It is desired to provide full ball rotary control valves for fluid control systems wherein means are provided for reducing both the aerodynamic and hydrodynamic noise within the system. It is especially desired to provide such noise attenuating means movable with the rotary ball control member so as to reduce the construction costs as well as the maintenance costs for such units.
Several combined full ball/attenuator units incorporate noise attenuator devices mounted within the ball bore such that full noise attenuation is obtained upon initial valve opening; a substantial reduction in attenuation is obtained as the valve is continued and zero attenuation is obtained when the valve is fully opened. In the fully opened valve position the flow stream is substantially unimpeded by the noise attenuator devices. Such units are desired where the control valve must handle a high capacity of fluid flow.
In certain applications a high capacity flow handling control valve is not needed. Also, it is desired in certain applications that the amount of noise attenuation should be fairly constant with respect to the control valve position, and in particular it may be desired to have almost full noise attenuation at the full-travel or fully opened valve position.