The centrifugal pump impeller mainly has the following 4 types, (a) closed type; (b) front semi-open type; (c) rear semi-open type; (d) open type
1—impeller; 2—rear cover; 3—wheel hub; 4—front cover; 5—impeller sealing ring; 6—reinforcing rib
Closed impeller
It is composed of blades and front and rear cover plates. Closed impellers are highly efficient and difficult to manufacture, and are the most widely used in centrifugal pumps. It is suitable for conveying clean water, solution and other clean liquids with low viscosity without particles.
Semi-open impeller
Generally, there are two structures: one is the front half-open type, which is composed of the rear cover and the blades. This structure has low impeller efficiency and needs to be equipped with an adjustable gap seal ring to improve efficiency; the other is the rear half-open type, It is composed of a front cover and blades. Since the same sealing ring as the closed impeller can be applied, the efficiency is basically the same as that of the closed impeller. In addition to transporting liquid, the blade also has a sealing effect (back blade or auxiliary impeller). The semi-open impeller is suitable for conveying liquids containing suspended solids such as solid particles and fibers. The semi-open impeller is less difficult to manufacture, low in cost, and highly adaptable. It is gradually used in centrifugal pumps for refining and chemical industries, and is used to transport clear water and liquids similar to clear water.
Open impeller
Impellers with only blades and blade stiffeners, without front and rear covers (open impellers have less than 2-5 blades). The impeller has low efficiency and few applications. It is mainly used to transport liquids with higher viscosity and slurry liquids.
The blades of centrifugal pump impellers are generally backward curved blades. There are two types of blades: cylindrical and twisted. The use of twisted blades can reduce the load on the blades, improve the suction performance of the centrifugal pump, and improve the anti-cavitation ability, but the manufacturing is more difficult and the cost is higher.
Centrifugal pumps used in refining and chemical industries require the impeller to be cast or fully welded integral impeller. Welded impellers have been developed and are mostly used in special centrifugal pumps for chemical industry made of metal materials with poor casting properties (such as iron and its alloys). The geometric accuracy and surface finish of the welded impeller are better than those of the cast impeller, which helps to improve the efficiency of the centrifugal pump.
