General procedure for pump selection

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1. Based on various factors such as the layout of the device, terrain conditions, water level conditions, operating conditions, economic plan comparison, etc. 2. Consider choosing horizontal, vertical and other types (pipe type, right-angle type, variable angle type, corner type, parallel type, vertical type, vertical type, submersible type, removable type, submerged type, non-clogging type, self-priming type, gear type, oil-filled type, water-filled warm type). The horizontal pump is easy to disassemble and assemble. 3. It is easy to manage, but it is large in size. 4. It is more expensive. 5. It requires a large floor area. ； Vertical pump, 6. In many cases, the impeller is submerged in water, 7. It can be started at any time, 8. It is convenient for automatic or remote control, 9. It is compact, 10. The installation area is small, 11. The price is cheaper. 3. According to the nature of the liquid medium, determine the clean water pump, hot water pump, oil pump, chemical pump, corrosion-resistant pump or impurity pump, or use a non-clogging pump. Pumps installed in explosion areas should use explosion-proof motors according to the level of the explosion area. 4. The amount of vibration is divided into: Pneumatic, electric (electric is divided into 220v voltage and 380v voltage). 5. Depending on the flow rate, choose a single suction pump or a double suction pump.: Depending on the lift, you should choose a single-suction pump or a multi-suction pump, a high-speed pump or a low-speed pump (air conditioning pump). The efficiency of a multi-stage pump is lower than that of a single-stage pump. If both a single-stage pump and a multi-stage pump can be used, a single-stage pump should be selected. 6. Determine the specific model of the pump and what series of pumps to use. After selecting the pump, you can determine the specific model on the type spectrum or series of characteristic curves according to the two main performance parameters of the maximum flow rate and the head after enlarging the margin by 5% to 10%. Use the pump characteristic curve to find the required flow value on the abscissa and the required lift value on the ordinate. Draw a vertical or horizontal line upward and rightward from the two values ​​respectively. If the intersection of the two lines falls exactly on the characteristic curve, then the pump is the one to be selected. However, this ideal situation is generally not rare, and the following situations are usually encountered.: A. The first type: The intersection point is above the characteristic curve, which means that the flow rate meets the requirements, but the head is not enough. At this time, if the head is about the same, or differs by about 5%, it can still be used. If the head differs a lot, choose a pump with a larger head. Or try to reduce pipeline resistance loss. B. The second kind: If the intersection point is below the characteristic curve and within the fan-shaped trapezoidal range of the pump characteristic curve, the model is initially determined, and then the impeller diameter is decided based on the difference in lift. If the lift difference is very small, it will not be cut. If the lift difference is large, cut the impeller diameter according to the required Q, H, and according to its ns and cutting formula. If the intersection point does not fall within the fan-shaped trapezoidal range, a pump with a smaller lift should be selected. When selecting a pump, it is sometimes necessary to consider the production process requirements and select different shapes of QH characteristic curves. A. If: To transport the liquid level to a container that must maintain a certain liquid level, B. At this time, it is expected that C. the expected volume will change greatly, and D. the head will change very little, E. a pump with a flat HO curve should be selected. F. Like: Send the oil to the tube heating furnace. G. If the flow rate changes little during operation, H. Coking will easily occur in the furnace tube. To avoid this situation, I. It is hoped that when the flow rate decreases slightly, J. the pressure of the oil in the pipe will increase greatly, K. so that the scorch scar that has just been formed will be washed away by the higher liquid flow pressure. L. At this time, M. it is advisable to choose an oil pump with a relatively steep QH curve. 7. After the pump model is determined, for water pumps or pumps whose transport medium has a physical and chemical medium similar to water, it is necessary to go to the relevant product catalog or sample and make corrections based on the performance table or performance curve of the model to see if the normal operating point falls in the priority working area of ​​the pump? Whether the effective NPSH is greater than (NPSH). Can you also use NPSH to correct the geometric installation height? 8. For liquid pumps with a viscosity greater than 20 mm2/s, the experimental pump characteristic curve based on water must be converted into a performance curve of that viscosity. In particular, the suction performance must be carefully calculated or compared. 9. Determine the number of pumps and backup rate: For normal operation of the pump, generally only one is used, because one large pump is equivalent to two small pumps working in parallel (meaning the lift and flow rate are the same), and the efficiency of the large pump is higher than that of the small pump. Therefore, from the perspective of energy saving, it is better to choose one large pump instead of two small pumps. However, in the following situations, two pumps can be considered to work in parallel.: The flow rate is very large, and a pump cannot achieve this flow rate. For large pumps that require a 50% backup rate, two smaller pumps can be used to work, and two backup pumps (three lifts in total). For some large pumps, pumps with 70% flow requirements can be used in parallel operation without a backup pump. When one pump is inspected, the other pump can still bear 70% of the production transportation. For pumps that need to operate continuously for 24 hours, three pumps should be kept in standby, one for operation, one for backup, and one for maintenance. 10. If you need to know in detail the working principles, main performance, characteristics of various pumps and choose a good pump that is economical, novel, efficient and energy-saving, please refer to the detailed introduction of various pumps below to facilitate your purchase.