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在华北低洼易涝易早地区以排为主、排灌结合的排灌站中,大多数采用低扬程卧式轴流(或卧式混流泵)及滑环式电动机。对于叶轮高于进水池水位的抽水装置,为了减少水头损失,一般都不安装底阀,出水管路较短,出口安装拍门,起动前用液环式真空泵抽真空充水。由于停机时拍门与门座的撞击,拍门止水橡皮易受到损坏或变形,以致封闭不严,故抽真空时需要有出水池(或压力水箱)有水淹没拍门,起到水封作用,才能达到抽真空充水和起动机组的要求。而以往有些安装卧式轴流泵以排为主的排灌两用站,在设计时忽略了这个问题,设计的出水池(或压力水箱)与泄水渠底部高程相同(没有陡坎)。这种形式的出水建筑物,在排涝
In northern China, low-lying flood-prone areas are dominated by drainage basins, most of which use low-lift horizontal axial flow (or horizontal mixed flow pumps) and slip ring motors. For the pumping device with the impeller higher than the inlet water level, in order to reduce the head loss, the bottom valve is not usually installed. The outlet pipeline is short and the exit is equipped with a flapper. Before starting, vacuum suction is carried out using a liquid ring vacuum pump. Due to the impact of shutting the door and the door when shutting down, the rubber sealing flap rubber is vulnerable to damage or deformation, resulting in closed laxity, so the need to have a vacuum tank (or pressure tank) flooded beat the door, play a water seal Role, in order to achieve vacuum pumping and starting unit requirements. In the past, some horizontal-axis axial-flow pumps had been installed as drainage-based dual-purpose stations. This problem was neglected in the design. The designed outflow tank (or pressure tank) had the same elevation (no scarp) as the bottom of the drainage channel. This form of effluent building, drainage