(9)
Put the air duct for the heater/air blower in the fuel tank through the tank access opening.
(10)
Bond the air duct to the airplane structure.
(11)
Continue to have a good flow of air through the fuel tank with the air mover until you prepare to the close the fuel tank.
(a) Read the combustible gas indicator values every half hour or less.
(12)
If fuel vapors get into the fuel tank that was in a fire-safe condition, get all persons out of the fuel tank until you make sure the air in the fuel tank is in a fire-safe condition again.
(13)
Go into the fuel tank per the "Fuel Tank Entry" procedure to do maintenance.
500 Combustion Gas Calculations
May 01/98 Figure 202 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 28-10-0 Page 233
G. Fuel Tank Entry
WARNING: OBEY THE PURGING AND FUEL TANK ENTRY PRECAUTIONS. FAILURE TO OBEY THE FUEL TANK ENTRY PRECAUTIONS CAN CAUSE SERIOUS INJURY OR DEATH TO PERSONS AND DAMAGE TO EQUIPMENT.
(1)
Read and obey the precautions in this task: Purging and Fuel Tank Entry Precautions.
(2)
Complete the confined space entry permit (if it is a requirement).
(3)
Use the pre-entry checklist (an example is given in Figure 206).
(4)
Do these steps to prepare the respirator s for fuel tank entry:
(a)
Use Table 203 to find out what level of respiratory protection is necessary.
(b)
If the fuel tank is in a fire-safe condition, wear a full-face respirator with an attached breathing-air supply.
WARNING: PUT ON AN APPROVED RESPIRATOR WITH ATTACHED BREATHING-AIR SUPPORT BEFORE YOU GO INTO A FUEL TANK THAT WAS FILLED WITH JP-4 FUEL. THERE IS NO HEALTH-SAFE LIMIT FOR JP-4 WHICH CONTAINS BENZENE. IT IS POSSIBLE THAT BENZENE CAUSES CANCER.
(c)
If the fuel tank is in a health-safe condition, wear a full face respirator with an attached breathing-air supply, or at a minimum, a half-face respirator with an organic vapor filter.
(d)
Connect the subsequent respirators to the air support (Fig. 204): 1) One respirator for the person who goes into the fuel tank.
2) Two emergency rescue respirators.
(e)
Make sure air gets to the respirators.
(f)
Make sure the respirator system (regulator, mask etc.) is clean.
NOTE: When you use the respirator, you should regularly drain moisture from the filter on the regulator. If you drain dirt or oil from the filter, or if the air in the respirator smells bad, replace the filter.
(g)
Make sure the emergency air supply and respirators operate correctly.
500
28-10-0 Page 234 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 1/98
FIRE-SAFE CONDITION
NOTE: A FIRE-SAFE CONDITION OCCURS WHEN THE VAPOR CONCENTRATION IS LESS THAN 10% OF THE LEL.
HEALTH-SAFE CONDITION NOTE: A HEALTH-SAFE CONDITION OCCURS WHEN THE OXYGEN CONTENT IS A MINIMUM OF 19.5% TO A MAXIMUM OF 23.5% BY VOLUME AT SEA LEVEL, AND THE VAPOR CONCENTRATIONS ARE BELOW THESE PERMISSIBLE EXPOSURE LIMITS:
FUEL Permissible Exposure Level Total Hydrocarbons TWA. (ppm) Lower Explosive Level (percent)
Aviation Gasoline 300 1.0
Jet A Jet A-1 JP-5 JP-8 160 0.7
Jet B 200 0.8
WARNING: THERE IS NOT A HEALTH-SAFE LIMIT FOR JP-4 FUEL WHICH CAN CONTAIN BENZENE. IT IS POSSIBLE THAT BENZENE CAUSES CANCER.
*TWA Time Weighted Average
500 Health Safe Condition Vapor Levels
May 1/98 Table 203 28-10-0
Page 235
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(5)
Remove these items before you go into a fuel tank:
(a)
All jewelry - rings, bracelets, wrist watches etc.
(b)
Matches
(c)
Pocket warmers
(d)
Hearings aid devices or other battery operated equipment.
(6)
Remove any clothes made of this material:
(a)
Wool
(b)
Silk
(c)
Nylon
(d)
Synthetic clothing.
(7)
Put on these approved protective clothes (Fig. 202):
(a)
Cotton or SARANEX 23P coveralls (non-sparking zippers or buttons)
(b)
Clean cotton head cover
(c)
Approved cotton or rubber gloves
(d)
Safety glasses or face shield
(e)
100% cotton socks and/or fuel cell boots
