There are on-going maintenance costs and production losses due to particulate erosion damage in slurry flow equipment used in slurry transport and processing equipment in alumina refineries. CSIRO has been conducting research under AMIRA P931 “Multiphase Flow Erosion” projects since 2006, under sponsorship funding support from Alcoa, BHPB, Rio Tinto Alcan, Vale and Pentair Valves (Tyco Flow). AMIRA P931 projects focused on building knowledge and methods to predict the erosion service life of flow equipment and developing strategies through case studies to alter flow design to reduce erosion and extend equipment life. Interestingly, none of the case studies requested by the industry partners involved simple impingement erosion or sliding bed erosion. As the emphasis has been on solving erosion problems using the principles of the underlying multiphase fluid dynamics, this called for an in-depth CFD treatment of non-uniform flows. In this the current study was very different from the usual treatment of erosion, which focuses on direct impingement simply because it is easy to model and measure, and rather addressed the much more common industrial problem of localised erosion.
The importance of several fluid dynamic mechanisms responsible for severe erosion attacks was reinforced during the P931 projects with quantitative measurements of the details of the erosion being made available. These include erosion by vortices, by flashing and by various non-uniform flows. For example, erosion by vortices which tend to cause more damage than “normal flow” was found to be caused by the effect of multiple hits by solids trapped in the vortices compared with single hits by solids in a direct impact condition. This finding of accelerated wear has allowed the diagnosis of vortex erosion being present in many flow geometries critically important in P931 sponsors’ plants, e.g. pipework around a valve, protrusions in a pipe and many conventional engineering designs. The present paper focuses on vortex erosion as noted in a variety of flow situations and examines the fluid dynamics and consequent erosion.