FIREFIGHTING SYSTEM -706880026

TM 5-4210-233-14&P-1

1-16. BRAKE SYSTEM - Continued

c. Front Brake System.

(1) To engage the front brakes, air pressure is supplied from the front service reservoir via the brake valve

assembly (front), quick release valve, to the front wheel brake air chambers. When the brake pedal is

released, the air pressure exhausts. Without pressure, the quick release valve opens and vents the air

chambers to atmosphere, thereby releasing the brakes.

(2) The front brake system is operational only when the front service reservoir is pressurized.

1-17. FIREFIGHTING SYSTEM Controls are provided in the cab and on the structural control panel to enable

firefighting. The system is controlled from the operator station. Pump engagement and disengagement,

however, is always controlled from the cab.

CAUTION

To prevent inrush surges and engine overspeeding, water must

always be available at the pump before it is engaged. While

operating, water supply to the pump must be continuous. If

discontinued, the pump must be shut down immediately to

prevent damage.

The pump must be disengaged immediately when the watertank

is emptied. Failure to do this can cause vehicle damage due to

engine overspeeding.

a. Water supply and discharge system.

(1) Water supply can be from tank or alternative sources via the suction manifold. The alternative sources

may be fire hydrants, remote pumping units or an open reservoir. If water is drawn from tank a

continuous supply must be secured via the automatic tank fill valve.

(2) Automatic priming of the fire pump takes place if the pump is void of water when initially engaged. The

priming pump, driven by the fire pump, evacuates the fire pump suction. As soon as water pressure is

available, the priming pump automatically disengages.

(3) From the pump the water flows via the discharge manifold to the aerial and hand line valves.

b. Foam Induction System.

(1) Foam concentrate is released from the foam tank and metered into the water flow to the pump. The

control valves through which the concentrate is released and metered are operated from the operator's

station. To produce foam, water (derived from the pump discharge) is cycled through the eductor and

into the pump suction. In the eductor, the water draws foam concentrate into the flow by venturi action.

(2) To remove residual foam from the foam lines after firefighting, the foam tank valve is closed and the

flush valve is opened. Water from the pump discharge is then cycled through the metering valve and

the eductor.

1-19