Impeller Shroud Wear Pattern Analysis

Common Impeller Shroud Wear Patterns

1. Abrasive Wear
   Manifestations: Small scratches and pits appear on the impeller shroud surface, similar to sandpaper marks. These scratches typically vary in depth and direction.
   Cause: Solid particles carried in the fluid, such as dust and sand, continuously impact the impeller shroud surface during high-speed flow, acting like countless tiny cutting tools, causing wear over time. For example, in some industrial wastewater pumps, impurity particles in the wastewater can cause abrasive wear on the impeller shroud.
2. Corrosion Wear
   Manifestations: Localized rust spots and pitting appear on the shroud surface, and in severe cases, perforation may occur. The metal color of these corroded areas differs from normal areas and typically exhibits discoloration and flaking.
   Cause: Chemicals in the fluid react with the impeller shroud material, destroying the protective film on the metal surface and accelerating corrosion. For example, in chemical production, pumps that transport corrosive liquids (such as acidic and alkaline solutions) are susceptible to corrosive wear on the impeller shroud.
3. Erosion Wear
   Manifestation: Noticeable material thinning occurs in specific areas of the impeller shroud, such as the blade inlet edge and the shroud-to-blade connection, forming a streamlined wear pattern. The surface of the worn area is relatively smooth.
   Cause: When high-speed fluid flows through the impeller shroud, the sudden change in flow direction creates a strong impact on the shroud surface, causing gradual material loss. For example, in hydropower station turbines, high-speed water flow is a common cause of erosive wear on the impeller shroud.
4. Cavitation Wear

Symptoms: Numerous small, honeycomb-like holes form on the impeller cover surface. These holes vary in size and are densely distributed. In severe cases, they can interconnect, causing large areas of cover material to peel.

Cause: When fluid flows through the impeller, pressure fluctuations generate bubbles in localized areas. These bubbles quickly collapse in high-pressure areas, generating powerful impact forces that continuously impact the impeller cover surface, damaging the material and causing cavitation wear. This condition is commonly seen in equipment such as centrifugal pumps.