JFD B44771, Operation And Maintenance Manual, Page: 34 / 136

22 OM131
Chapter 2 P1939-OM-131 R11
Fig 2.7 Single stage regulator
The function of the single stage regulator is to maintain a positive pressure inside the SLS System
while it is in its stand-by mode. Gas is supplied to the regulator from a connection on the Helmet
side-block. The regulator is of a diaphragm type (similar to the second stage of the two-stage
regulator).
The SLS System is designed to cope with diver upward and downward excursions at a controlled
rate not exceeding 22 msw / minute (75 fsw/ minute). The single stage regulator is designed to flow
sufficient gas at all operating depths to maintain 138 mbar (2 psi) over ambient pressure within the
SLS System.
The valve pin (Fig 2.7, Item 8) is held off the valve seat (Fig 2.7, Item 7) by the diaphragm (Fig 2.7,
Item 20) and the support plate (Fig 2.7, Item 4), under the action of the spring (Fig 2.7, Item 14). As
the pressure in the space to the right of the diaphragm increases the diaphragm and hence the
valve pin moves to the left sealing off the valve seat fully at the set outlet pressure.
The outlet pressure is adjusted by varying the spring (Fig 2.7, Item 14) tension by slackening the
locknut (Fig 2.7, Item 17) and adjusting the grub screw (Fig 2.7, Item 16) until the desired pressure
is reached.
2.3.7 Demand regulator
Fig 2.8 shows a cross-section through the demand regulator. The SLS System’s overpressure valve
is also incorporated in the demand regulator body but is excluded from this drawing for clarity.