777 AMM 飞机维护手册 Water and Waste(21)

WATER TANK PRESSURIZATION -IN-LINE AIR FILTER

EFFECTIVITY BEJ ALL  38-42-00 
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D633W101-BEJ  Jan 05/2002 

WATER TANK PRESSURIZATION -FUNCTIONAL DESCRIPTION -CONTROL

General
The compressor or the pneumatic system pressurize the potable water tanks. The compressor operates if pressure from the pneumatic system is not sufficient.
Power
The water system 28v dc power relay supplies power for control from the ground handling bus. If the ground handling bus has no power, the relay supplies power from the right bus.
Power for compressor operation comes through the water pressure system relay. The compressor operates when the relay is energized. The relay energizes when the pressure limit switch and the compressor interlock switch are closed.
The pressure limit switch closes when tank pressure is 35 psig or less. It opens when tank pressure is 45 psig.
The compressor interlock switch is on the fill/overflow valve. The switch is closed when the valve is closed. The switch is open when you open the valve to fill the tanks.
Overcurrent and Overtemperature Protection
Three overheat switches give protection to the compressor motor. They stop the motor when the temperature of a phase is too high or there is too much current. The switches automatically go back to the normal position when the motor is cool.
EFFECTIVITY BEJ ALL  38-42-00 
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D633W101-BEJ  Sep 05/2002 

WATER TANK PRESSURIZATION -FUNCTIONAL DESCRIPTION -CONTROL

EFFECTIVITY BEJ ALL  38-42-00 
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D633W101-BEJ  Jan 05/2002 

WATER TANK PRESSURIZATION -AIR FLOW -FUNCTIONAL DESCRIPTION

Functional Description
The water tank pressurization system pressurizes the potable water tanks for distribution.
The pressure line goes into the inboard tank. The air for pressurization goes into the outboard tank through the fill and overflow lines at the tops of the tanks.
Pressure for the water tanks comes from the pneumatic system
or a compressor. 
The  pressure  regulator  controls  the  pressure  from  the 
pneumatic system.  The  regulator keeps  pressure  at  a 

maximum of 45 psig.
The compressor operates when the pressure limit and compressor interlock switches are closed. The pressure limit switch closes when pressure from the water tanks is 35 psig or less. It opens when pressure is 45 psig or more. The compressor interlock switch is closed when the fill/overflow valve is closed. The switch is open when the fill/overflow valve is open.
The unloader check valve has two functions: it vents pressure in the line between it and the compressor when the compressor stops. This makes it easier for the compressor to start. The valve also does not permit air from the pneumatic system to flow into the compressor.
The APU bleed air check valve does not permit the compressor to pressurize the pneumatic system.
The two air filters keep particles out of the air that pressurizes the tanks.
The pressure relief valve prevents pressure of more than 60 psig in the water tank pressurization system.
EFFECTIVITY BEJ ALL  38-42-00 
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D633W101-BEJ  Sep 05/2002 

WATER TANK PRESSURIZATION -AIR FLOW -FUNCTIONAL DESCRIPTION

EFFECTIVITY BEJ ALL  38-42-00 
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D633W101-BEJ  Jan 05/2002