Main Overboard Vent

Figure 2.6-18. Burst Diaphram Assembly - Functional Schematic Oxygen Filters.

Filters at the inlets to the oxygen control module and the PLSS disconnect remove particulate matter from the oxygen. Filtering capability is 18 microns nominal and 40 microns absolute. Oxygen Control Module. (See figure 2. 6-2.)

The oxygen control module is mounted on the suit circuit package located to the right rear of the LM Pilot's station. It consists of a cast housing that contains filters, a PLSS oxygen shutoff (PLSS FILL) valve, descent and ascent oxygen shutoff (DES O2. ASC O2, ASC O2) valves, oxygen demand regulators (PRESS REG A and PRESS REG B) valves, and a cabin repressurization and emergency oxygen (CABIN REPRESS) valve. An interlock prevents opening the ascent oxygen shutoff valves until the descent oxygen shutoff valve is closed.

PLSS and Oxygen Tank Shutoff Valves. Four positive-action, manually operated shutoff valves control oxygen flow into the oxygen control module. Rotating the valve handle to OPEN displaces a spring-loaded seal. The valves have detents in the OPEN and CLOSE positions; mechanical stops 011 the handle prevent | overtravel. (An additional PLSS FILL valve, installed in the cabin, is used for the high pressure PLSS fill line from the second descent stage oxygen tank. It is not part of the oxygen control module.

Oxygen Demand Regulators. (See figure 2. 6-19.) The PRESS REG A and PRESS REG B valves, in parallel, regulate oxygen from the tanks to the suit circuit. Both regulators are manually controlled by individual four-position selector handles. Suit circuit pressure is fed back to an aneroid bellows that actuates a poppet. Rotating the valve handle to CABIN or EGRESS changes the spring force acting on the poppet and establishes two outlet pressure levels.

Selecting the DIRECT O2 position, fully opens the valve. With an upstream pressure of 900 psia and a temperature of +70°F, one regulator can flow approximately 7. 0 pounds per hour into the suit circuit. In the CLOSE position, an auxiliary poppet stops all flow through the regulator. Each regulator has a valve position indicator (VPI) switch, and a functional switch which controls electrical circuits in the ECS.

Cabin Repressurization and Emergency Oxygen Valve. (See figure 2. 6-20.) The CABIN REPRESS valve is a solenoid-operated valve with manual override (MANUAL and CLOSE positions). It is used to repres-surize the cabin after a deliberate decompression and provides an emergency flow of oxygen if the cabin is punctured. If the cabin is punctured and the diameter of the hole does not exceed 0. 5 inch, the valve can r

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