Pump performance parameters such as flow Q head H-axis power N speed η efficiency between the existence of a certain relationship. The relationship between the magnitude of their changes is represented by a curve, which is called the performance curve of the pump. Pump performance parameters between the mutual changes and mutual constraints: first of all the top speed of the pump as a prerequisite. Pump performance curve has three main curves: flow - lift curve, flow - power curve, flow - efficiency curve. A, flow - lift characteristic curve It is the basic performance of the centrifugal pump curve. Than the speed of less than 80 centrifugal pump has the characteristics of rising and falling (both in the middle convex, both sides of the bend), said the hump performance curve. Centrifugal pumps with speeds greater than 80 to 150 have flat performance curves. Centrifugal pumps with specific rotations above 150 have sharp drop performance curves. In general, when the flow is small, the lift is high, and as the flow increases, the lift gradually decreases. B, flow - power curve Shaft power is increased with the flow, when the flow Q = 0, the corresponding shaft power is not equal to zero, but a certain value (about about 60% of normal operation). This power is mainly consumed by mechanical losses. At this time the pump is full of water, if the long run, will lead to continuous temperature rise in the pump, the pump housing, bearings will be heated, may cause severe thermal deformation of the pump body, we call "stuffy head" at this time The maximum lift, when the valve is gradually opened, the flow will gradually increase, the shaft power is also slowly increasing. C, flow - efficiency curve Its curve like the shape of the hill, when the flow is zero, the efficiency is also equal to zero, with the flow rate increases, the efficiency also gradually increased, but increased to a certain value after the efficiency of decline, the efficiency of a Highest value, near the highest efficiency point, the efficiency is relatively high, this area is called the high efficiency area.