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757 MAINTENANCE MANUAL
(c)
The vent connection is connected to the high and low-differential-pressure-servo assemblies, the electro-magnetic-control valve, the reference pressure regulator, and to ambient.
(d)
Ice in the condensor causes one of the servo assemblies to open when it blocks the air that flows through the condensor. Thus, the pressure upstream of the ice increases and the pressure downstream of the ice decreases. The pressures upstream and downstream of the ice are transmitted to the inlet chambers of the servo assemblies. If the upstream pressure is sufficient, it pushs the actuator rod and open the poppet valve. Thus, air flows from the vent connection, through the poppet valve, to the open chamber of the pneumatic actuator. This causes the low-limit-control valve to open so that hot air can flow to the turbine outlet to melt the ice. 1) The condensor inlet is the upstream pressure and the
condensor outlet is the downstream pressure for the high-differential-pressure-servo assembly. The turbine outlet is the upstream pressure and the pack outlet is the downstream pressure for the low-differential-pressure-servo assembly. Ice between the upstream and the downstream pressures will cause the applicable servo assembly to open.
(e)
The standby-pack-temperature controller or the applicable (left or right) automatic-pack-temperature controller supplies the electrical current to the torque motor of the electro-magnetic-control valve. The electrical current causes the torque motor to move the flapper away from the supply nozzle port. When the supply nozzle port is open, air flows from the vent connection to the open chamber of the pneumatic actuator. Thus, the low-limit-control valve opens to let air flow around the air cycle machine. The smaller amount of air in the air cycle machine causes it to operate more slowly, so that the compressor outlet temperature is decreased.
K. Temperature Control Valve (Fig. 10)_________________________
(1) The temperature control valve is used to control the temperature of the air-cycle-machine-compressor outlet. To do this, it controls the amount of air that flows through the air cycle machine. If more air flows through the temperature control valve, then less air flows through the air cycle machine. The less air that flows through the air cycle machine, the slower it operates. Thus, the temperature at the compressor outlet decreases.
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757
MAINTENANCE MANUAL
VISUAL ELECTRICAL
POSITION MOTOR
SEE A INDICATOR
ROTARY
ELECTRO-
MECHANICAL
ACTUATOR
MANUAL
CAPACITOR OVERIDE
VALVE
RESISTOR BODY
ADAPTOR
ASSY
VISUAL POSITION INDICATOR ELECTRICAL MOTOR LINEAR VARIABLE RESISTOR ASSY RESISTOR COVER
FULL OPEN
LIMIT SWITCH
FULL CLOSE REDUCTION GEAR
LIMIT SWITCH A
ROTARY
ELECTROMECHANICAL
SECONDARY WORM ACTUATOR
GEAR SHAFT
MANUAL SLIP CLUTCH
OVERRIDE
PRIMARY WORM
SECTOR GEAR GEAR SHAFT
BUTTERFLY
PLATE ASSY
VALVE BODY
AIR ASSY
FLOW
SHOULDERED
LINEAR SHAFT
VARIABLE
RESISTOR LINEAR VARIABLE
(10K OHMS) RESISTOR (1K OHMS)
Temperature Control Valve
Figure 10
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