Minimizing Impeller Slurry Wear through Multilayer Paint Modelling

Abstract

I n industries such as mineral processing, high agitation intensity is sometimes used to achieve the required solids suspension and gas-to-liquid mass transfer rate in threephase systems. However, the high slurry velocities used in a high-intensity agitation vessel may result in particle impingement wear on the impeller blades.Wear by particulates on industrial equipment, and metal materials in general, has been the subject of substantial research efforts over many years (e.g. Blau, 1997;Deuis et al., 1996;Hutchings, 1987). It is general practice in industry to use wearresistant materials, coatings or surface treatments to reduce the wear rate. The present work aims to reduce wear rates by modifying the geometry of mixer impeller blades. This approach, when coupled with correct selection of blade material, will greatly extend the service life of impellers used in high-intensity agitation applications. This fl uid mechanics-based approach is justifi ed, as wear rate is sensitive to the fl ow fi eld, since it is a function of particle velocity and particle impingement angle (Laitone, 1979;Humphrey, 1990;Finnie, 1995 1995;Zhang et al., 2000), for given material and physical properties of the particles.Wear on mixing impeller blades is a somewhat less frequently discussed topic in the mixing research community, with only a handful of papers in the literature reporting research on this issue. Weetman (1998) used computational fl uid dynamics (CFD) simulations to redesign the blade geometry, so as to modify the velocity distribution along an aerofoil section of an axial fl ow impeller. He was able to reduce the maximum velocity at the leading edge of the impeller blade, leading to a signifi cant reduction in the wear rate. Fort and Ambros (1999) carried out an analytical study of the erosion of blades of pitch bladed impellers.Much experience can be drawn from the substantial amount of literature available on centrifugal pump impeller wear. Walker (2001;2002) studied in detail the wear patterns developed onThe present paper describes an experimental study using a multilayer paint technique to illustrate the wear patterns developed on an eightbladed disc turbine in a gas/liquid/solids three-phase mixing tank. A distinctive wear pattern was found to develop on the low-pressure side of the blades. The patterns were found to be caused by the two intersecting vortices that developed along the blades. Several modifi cations were made to the impeller geometry to reduce wear. A new impeller design, which experienced a lower wear rate and showed an improved offbottom solids suspension performance, is recommended for operating in gas/liquid/solids reactors.On décrit dans le présent article une étude expérimentale utilisant une technique de peinture multicouche afi n d'illustrer les modes d'usure sur une turbine à disque à huit pales dans un réservoir de mélange triphasique gaz-liquide-solide. On a trouvé qu'un mode d'usure distinct se développait du côté basse pression des pales. On a trouvé que les modes d'usure étaient causés...

Laboratory Modelling of Equipment Erosion by Sand Particles

“…The erosion developed on the back of the blades after the turbine operated in a slurry tank for less than 10 months period at a gold processing plant. The extensive damage developed on the blades was caused by the trailing edge vortices rolling over the blades; refer to Wu et al (2005) for a more detailed description of the mechanism. This impeller erosion was investigated in an extensive laboratory modeling program using the paint technique.…”

“…Thus currently it is still critical to use experiments to validate CFD and to use physical experiments to make assessment of the new design concepts. Wu et al (2005) and Noui-Mehidi et al (2008) have shown the feasibility of using the multilayer paint technique to produce highly visible and accelerated erosion damage on various flow geometries to assist developing improved geometrical designs, in order to minimize the erosion. This paper extends these previous studies and summarizes the basic technical procedures and assessment of the paint modeling technique in relation to actual erosion damage and CFD modeling.…”

Erosion–Corrosion of 30°, 60°, and 90° Carbon Steel Elbows in a Multiphase Flow Containing Sand Particles

“…Multilayer paint modeling (MPM) is an inexpensive qualitative visual tool for accurately mapping the erosion location in significantly less time, using the flow loop at high transportation velocities [28,29,30]. The MPM technique is a qualitative tool and cannot yield any quantitative data related to the erosion–corrosion rate of the pipe wall.…”

Modeling Erosion Wear Rates in Slurry Flotation Cells

“…A qualitative way to measure erosion damage is the multilayer paint scheme [22]. The technique presents a way to produce highly visible and accelerated erosion damage.…”