*[1] EIRP is Effective Isotropic Radiated Power in watts
*[2] This separation distance does not apply to airplane installed radio transmitters. Any limits on operations for the airplane VHF, SATCOM, HF, weather radar, etc., are listed in the airplane operations manuals.
*[3] This category includes mobile phones, pagers, two-way radios, etc. There are low power (explosion proof) radios that are approved for use in Class I division 1 hazardous locations that can be used safely in the vicinity of open, not purged, fuel cells and other areas containing fuel vapors.
Radio and Radar Precautions 500
28-10-0 Page 208 Table 201 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 1/98
(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.
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, 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.
(4)
Figure 201 shows the different classification of hazardous locations around airplanes with open fuel tanks.
(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 allowed only by approved persons. The air in the fuel tank must be 10 percent or less of the lower explosive limit (LEL).
(6)
Only use explosion-proof flood extension lights and power cards which are approved to supply external light.
(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.
(8)
Do not use electrical test equipment which can cause sparks in a fuel tank.
E. Purging and Fuel Tank Entry - Equipment Precautions
(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.
(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.
(3)
Air ducts must be bonded to form a continuous electrical conductor, and grounded in at least one place to a static
electrical ground.
(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.
(5)
Equipment used to ventilate the fuel tanks or provide warm or cool air must not be turned off with the air duct in the fuel tank. The fuel vapor from the fuel tank can enter the air duct and cause an explosion at the motor. Make sure the blower is on before you put the air duct in the fuel tank. Make sure the blower remains on until the air duct is removed from the fuel tank.
(6)
When you remove an air duct from the fuel tank or disconnect the air duct at the blower, turn the duct 180 degrees away from the purging area, to stop the flow of fuel vapor into the air duct line.
(7)
During fuel tank maintenance, make sure there is continuous mechanical ventilation. The fresh air flow from the ventilation equipment must maintain the oxygen levels between 19.5% and 23.5% by volume and the fuel vapor levels below 10% LEL (fire safe limit).
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