747-400 AMM 飞机维护手册 气动系统 WATER/WASTE(49)

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 9.  Overflow Line
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 A.  An overflow line is installed on the toilet waste tank to drain fluid from the toilet tank if it is filled above capacity during servicing. The overflow line connects into the drain line between the toilet drain valve and the ball valve.
 10. Tank Drain Valve (Fig. 1)
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 A.  The drain valve allows toilet wastes to be drained from the tank when actuated with the airplane on the ground. The valve is positioned to completely drain the tank. When closed, the valve keeps the fluid in the toilet tank under all ground and flight conditions.
 B.  The drain valve is a plunger-style valve that is moved open and closed by a 28v dc electric motor. It opens or closes completely within 2 seconds of actuation. The valve has a manual override which allows the valve to be manually opened or closed. The motor used for the valve has a thermal protector to detect and prevent any damage from heat. A proximity switch on the toilet drain valve controls power to the drain valve light on the service panel. The drain valve light comes on whenever the toilet drain valve is not closed.
 11. Tank Drain Line
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 A.  The drain line has a 4-inch diameter run and a 3.5-inch diameter run. The two runs are made of stainless steel tubes.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL

 B.  The 4-inch diameter run connects the toilet tank drain valve to the ball valve. Flexible connectors are used to connect the line segments together. Standard hose clamps are used at these flexible connections. A stainless steel clamshell coupling connects the 4 inch diameter line to the ball valve.
 C.  A 3.5-inch diameter stainless steel tube connects the ball valve to the drain valve assembly on the service panel. V-band clamp connectors used to attach the tube at the ball valve and the drain valve assembly.
 12. Ball Valve
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 A.  The ball valve is a manually operated, 4-inch diameter, ball-type valve which incorporates two seals (a top and a bottom seal). The two-section stainless steel valve body is fastened together with six stainless steel bolts and nuts. A 3.5-inch operating arm is attached to the valve. Operating travel (fully open to fully closed) is 90° with approximately 10° of allowable overtravel in the closed direction. A microswitch is installed on the ball valve which causes the tank drain valve to open when the ball valve is between 20° to 30° from the fully open position. As a result, the toilet drain valve opens when the ball valve is opened, to let the toilet tank drain. When the ball valve is closed, the switch causes the tank drain valve to close.
 13. Toilet Service Panel (Fig. 1)
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 A.  The toilet service panel allows the ground servicing personnel to service the toilet tank. The connections and controls that are necessary to drain, rinse and fill the toilet tank are installed on the panel. The panel is installed at approximately station 590 near the airplane bottom centerline. The door for the service panel has bumpers that keep the door open when the ball valve handle, drain cap, or rinse cap are not fully closed.
 14. Service Panel Drain Valve Assembly (Fig. 1)
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 A.  The drain valve assembly (DVA) at the service panel is the interface between the airplane and the ground service equipment (GSE) drain lines. The DVA has these parts:
 (1)  
A drain nipple that has a machined outlet that can connect to a 4-inch coupling on the GSE drain line.

 (2)  
An inner door that keeps the contents of the airplane drain tube in the drain tube. The inner door is opened by a lever that releases the detent that keeps the inner door closed. A rubber seal that can be replaced is installed around the edge of the inner door.

 (3)  
A hinged cap that fits over and seals the nipple outlet. The cap has a handle and latch mechanism that keeps the door closed. A rubber seal that can be replaced is installed on the inner surface of the cap. The inner door is forced to close when the cap is closed.

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