The blades of centrifugal pump impeller are generally backward curved blades. There are two types of blades: cylindrical and twisted. The application of twisted blades can reduce the load of blades, improve the suction performance of centrifugal pumps and improve the cavitation resistance, but it is difficult to manufacture and the cost is high. The impeller of centrifugal pump for oil refining and chemical industry is required to be cast or welded as an integral pump impeller. The welded pump impeller is developed in recent years and is mainly used for special centrifugal pumps for chemical industry made of metal materials with poor casting performance, such as iron and its alloys. The geometric accuracy and surface finish of the welded pump impeller are better than that of the cast impeller, which is conducive to improving the efficiency of the centrifugal pump.

There are generally two types of semi-open impeller structures. One is the front semi-open impeller, which is composed of the rear cover plate and the blade. The impeller efficiency of this structure is low. To improve the efficiency, it is necessary to use the seal ring with adjustable clearance. The other is the rear semi-open impeller, which is composed of the front cover plate and the blade. Since the same seal ring as the closed pump impeller can be used? The efficiency is basically the same as that of the closed impeller. Besides conveying liquid, the blade also has the sealing function of back blade or auxiliary impeller. The semi-open impeller is suitable for conveying liquid containing suspended solids such as solid particles and fibers. The semi-open impeller has less difficulty in manufacturing, lower cost, and strong adaptability. In recent years, it has been increasingly used in centrifugal pumps for oil refining and chemical industry, and is used to transport clean water and liquid similar to clean water.