Dive_Man_ChangeA

Navy Diving Manual
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CHAPTER 8 — Surface Supplied Air Diving Operations Change A 8-3 = 28.38 scf Air required for ascent to reach the first stop: For this example, you need to determine ascent time and average depth. Ascent time is 7 minutes (rounded up from 6 minutes 20 seconds) from 190 fsw to the surface at 30 feet per minute. Average depth is calculated as follows: = 38.01 scf Total V_r = 28.38 + 38.01 = 66.39 scf 2. The next step is to convert the required scf to an equivalent cylinder pressure in psig. In this example, we are using an 80 ft³ aluminum cylinder to support this dive. Refer to Table 7-1 for cylinder data used in this calculation: Where: FV = Floodable Volume (scf) = 0.399 scf 14.7 = Atmospheric Pressure (psi) P_m = Minimum cylinder pressure Minimum Cylinder Pressure = First stage regulator setting + bottom pressure at final stop: [135 psig + (0 fsw x 0.445 psi)] = 135 psig 8-2.2.2 Flow Requirements. When the MK 21 MOD 1 system is used, the air supply system must be able to provide an average sustained flow of 1.4 acfm to the diver. The air consumption of divers using the MK 21 MOD 1 varies between 0.75 and 1.5 acfm when used in a demand mode, with occasional faceplate and mask clearing. When used in a free-flow mode, greater than eight acfm is consumed. NOTE When planning a dive, calculations are based on 1.4 acfm. To satisfactorily support the MK 21 MOD 1 system, the air supply must: ! Replenish the air consumed from the system (average rate of flow) ! Replenish the air at a rate sufficient to maintain the required pressure ! Provide the maximum rate of flow required by the diver average depth 190 2 --------- 95fsw = = Ascent V_r 95 33 + 33 ------------------ 1.4 7 = psig required V_r FV -------- 14.7 P_m + = 66.39 0.399 ------------- 14.7 135 + = 2580.95(round to 2600 psig) =

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