Bailey Japan Co., Ltd.

Nippon Gear Co., Ltd.

Takeshi Saito

Yutaka Utsumi

Toshio Endo

Takeshi Suguro

A high differential pressure control valve having a plurality of stages of high resistance ports forming a high resistance passage and one or more low resistance ports forming a low resistance passage in a cage. The number of stages of low resistance ports is smaller than that of the high resistance ports so that a fluid at the side of an inlet passage is introduced into the high resistance passage under a low open degree range and into both the low resistance passage and the high resistance passage under a medium and a high open degree ranges.

High differential pressure control valve

An electric actuator for a control valve for fluids utilizes an induction motor to control the degree of opening of the valve and is provided with a control system which determines the deviation of the actual opening degree from the demand opening degree, generates a valve opening or closing speed command in accordance with the opening deviation, determines the deviation of the actual opening or closing speed from the command speed, generates a torque command in accordance with the speed deviation, and computes by means of the vector computing method the primary current to be supplied to the induction motor to enable the induction motor to output the required torque. When the valve is in the fully closed position, the control system stops the supply current to the induction motor and activates a braking device which locks the motor shaft to prevent reverse rotation of the motor shaft due to load reaction. The actuator has a means for re-starting the induction motor to optimize the thrust load should any change occur in the level of thrust acting on the valve rod. The actuator is furthermore provided with a means for diagnosing whether any abnormal performance is due to wear and/or deterioration of the induction motor, of the torque transmitting system or of the valve body.

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Mishima, Japan

Takeshi Saito