Cavitation is not allowed during centrifugal pump operation, so NPSHa-NPSHr> S must be guaranteed. When NPSHa can not meet this requirement, the purchaser (user) may be advised to try to increase the NPSHa value by reducing the installation height of the pump (increasing the suction level or reducing the installation position of the pump), if necessary, The ways to reduce the NPSHr value (for example, the overcurrent components are made of cavitation-resistant materials such as cemented carbide, phosphor bronze, 18-8, Cr-Ni steel, etc.) are shown in the table below. Method Advantages Disadvantages Remarks Buyer adopted Method 1, reduce the installation of the pump height (to enhance the position of the suction surface or reduce the installation of the pump), if necessary, the use of Inverted way to choose a higher efficiency, easy maintenance of the pump to increase the installation cost of the best secondary method, it is recommended to use 2 , Reduce the resistance of the suction pipe, such as increasing the pipe diameter, reduce the pipeline attachment, the end of the valve, elbow, gate valve, etc. can improve the suction conditions, saving energy consumption increase investment costs (referring to diameter amplification) - 3, Taiwan booster pump can reduce the price of the main pump to improve the efficiency of the main pump to increase the amount of equipment and piping maintenance - 4, lower pumping liquid temperature to reduce the gasification pressure can be used more efficient and easy maintenance Need to increase the cooling system - 5, to avoid the use of throttle in the inlet pipe to avoid the loss of local resistance - - 6, in the same circumstances under the flow, lift, with a double suction pump, the NPSHr value is small - - sometimes also consider the seller to take Method 1, to improve the surface finish of the runner, sanding and cleaning the runner simple processing costs are often used to increase 2, increase the diameter of the impeller inlet to reduce the import flow rate increases the possibility of simple reflux is not conducive to stable operation Rarely used 3, to reduce the pump speed is simple and easy Flow of the same head, low-speed pump high cost, low efficiency generally less used 4, the pump inlet induction pump easy to increase the maximum working range has been narrowed often used 5, the adjustable vane pump flow pump, axial flow pump can be used to adjust the blade installation angle method - often 6, the flow of parts using cavitation-resistant materials such as cemented carbide, phosphor bronze, 18-8, Cr -Ni steel pumps and other structures, performance curves are unchanged Material costs less used less