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APPENDIX A
TM 07661B-14/1
of the tank. The system pressurizes within a few seconds when the quick-opening gas valve on the AFFF system
nitrogen cylinder is opened. With the product valve and charge valve in the open position, the AFFF tank will be charged
almost instantaneously up to the AFFF shut-off valve. To bring the AFFF solution up to the nozzle, the operator opens
the AFFF shut-off valve by turning the control rod one-quarter turn counterclockwise. A check valve between the
pressure regulator and the charge valve prevents agent back-up and subsequent regulator damage in event of low
charge in the nitrogen cylinder. A pressure relief valve on top of the tank protects against over-pressurization in event of
pressure regulator failure. For cold weather operation, a heater with thermostat is provided to keep the AFFF solution in
a liquid and free-flowing condition.
c. Hose Reel. The hose reel attached to the skid frame provides a convenient method of storing the hoses used in
dispensing of the twin fire-fighting agents. Rotating joints on each side of the hose reel are the inlets. The rotating joints
also act as bearings to support the drum and allow it to turn freely. The chemical agents flow through tubes inside the
drum to side-by-side outlets which protrude through an opening at one end of the drum. These two outlets connect to the
dispensing hoses and turn with the drum to allow the hoses to be wound on the drum. A sprocket and chain drive with a
hand crank is provided for rewinding of the hoses onto the drum. The hose reel stores 150 feet of twin handline, and can
be secured against rotation by an adjustable brake on the hand crank drive bearing.
d. Remote Hose Reel. The remote hose reel (figure 1-3) is the same as the one attached to the skid frame except
that it is mounted on a two-wheel cart and can be easily moved as needed to increase the area coverage of the fire
extinguisher. Inlets to the hose reel are equipped with quick disconnect fittings for coupling the hoses to the nozzle ends
of the two main discharge hoses. The nozzles can be quickly removed from the fire extinguisher handline and attached
to the remote hose reel handline. The quick disconnect fittings are oriented to prevent wrong connections.
e. Twin Agent Nozzles. Two discharge nozzles, one for each chemical agent, are fastened together with a tie bar
at the end of the twin handline. Each tip is designed to provide the optimum discharge pattern for the chemical agent
being dispensed. Disc shutoffs inside the nozzles control the discharge from the handlines. Squeezing the trigger fully
completely opens the shutoff valve, allowing unrestricted flow of chemical agent through the nozzle body to the tip. The
nozzle tips are easily removed for cleaning in event of plugging.
A 2-3. ELECTRICAL THEORY.
a. Description. The only electrical component in the fire extinguisher is the AFFF tank heater (figure 2-2), used
only in cold weather operation. The heater installation consists of two resistance-type heater strips installed around the
lower circumference of the AFFF tank and two 45-inch long strips of heat tape wrapped around the outlet tube and the
shutoff valve. The heater strips and tape are connected as
A 2-3
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