Centrifugal pump impeller mainly has the following four forms, (a) closed; (b) front half open; (c) back half open; (d) Open
1 - impeller; 2 - rear cover plate; 3 - wheel hub; 4 - Front cover plate; 5 - impeller seal ring; 6 -- Reinforcing tendons
Closed impeller
It is composed of blades and front and rear cover plates. Closed impeller is more efficient and difficult to manufacture, so it is used most in centrifugal pumps. Suitable for conveying clean water, solution and other viscosity small particles do not contain clean liquid.
Semi-open impeller
Generally, there are two kinds of structures: one is the front semi-open type, which is composed of the rear cover plate and blade. The efficiency of the impeller of this structure is low, and the sealing ring with adjustable clearance is needed to improve the efficiency. The other is the back semi-open type, composed of the front cover plate and blade, because the same sealing ring can be applied with the closed impeller, the efficiency is basically the same with the closed impeller, and the blade in addition to conveying liquid, but also has the sealing effect (back blade or auxiliary impeller). Semi-open impeller is suitable for conveying liquid containing solid particles, fibers and other suspended solids. Semi-open impeller manufacturing difficulty is small, low cost, and strong adaptability, in oil refining and chemical industry centrifugal pump applications gradually increased, and used for conveying water and liquid similar to water.
Open impeller
Impeller with only blades and blade stiffeners, without front and rear cover plates (open impeller blade number is less 2-5 pieces). Impeller low efficiency, less application, mainly used for conveying high viscosity liquid, as well as slurry liquid.
The impeller blade of centrifugal pump is generally curved blade. The blade has two kinds of cylindrical shape and twisted shape, the application of twisted blade can reduce the load of the blade, and can improve the suction of the centrifugal pump, improve the anti-cavitation ability, but the manufacturing difficulty is larger, the cost is higher.
The impeller of centrifugal pump used in oil refining and chemical industry is required to be cast or whole welded impeller. The development of welding impeller, used for casting poor performance of metal materials (such as iron and its alloy) manufacturing of chemical special centrifugal pump. The geometric accuracy and surface finish of the welded impeller are better than that of the cast impeller, which is conducive to improving the efficiency of the centrifugal pump.