创建于05.07
Wet Parts Of Slurry Pump
Slurry Pump Flow Components: Principles, Failures and Material Selection
In the industrial field, slurry pumps, as a key piece of equipment, are widely used in industries such as mining, metallurgy, power generation, and coal, for transporting slurries containing solid particles. The flow components of slurry pumps, as the parts that come directly into contact with the slurry and guide its flow, play a decisive role in the performance, efficiency, and service life of the pumps. A deep understanding of the relevant knowledge about the flow components of slurry pumps is of great significance for optimizing pump operation, reducing maintenance costs, and improving production efficiency.
Composition and Working Principle of Slurry Pump Flow Components
The flow components of slurry pumps mainly include the impeller, volute, and wear plates. The impeller, known as the "heart" of the slurry pump, is composed of four parts: the front shroud, rear shroud, blades, and hub. Inside the pump body, the impeller is driven by the pump shaft to rotate at high speed. Through the action of centrifugal force, it transfers mechanical energy to the slurry, enabling the slurry to gain dynamic pressure energy, accelerate, and be propelled towards the pump body. The design and arrangement of the impeller blades are crucial, directly determining the performance and efficiency of the slurry pump.
The volute is located behind the impeller. Its design is based on the flow trajectory of the slurry after leaving the impeller. The main functions of the volute are two: one is to receive the liquid discharged from the impeller; the other is to convert the kinetic energy of the liquid into pressure energy. As the slurry flows outward in the volute, the special shape of the volute is conducive to this energy conversion, and the gradually increasing structure at the outlet part of the slurry pump further strengthens this energy conversion process.
The guard plates are divided into the front guard plate and the rear guard plate (some small pumps have only one guard plate). The front guard plate usually has an inlet, and the rear guard plate has an axle hole. The guard plates mainly cooperate with the volute to form a closed space for the flow of slurry, and their function is to protect the impeller and the pump body from direct impact and wear by larger particles, thereby prolonging the service life of slurry pump the impeller and the pump body.
Wetted components of slurry pumps Analysis of Common Failure Causes
In practical applications, the flow components of slurry pumps are exposed to complex and harsh working conditions, which makes them prone to failure. Under normal circumstances, the flow components such as the pump casing, the front and rear guard plates, the impeller, the shaft seal, the shaft sleeve, and the suction inlet are severely worn.
Abrasive wear and erosion are among the major causes of failure for flow components. The impeller is mainly subjected to cutting damage due to low-angle impacts, while the pump casing is mainly affected by high-angle impacts resulting in the shedding of metal surface flakes. The flow channel wall is prone to fatigue damage caused by the long-term and repeated impact of solid particles. Meanwhile, the surface material of the flow components is also severely corroded by the carbide phase boundaries, causing the carbides to lose their support from the matrix and break during the process of abrasive wear and erosion.
Strong alkaline corrosion is also an issue that cannot be ignored. In some working conditions, the slurry is highly alkaline. The slurry pump matrix of the flow passage components may develop alkaline brittle cracks due to strong alkaline corrosion, which is known as anodic dissolution type stress corrosion cracking. The cracks extend from the surface layer to the sub-surface layer and are distributed in a network-like pattern, greatly peeling off the matrix and eventually causing peeling during erosion wear. If the material of the flow passage components lacks sufficient resistance to high-temperature strong alkaline corrosion, anodic activation dissolution corrosion peeling will also become one of the reasons for failure.
The cavitation phenomenon can also cause damage to slurry pump the flow passage components. In the slurry, slurry pump the bubbles in some parts of the flow passage rapidly shrink due to high pressure and collapse. At the same time, the liquid fills the voids at high speed, forming water hammer. The high-frequency and high-speed micro-jet flow impact causes the metal on the surface of slurry pump the flow passage components to peel off due to impact fatigue, resulting in material loss. Generally, cavitation occurs mostly at the outlet of the impeller and the inlet of the water extraction chamber. In summary, the failure of flow passage components such as the pump casing and impeller of the slurry pump is often the combined result of the mutual promotion of strong alkaline corrosion and erosion wear, and the role of corrosion is more crucial.
Wetted components of slurry pumps material selection considerations
Given the harsh working environment of the flow components, the selection of materials is of vital importance. In recent decades, numerous wear-resistant materials for the flow components of slurry pumps have been developed both at home and abroad, mainly falling into three categories.
High chromium cast iron and nickel hard cast iron are common types of materials. High chromium cast iron is hailed as "the third-generation metal anti-wear material", featuring excellent anti-wear performance and being suitable for the beneficiation and ore processing industries where the slurry contains coarse and sharp particles. Generally speaking, the hardness of the alloy determines the resistance of slurry pump the flow passage components to the particles. High chromium cast iron has a relatively high shear hardness and compressive strength, which can effectively enhance the wear resistance of the slurry pump components. Currently, in terms of the material of the impeller of the slurry pump in China and abroad, white cast iron is still the main metal anti-wear material, including ordinary white cast iron, nickel-hard white cast iron and ordinary high chromium white cast iron. However, ordinary white cast iron has relatively low hardness and impact toughness due to the fact that the carbides are mainly in the form of reticular cementite and the matrix structure is mainly pearlite, resulting in poor wear resistance. Moreover, the electrode potential difference between phases is large, leading to severe electrochemical corrosion, and it is rarely used. Ordinary high chromium white cast iron has high wear resistance, but poor toughness. When subjected to high-speed scouring by large solid particles, the surface material of the impeller is prone to fall off, and the fracture surface is prone to form pits due to corrosion. In addition, due to the scarcity and high price of nickel resources in China, nickel-hard cast iron is not widely used in China.
Rubber and ceramic materials also play their roles in specific scenarios. Rubber is suitable for conveying slurry with the maximum particle size less than 10mm (average particle size 3mm) in a slurry pump. When conveying fine-grained slurry without sharp edges, its wear resistance is superior to that of metal materials. Ceramic materials possess high hardness, wear resistance, corrosion resistance and other characteristics. However, their disadvantage of high brittleness limits their direct application in slurry pumps. Nevertheless, by means of surface coating, a ceramic coating can be formed on the metal surface, which can balance the wear resistance, corrosion resistance of ceramic materials and the toughness of metal materials, thereby enhancing the service life of the metal materials.
The flow components of slurry pumps play an indispensable role in industrial production. Understanding their composition, working principle, failure causes, and rational material selection is of profound significance for ensuring the stable and efficient operation of slurry pumps, reducing enterprise production costs, and enhancing production efficiency. With the continuous development of materials science and manufacturing techniques, it is believed that more superior flow component materials and designs with excellent performance will emerge in the future, promoting the advancement of slurry pump technology to new heights.
FINALLY
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Hedunpump Is not affiliated nor a distributor for any pumps company.
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