20-11-24
ALL ú ú 01 Page 405 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
HEAT GUNS, SOLDERING GUNS, AND/OR SOLDERING IRONS -
___________________________________________________ MAINTENANCE PRACTICES
_____________________
TASK 20-11-25-912-001
1. Use of Heat Guns, Soldering Guns, and Soldering Irons_____________________________________________________
A. General
(1)
This procedure gives the minimum recommended safety procedures for heat guns, soldering guns, and soldering irons used near airplanes. These are general procedures. If regulations made by local agencies or procedures made by the airline are more applicable, use them. Boeing cannot know or write about all possible conditions which the airlines can have.
(2)
You must examine the conditions and be careful. Customer airlines must know how heat guns, soldering guns, and soldering irons are used.
(3)
Heat guns, soldering guns, and soldering irons can cause an explosion. Components in all of these devices can operate at temperatures higher than the fuel ignition temperature (450°F). Heat guns and soldering guns also can contain electrical switches which can cause sparks. These sparks can cause the fuel to burn.
(4)
We do not recommend you use a device to supply heat in the fuel tanks. You must have a good flow of air in the fuel tanks. You can make them safe when you fill the fuel tanks with nitrogen. For the repair of the wires in the fuel tanks, we recommend you use procedures that use crimped splices and sleeves with nylon ties. These procedures are specified in WDM Chapter 20.
(5)
Do not use heat guns, soldering guns, or soldering irons less than 100 feet from an airplane during these operations:
-
When you fuel
-
When you defuel
-
When the fuel tanks are open.
(6)
You can use heat guns, soldering guns, and soldering irons when and where smoking is permitted. If you use these devices where smoking is not permitted, you must first make sure there are not dangerous levels of fuel fumes in the work area.
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20-11-25
ALL ú ú 01 Page 201 ú Oct 10/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(7)
Zero is the safe fuel fume level at which to use devices that can cause ignition.
(8)
Measure the fuel fume level with a combustible gas indicator that reads in "PERCENT LOWER EXPLOSIVE LIMIT" or "PERCENT EXPLOSIVE". For example, you can use Mine Safety Appliances, Model 2A or Davis, Model D-16. If you can read a fuel fume level on this equipment, two conditions occurred:
-A liquid fuel or fume source is near
-The local fuel fume levels are high or the ventilation is not
sufficient. Use the equipment to measure the initial fuel fume levels. Make sure the fuel fume levels are sufficiently low. Continue to monitor the fuel fume levels during the repair.
(9)
Do not use a possible ignition source near open fuel tanks, fuel vents, or fuel leaks where fume concentrations cannot be known or controlled.
(10)
If you use a possible ignition source near an airplane where smoking is not permitted, make sure a person monitors the work and any other work in the area. The person must be authorized to monitor airplane fire safety.
(11)
A person who can measure the risk of the repair to be done must identify the emergency or fire fighting equipment necessary at the work area of the repair. The person must be authorized to monitor airplane fire safety.
(12)
Do not start or continue to do work on a fuel system component while equipment that can cause the fuel to burn is near.
(13)
Keep the number of maintenance and safety persons included to a minimum.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
20-11-25
ALL ú ú 01 Page 202 ú Oct 10/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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