| 摘要 |
<p>PURPOSE: To obtain a gas suction system reduced in required power by connecting a plurality of tanks and a plurality of compressors stepwise different in pressure range by changeover valves and raising the pressures in the tanks stepwise by the compressors after injecting gas into the tanks. CONSTITUTION: (n) Tanks T and (m) suction compressors C different in pressure range stepwise are connected by (n×m) changeover valves V and (n) stop valves SV attached to the gas introducing pipes of the tanks T. At first, all of the stop valves SV are opened while all of the changeover values V are closed and, when the tanks T1-T3 are filled with gas, the inner pressures of the tanks T become P4. Next, all of the stop valves SV are closed and only the valve V13 is opened to allow the compressor C3 to communicate with the tank T1 to reduce the pressure P4 in the tank T1 to pressure P3. The same operation is successively performed to achieve pressure P1 highest in vacuum degree and, thereafter, the tank T1 is again filled with the gas to be brought to the initial state. By dividing a pressure range over a plurality of stages, a necessary vacuum degree is obtained in low cost.</p> |
