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They have a flow direction arrow cast into their flow bodies.
Training Information Point
The trim air check valves are identical and interchangeable.
AIR CONDITIONING - TEMPERATURE CONTROL - TRIM AIR CHECK VALVE
EFFECTIVITY
GUN 001-099, 201-999 21-60-00
Page 60
D633A101-GUN Oct 10/2005
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-60-00-815
AIR CONDITIONING - TEMPERATURE CONTROL - TRIM AIR CHECK VALVE
AIR CONDITIONING - TEMPERATURE CONTROL - TRIM AIR CHECK VALVE
EFFECTIVITY
GUN 001-099, 201-999 21-60-00
Page 61
D633A101-GUN Oct 10/2005
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-60-00-815
Purpose
The trim air pressure regulating and shutoff valve controls the
flow and pressure of air to the zone trim air modulating valves.
Location
The trim air pressure regulating and shutoff valve is in the right
air conditioning compartment.
Physical Description
The trim air pressure regulating and shutoff valve is a
modulating and shutoff butterfly-type valve. The valve is
spring-loaded to the closed position. It is electrically
controlled and pneumatically actuated.
The valve has these parts:
* Solenoid valve assembly
* Actuator assembly
* Servo regulator assembly
* Manual override cam and position indicator
* Electrical connector.
Functional Description
The trim air pressure regulating and shutoff valve is the master
trim air valve. It supplies trim air to the three zone trim air
modulating valves. If the trim air pressure regulating and
shutoff valve is closed, the three zone trim air systems are
mechanically and electrically disabled.
The valve is spring loaded-closed. When the control solenoid is
energized, it sends upstream pressure to the valve actuator.
Pressure in the actuator opens the valve. The servo regulator
moves the valve to keep pressure downstream of the valve 4.0
psi above airplane cabin altitude. This prevents pressure
variation due to various flow demands of the zone trim air
modulating valves.
When the control solenoid de-energizes, it bleeds off the
actuator pressure. The trim air pressure regulating and shutoff
valve spring then pushes the valve closed.
Put the TRIM AIR switch to ON to open the trim air pressure
regulating and shutoff valve. This also enables the zone trim air
channels in the pack/zone temperature controllers.
Put the TRIM AIR switch to OFF to close the trim air pressure
regulating and shutoff valve. This also disables the zone trim air
system.
Training Information Point
There is a manual override cam and position indicator on the
trim air pressure regulating and shutoff valve. You can
manually turn the valve to the MANUAL CLOSED position.
This vents the valve actuator and the valve closes.
AIR CONDITIONING - TEMPERATURE CONTROL - TRIM AIR PRESSURE REGULATING AND SHUTOFF VALVE
EFFECTIVITY
GUN 001-099, 201-999 21-60-00
Page 62
D633A101-GUN Oct 10/2005
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-60-00-816
AIR CONDITIONING - TEMPERATURE CONTROL - TRIM AIR PRESSURE REGULATING AND SHUTOFF VALVE
AIR CONDITIONING - TEMPERATURE CONTROL - TRIM AIR PRESSURE REGULATING AND SHUTOFF VALVE
EFFECTIVITY
GUN 001-099, 201-999 21-60-00
Page 63
D633A101-GUN Oct 10/2005
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
21-60-00-816
Functional Description
The trim air pressure regulator and shutoff valve (PRSOV) gets
unregulated air from the flow control and shut off valves
(FCSOV).
The unregulated air goes to these components:
* Solenoid valve
* Relief valve
* Servo regulator (chamber A).
The servo regulator decreases the unregulated air to a constant
control pressure.
The relief valve prevents damage to the pneumatic actuator if
the servo regulator fails.
The solenoid valve controls the flow of control air to chamber B.
Control air to chamber B opens the trim air PRSOV. Air then
flows to the downstream sense port.
The downstream sense port supplies bleed air to the following:
* Chamber C
* Chamber D
Bleed air in chamber C helps the actuator spring control the
trim air PRSOV.
Bleed air in chamber D acts against cabin pressure and a
spring in chamber E. This action controls the control air to
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