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through a strut access panel.
Functional Description
The operation of the precooler control valve sensor is
automatic.
The lower part of the sensor is in the bleed air duct downstream
of the precooler. This portion of the sensor has oil-filled sense
coils. As heat causes the oil to expand, it pushes a ball valve in
the upper part of the sensor to open. The higher the duct
temperature, the more the oil expansion, and the more the ball
valve opens.
The sensor ball valve starts to open at 390F (199C) and is full
open at 440F (227C) (nominal values).
The open sensor ball valve bleeds off pressure to operate the
precooler control valve actuator. This causes the precooler
control valve to move toward open by spring force.
The precooler control valve sensor operates in parallel with the
WTAI solenoid valve to control the precooler control valve. The
energized WTAI solenoid valve bleeds off all of the pressure
that operates the precooler control valve. The sensor does not
have any effect for this operation. The WTAI makes sure that
bleed air will receive maximum cooling for ground operations
of the WTAI system.
See the ice and rain chapter for more information on the WTAI
solenoid valve (SECTION 30-11).
PNEUMATIC - BLEED AIR PRECOOLER SYSTEM - PRECOOLER CONTROL VALVE SENSOR 390F
EFFECTIVITY
GUN ALL 36-12-00
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D633A101-GUN Oct 10/2002
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
36-12-00-219
PNEUMATIC - BLEED AIR PRECOOLER SYSTEM - PRECOOLER CONTROL VALVE SENSOR 390F
PNEUMATIC - BLEED AIR PRECOOLER SYSTEM - PRECOOLER CONTROL VALVE SENSOR 390F
EFFECTIVITY
GUN ALL 36-12-00
Page 9
D633A101-GUN Feb 10/2003
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
36-12-00-219
Purpose
The wing thermal anti-ice (WTAI) solenoid valve bleeds actuator
pressure from the precooler control valve. The WTAI solenoid
valve operates when you use the wing thermal anti-icing
system on the ground.
Physical Description
The WTAI solenoid valve has these parts:
* Control pressure port
* Bolt mounting bosses
* Electrical connector.
Location
There are two WTAI solenoid valves, one for each bleed air
precooler system. The valves are on top of the compressor
section of each engine.
General
The wing thermal anti-icing system prevents ice formation on
the wing leading edge during ground operations and in flight.
During flight there is a large airflow over the wing. This airflow
has a cooling effect on the leading edges. The wing thermal
anti-icing system heat output is enough to overcome this
cooling effect.
When the wing thermal anti-icing system is used on the ground,
there is very little cooling airflow over the wing. In these
conditions, the wing thermal anti-icing system heat output can
overheat the wing leading edges. This can do damage to the
temper of the leading edges devices. The precooler system
gives maximum cooling to the engine bleed air during ground
operations to prevent overheat damage.
Functional Description
During ground operations of the wing thermal anti-icing system,
the anti-ice panel energizes the WTAI solenoid valves. This
opens the solenoid valves. The solenoid valves bleed actuating
pressure from the precooler control valve. This causes the
precooler control valves to go wide open.
The wide open precooler control valve gives maximum cooling
to the engine bleed air. This protects the wing leading edges
from overheat damage.
See the ice and rain chapter for more information on the WTAI
solenoid valve (SECTION 30-11).
PNEUMATIC - BLEED AIR PRECOOLER SYSTEM - WTAI SOLENOID VALVE
EFFECTIVITY
GUN ALL 36-12-00
Page 10
D633A101-GUN Oct 10/2002
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
36-12-00-221
PNEUMATIC - BLEED AIR PRECOOLER SYSTEM - WTAI SOLENOID VALVE
PNEUMATIC - BLEED AIR PRECOOLER SYSTEM - WTAI SOLENOID VALVE
EFFECTIVITY
GUN ALL 36-12-00
Page 11
D633A101-GUN Feb 10/2003
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
36-12-00-221
Purpose
The precooler system controls the temperature of the bleed air
to the pneumatic manifold.
Functional Description
The precooler control valve gets unregulated air pressure from
the interstage manifold. The unregulated air pressure goes to
　
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