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ú ú ú 01.101 ú BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details. Page 322Jul 12/02
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737-300/400/500MAINTENANCE MANUAL
FUEL SYSTEM DRAINAGE - SERVICING
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1. General
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A. This procedure has these tasks:
(1) Drain fuel from the sump drain valves for each tank.
B. You must not permit the fuel tanks to collect too much water. Do the procedure to drain the sumps drain valves for each tank regularly.
C. Obey all of the safety precautions supplied in the task: "Precautions and Limits for the Refuel Operation" (AMM 12-11-01/301).
TASK 12-11-01-683-103
2. Fuel Sump Drainage
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A. General
(1)
The fuel tank sumps must be drained regularly for the removal of the water from the fuel tanks. Each fuel tank sump has a drain valve that drains the water from the fuel tank. Before you sump the tank, a quantity of time is necessary for the separation of water from fuel. The time rate to isolate the fuel from the water is 1 hour for each foot of fuel depth. The best airplane attitude to drain the sumps is a pitch of 0.15 degree nose-down and a roll of zero degrees.
(2)
Do not drain the sumps while you fill the airplane with fuel or immediately after you fill the airplanes with fuel. The water will be mixed with the fuel. In cold weather the water can freeze. This could cause the drain valve to stay in the closed position. You must melt the ice with heat around the sump to open the valve. You can also use an approved anti-ice liquid that you add to the fuel. For example, you can use Phillips PFA 55 MB in a maximum concentration of 0.1% by volume, refer to AMM 12-33-01/301.
(3)
Look at each fuel sample for water, for ice, or for contamination. Water in the fuel usually shows as a layer below the fuel or as small bubbles in the fuel. The ice crystals usually show as cloudiness or a haziness in the fuel. Fuel with no water, ice or contamination is clear and bright. You can easily see material through it.
NOTE:____Jet-A fuel can have diffenent colors. It can have a range of colors from yellow (straw) colors to no color. The words "clear and bright" do not refer to the color of fuel. Yellow fuel or fuel that has no color can be "clear and bright" as specified above.
(4)
Put one or two drops of food coloring into the transparent container, before you drain fuel samples from each sump valve into it. This will help you find water in the fuel, since the water will have color.
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12-11-01
ALL ú ú 01A Page 301 ú Mar 12/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
B.
C.
D.
A
737-300/400/500MAINTENANCE MANUAL
(5)
Drain the tank sumps sufficiently to make sure you remove water or other contamination from the system.
(6)
Drain the sumps a maximum time of one hour after you remove the airplane from the hangar if the temperature has these conditions:
(a)
The ambient temperature is less than 0 degrees Celsius (32 degrees Farenheit).
(b)
The temperature of the hangar is more than the ambient temperature.
(7)
If the ambient temperature is less than 0 degrees Celsius (32 degrees Farenheit), supply heat before you drain the sumps to make sure the fuel drains freely.
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