Abrasion wear occurs when hard particles are forced against and move relative to a solid surface. There are three major types of abrasion: Gouging, High Stress Grinding and Low Stress Grinding.
In a centrifugal slurry pump, abrasion only occurs in two areas:
i) Between the rotating impeller and stationary throatbush, and
ii) In between the rotating shaft sleeve and the stationary packing
Abrasion, although used to cover all types of wear, is quite distinct to erosion.
In slurry pump applications, the dominant mode of wear is erosion. Erosion is a form of wear involving the loss of surface material by the action of particles entrained in the fluid. Erosion involves a transfer a kinetic energy to the particles, which does not occur in abrasion.
The transfer of kinetic energy from the particle to the surface results in a high contact stress. Whilst the overall contact pressure at each impact site is small, the specific contact pressure is high, because of the irregular shape of the particles.
There are three basic types of erosion: sliding bed, random impact and directional impact.
Pump impellers, side liners and volutes wear due to quite different mechanisms as follows:
i) Pump impellers are subjected to a combination of direct impingement (on the leading edge of vane and at the base of the vane where it joins the back shroud), sliding bed wear and low angle impingement (along the vanes and further inside the passage between the shrouds).
ii) Side liners are mainly subjected to sliding bed wear and some low angle impingement
iii) Volutes are subjected to direct impingement on the cutwater and sliding bed erosion around the periphery.