First, the working principle of the centrifugal pump

　　The centrifugal pump works by using the centrifugal force of the impeller to rotate the water. Before the centrifugal pump starts, the pump casing and the suction pipe must be filled with water, and then the motor is started, so that the pump shaft drives the impeller and the water to perform high-speed rotary motion. Under the action of centrifugal force, it is smashed to the impeller for external assistance, and flows into the water pressure pipeline of the water pump through the flow path of the pump casing. At the center of the pump impeller, the water is formed by the centrifugal force, and the water in the suction pool is pressed into the pump casing under the action of atmospheric pressure. The impeller rotates continuously to make the water act in the impeller. Under continuous inflow and outflow, the purpose of conveying water is achieved.

Second, the main components of the centrifugal pump

1, centrifugal pump impeller

　　The impeller is the core component of the pump, which allows the water to acquire kinetic energy to create flow. The impeller oil blade, the cover plate and the hub are composed. When selecting the impeller material, in addition to considering the mechanical strength under the centrifugal force, the wear resistance and corrosion resistance of the material should also be considered. The function of the centrifugal pump impeller is to directly transfer the mechanical energy of the prime mover to the liquid to increase the static pressure and kinetic energy of the liquid, and mainly increase the static pressure energy.

　　The impeller generally has 6 to 12 back curved blades.

　　The impeller has three types: open type, semi-closed type and closed type.

　　The open impeller has no cover on both sides of the blade, which is simple to manufacture and convenient to clean. It is suitable for conveying materials containing a large amount of suspended solids. The efficiency is low and the liquid pressure is not high. The semi-closed impeller has no cover on the suction side. The plate has a cover plate on the other side, which is suitable for conveying materials that are easy to precipitate or contain particles, and the efficiency is also low; the closed impeller has a front and rear cover plate on both sides of the blade, and the efficiency is high, and is suitable for conveying impurities. Cleaning liquid. The general centrifugal pump impeller is mostly of this type.

　　The impeller has two suction and double suction modes. Generally, large-flow centrifugal pumps mostly use double-suction impellers.

2, the centrifugal pump casing

　　The function is to close the impeller in a certain space so that the liquid can be sucked in and out by the action of the impeller. The pump casing is often made into a volute shape, so it is also called a volute. As the flow path is gradually enlarged, the high-speed liquid drawn from the periphery of the impeller gradually reduces the flow rate, so that part of the kinetic energy is effectively converted into static pressure energy. The pump casing not only collects the liquid that is pumped out by the impeller, but is also an energy conversion device.

　　The water passing portion requires good hydraulic conditions. Pump and pump station design When calculating the impeller operation, the flow rate is gradually increased along the divergent section of the volute. Therefore, the material selection of the pump casing, in addition to considering the corrosion and wear of the medium to the overcurrent portion, should also provide the casing with sufficient mechanical strength as a pressure vessel.

3, centrifugal pump shaft sealing device

　　The function is to prevent the liquid in the pump casing from leaking out along the shaft or the outside air leaking into the pump casing.

　　The shaft sealing device commonly used in centrifugal pumps has two kinds of packing seals and mechanical seals.

　　The filler is generally impregnated with oil or graphite coated asbestos rope. The mechanical seal mainly relies on the opposite movement between the moving ring mounted on the shaft and the stationary ring fixed on the pump casing to achieve the purpose of sealing.