| 摘要 |
PROBLEM TO BE SOLVED: To provide a vertical shaft pump capable of increasing a limit value of flow rate in a closed section water channel, miniaturizing a closed type water tank and a semiclosed type water tank markedly, and reducing construction cost accompanying the miniaturization. SOLUTION: A vertical shaft pump P is installed in a closed type water tank 4 which is provided with a closed section water channel 3 with which a lower end opening part 2A of a pump installation hole 2 in the vertical direction is communicated and in which a level of a ceiling 3B of the closed section water channel 3 is set below a pump operation minimum water level LWL, and a lower end part of a suction bellmouth 6 faces and protrudes into the closed section water channel 3 from the pump installation hole 2. The water flowing in the closed section water channel 3 collides against a face directed on the upstream side of the closed section water channel 3 in a lower end part of the suction bellmouth 6 to reduce a flow rate V at just upstream position of the vertical shaft pump P in the closed section water channel 3.
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