(9)
LOWER EXPLOSIVE LIMITS (LEL):
(a) The minimum concentration of flammable vapors in air below which propagation of flame does not occur on contact with a source of ignition.
(10)
PERMISSIBLE EXPOSURE LEVEL (PEL):
500
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(a) The time weighted average airborne concentrations of substances at which it is believed that nearly all workers may be repeatedly exposed 8 hours a day, 40 hours a week, without adverse health effects.
NOTE: The PEL Limits used in this procedure are the PEL limits used by Boeing personnel during fuel tank entry. If the local PEL limits are more restrictive than the ones given in this procedure, use the equivalent local PEL limits.
(11)
PURGING (FOR FUEL TANK ENTRY):
(a) Purging an aircraft fuel tank is defined as the removal of any fuel or fuel vapor that remains after the fuel tanks are sumped. A purged fuel tank contains a nonflammable atmosphere that can be maintained by mechanical ventilation.
(12)
UNWANTED SOURCES OF IGNITION:
(a) Unwanted sources of ignition include: 1) open flames (matches, cigarette lighters etc.) 2) electrical equipment (lights, motors, sparks from engine exhaust etc.) 3) frictional hot spots 4) electromagnetic energy (radio transmissions or radars) 5) static electricity 6) lightning
C. Purging and Fuel Tank Entry - Airplane Precautions
(1)
Do the maintenance on the fuel tanks in areas which allow the free movement of air, fire fighting equipment and other emergency equipment.
(2)
A rope barrier must be placed around the airplane, to identify the Class I, Division 1 hazardous Locations. See Figure 201 for the distance requirements. The rope barrier must include signs or placards which state "DANGER - OPEN FUEL TANKS.
(3)
The airplane must be correctly grounded to an approved ground before you defuel the airplane or open any fuel tanks.
(4)
Before the fuel tank access doors are opened, all of the electrical power to and from the airplane must be removed. Placards which state that power should not be restored on the airplane until the fuel tank(s) are closed should be attached to applicable locations.
WARNING: DO NOT USE AIRPLANE ELECTRICAL POWER WHEN FUEL TANK ACCESS DOORS ARE OPEN. A FIRE OR EXPLOSION CAN OCCUR IF FUEL VAPOR IS IGNITED BY SPARK(S) FROM ELECTRICAL EQUIPMENT. A FIRE OR EXPLOSION CAN CAUSE SERIOUS INJURY OR DEATH TO PERSONS AND CAN CAUSE DAMAGE TO EQUIPMENT.
(5)
The main and APU batteries must be disconnected. Placards which state not to connect the batteries unit the fuel tanks are closed should be attached to all disconnected battery locations.
(6)
All safety, support and maintenance equipment must be in place before you open the fuel tank access doors. Movement of equipment can cause sparks which can cause fuel vapors to ignite.
(7)
No painting operations are allowed on airplanes with open fuel tanks.
WARNING: WHEN YOU GO INTO THE FUEL TANK, DO NOT STAND ONE FOOT OR LESS DIRECTLY IN FRONT OF THE DENSITOMETER EMITTER FOR MORE THAN 15 HOURS PER WEEK. THE DENSITOMETER EMITTER CONTAINS A LOW LEVEL RADIOACTIVE SOURCE. IF YOU STAND IN FRONT OF THE EMITTER FOR LONGER THAN THE ALLOWED TIME, IT IS POSSIBLE THAT IT CAN CAUSE HEALTH PROBLEMS.
(8)
AIRPLANES WITH THE HONEYWELL FUEL QUANTITY INDICATING SYSTEM; The densitometer emitter contains a low level radioactive source. If maintenance is necessary on the densitometer emitter, contact your nearest Honeywell, INC. representative.
500
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500
May 1/98 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 28-10-0 Page 207
D. Purging and Fuel Tank Entry - Electrical Equipment Precautions
WARNING: FOLLOW THE SUBSEQUENT RADIO AND RADAR LIMITS. FAILURE TO FOLLOW THE SUBSEQUENT RADIO AND RADAR LIMITS CAN CAUSE A FIRE OR EXPLOSION. A FIRE OR EXPLOSION CAN CAUSE SERIOUS INJURY OR DEATH TO PERSONS AND CAN CAUSE DAMAGE TO EQUIPMENT.
(1) No radio or radar equipment should operate nearer to an open fuel tank than the distances specified in Table 201.
POWER (EIRP *[1]) OF EQUIPMENT TRANSMITTING RADAR OR RADIO *[2] SEPARATION DISTANCE (FEET)
MAINTENANCE WITH OPEN FUEL TANKS PURGED MAINTENANCE WITH OPEN FUEL TANKS NOT PURGED (or during purging)
More than 100 watts 200 200
25 to 100 watts 50 50
Less than 25 watts *[3] 10 50
Radiating ground approach control or pattern surveillance radar 300 300
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