Mid-open pump is also called mid-open double suction pump. There is a gap at the edge of the inlet and the inner wall of the pump. The gap is high and low pressure area on both sides. The gap is relatively large. High-pressure water will leak into the low pressure area through this gap, which means the inlet position, so as to reduce the efficiency of mid-open pump.
In fact, from the point of view of reducing backflow and improving impeller condition, the smaller the leakage gap is, the better, but we need to pay attention to the gap is not too small, otherwise it will produce a lot of mechanical wear.
But if the gap between the middle and open pumps is relatively small, the impeller will friction with the pump when it rotates, causing a certain degree of wear and tear. Usually, leak detection is used, which requires professional inspection.
If the gap is large, the slight wear and tear will occur. Impeller faults may occur in the heavy pump, which will affect the efficiency of the pump. It is suggested that the gap should be within 5 mm.