| 摘要 |
PROBLEM TO BE SOLVED: To smoothly control a flow rate, and to fully utilize the capabilities of a valve. SOLUTION: Two large and small control valves 4 are connected in parallel with piping so that the flow rate of fluid flowing through the piping can be controlled. When the flow rate of the fluid is small, a large control valve 4a is fully closed, and the opening degree of a small control valve 4b is changed between a fully closed state and a fully opened state so that the flow rate can be controlled, and when the flow exceeds the control range of the small control valve 4b, the opening degree of the large control valve 4a is changed between the fully closed state and the fully opened state so that the flow rata can be controlled. At the time of changing the opening degree of the large control valve 4a from the fully closed state to the slightly opened state, the opening degree of the large control valve 4a is changed from the fully opened state to the fully closed state, and at the time of changing the opening degree of the large control valve 4a from the slightly opened state to the fully closed state, the opening degree of the small control valve 4b is changed from the fully closed state to the fully opened state, and at the time of changing the opening degree of the small control valve 4b from the fully closed state to the fully opened state or from the fully opened state to the fully closed state in a state that the opening degree of the large control valve 4a is set so as to be a required opening degree between the fully closed state and the fully opened state, the large control valve 4a is slightly closed or slightly opened from the required opening degree so that the change of the flow rate of the small control valve 4b can be offset.
|
