| 摘要 |
PURPOSE:To prevent the generation of noise and suction of foreign material and correctly control the concentration of the constituents of the sucked gas by installing a cavitation preventing means into a communication pipe between the discharge pipe of a vacuum pump or a gas-liquid separating sound arresting means and the suction pipe of the vacuum pump or a communication pipe between the suction and discharge pipes of the vacuum pump and a vacuum tank equipped with a sand separator. CONSTITUTION:When the negative pressure side of a vacuum pump 1 becomes below a saturated vapor pressure, the signal of a detecting means is input into a cavitation preventing means 11, which is operated. Then, a suction pipe 4 communicates with a communication pipe 10, and the exhaust gas in a discharge pipe 6 is sucked into the suction pipe 4, and introduced to the negative pressure side of the vacuum pump 1, thus suppressing cavitation, and noise is prevented. Even if the installation place is in the bad environment where powder dusts float, attraction of foreign material is prevented, and a large difference in the concentration of constituents on the upstream and downstream sides from the connection part of the connecting pipe 10 is not generated, in the detection of concentration of the constituents of the sucked gas from a vacuum container 5 and the concentration control on the basis of the exhaust concentration, and correct control for concentration can be carried out.
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