Cavitrol 4

As a representative example, the control valves for the flow rate regulation in feed water recirculation are exposed to extremely high pressure difference condition and required to perform continuous control. In these valves, it has been desired that the bodies and internal valves are not damaged due to cavitation and they accomplish the functions sufficiently, but it has been one of difficult subjects until recent years to satisfy these requirements. Fisher Co. succeeded to solve this subject by producing the Cavitrol 4 trim in 1975. This trim is a cavitation-enduring trim capable of continuous control under the condition of 210 kg/cm2 valve pressure difference, and its endurance has been already confirmed at the time of periodic inspection in U.S.A. In Japan also, the results of production and delivery are obtained by Nippon Fisher Co., Ltd. The newly developed Cavitrol 4 trim is so constructed that the occurrence of cavitation is prevented by reducing the inlet pressure of fluid successively in the downstream of the totally closed part of the valve, different from former types having the limitation in the allowable pressure difference. The principle and features of the Cavitrol 4, the noise of liquid in a cavitation-enduring trim, the guide for selecting the Cavitrol 4, the materials used for the main components, the actual results of application, and the future outlook are described. (Kako, I.)