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Pushes and locks the position indicator to the valve closed position
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Moves the cam follower so that it pushes in on the vent valve pin and locks the hex cam in the valve closed position
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The vent valve pin sets the vent valve to vent
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The vent valve removes pressure from the actuator and blocks incoming control pressure.
When you turn the hex cam in the opposite direction as indicated on the cam it returns the valve to normal operation.
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ENGINE AIR SUPPLY SYSTEM -HPSOV/PRSOV -TRAINING INFORMATION POINTS
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ENGINE AIR SUPPLY SYSTEM -PRESSURE REGULATING AND SHUTOFF VALVE CONTROLLER
Purpose
The pressure regulating and shutoff valve controller (PRSOVC) supplies control pressure to the PRSOV.
Location
The PRSOVC is on the right side of the engine fan case at the
2:00 position.
Physical Description
The PRSOVC is an electropneumatic controller. The PRSOVC has these parts:
*
Two reference pressure regulators
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Torque motor
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Electrical connector
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Two pneumatic line connectors
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Filter (internal)
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Heater.
The reference pressure regulators set control pressure to a fixed value. The regulators are in series with each other. The torque motor adjusts the control pressure to values less than the reference pressure regulators. The torque motor always lets control pressure go to the PRSOV if it has no electrical power (fail safe on).
The heater prevents the controller from freezing.
Training Information Point
The mounting bolt hole pattern on the PRSOVC helps you install it correctly. The two pneumatic line connectors are of different sizes. This also helps you install the PRSOVC correctly.
The filter is line replaceable.
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ENGINE AIR SUPPLY SYSTEM -PRESSURE REGULATING AND SHUTOFF VALVE CONTROLLER
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ENGINE AIR SUPPLY -PRESSURE REGULATING AND SHUTOFF VALVE CONTROLLER -FUNCTIONAL DESCRIPTION
Functional Description
The pressure regulating and shutoff valve controller (PRSOVC) sets the pressure of the control air for the PRSOV. The PRSOVC uses two pressure regulators and a torque motor to set control air pressure. These devices are in series with each other.
Two regulators in series give an accurate control air pressure, at a fixed value. The fixed value gives these functions:
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Pneumatic and backup modes of operation for the PRSOV (PRSOV regulates to approximately 65 psig)
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Protection for the PRSOV actuator by setting the maximum pressure limit of the control air.
The primary and backup modes of the ASCPC use the torque motor to change the position of the PRSOV. The torque motor changes the amount of control air pressure to the valve.
The torque motor supplies maximum control air pressure to the PRSOV when it gets no current. When the ASCPC sends current to the torque motor, the flapper moves to let control air pressure vent to ambient. The amount of air that vents has a relation to the amount of current that goes to the torque motor. This is an example: if the ASCPC wants to close the PRSOV, it supplies full current to the torque motor. This sets the position of the flapper in the torque motor to stop supply air and vents control air pressure. A spring in the PRSOV (not shown) and duct pressure downstream of PRSOV moves the valve closed.
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ENGINE AIR SUPPLY -PRESSURE REGULATING AND SHUTOFF VALVE CONTROLLER -FUNCTIONAL DESCRIPTION
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ENGINE AIR SUPPLY SYSTEM -PRECOOLER
Purpose
The precooler decreases the engine bleed air temperature.
Location
The precooler is on the bottom of the engine strut above the high pressure turbine section of the engine.
Physical Description
The precooler is a cross flow air-to-air heat exchanger. The precooler weighs 152 pounds (69 kg). 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：777 AMM 飞机维护手册 气源 Pneumatic(9)
