Abstract: A rotary control valve with a variable area orifice (or orifices) which communicate with a bypass channel in order to provide infinite control of flow across the valve. The bypass channel may contain a silencing means. This arrangement allows for in-line maintenance of, or modification to, either the silencing means or the valve body itself through top entry of the valve. The cross-sectional void area of the bypass channel may be sized to be the same as the cross-sectional area of the upstream and downstream valve ports in order to provide silencing without throttling the flow through the valve.

Abstract: A rotary control valve is provided with a variable area orifice in the control element that communicates with a bypass channel, which contains noise silencing means, when the valve is in the less than full-open position. This arrangement minimizes cavitation and noise when the valve is not in the full-open position while providing maximum flow with minimum friction and pressure drop when the valve is in the full-open position. The removable bypass channel configured with a single variable orifice in the control element allows for in-line maintenance of, or modification to, either the noise silencing means in the removable bypass channel or the valve body itself through top entry to the valve. The cross-sectional void area of the upstream and downstream ports as a means of further reducing noise and controlling velocities. The silencing means located within the bypass channel can be a multiplicity of balls or other such means that can be placed within the bypass channel.