Balanced Pressure Proportioner System.

A balanced pressure proportioner has been developed for shipboard Aqueous Film Forming Foam (AFFF) systems. The proportioner employs two ratio controllers: Type 2 to cover the range of 50 to 5000 gpm and Type 3 for 50 to 1000 gpm. The system has been tested in the laboratory over the flow rate range of 50-1000 gpm at firemain pressures of 100-200 psi and found to meet the requirements of the specification for concentration of AFFF and for pressure drop with one exception, namely, the pressure drop for the Type 2 exceeded the limits at 500 gpm. It was recommended that the specification be modified to allow for this excessive pressure drop.