Analysis of Severe Erosion in Industrial Centrifugal Slurry Pumps

摘要

Centrifugal pumps designed for homogenous slurries experience inefficiency, off-design operations, shorter service-life expectancy, and rapid geometry change due to localized and uneven erosion. Experimental and numerical research to design erosion-free pumps has been inconclusive due to complexity of heterogeneous, multiphase slurry flows and mechanism of the localized material losses. This paper reports on erosion-effects of slurry flows on a number of industrial centrifugal pumps selected from an active copper mine field. The field samples include three metallic pumps operating in a serial-arrangement, and a number of worn pump-components with fully rubber-lined or metallic wetted-surfaces. Physical samples were also collected and photographed under an electronic microscope. The analysis of the photographs shows directional groves, ripples-formations, pitting, cavities, spots, and abrasive-embedding on the pump surfaces. The effected regions included a) hub or tip of the vane leading edge of impellers, b) internal and external surfaces of shroud and downstream of expellers, c) front-liners/throat bush all at the proximity of the inlet throat/tube, and d) Volute surface close to the discharge throat/tube on the spiral tail. Analysis of eroded regions suggests a combination of mechanisms some similar with those found with a sustained flow acceleration and momentum change towards a surface. A wear model is therefore recommended for the severe erosion in pumps which resembles erosion by cavitation. To further understand and verify the finding and to be able to predict and to avoid accelerated-erosion, an experimental modelling and a numerical modelling of slurry flows in two identical-centrifugal-pumps are conducted in series and preliminary results are presented. The project is in progress.