Because of the direct contact with water, only protein based foam concentrates with a specific gravity of 1.1 or higher can be used with this type of proportioning system. The pressure proportioning system is pressurized during operation and can be refilled with concentrate only when system is not in use. Less expensive than bladder tank systems. Easier to refill than bladder tanks. Does not require power other than the water supply.
Installation requires less space than horizontal tank.
The pressure proportioning system tank shall be a welded carbon steel pressure vessel constructed in accordance with ASME code, Section 8. All tank valves shall be brass or bronze construction with identification labels on the handles, and shall be a locking type in accordance with NFPA requirements for valve supervision. A PPH pressure proportioning head shall be installed on the pressure vessel. The PPH head shall be a fabricated steel unit consisting of a water inlet pipe, proportioning head with a stainless steel water orifice and a brass foam concentrate orifice with PVC pickup tube, and a solution discharge pipe. See chart for proportioning range of each pressure proportioning head.