Currently, there are many types of self-priming centrifugal pump products, and the quality varies. The selection of self-priming centrifugal pumps is based on the design flow, required head, and pipeline diameter. As the name suggests, a self-priming centrifugal pump is a self-priming pump product based on the centrifugal principle.
The impellers of self-priming centrifugal pumps are divided into closed impellers and open impellers. The closed impeller can only transport liquids similar to clean water without particulate impurities, and has high-head models for users to choose from. The characteristic of the open impeller self-priming centrifugal pump is that it can not only transport clean water but also liquids containing solid particles and impurities. However, the head range is lower than that of the closed impeller self-priming centrifugal pump.
The selection method should be adapted to local conditions to select a self-priming pump. The working process of the gas-liquid mixing self-priming pump is that due to the special structure of the self-priming pump body, after the water pump stops, there is a certain amount of water in the pump body. After the pump is started again, due to the rotation of the impeller, the air and water in the suction pipeline are fully mixed and discharged to the gas-water separation chamber. The gas in the upper part of the gas-water separation chamber escapes, and the water in the lower part returns to the impeller and re-mixes with the remaining air in the suction pipeline until all the gas in the pump and the suction pipe is discharged, completing self-priming and pumping water normally. The water ring wheel self-priming pump combines the water ring wheel and the water pump impeller in a shell, and uses the water ring wheel to discharge the gas to achieve the self-priming function.
It is necessary to select a water pump appropriately beyond the standard. After confirming the type of water pump, its economic performance should be considered, and special attention should be paid to the head and flow of the water pump and the selection of its supporting power. It must be noted that the head (total head) indicated on the water pump label is different from the water discharge head (actual head) during use. This is because there will be a certain resistance loss when the water flows through the water pipe and the pipeline. Therefore, the actual head is generally 10%-20% lower than the total head, and the water output is also reduced accordingly.
Therefore, in actual use, it can only be calculated according to 80%-90% of the head and flow indicated on the label. The selection of the supporting power of the water pump can be selected according to the power indicated on the label. In order to make the water pump start quickly and use it safely, the power of the power machine is also slightly greater than the power required by the water pump, generally about 10% higher. If there is already power, when choosing a water pump, you can choose a matching water pump according to the power of the power machine. Strict procedures must be followed when purchasing a water pump. When selecting a water pump, it must also be inspected. Only when the three certificates are complete can you avoid purchasing obsolete products and inferior products.
When there is no adjustment facility in the water supply network, it is advisable to use a speed-controlled pump group or a rated speed pump group to operate the water supply. The water output of the pump group should not be less than the design flow rate of the community water supply, and should be checked according to the fire protection conditions. When selecting the lifting pumps for water tanks and water towers, the number of pumps should be minimized as much as possible, and one pump should be used and one pump should be used as a backup; when a single pump can meet the requirements, it is not advisable to use multiple pumps in parallel; if multiple pumps must be operated in parallel or large and small pumps are matched, the models and numbers should not be too many, and the models should generally not exceed two. The head range of the self-priming centrifugal pump should be similar; when running in parallel, each pump should still operate within the effective area.
The design water supply flow rate of the variable frequency speed regulating pump (group) should ensure that it meets the design second flow rate 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 self-priming centrifugal pump should be selected in the effective working area of the self-priming centrifugal pump characteristic curve (Q-H curve), and should 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 effective section of the self-priming centrifugal pump characteristic curve, that is, the self-priming centrifugal pump has a large water output.
The point where the head is low but can meet the requirements is the intersection of the low point of the effective area of the characteristic curve of the self-priming centrifugal pump and the pipeline characteristic curve. The speed regulation working range of the self-priming centrifugal pump can be as far as possible within the effective section of the self-priming centrifugal pump; the speed regulation range should be set between 25% and 100% of the water supply of the self-priming centrifugal pump; the equipment should have an automatic water level control function. The self-priming centrifugal pump unit of the domestic pressurized water supply system should be equipped with a standby pump. The water supply capacity of the standby pump should be greater than the water supply capacity of any running self-priming centrifugal pump. The self-priming centrifugal pump should be automatically switched and run alternately. The voltage of the motor equipped with the self-priming centrifugal pump should be the same, and the power supply system should be the same as the power supply system of the national power grid.
