Vertical multistage centrifugal pumps are the most commonly used in the field of water treatment, because of their characteristics, wide application coverage, small size, simple structure, very easy actual operation, uniform total flow, long service life, purchase cost and actual operation cost Both are less prominent. The basic components of the pump are a high-speed running impeller and a snail-shaped pump casing. The impeller with a plurality of backward curved blades is screwed on the pump shaft, and is driven by the motor to run at high speed along with the pump shaft. The impeller is a component that performs work on the liquid in the pump at the same time, and is the phosphate generator of the pump. The suction port in the middle of the pump casing is connected with the suction pipeline, and the bottom end of the suction pipeline is equipped with a unilateral pump bottom valve. The discharge inlet on the side of the pump casing is connected to the discharge line equipped with a regulating valve.
When the vertical multi-stage centrifugal pump is running, the pump shaft pushes the impeller together to make a high-speed running fitness movement, which drives the liquid filled between the blade surfaces to rotate. Under the effect of inertial centrifugal force, the liquid makes a tangential fitness movement from the center of the impeller to the periphery . The liquid gets kinetic energy in the whole process of flowing through the impeller, the negative pressure energy is increased, and the flow speed is expanded. When the liquid leaves the impeller and enters the pump casing, the speed is reduced due to the slow expansion of the gate in the casing, and part of the mechanical energy is converted into pressure energy, which is finally injected into the discharge pipeline along the normal direction. Therefore, the volute pump casing not only collects the components that discharge the liquid from the impeller, but also is an energy conversion device. When the liquid is thrown from the center of the impeller to the periphery, a low pressure area is generated in the center of the impeller. Under the effect of the total potential difference between the liquid level in the storage tank and the center of the impeller, the liquid is sucked into the center of the impeller.
It must be emphasized that if the pump casing is not filled with the liquid to be transported before the operation of the vertical multistage centrifugal pump, because the density of the air is low, the centripetal force formed after the impeller rotates is small, and the central area of the impeller cannot generate a suction storage tank. The low voltage of the liquid inside, so even if the centrifugal pump is running, the liquid cannot be transported. This means that the centrifugal pump has no self-priming ability, which is called air binding. The unilateral pump bottom valve is assembled in the suction line to prevent the liquid poured into the pump casing from being discharged from the casing before operation.
