PURPOSE: To prevent the divergence of the self-excited vibration of fluid and to stably operate a separation barrel at a revolving speed above the primary critical speed by freely rotatably hanging the barrel by a drive shaft like a pendulum and providing plural axial baffle plates on the inner face of the barrel.

CONSTITUTION: The inside of a cylindrical casing 20 is vertically divided by a partition plate 21 into an upper chamber 22 and a lower separation chamber 23, and a cylindrical separation barrel 24 is set in the separation chamber 23. Plural axial baffle plates 27 are equidistantly arranged in the barrel 24 in the circumferential direction, the lower end plate 26 at the lower end of the barrel 24 is connected to a drive shaft 30 through a rib 28, and the shaft 30 is borne by the upper and lower bearings 35 and 36. In this case, a bearing housing 37 contg. the upper bearing 35 is freely vibrationally supported like a pendulum around the center O of the bearing, and a bearing housing 38 contg. the lower bearing 36 is supported through plural buffer mechanisms 41 in which a coil spring 39 and an oil damper 40 are provided in parallel.