(b)
If electrical power has not been supplied, do this task: "Supply Electrical Power" (AMM 24-22-00/201).
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 747-400 MAINTENANCE MANUAL
(c) (d) Do this task: "Water System Pressurization" (AMM 38-15-60/201).Make sure the compressor operates correctly.
(5) S 864-026Remove electrical power if it is not necessary (AMM 24-22-00/201).
(6) S 014-027Close the access door for the center equipment panel.
(7) S 014-028Close the access door for the center electronic bay, 125B (AMM 06-09-02/201).
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
WASTE WATER SYSTEM - DESCRIPTION AND OPERATION
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General (Fig. 1)
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A. The waste water system gathers the waste water from the lavatory compartment washbasin, the lavatory floor drain, the galley sink drain, and directs the water overboard through the drain mast. The waste water flows to the drain mast in tubes that are made from corrosion resistant steel. Included in the waste water system are the sink drain mufflers installed in the overflow line of each washbasin. The sink drain muffler reduces the noise level of the air drawn through the system by differential pressure at the drain mast. The drain mast is electrically heated to keep it clear of ice (Ref 30-71-00/001). The section of tubing installed at station 840 is also electrically heated.
Drain Mast
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A. The drain system terminates in an electrically heated drain mast through which waste water from the galley sink, lavatory washbasin and lavatory floor drain is dumped overboard. The drain mast is installed on the underside of the fuselage. The drain mast is designed to draw waste water out of the system while airplane is in flight.
Sink Drain Muffler
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A. The washbasin overflow line, having no stopper, is open overboard through the drain mast. To prevent the noise that come from the flow of air through the drain lines, a muffler is installed in the overflow line.
Sink Drain Stopper
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A. There is a stopper in the washbasin bowl that will let the water drain if it is open. If the stopper is closed, the water cannot drain from the washbasin. An actuator is mounted in the faucet assembly. The actuator operates the stopper with an actuator arm. Push the actuator down to open the drain line. Release the actuator to close the drain line. To remove the stopper, push the actuator down and turn the basin stopper 1/4 turn, and then lift the stopper up.
Operation
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A. Functional Description
(1) The waste water system operation uses the gravity flow of water and the difference in air pressure between the pressurized cabin and the exhaust end of the drain mast. The washbasin stoppers are spring-loaded to the closed position to reduce cabin pressure loss. When the stopper plunger (between the faucets) is depressed by hand, the basin stopper is raised to allow waste water to flow down the drain. When all waste water has passed down the drain, the plunger is released and the stopper returns to the closed position. The washbasin overflow line, and the lavatory floor drain, are not stoppered; thus, there is a constant flow of air through the drain system overboard through the drain masts. A sink drain muffler, just downstream of the basin overflow connection, reduces the noise level that is caused from the flow of air through the drain. The flow of warm cabin air through the drain system and heated drain hoses in some critically cold areas keep the lines clear of ice.
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本文链接地址：747-400 AMM 飞机维护手册 气动系统 WATER/WASTE(42)
