The water pump impeller is a key accessory of a multi-stage centrifugal pump, made of cast iron. Stainless steel material can also be used, and the blades on the water pump impeller play a major role. The shape and size of the water pump impeller are closely related to the performance of the water pump. Water pump impellers can generally be divided into two types: single suction and double suction. Single suction impellers absorb water from one side, while small flow pump impellers are mostly of this type. The double suction impeller absorbs water from both sides, and the high flow water pump impeller adopts the double suction impeller.
There are four main forms of impellers for multi-stage centrifugal pumps: (a) closed; (b) Front half open; (c) Rear half open; (d) Open form
1. Closed impeller: composed of blades and front and rear cover plates. Closed impeller has high efficiency and manufacturing difficulty, and is widely used in multi-stage centrifugal pumps. Suitable for conveying clean liquids with low viscosity, such as clear water and solutions, that do not contain particles.
2. Half open impeller: There are generally two types of structures. One is the front half open impeller, which is composed of a rear cover plate and blades. This structure has low efficiency and requires adjustable clearance sealing rings to improve efficiency. The other is the rear half open impeller, which is composed of a front cover plate and blades. Due to the application of the same sealing ring as a closed water pump impeller, the efficiency is basically the same as that of a closed impeller, and the blades are not only used to transport liquid, It also has a sealing effect on the back blade or auxiliary impeller. The semi open impeller is suitable for conveying liquids containing suspended solids such as solid particles and fibers. The manufacturing difficulty of semi open impeller is relatively small, the cost is low, and the adaptability is strong. In recent years, its application in multi-stage centrifugal pumps for refining and chemical industry has gradually increased, and it is used to transport clean water and liquids similar to clean water.
3. Open impeller: Impeller with only blades and blade reinforcement ribs, without front and rear cover plates (open impeller has 2-5 fewer blades). The impeller of a water pump has low efficiency and is rarely used, mainly for conveying liquids with high viscosity and slurry like liquids.
The blades of the impeller of a multi-stage centrifugal pump are generally backward curved blades. There are two types of blades: cylindrical and twisted. The application of twisted blades can reduce the load on the blades, improve the suction performance of multi-stage centrifugal pumps, and enhance their resistance to cavitation. However, manufacturing is difficult and the cost is high.
The multi-stage centrifugal pump used in oil refining and chemical engineering requires the impeller to be a cast or fully welded integral water pump impeller. Welded water pump impeller is a special multi-stage centrifugal pump developed in recent years, mainly used in the manufacturing of metal materials with poor casting performance (such as iron and its alloys) for chemical industry. The geometric accuracy and surface finish of welded water pump impellers are better than those of cast impellers, which is beneficial for improving the efficiency of multi-stage centrifugal pumps.
