PURPOSE: To make the drainage starting position and the drainage stop position different easily for each pump, maintaining interchangeability by installing weirs having different height for the respective sub water suction tanks at the inlet parts of a plurality of sub water suction tanks.
CONSTITUTION: When the inflow of water from a raceway 2 increases, and the water level of a water suction tank 1 gradually rises, water flows into sub-water suction tanks 13-15, getting over weirs 10-12 in the order from the lower weir 10 to the higher weir 12, and water reaches each drainage starting water level of pumps 7-9 in the order of the lower weir 10 to the higher weir 12, and drainage is started in succession. When the inflow from the raceway 2 reduces and the water level lowers gradually, water can not get over the weirs 10-12 in the order of the higher weir 10 to the lower weir 12, and the supply of water into the sub-water suction tanks 13-15 is cut off, and the water in the sub-water suction tanks 13-15 is drained in succession, and drainage is suspended in succession at each drainage stop position. Accordingly, the drainage starting position and the drainage stop position can be easily made different for each pump 7-9, maintaining interchangeability.
TAKADA KUNIO
TANAKA TEIJI
