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EFFECTIVITY
GUN 101-118 21-50-00
Page 12
D633A101-GUN Oct 10/2006
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-50-00-008
AIR CONDITIONING - COOLING - FLOW CONTROL AND SHUTOFF VALVE
AIR CONDITIONING - COOLING - FLOW CONTROL AND SHUTOFF VALVE
EFFECTIVITY
GUN 101-118 21-50-00
Page 13
D633A101-GUN Oct 10/2006
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-50-00-008
Functional Description
The flow control and shutoff valve is electrically controlled and
pneumatically actuated. It is spring-loaded to the closed
position. The valve operates by a pneumatic actuator which
moves a butterfly plate. When the pack switch is in the OFF
position, 28v dc energizes solenoid C to the close position. This
moves a ball valve to a position that removes air pressure to the
actuator. This closes the valve.
When the pack switch is in the AUTO or HIGH position, solenoid
C receives power to the open coils. The pressurized air flows to
the actuator. It pushes against spring force in the actuator to
open the butterfly plate (valve open). When the valve opens, air
flows to the static pressure sense port and the downstream
(total pressure) sense port.
The static and total pressure sense ports balance actuator
opening pressure for the auto and high flow servos. These ports
permit a measure of differential pressure in the venturi which
relates to the rate of air flow.
Solenoid B changes between the normal flow and the high flow
modes. It energizes when the pack switch is at the AUTO
position. This lets airflow go to the auto flow servo (normal flow
mode). The auto flow servo biases an internal bellows with
cabin air to control the flow rate. This controls the air flow rate to
cabin (altitude) pressure. Normal flow mode has an airflow rate
of approximately 55 pounds per minute (ppm).
When the pack switch is in the HIGH position, solenoid B deenergizes
(high flow mode). Actuator air flows to the APU/high
flow servo. The high flow servo has a strong bias to close. This
lets more air pressure go to the valve actuator. This increases
airflow. High flow mode is approximately 80 ppm.
In cruise, if a pack shuts down from an overheat or a (L or R)
pack switch is OFF, solenoid B deenergizes. This causes the
pack in operation to go to the high flow mode.
The APU high flow mode energizes solenoid A. The APU/high
flow servo has one more actuating piston than high flow. This
gives a higher spring bias to close the servo. This lets more
pressure go to the valve actuator. APU/high flow mode has an
airflow rate of 100 ppm.
Training Information Point
A manual control shaft on solenoid C lets you open the solenoid
manually.
AIR CONDITIONING - COOLING - FLOW CONTROL AND SHUTOFF VALVE - MECHANICAL FUNCTIONAL DESCRIPTION
EFFECTIVITY
GUN 101-118 21-50-00
Page 14
D633A101-GUN Oct 10/2006
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-50-00-005
AIR CONDITIONING - COOLING - FLOW CONTROL AND SHUTOFF VALVE - MECHANICAL FUNCTIONAL DESCRIPTION
AIR CONDITIONING - COOLING - FLOW CONTROL AND SHUTOFF VALVE - MECHANICAL FUNCTIONAL DESCRIPTION
EFFECTIVITY
GUN 101-118 21-50-00
Page 15
D633A101-GUN Oct 10/2006
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-50-00-005
Pack Switch OFF
When the pack switch is in the OFF position, 28v dc (battery bus)
energizes the close coil of solenoid C. When the close coil
energizes, the flow control and shutoff valve closes.
Pack Switch AUTO
When the pack switch is in the AUTO position, 28v dc energizes
the open coil of solenoid C. When open coil of solenoid C
energizes, the FCSOV opens. This also moves a position switch
to open. The position switch gives a discrete signal to these
systems:
* Flight management computer system
* Common display system
* Pressurization system
* Temperature control system
* Recirculation system.
When one of the two engine bleed switches is ON, 28v dc
energizes solenoid B through the left flow mode relay K18.
When solenoid B energizes, the FCSOV operates in the low flow
mode.
Solenoid B deenergizes when the left flow mode relay K18
energizes. The left low flow mode relay K18 energizes when the
two engine bleed switches are in the OFF position.
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