Air Ladder

[tomcatbubba]

Does anyone here run an "air ladder"? By that I mean, do you mark certain points in your run-time that you have marked anticipated pressure left and compare with actual, such that you would know if for some reason you start to get ahead of anticipated consumption (air leak, SAC higher than anticipated etc)?

Seems to be a no-brainer way to keep track of your actual dive profile vs. what you planned.

Cheers!

 

[PfcAJ]

Not quite like that, but I know what to expect before I look at the spg.

A trick ic ki like to do is to figure out how long 200psi lasts and verify what I expect vs reality.

 

[LiteHedded]

this is what's taught in gue courses. figure out what say, a .6 sac would be in terms of psi per five minutes.

glance every five mins and compare to see where you are with it

 

[tomcatbubba]

Interesting. I've only taken PADI, TDI and IANTD classes to date, but would love to take either UTD and/or GUE . I'm a big proponent of adopting "best of" practices.

 

[LiteHedded]

Interesting. I've only taken PADI, TDI and IANTD classes to date, but would love to take either UTD and/or GUE . I'm a big proponent of adopting "best of" practices.

I can't speak to UTD but the gue courses are filled with little tricks like this

 

[rjack321]

I can't speak to UTD but the gue courses are filled with little tricks like this

And eventually it just becomes intuitive, no multiplication required.

 

[Kevrumbo]

The "secret" trick is to use the Metric System --depth in ATA (easy to figure out from meters: divide-by-10 and add 1, so 30 meters for example is 4 ATA) actually turns out to translate directly to bar/min consumption rate at depth. Example: Using double 11L Cylinders (AL80's) at 30 meters depth is 4 ATA -->translates directly to 4 bar/min Depth Consumption Rate. So for a convenient time interval of say 10 minutes, 40 bar of gas will be consumed (4 bar/min multiplied by 10min is 40 bar). You will know that your SPG will read a delta of 40 bar down from the previous reading before even looking at it to confirm.

Parameters: 0.75 cuft/min SAC rate (also known as RMV -Respiratory Minute Volume, or also referred to as Surface Consumption Rate "SCR", a term I like better), a common rate that most novice divers can achieve. 0.75 cuft/min in Imperial is approximately 22 litres/min in Metric.

With a 22 litres/min volume SCR and a variety of different tank sizes, your pressure SCR in bar/min obviously varies inversely, depending on the size tank in use :

22 litres per minute -divided-by- 11L/bar tank (AL80): 2 bar/min
22 litres per minute -divided-by- 13L/bar tank (AL100): 1.7 bar/min
22 litres per minute -divided-by- 22L/bar twinset (double AL80's): 1 bar/min
22 litres per minute -divided-by- 34L/bar twinset (double Pressed Steel 104's with a cave fill): 0.7 bar/min

 

[Diver0001]

Does anyone here run an "air ladder"? By that I mean, do you mark certain points in your run-time that you have marked anticipated pressure left and compare with actual, such that you would know if for some reason you start to get ahead of anticipated consumption (air leak, SAC higher than anticipated etc)?

Seems to be a no-brainer way to keep track of your actual dive profile vs. what you planned.

Cheers!

I did something similar early on. I noted the anticipated pressure at the planned turn point of the dive. In reality, it would take a major malfunction to get in neighbourhood of that number because I plan the dive using 20lpm but I only normally use around 12. Seeing as how a major malfunction means the dive ends early anyway that number became less and less interesting over time.

These days I don't bother with that number. I just calculate the dive to fit in a certain bottom time and go diving.

R..