B.  The cargo compartment fire extinguishing system uses 28 VDC power. The power is supplied through the circuit breaker CARGO FIRE EXTINGUISHING, installed on the P6 or P18 panel.
 2.  Component Details (Fig 1)_________________
 A.  Cargo Fire Extinguishing Bottle
 (1)  One cargo fire extinguishing bottle is installed in the Mix Manifold Bay, located in the aft end of the forward cargo compartment. The bottle is a hermetically sealed container which is filled with bromotriflouromethane (halon) and nitrogen. The nitrogen is added to increase the pressure in the bottle. The bottle includes two discharge heads, a temperature compensated pressure switch, and a filler/safety port.
 (a)  Two Discharge Heads are installed on the bottle to release the halon to the applicable areas. The FWD head will release halon into the tubing that goes to the forward cargo compartment. The AFT head will release halon into the tubing that goes to the aft cargo compartment. The FWD discharge port is a different size than the AFT discharge port to prevent cross connecting the tubing. Also, the electrical receptacle on the FWD and AFT squib are different sizes to prevent cross connection of the wiring. The discharge heads contain a disc that holds the halon in the bottle. When the disc is broken, then the halon from the bottle is released through the discharge ports into the tubing. The disc is ruptured by an electrically stimulated squib. The squib breaks the disc using shock wave propagation (a small explosion) not a mechanical cutting device.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH LOWER CARGO FIRE ú

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 EXTINGUISHING SYSTEM  ú ú 01 Page 1 ú Nov 15/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

737-300/400/500
MAINTENANCE MANUAL

MASTER CAUTION AND FIRE WARN LIGHTS (P7)
SEE A
FIRE MASTER WARN CAUTION
BELL CUTOUT PUSH TO RESET
CARGO FIRE CONTROL PANEL (P8)
SEE B
MASTER CAUTION AND FLIGHT COMPARTMENT FIRE WARN LIGHTS (P7) (EXAMPLE)
A
EXT DET SELECT
FWD AFT NORM NORM DETECTOR
A

BA B
FAULT
C
gg
F
A I
R  FWD AFT DISCH
R
G TEST  ARMED
E
O

ARMEDARMED DISCH
r r
CARGO FIRE CONTROL PANEL (P8) B
Cargo Bay Fire Extinguishing - Component Location Figure 1 (Sheet 1)
G96405
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH LOWER CARGO FIRE ú

 26-23-00
 EXTINGUISHING SYSTEM  ú ú 01 Page 2 ú Jul 12/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
AFT CARGO 
COMPARTMENT  CARGO 
MIX BAY  CEILING 
COMPARTMENT  (REF) 
FORWARD 
CARGO 
COMPARTMENT 
DISCHARGE 
NOZZLE 
SEE  C 
CARGO FIRE 
EXTINGUISHER  DISCHARGE NOZZLE 
CSEE NOZZLE DISCHARGE  DSEE BOTTLE  CONNECTOR ELECTRICAL  C (EXAMPLE) 
PRESSURE 
SWITCH 
CARGO FIRE 
EXTINGUISHER 
BOTTLE 

FORWARD
SQUIB

DISCHARGE TUBES
ELECTRICAL CONNECTOR (2 LOCATIONS)
AFT SQUIB
CARGO FIRE EXTINGUISHER BOTTLE
FWD
D
Cargo Bay Fire Extinguishing - Component Location
Figure 1 (Sheet 2)

G96412
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH LOWER CARGO FIRE ú

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 EXTINGUISHING SYSTEM  ú ú 01 Page 3 ú Nov 15/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (b)  
The Pressure Switch monitors the pressure in the bottle. The switch will be open when the bottle is fully charged. If the pressure in the bottle is below 300 psig (at 70°F), then the switch will close and will send a signal to the flight compartment that the pressure in the bottle is too low. The pressure switch compensates for the temperature of the bottle to maintain an accurate pressure indication.
　
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