Question

# You have spent 50 minutes at an average depth of 20 fsw, with a maximum depth...

You have spent 50 minutes at an average depth of 20 fsw, with a maximum depth of 42 fsw. You started with 2800 psi, and ended with 300 psi in an 80cu.ft./3000 psi cylinder. What is your DACR (depth air consumption rate) and SACR (surface air consumption rate)?

Solution

Depth air Consumption rate = total air used / total time \\Depth air consumption rate is defined as the amount of air one consume in a unit time underwater, it can be tank water or seawater.

total air used = initial air cylinder volume - final volume = 2800-300 = 2500 psi

so Depth air Consumption rate = 2500psi/50min = 50 psi/min.

Surface air consumption rate = total gas consumed/total time take/ pressure at the depth

Now                         = DACR/ pressure at the depth

In order to calculate the pressure under tank water or sea water = Depth/33 +1 = (Depth+33)/33.

Now Surface air consumption rate = (DACR x 33)/(Depth +33)

As Average depth = 20feet in salt water , Now using above formula , we have

SACR = (2500x33)/(20+33) = 1556.60 psi/min

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