To surely open and close a relief valve for discharging a gas-enriched liquid separated from a liquid into a gas separating chamber.

In the relief valve 38, when the gas-enriched liquid is accumulated at the upper part of a cyclone 32, a pressure in a pressure chamber 114 is reduced by bubbles, and a valve element 100 is slid in the Xb direction by the spring force of a coiled spring 102. When the valve element 100 is returned to a valve opening position, a cylindrical valve part 1001 extends through an inflow port 110 and an outflow port 120, and the groove 100d of the valve element 100 is communicated with the inflow port 110 and the outflow port 120 while facing each other. The gas-enriched liquid accumulated at the inflow port 110 is pushed up by a hydraulic pressure from the cyclone 32, and discharged from the groove 100d of the valve element 100 to the gas separating chamber 60 through the outflow port 120, a bypass passage 122, a through hole 61, and a pipe member 62.

COPYRIGHT: (C)2007,JPO&INPIT