| 摘要 |
PROBLEM TO BE SOLVED: To prevent occurrence of cavitation irrespective of a variation of sealed water temperature in a decompression device employing a water-sealing type vacuum pump, and to prevent a leak valve from being opened uselessly and improve an operation efficiency of the vacuum pump, in a case that there is no possibility of occurrence of cavitation.SOLUTION: This invention comprises: a water-sealing type vacuum pump for sucking gas in a segment 2 to be decompressed and discharging the sucked gas outside; a sealed water temperature sensor 20 for detecting a temperature of sealed water in this water-sealing type vacuum pump 8; a leak valve 19 capable of flowing in ambient air into a discharging passage 5 from the segment to be decompressed to the water-sealing type vacuum pump 8; and a pressure sensor 21 for detecting a pressure in the discharging passage 5. A controller adjusts a degree of opening of the leak valve 19 in such a way that the detected pressure of the pressure sensor 21 may become a higher pressure than a saturation vapor pressure at the detected temperature by the sealed water temperature sensor 20 by a set pressure. |
