The impeller of the water pump is made of cast iron, and generally can be divided into two types: single-suction type and double-suction type. The water pump impeller can adopt this kind of impeller. It can also be divided into three types: closed type, semi-open type and open type. The closed type impeller is composed of blades and front and rear cover plates. It has high efficiency and is most used in centrifugal pumps. It is suitable for transporting clean water such as clear water. Such as fire pumps, water supply equipment; the semi-open impeller is composed of one of the blades and the front and rear cover plates, and the gap can be adjusted to improve the efficiency. Liquids with suspended solids such as particles and fibers are widely used in centrifugal pumps for oil refining and chemical industries; open impellers only have blades and blade reinforcement ribs, no front and rear cover plates, and the number of blades is generally 2-5. The impeller efficiency is low. There are few applications, and it can be used to transport slurry liquid with high viscosity.
The cavitation of the impeller is the flow of liquid in the diesel engine fire pump. Since the pressure at the inlet of the impeller is lower than the saturation pressure of the working liquid, part of the liquid will evaporate. The surrounding liquid is replenished here, causing hydraulic impact, which gradually fatigues and damages the impeller surface, causing the metal surface to be peeled off, and then large and small honeycomb pits and even corrosion holes appear. This is a relatively common phenomenon in the operation of fire pumps. The most harmful problem is the impeller of the water pump.