Patent ID: 6991041

Claim:
A compressed air foam system for use in extinguishing fire comprising: a mixer having an inlet and an outlet; a solution discharge device configured to receive mixed aerated foam solution from the outlet of the mixer and output the mixed aerated foam solution from the system; a fire pump having a suction port and a discharge port, the fire pump being configured to pump water under pressure from the discharge port, the suction port being in fluid communication with a water source; a conduit providing a fluid path between the discharge port of the fire pump and the inlet of the mixer; a water flow sensor configured to sense a water flow rate of the water flowing through the conduit; a foam proportioning apparatus configured to inject foam chemical into the water flowing through the system; an air conduit configured to inject compressed air at an air injection point into the water flowing through one of the conduit and the mixer, the air conduit being in fluid communication with a source of compressed air; an air flow sensor configured to sense an air flow rate of the air flowing through the air conduit; an air flow control valve configured to control the flow of the compressed air through the air conduit; and a system controller having a user adjustable ratio input, the system controller being configured to receive the sensed water flow rate from the water flow sensor, to receive the sensed air flow rate from the air flow sensor, to output a first control signal to the air flow control valve for regulating the flow of compressed air and to output a second control signal to the foam proportioning apparatus for regulating the flow of foam relative to the sensed water flow rate, the system controller automatically adjusting the first and second control signals to maintain a ratio of air flow to foam flow based upon the user adjustable ratio input.