1. The vertical distance from the liquid level to the center of the centrifugal pump inlet flange refers to the energy difference between the inlet and outlet of the liquid pump per unit mass. Specific example: If it is a normal clean water pump, the lift of the pump is 50 meters. In fact, the value of 50 meters minus the loss along the path and the local loss of the pipeline line is the distance between the pump suction liquid level and the lift height.
2. Line pipe losses include loss along the path and local losses in the pipeline. The loss along the path is related to the material of the pipe, the diameter of the pipe, the flow rate and viscosity of the conveying medium; the local loss mainly refers to the loss caused by the reducer, the elbow, and various valves. The algorithm for the two losses can refer to the related fluid mechanics. books. In the actual calculation, the local loss is relatively small and can be estimated directly. The general description of the heads in the general centrifugal pump catalogue is based on the average estimate of each manufacturer. The actual application is combined with different occasions for actual field scientific analysis. I will not give an example here.
3. For general centrifugal pumps, the head will decrease as the pump flow increases. This is the characteristics of the pump itself. For piping systems, the greater the flow delivered, the higher the required head. There is a balance between the pump's own characteristics and the piping characteristics (professional point is that the intersection of the pump's characteristic curve and the pipeline characteristic curve) is the operating point of the pump. When selecting the type, the required head is calculated according to the flow rate of the pipeline, and the appropriate pump type is selected according to the medium condition, flow rate, and lift, as well as the shaft seal, material and supporting motor of the pump.
