| 摘要 |
PROBLEM TO BE SOLVED: To provide a preceding standby operation pump by which a pumping operation can be securely shut off on an occasion when shut-off of pumping is wanted, and occurrence of whirlpools and vibration can be suppressed. SOLUTION: In this pump, a first air-intake 21b, a second air-intake 22b, and steam-mixing and pumping shut-off air pipes 21, 22 provided. Under conditions that fed-water level WL is not higher than the lowest water-level LWL, the first air-intake 21b serves to decrease a displacement by pumping up water, while introducing air into a casing 3 below an impeller 11. By the second air-intake 22b, when the fed-water level WL has reached a pumping shut-off level SWL lower than the lowest water-level LWL, air is introduced into the casing 3 lower than the impeller 11 to shut off the pumping. By the air-pipes 21, 22, the two kinds of air intakes 21b, 22b are allowed to communicate with the inside of a casing 3. The position of the opening 26 in the casing 3 for the pumping shut-off air pipe 22 is set upper than the opening 25 in the casing 3 for the air pipe 21 for the steam mixing so that efficiency of air-introduction (intake) in the casing 3 at the pumping shut-off time is improved. COPYRIGHT: (C)2010,JPO&INPIT
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