Air Consumption A diver started a dive using an 80 Ft3 cylinder (rated at 3000)

Question

Air Consumption

A diver started a dive using an 80 Ft3 cylinder (rated at 3000) psig with 2700 psig. The dive was finished with a total pressure of 600 psig. Total bottom rime was 22 minutes, depth was 55 fsw. (assume air consumption was constant for entire dive.)

52. How much air was used in psig?

53. How much air was used in Cubic feet?

54. What was the diver's DCR in cfm?

55. What was the diver's SAC in cfm?

56. Based on the answer obtained in the prior question, calculate the amount of time a diver could theoretically spend at 35 fsw if he/she were to use a fully charged 63 Ft3 cylinder rated at 3000 psi. Assume the dive will be ended with a 500 psi reserve. (remember to calculate the cubic feet available with this in mind first.)

Explanation / Answer

psig consumption = 2700 - 600 = 2100 psig

Since consumption = P1V1 - P2V2,

air consumed = 80*(2100)

If you keep pressure at 2700 psig, volume consumed

= 80*2100/2700 cubic feet

= 62.22 ft3

Air used = 2700 - 600 = 2100 psig

In cu.ft, 80 * 2100/ 3000 = 56 cu.ft

DCR = 56/22 = 2.545 cfm

SAC = 2.545 * 33 / (55 + 33) = 0.954 cfm

At 35 fsw,

t = (3000 - 500)*(63/3000) / [0.954 * (35+33)/(33)] = 26.71 minutes

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