To prevent it from erroneously detecting that a water level lowers when a float lowers by a stay of bubbles by constituting so that a pump pumping-up liquid containing bubbles is discharged by introducing it to upper connecting piping from lower connecting piping of a detector by differential pressure in a connecting position of the detector.
When a horizontal shaft pump 1 is operated, a pumping liquid is sucked in the pump 1 from suction piping 8, and is discharged from delivery piping 9 by increasing pressure by rotation of an impeller. In this case, when connecting a float type liquid level detector 2 attached to the horizontal shaft pump 1, it is connected by upper and lower connecting piping 4 and 5 communicated with an intake port 6 higher than a height of an underwater bearing and an intake port 7 lower than a height of the underwater bearing so that a pumping liquid of the horizontal shaft pump 1 is introduced upward from below the liquid level detector 2. In this case, the upper connecting piping 4 is set as an upward gradient from the liquid level detector 2 to the intake port 6, and the lower connecting piping 5 is set as an upward gradient from the intake port 7 to the liquid level detector 2, and a stay of bubbles in the liquid level detector 2 is prevented.
TSUNEMITSU AKIRA
MATSUI SHIRO
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