| 摘要 |
PROBLEM TO BE SOLVED: To provide a vertical shaft pump for performing precedence standby operation without hunting operation and severe air-water mixture drainage operation in which the mixture contains large quantity of air. SOLUTION: The vertical shaft pump 11 comprises: a first pipe 21 whose one end communicates to the inside of a casing 12 below an impeller 14, and other end communicates to the inside of the casing 12 above at least a highest high-water level in a suction tank 10; a second pipe 22 whose one end is connected to the first pipe 21, and other end is opened to the atmosphere. Until the water level lowers from a drainage water level WL4 to a drainage stop water level WL2, water flows out of the other end of the first pipe 21 to one end of the first pipe 21 and the other end of the second pipe 22. When the water level is lowered to the drainage stop water level WL2, air around water surface is sucked from a lower end opening 12e of the casing 12 into an area below the impeller 14 in the casing 12 to form an air reservoir 25. COPYRIGHT: (C)2004,JPO
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