Vertical centrifugal pump selection method：
The main control parameters for the selection of vertical centrifugal pumps are the flow rate Q, head H, efficiency η, power, speed n, working pressure, required cavitation margin (NPSH), etc. of the water vertical centrifugal pump.To select a vertical centrifugal pump reasonably, it is necessary to comprehensively consider the comprehensive technical and economic indicators such as the investment and operating costs of the vertical centrifugal pump unit and the vertical centrifugal pump station to make it conform to the principles of economy, safety and applicability. Specifically, it includes the following aspects:
1) You should choose a high-efficiency, low-noise, energy-saving water vertical centrifugal pump, and it is strictly forbidden to choose obsolete products.
2) The vertical centrifugal pump should be selected according to the design flow rate and required head. Considering the decrease in the output of the water vertical centrifugal pump due to wear and other reasons, the vertical centrifugal pump can be selected by multiplying the calculated head H by a coefficient of 1.05 to 1.10; the water vertical centrifugal pump with a characteristic curve that gradually decreases its head as the flow rate increases should be selected. Such a vertical centrifugal pump works stably and is reliable when working in parallel; and the operating point of the water vertical centrifugal pump should be maintained in the high-efficiency range, which is energy-saving and not easy to damage the parts.
3) When there is no adjustment facility in the water supply network, it is advisable to use a speed-controlled vertical centrifugal pump group or a rated speed vertical centrifugal pump group to operate the water supply. The water output of the vertical centrifugal pump group should not be less than the design flow of the community water supply, and should be checked according to the fire protection conditions.
4) When selecting vertical centrifugal pumps for water tanks and water towers, the number of vertical centrifugal pumps should be minimized, and one should be used and one should be reserved; when a single vertical centrifugal pump can meet the requirements, it is not advisable to use multiple units in parallel; if multiple units must be operated in parallel or large and small vertical centrifugal pumps are matched, the models and number should not be too many, and the models should generally not exceed two. The head range of the water vertical centrifugal pump should be similar; when operating in parallel, each vertical centrifugal pump should still operate within the high-efficiency zone.
5) The design water supply flow of the variable frequency speed regulating vertical centrifugal pump (group) should ensure that it meets the design flow per second requirements of the domestic water supply system. The power supply must be reliable (dual power supply or dual circuit power supply); the working point of the water vertical centrifugal pump should be selected in the high-efficiency working area of the water vertical centrifugal pump characteristic curve (Q-H curve), and must not be selected on the extension line of the Q-H curve. The unfavorable working point of the design should be at the right end point of the high-efficiency section of the water vertical centrifugal pump characteristic curve, that is, the point where the water discharge of the water vertical centrifugal pump and the head are low but can meet the requirements, that is, the intersection of the low point of the high-efficiency area of the water vertical centrifugal pump characteristic curve and the pipeline characteristic curve. The speed regulation working range of the water vertical centrifugal pump can be as far as possible within the high-efficiency section of the water vertical centrifugal pump; the speed regulation range should be set between 25% and 100% of the water supply of the water vertical centrifugal pump; the equipment should have an automatic water level control function.
6) The water vertical centrifugal pump unit of the domestic pressurized water supply system should be equipped with a spare vertical centrifugal pump. The water supply capacity of the spare vertical centrifugal pump should be greater than the water supply capacity of a running water vertical centrifugal pump. The water vertical centrifugal pump should be automatically switched and operated alternately.
7) The voltage of the motor equipped with the water vertical centrifugal pump should be the same, and the power supply system should be the same as the power supply system of the power grid.
Precautions for selecting vertical centrifugal pumps：
- Corrosion resistance: For a long time, corrosion has been one of the most troublesome hazards of chemical equipment. If you are not careful, it will damage the equipment at the least, and cause accidents or even cause accidents at the worst. According to relevant statistics, about 60% of the damage to chemical equipment is caused by corrosion. Therefore, when selecting chemical pumps, you must first pay attention to the scientific selection of materials. There is usually a misunderstanding that stainless steel is a “material”. It is very dangerous to use stainless steel regardless of the medium and environmental conditions.
- Meet the cleaning requirements of parts and components. Different parts have different cleaning degrees. For the surface of sprayed, plated, and bonded workpieces, the cleaning requirements are very high. When cleaning, different cleaning agents and cleaning methods must be adopted according to different requirements to ensure the required cleaning quality.
- To avoid corrosion of parts, the anti-rust ability of the cleaning liquid should be considered or other anti-rust measures should be considered. Take anti-rust measures for parts.
- Ensure safe operation to prevent fire or poisoning of the human body and pollution to the environment.