Overbottom Pressure Requirements.

TM 5-4220-225-14 2-15. Overbottom Pressure Requirements. The normal method of determining console operating pressure has been derived by adding 60 psig and 100 psig to depth pressure for 300 and 600-ft. hoses, respectively. However, there will be instances of limited compressor capability at the diving platform. Minimum compressor, or manifold pressure demands have been formulated to reduce overbottom pressure requirements while retaining the ACFM flow obligation. The formula for the 300-ft. hose is: (diver's depth (FSW) x .50) + 42 = minimum manifold pressure (psig) The formula for the 600-ft. hose is: (diver's depth (FSW) x .62) + 42 = minimum manifold pressure (psig) Figure 2-10 is a graphic display of these formulas plotted in a straight line. There may be a small variation between formula results and graphic interpolation. In such cases, the greater pressure will be used. Figures 2-11, 2-12, and 2-13 are graphic displays of the flowmeter Capsuhelic gage readings for constant air supply pressures at depth. Figure 2-11 shall be used to determine the essential flowmeter gage readings (inches of H20) when a desired flow of 6 ACFM is required by the diver, utilizing the adjustable helmet supply valve. To find the proper flowmeter gage reading, locate the diver's depth (FSW) on the graph. If the depth is not exact, use the next greater depth represented on the graph. Follow the depth line up to the known constant manifold pressure (psig) line. If manifold pressure is not exact, use the next lowest pressure. To find the desired flowmeter reading (inches of H20), follow this intersection point (depth and pressure) to the left margin of the graph. These flowmeter Capsuhelic gage readings from the graph should always be rounded up to the next half-tenth (0.05) inch of H20 as an additional diver safety factor. Topside may instruct the diver to adjust the helmet supply valve until the flowmeter gage readout is at the desired setting. Figures 2-12 or 2-13 shall be used if flow rates of 4 ACFM or 2 ACFM are desired. 2-16. Doffing Procedures. The MK12 SSDS is most easily doffed in the sequence given in Table 2-5, Doffing Procedures. Doffing the bottom (drysuit) configuration consists of all the listed steps. Doffing the neckdam configuration consists of the steps marked by asterisk (*). 2-43