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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
 S 482-371
 WARNING: MAKE SURE THE COMBUSTIBLE GAS INDICATOR IS EXPLOSION-PROOF
_______ (CLASS I, DIVISION 1 OR EQUIVALENT STANDARD) AND IS SATISFACTORY FOR USE IN A FUEL TANK. IF YOU USE A COMBUSTIBLE GAS INDICATOR THAT IS NOT INTENDED FOR USE IN A FUEL TANK, AN EXPLOSION CAN OCCUR. AN EXPLOSION CAN CAUSE SERIOUS INJURY OR DEATH TO PERSONS AND DAMAGE TO EQUIPMENT.
 (9)  Do these steps to prepare the combustible gas indicator (Fig. 205):
 NOTE: These steps are for the combustible gas indicators called out
____ in the equipment section of this procedure. If you use a different combustible gas indicator, use the instruction manual supplied with the indicator.
 (a)  Make sure the indicator is calibrated for each of these scales:
 NOTE: Make sure the GASTECH GT-series combustible gas
____ indicators are labeled for calibration with hexane gas, and that the ppm range in the channel set-up menu is set to 5000 ppm hexane.
 1) Oxygen
 2) Lower Explosive Limit (LEL)
 3) Parts Per Million (PPM)

 (b)  
Make sure the calibration on the combustible scales are specific to hexane gas.

 (c)  
Make sure the alarm values are set to these limits:
 1) 160 PPM
 2) 10% of the LEL
 3) 19.5% oxygen by volume.

 (d)  
Do these steps to make sure the combustible gas indicator operates correctly: 1) Make sure the indicator, sampling line, and sampling probe

 (with dust filter) are clean and not damaged. 2) Put the indicator switch to the ON position. 3) Make sure there is enough charge on the battery for the
 scheduled time in the fuel tank. 4) Let the indicator warm-up for 20 minutes before you look at the readings.
 5)  Adjust the indicator to zero in clean air for these scales: a) Oxygen b) PPM c) LEL
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 28-10-00
 ALL  ú ú 03 Page 234 ú Nov 15/98
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 6)  If there is a negative value during the use of the indicator, adjust the indicator scale(s) to zero in clean air.
 NOTE: Do not turn the indicator off before you adjust the
____
 scales.

 (e)  
Do these steps to do a check of the alarms: 1) To do a check of the oxygen alarm, blow across the probe until the alarm comes on (19.5%).

 2)  To do a check of the PPM and LEL scales, hold the tip of the probe over a solvent bottle or some solvent on a rag until the alarm comes on.

 (f)  
Put the combustible gas indicator on a stand or ladder next to the access door where you will enter the fuel tank. 1) To prevent the accidental movement of the combustible gas

 indicator, safely attach the indicator to the stand or ladder.
 H.  Purging of the No. 1 and No. 2 Tanks
 S 912-372
 WARNING:_______OBEY THE PURGING AND FUEL TANK ENTRY PRECAUTIONS. FAILURE TO OBEY THE PURGING AND FUEL TANK ENTRY PRECAUTIONS CAN CAUSE SERIOUS INJURY OR DEATH TO PERSONS AND CAN CAUSE DAMAGE TO EQUIPMENT.
 (1)  
Read and obey the precautions in this task: Purging and Fuel Tank Entry Precautions.

 S 492-373

 (2)  
VENTURI TYPE VENTILATION EQUIPMENT; Do these steps to install the air ventilation equipment (Fig. 203):

 (a)  
Remove one or more main tank access doors to have a good flow of air through the fuel tank (AMM 28-11-11/401).

 (b)  
Install rubber protectors around the openings of the main tank access doors.

 (c)  
Start the air supply connected to the air mover.

 S 492-374
 (3)  AIR BLOWER TYPE VENTILATION EQUIPMENT (BOE-501 OR EQUIVALENT); Do these steps to install the air ventilation equipment (Fig. 204):
 WARNING: DO NOT STOP OR START THE VENTILATION BLOWER WHILE THE AIR
　
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