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Abstract

A system for controlling the rate of flow of a liquid in a liquid flow system, especially a system for controlling the rate of flow of treated water in a municipal water treatment and pumping system, the flow control system utilizing a venturi (10) having an inlet (12), a restricted throat (14) and a diffuser (16) through which the liquid flow is in series. The rate of flow of liquid through the venturi is adjusted by a flow rate control valve (18) in fluid communication with the diffuser of the venturi, and the flow control valve has a spool (22) that moves linearly to selectively permit a variable volume of liquid to flow through the valve into an outlet main (20). The movement of the spool is actuated by an electrically operated linear actuator (44) that operates in response to an electrical signal from a digital controller (40), which is indicative of a pressure differential between liquid pressure at the inlet of the venturi and liquid pressure at the throat. A set point adjustment device (46) is provided to adjust the set point of the rate at which the linear actuator operates to actuate the position of the spool of the flow control valve.

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