Importance

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Abstract

A balanced pressure proportioning system for injecting firefighting foam concentrate into a stream of water is provided. The system includes a primary conduit having a central and a spring-biased piston disposed immediately downstream of the restriction. Foam is supplied to the conduit from a chamber which is in communication with the conduit through a foam passageway at a point disposed immediately downstream of the restriction. The chamber is divided into a foam section and into a water section by a diaphragm or other suitable member. The water section of the chamber is maintained at the upstream water pressure by way of a water passageway which provides communication between the water section and the conduit at a point disposed upstream of the restriction. Pressure is communicated from the water section of the chamber to the foam section of the chamber by the diaphragm or other suitable movable member. Movement of the diaphragm also activates or deactivates a foam pump which supplies additional foam concentrate to the foam section of the chamber. Accurate proportioning is further achieved by the employment of an adjustable metering valve disposed between the foam chamber and the primary conduit. The geometry of the piston or check valve and the interior of the primary conduit further contributes to the accurate proportioning of the system.

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First Claim