The abrasive wear of solid particles is the root of the difference between the design of slurry pumps and their applications in centrifugal slurry pumps. Wear is a complex phenomenon that depends on the inherent characteristics of the pump and the pumped slurry. For many years at home and abroad Scholars have been conducting theoretical and experimental research on the wear mechanism. However, it is still not fully understood.
Slurry pump wear has many factors, and the wear mechanisms of different parts and parts are not the same, but in general it can be summarized into three categories:
During the operation of the slurry pump, the solid particles carried in the liquid impact the surface of the flow-through component at a certain speed, causing material loss. According to the analysis of the worn surface of the failed component, the erosion wear mechanism can be divided into cutting wear, deformation fatigue wear and cutting + deformation coincident wear. The failure analysis of the volute and guard plate of the slurry pump for iron ore shows that the cutting mechanism is the main reason for the wear of the volute, and the deformation fatigue wear is the main reason for the wear of the guard plate.
During the operation of the pump, in a local area of the flow-through component (usually behind the impeller inlet), for some reason, when the absolute pressure of the pumped liquid drops to the vaporization pressure at the current temperature, the liquid starts there. Vaporization, producing steam, forming bubbles. These bubbles flow forward with the liquid, and when reaching a certain high pressure, the bubbles shrink sharply and even collapse. While the bubbles are condensing, the liquid particles fill the voids at a high speed and have a strong impact on the metal surface. The metal surface will peel off due to fatigue caused by this impact, causing material loss. In severe cases, the metal surface will appear honeycomb. Generally, cavitation occurs at the exit of the impeller and the entrance of the volute.
Centrifugal Slurry Pumps
When the conveyed medium has a certain pH, the flow parts of the slurry pump will also undergo corrosion and wear, that is, the loss of materials under the combined action of corrosion and wear. Corrosion can be divided into chemical corrosion and electrochemical corrosion. Chemical corrosion is the direct reaction between metal and liquid medium to cause metal loss. Electrochemical corrosion is the formation of micro-batteries on the surface of the metal under the action of liquid medium to cause material loss. Since the metal materials actually used are polycrystalline and multiphase materials, electrochemical corrosion mainly occurs, and the occurrence of slurry pump corrosion, especially the corrosion of the crystal boundary, causes the formation of cracks between the grains on the metal surface, and Isolate the crystal grains or hard phases and lose their support, so that they will fall off under the erosion of solid particles; and the erosion of solid particles will cause the passivation layer produced by corrosion on the metal surface to be worn away. The liquid medium and the metal are new Surface contact increases corrosion. Corrosion has been found in the failure analysis of the slurry pump.
The wear rate is closely related to the following three factors:
1. Paste characteristics. Including solid characteristics, liquid characteristics and comprehensive characteristics depending on the above factors and other factors;
2. Characteristics of pump structure materials;
3. Pumping slurry contact characteristics.
Corrosion and cavitation damage have a huge impact on fluid machinery. To improve the abrasion, corrosion, and cavitation resistance of fluid machinery, not only the overall material must be studied, but also the surface protection of parts must be paid attention to. Therefore, the application of protective materials will be particularly important. Among the above three factors, only the characteristics of pump structural materials can be controlled artificially, so the reasonable choice of pump materials has become the primary task of today's pump industry.