PURPOSE: To pump up lubricant liquid from the lower part having almost the limit of the suction capability of a pump by branching lubricant liquid supplying piping from suction piping at its vertical part located immediately before a suction opening or a suction causing and by connecting the lubricant liquid supplying piping to a lubricant liquid supplying source.
CONSTITUTION: Upwardly and vertically expanded reverse U-shaped suction piping 4 is connected to a suction casing 3 at its upper part for a uniaxial screw pump 1 driven by means of a motor 2. A suction liquid level L immersing the suction opening 5 of the suction piping 4 is located lower than the height of the upper surface of the suction casing 3, i.e., a pump suction opening. Discharge piping 6 is connected to the discharge side of the uniaxial screw pump 1. In starting, a flow rate adjusting valve 12 is opened to actuate a lubricant liquid supplying pump, supplying lubricant liquid to the suction piping 4. The lubricant liquid is supplied as long as handling liquid sucked from the suction opening 5 has reached the suction casing 3. Thus starting is assured even if the pump suction opening is higher than the suction liquid level L.
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