Angus Balanced Pressure Foam Proportioners (BPPs) are designed for use in fixed systems to introduce foam concentrate at a predetermined rate into the fire-water supply, over a varying range of foam solution demands. For example, where a number of discharge outlets may be required to operate individually or simultaneously.
There are five basic models with capacities from 220 litres/min. to 22,000 litres/min. and each unit is factory-calibrated to suit proportioning rates of 1%, 2%, 3% or 6% of a specified foam concentrate. A trimming screw facility on the foam inlet, permits adjustment during commissioning for exceptional operational accuracy.
The upper performance limit is defined as the flow at which the maximum specified pressure drop of 1.25 bar is reached. A pressure recovery improver is available as a cost option which extends the upper flow limit of the BPP by reducing pressure losses at high flows.
Without the improver section there is a 7:1 ratio between the maximum and minimum flows and with the improver, this increases to 10:1.
The BPPs are wafer type, designed to be installed between ANSI 150 flanges and are manufactured from high grade corrosion resistant materials. They are simple to install, require no maintenance and their modular construction gives the engineer considerable flexibility in terms of selection of flow rate and positioning within the system.
To ensure accurate proportioning, the foam concentrate must be supplied to the unit at exactly the same pressure as that at the water inlet. This can be achieved by using the proportioner in conjunction with either a Balance Valve (Data Sheet 5043) or a Bag Tank Module (Data Sheet 5045) and it must be stated at the time of order which will be used.