| 摘要 |
PROBLEM TO BE SOLVED: To provide a drainage pump device that can improve pump efficiency and drainage efficiency even under a high flow rate by evening and smoothing a flow about a pump and thus reducing a loss of head resulting from generation and accumulation of vortexes and reducing air entrainment as well. SOLUTION: The drainage pump device inserts the drainage pump 2 in an open water tank 1 opening upward so that a pump shaft 3 is perpendicular to a water flow direction. An outer circumferential region of a suction bell mouth 7, a pump casing 6 and a lifting pipe part 8 all situated in the open water tank 1 is enclosed with a cylindrical cover 11 with a water contact surface 12 shaped smoothly along an axis of the pump shaft 3. A lower end portion 11A of the cover 11 is bent round into the cover, and a free end opening thereof is connected to a tip opening of the suction bell mouth 7.
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