| 摘要 |
PROBLEM TO BE SOLVED: To provide an increased life for a diaphragm type vacuum pump without needing any troublesome work. SOLUTION: When exhaust of a pressure reduction distilling plant 12 is effected as a system to be exhausted, by exciting the solenoid part 18 of a three-port electromagnetic switching valve 16, an intake port 17a and a common port 17c are intercommunicated and drive is a vacuum pump 19 is started. This constitution cause exhaust of a pressure reducing distilling plant 12 to effect desired pressure reducing distilling operation. When a switch is turned OFF so that operation of the pressure reducing distilling plant 12 is stopped, the solenoid part 18 of the solenoid valve 16 is brought into a non-excited state, the intake port 17a and the common port 17c are disconnected. However, the common port 17c is communicated with an atmosphere introduction port 17c, and the atmosphere is sucked and is caused to pass through the internal part of the vacuum pump 19. In this case, an exhaust gas component adhered on a current gas contact surface is removed to the outside togetherwith the atmosphere to perform automatic cleaning. Since a cleaning time is set by a timer 20, cleaning is automatically stopped after a lapse of a given time. The internal part of the vacuum pump 19 is always cleaned. |
