The screw pump is a positive displacement rotor pump, which sucks and discharges liquid by the displacement of several sealed cavities formed by the screw teeth in the pump and the pump sleeve. If there is no theoretical leakage channel between two adjacent sealed cavities in the screw pump, it is called a strictly sealed screw pump, otherwise, it is a non-strictly sealed screw pump.
According to the current practical application and related data, the screw pump has a wide range of applications. It is characterized by stable flow, small pressure pulsation, self-priming ability, low noise, high efficiency, long life, small size, reliable operation, and outstanding performance. The advantage is that no eddy current is formed when transporting the medium, and various media with a wide range of viscosity can be transported. It can transport lubricating or corrosive media of various viscosities, non-Newtonian liquids of various viscosities, and gas-liquid mixing It is widely used in industrial sectors such as offshore platform engineering, petrochemical industry, shipping, electric power, mechanical hydraulic system, food, paper-making, sugar refining, military industry and sewage treatment. According to the sales manager of Aerweiler company in Germany Said: “There is no medium in the world that cannot be transported by a screw pump.”
It is said that the screw pump can transport any medium. Of course, it does not mean that a certain type of screw pump can transport all media, but different types of screw pumps can be selected according to the characteristics of the medium and the number of performance parameters. Screw pumps are usually divided into single screw pumps, double screw pumps and triple screw pumps according to the number of screws. , Each has its own advantages, and there must be a choice when promoting the application of screw pumps. Only by making full use of their respective characteristics can better energy saving, material saving, benefits increase or meet certain special requirements.
The pump sleeve of the single-screw pump is made of non-metallic elastic material (usually rubber), and the inner hole is in the shape of a spiral groove. Several sealed cavities are formed between it and a helical metal screw. The sealing chamber is moved from the low-pressure area of the pump to the high-pressure area, and the whole process of suction, liquid discharge and pressure formation is completed. In addition to general media, single screw pumps can transport suspensions and special media containing metal particles and fibres. When dealing with sewage and mud, single screw pumps are commonly used, and the working pressure is usually not high.
The traditional twin-screw pump is a non-strictly sealed screw pump. The pump sleeve made of metal material has two intersecting cylindrical cavities and the two screws in the cavity mesh with each other. A number of sealed cavities are formed between them. When the screw rotates, the sealing cavity is displaced from the low-pressure area of the pump to the high-pressure area. There are single-ended screw pumps and double-ended screw pumps. For the lubricating medium, if the helix angle is large enough, the main screw can directly drive the auxiliary screw. If it is equipped with synchronous gear, there can be no contact between the two screws in theory. Although the traditional twin-screw pump is not strictly sealed and the working pressure is not high, it can transport various media with a very wide viscosity range, non-Newtonian liquids with various viscosities, and mixed gas-liquid and solid-liquid mixed transport. Therefore, various industries have placed great interest in it, especially the petroleum and chemical industries.
The three-screw pump is theoretically a strictly sealed screw pump. In textbooks, it is usually introduced as a typical screw pump. The three-screw pump is composed of a main screw in a metal pump casing driving two driven screws. Each screw has two helical lines, forming a number of sealed cavities between the pump sleeve and the screw. When the screw rotates, the sealed cavity is displaced from the low-pressure area of the pump to the high-pressure area. The maximum working pressure of the three-screw pump can reach 30Mpa, and the conveying medium is clean. Non-corrosive lubricating oil, with high viscosity, can be delivered on special occasions. Non-corrosive media (such as ink. Glue, etc.). Due to the structural size of the three screws at a ratio of 1:3:5 and other reasons, the viscosity range of the medium conveyed by the three-screw pump is limited, generally limited to lubricating medium.
