Calculation method for impeller cutting of multi-stage pumps
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One of the multi-stage pumps (3 stages) in our factory has an excessively high head, resulting in significant excess capacity in its performance. The pump manufacturer reduced the head by 50 meters (to 312 meters) by cutting the impeller diameter from 262/363/363 to 253/350/350; even after this modification, there was still a considerable amount of head left over. For another identical pump, the final impeller was simply removed; after the modification, the head increased to 218 meters. May I ask, how is the cutting of the impeller in a multi-stage pump or the removal of one of the impellers calculated? Are there any relevant standards?
Original parameters: flow rate of 520 m3/h, density of 606 kg/m3, inlet pressure of 0.15 MPa, outlet pressure of 2.3 MPa (this value does not correspond to the actual value), and head of 362 meters. Parameters of the first unit after modification: flow rate 520 m3/h, density 606 kg/m3, inlet pressure 0.15 MPa, head 312 meters. Parameters after modification for the second unit: flow rate of 520 m3/h, density of 606 kg/m3, inlet pressure of 0.15 MPa, outlet pressure of 1.45 MPa, and head of 218 meters.
Each pump manufacturer has its own set of performance curves, which serve as the theoretical basis for defining the specifications of their products. It shows the variations in flow rate, head, and power of the pump for different impeller diameters; furthermore, by applying the cutting law for impellers, the turning of the impeller diameter is carried out to meet the buyer’s process requirements. Moreover, the turning of the impeller in segmented multi-stage pumps requires careful attention, as it relates to the hydraulic losses caused by the gap between the impeller and the guide vane base circle, as well as the balance of axial forces. If necessary, please add me on WeChat for further communication.