Prior to the early 1990’s, to make CAF work, the pump and compressor each had to have a separate engine driver. The Solution (W + Con) and air (+A) must be equal for both to enter the discharge hose (+A – Agitation) to make foam. As the system would fluctuate, one pressure would go higher than the other, interrupting the smooth flow of a Sol + Air mixture. The system operator was required to maintain vigilance and make constant throttle adjustments on both engines.
In the early 1990’s, the pilot balance valve (PBV) was introduced. The PBV is a double diaphragm device that monitors the water pressure and automatically adjusts the air intake to match the water pressure. CAF systems could now be built with a shared driver and one throttle that requires no adjustment and delivers a smooth flow of Sol + Air (W + Con + A) mixture.
The PBV device has no firefighter adjustments. This unit should only be maintained by a qualified F-7 EVT Certified mechanic.
