36-11-05
ALL ú ú 01 Page 7 ú Jul 15/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
4. Pressure Regulator and Shutoff Valve (Fig. 4)
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A. The pressure regulator and shutoff valve (PRSOV) is a pneumatically actuated, spring loaded closed, butterfly type valve. The valve, in conjunction with a remotely mounted bleed air regulator, provides pneumatic signals to open, close, and regulate pressure for downstream bleed air.
B. The valve consists basically of an actuator, manual override with closed position lock, and flow body with a butterfly plate.
C. Pressure regulated bleed air, routed from the remotely mounted bleed air regulator, supplies air to the control pressure connection Chamber B at a constant reference pressure level, independent of the upstream pressure variation. The reference pressure in Chamber B overcomes the spring force, causing the valve to start opening. Then, as bleed air flows downstream of the valve and is routed to Chamber C through the downstream sense connection. The valve continues to open until downstream pressure force in Chamber C and spring closing force are balanced by the reference pressure in Chamber B. Any further change in downstream pressure, due to changes in valve upstream pressure or downstream flow demand, will cause the valve to modulate to maintain downstream pressure at a nominal 42 psig.
D. Shutoff operation occurs whenever Chamber B pressure is reduced below 10 psig. At this point, spring force and Chamber C residual pressure will force the valve to close.
E. The valve may be manually locked in closed position by rotating the manual wrenching hex (butterfly shaft) so that the lock screw/position indicator aligns with closed position, loosening lock screw/position indicator and then sliding the detented locking knob into the recess in the retainer plate. The manual lock is retained in the override position by retightening the lock screw/position indicator. Also the valve may be unlocked by loosening the lock screw/position indicator, centering detented locking knob in the retainer plate, sliding detented locking knob out of the recess in the retainer plate, and then retightening the lock screw/position indicator.
5. Bleed Air Regulator (Fig. 4)
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A. The bleed air regulator is a pneumatic controller designed to provide regulated control pressure, with electrically controlled shutoff, from a bleed air source. Other functions incorporated are electrical indication of excessive bleed air supply pressure, automatic electrical shutoff of regulated control pressure in the event that downstream pressure exceeds bleed air supply pressure, and a relief valve to maintain regulation of control pressure in the event of pressure regulator failure.
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36-11-05
ALL ú ú 01 Page 8 ú Jul 15/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
REVERSE
SWITCH FLOW CHAMBER E PRESSURE REFERENCE
ASSEMBLY REGULATOR CHAMBER A
1
RELIEF
CONTROL VALVE
ORIFICE
CHAMBER D
M324
OVERPRESSURE
LATCHING SWITCH
SOLENOID
BLEED AIR REGULATOR
CHAMBER B
CHAMBER C
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