PURPOSE:To sufficiently control the valve closing speed and to prevent water hammer phenomena in such a way that air cylinders and a hydraulic cylinder are provided as drives for an emergency shut off valve, and the hydraulic cylinder takes charge of the final phase of drive from nearly the end of opening or closing of the valve to the complete end. CONSTITUTION:Air cylinders 1, 2 and a hydraulic cylinder 15 are connected to a piston rod 3 which is connected to an emergency cutoff valve, the air cylinder 2 is connected to a throttle 13, the hydraulic cylinder 15 is connected to a throttle 16, the air cylinder 2 drives the valve at a high speed from the full open position to the position near to the full closed position, and the hydraulic cylinder 15 drives the valve at a slow speed from the position near to the full closed position to the full closed position. Thus, it becomes possible to close the valve always at a constant speed, and to reduce water hammer pressure produced in the pipe without influence of fluid pressure in the pipe.
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