| 摘要 |
PURPOSE:To secure the reliability of the flow rate control for a long period of time, by exercising a stepped control over the flow rate of a separate cascade by means of an ON/OFF valve. CONSTITUTION:For a separate cascade which has no trouble even with the + or -5% fluctuation of the rated flow rate, the ratio of the flow rate that can be supplied to flow rate throtting mechanisms 2-5 like orifices, etc. is set at 80, 20, 10 and 5% of the rated flow rate. Thus various different flow rates can be obtained from the combinations of the above-mentioned flow rate ratios. In other words, the flow rate ratio is set with every 5% and at maximum 115% at the level near the rated flow rate. Thus the following advantages are obtained by controlling the flow rate by opening and closing the ON/OFF valves 6-9. First, the solenoid valves are available to the ON/OFF valves to increase the reliability, and an electrical function suffices. Second, the accuracy is improved for the flow rate, and at the same time the control is facilitated for the flow rate in spite of a stepped control. Third, the maximum flow rate that gives no trouble to the main body of a gas separating cascade can be selected by means of a fail-open valve even if all valves have troubles. |
