Each container assembly (fig. 1-24) consists of the following components: A fusible plug, pressure gage, frangible disc, cartridge, bonnet, and the container itself. The container is a spherical assembly, designed to contain 6.5 pounds of CF3Br and a precharge of 600 psi of nitrogen at (70 F). NOTE: The capacity and precharge of the container assembly will vary with the type of installation.

Figure 1-24.- CF3Br container assembly.

The combined nitrogen charge and CF3Br is retained in the container by the frangible disc and the fusible plug. The fusible plug protects the container from possible damage by excess pressure caused by an increase in ambient temperature. The metal of the fusible plug melts at temperatures between 208 and 220 F, releasing the contents of the container overboard.

Discharge Indicator

One discharge indicator is mounted on each nacelle as shown in figure 1-23. The indicator consists of a red disc and an aluminum alloy tube that connects to the container at the fusible plug. If thermal expansion in the container is great enough to rupture the fusible disc, the red disc will rupture and the CF3Br will flow overboard through the line to the indicator. Therefore, when the discharge indicator is missing, the container must be checked for proper pressure. Some CF3Br containers have a relief valve in place of the fusible plug. On some, the fusible plug is called a safety plug. The relief valve relieves the excess pressure in the container instead of completely emptying the container. Some larger aircraft use more than one fire extinguishing agent container to direct the agent to several points within an area. With cockpit switches set at various positions, the agent can be released through specific discharge outlets; and if the fire persists, the switch positions can be changed to release agent from a second container to different discharge outlets within the same area. The fire extinguishing system of the P-3 air-craft is an example of this type of system. The containers used in the P-3 system are also equipped with two-valve (bonnet) assemblies for discharging the container; however, only one assembly is fired at any one time to discharge the container. This dual arrangement provides a secondary means of discharging a cylinder in the event a cartridge fails for any reason to fire and discharge the container.

MAINTENANCE

Maintenance of the CF3Br fire extinguishing system at the organizational level of maintenance consists of replacement of faulty components and discharged or below pressure containers, maintenance of associated plumbing, and per-forming operational checks. Containers should be replaced when the pressure falls below that indicated on the container or in the applicable MIM. Each container has a pressure indicating gage. Suspected leakage in system plumbing requires disconnection of the container( s) and pressure leakage testing of all lines by using nitrogen pressure and a leakage tester. The leakage tester measures pressure drop over a specified period of time, as outlined in the MIM. The operational checkout of the fire ex-tinguishing system, primarily a checkout of electrical circuitry such as wiring continuity checks, proper switch operation, etc., is per-formed by personnel of the AE rating.