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28-11-00
ALL ú ú 01 Page 211 ú Jun 10/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
S 912-392
(2) Fuel in the beam of operational high-powered radar which can produce a peak power density that exceeds 5 watts per square centimeter is hazardous. Electromagnetic energy of this intensity can ignite fuel vapors and cause a fire.
S 912-545
WARNING: DURING OPEN FUEL TANK OPERATIONS, THE ENTIRE AREA AROUND THE
_______ AIRPLANE AND ANY ADJACENT AREAS THAT COULD COLLECT FUEL VAPORS ARE CLASSIFIED AS CLASS I DIVISION 1 HAZARDOUS LOCATIONS. THE HAZARDOUS LOCATION CLASSIFICATION APPLIES TO AIRPLANES BEFORE AND AFTER A FUEL TANK IS PURGED.
THE CLASS I DIVISION 1 HAZARDOUS LOCATION EXTENDS FROM THE GROUND UP TO 18 INCHES ABOVE THE GROUND. ONLY USE ELECTRICAL EQUIPMENT WHICH IS APPROVED FOR THE APPLICABLE HAZARDOUS LOCATION.
(3)
Electrical equipment which is energized or operated within 50 feet horizontally and 18 inches or less above the ground of an open fuel tank and as shown in Fig. 201, must be rated explosion-proof for Class I, Division 1 hazardous locations. This includes energized plugs and receptacles. For radio and radar equipment (transmitting equipment), see Table 201 for separation distance requirements.
S 912-394
(4)
Figure 201 shows the different classification of hazardous locations around airplanes with open fuel tanks.
S 912-395
(5)
Only use approved explosion-proof flashlight that operate correctly in the fuel tanks.
NOTE: The use of explosion-proof lights in or near an open fuel
____ tank is permitted only by approved persons. The air in the fuel tank must be 10 percent or less of the lower explosive limit (LEL).
S 912-396
(6)
Only use explosion-proof flood extension lights and power cords which are approved to supply external light.
S 912-397
(7)
Do not connect or disconnect electrical equipment from energized outlets (within 100 feet of an open fuel tank) unless the equipment is fitted with explosion-proof plugs.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
28-11-00
ALL ú ú 01 Page 212 ú Feb 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
S 912-398
(8)
Do not use electrical test equipment which can cause sparks in a fuel tank.
E.
Purging and Fuel Tank Entry - Equipment Precautions
S 912-400
(1)
All metal work platforms or stands used for entry into the fuel tanks or located within a 50-foot radius of an open fuel tank (before and after the fuel tank purging) must be bonded to the airplane and grounded to an approved earth ground.
S 912-401
(2)
Before you use ventilation equipment make sure the blower or venturi is connected to the airplane ground. The ventilation blower or the venturi must be explosion-proof.
S 912-402
(3)
Air ducts must be bonded to form a continuous electrical conductor, and grounded in at least one place to a static electrical ground.
S 912-403
(4)
If you use the ventilation equipment to exhaust fuel vapors from the tank, static build-up on or in the air ducts can reach a level where a spark can ignite the vapors and an explosion can occur. The air ducts must be coated inside and out with a conductive coating and each section correctly bonded to each other. Air ducts made from vinyl fabric are not recommended because vinyl is an insulator of static charges. If the air duct uses a metal helical wire to create a non-collapsible duct, make sure the wire is permanently attached to a metal or conductive plastic connection on each end of the duct section.
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