The definition of abrasion refers to a component’s size (volume) becomes smaller and loses its original designed function. The abrasion of centrifugal pumps
including impeller abrasion and seal abrasion.
l Reasons for seal abrasion
1. The medium of water transport by centrifugal pumps
has a bad quality and contains solid particles. Due to small solid particles and salt in hydrochloride are forming to abrasive materials which will wear down the surface of mechanical seal of the self-balancing multistage pump
2. Dry grinding because of lack of water This phenomenon is more common in the inlet pipe with air, there is air in the pump chest, after the pump is turned on, the friction of the machine seal generates high temperature when running at high speed, and cannot be cooled.
3. The mechanical seal is too tightly installed to cause blackening and deep marks on the surface, and the sealing rubber becomes hard and loses elasticity.
4. Leakage of water in mechanical seal.
5. The mechanical seal is loosely installed, resulting in a thin layer of scale on the surface that can be wiped off. The surface is basically free of wear, which is caused by the loss of elasticity and poor assembly of the spring, or the axial movement of the motor.
l Reasons for impeller abrasion
1. The material of impellers is not adaptable for corrosive liquids.
2. The nut becomes less crowded which causing impeller abrasion of centrifugal pump.
3. The centrifugal pumps often in a cavitation status which increases impeller abrasion.
l Precautions on abrasion
1. Correctly determine the water absorption height of the pump to ensure that the inlet pressure is not lower than the vaporization pressure.
2. Try to reduce water flow lost in the suction pipeline. Because the greater the water flow loss, the more pressure is reduced at the pump inlet, and the water can be easily vaporized. Therefore, the length of the suction pipe should be shortened as much as possible, and the accessories on the pipe should be reduced. The inner wall of the pipe should be smooth and the diameter of the suction pipe should be appropriately increased.
3. The centrifugal pump
should be installed underground. If cavitation is caused by excessive water absorption, the pump can be installed underground or below the surface, near the water surface.
4. Using jet flow to increase the inlet pressure.
5. Try to keep the pump running under rated conditions. If the pump is running below the rated head or greater than the rated speed, the pump flow must be greater than the rated flow. The water flow at the impeller inlet must increase, and the pressure will be further reduced. Therefore, the pump head cannot be lowered and the pump speed can not be increased.
Set up guide vane at the inlet of centrifugal pump or use anit-cavitaion pump parts.