The pump is in such a poor condition already

At the pump inlet, it’s honeycomb-shaped; it’s a desulfurization circulation pump

Well, yes. Is the honeycomb also ground?

Is the particle size of the first limestone too large, causing an increase in the particle size of the slurry and thereby increasing wear? At the pump inlet, near the impeller inlet, the condition is more severe compared to the pump inlet flange; the condition at the flange is milder. This is because, due to the viscosity of the medium, the rotation of the impeller causes the medium located near the impeller inlet to rotate as well. The fluid thus has a circumferential velocity before it enters the impeller. Since the medium contains particles, these particles cause abrasion on the part of the inlet flange that is close to the impeller, resulting in pitted surfaces. Secondly, if there is a filter in front of the pump, large particles can easily clog the filter, which may lead to cavitation in the pump and accelerate the damage to the impeller. Is the pH value of the third medium low? An excessively low pH value can exacerbate corrosion. Is the chloride content in the fourth medium high? A high level leads to increased corrosion.

Is the degree of damage to the inner wall of the inlet flange the same everywhere? Is it more severe in the lower area? It should be tighter at the bottom, because the solid particles settle there as well.

The explanation upstairs is very comprehensive. I remember that the Fisher Handbook mentioned that the honeycomb pattern is caused by cavitation.

Filled with a sense of vicissitudes·~~~