my formula, I just took it out represent effective (lung filling) volume at each depth.

Pete

Good job

Gary D.