US Patent 7703543 Fire fighting foam dispensing system and related method

A fire fighting foam dispensing system includes a water inlet adapted to receive a flow of water, a first variable speed pump adapted to inject foam concentrate into the flow of water, a second variable speed pump adapted to inject foam concentrate into the flow of water, a foam outlet adapted to discharge fire fighting foam, a measuring apparatus adapted to measure flow rate in at least one of the water inlet and the foam outlet, and a system controller adapted to detect the flow rate from the measuring apparatus, and activate the second variable speed pump only upon the measured flow rate exceeding a predetermined flow rate value.