Hydrocyclones refer to an essential device for classifying materials through their size and density. Two important terms that help in comprehending the working principle of hydrocyclones include the vortex finder and the apex. The vortex finder refers to the central top pipe through which light and fine materials pass as overflow. Apex refers to the narrow bottom end of the hydrocyclone through which heavier materials pass as underflow. Both of these features are exposed to very strong inner forces, hence their vulnerability to wear and tear.
The state of health of hydrocyclones has immense importance in determining their ability to classify material. This is because when hydrocyclones are in action, the slurry enters the cyclone with very strong velocity resulting in the formation of centrifugal vortex of fluid. Due to the fact that materials used in the industries are usually full of abrasive substances, the materials inside undergo fast wear and tear (Kanyemba et al., 2023). Since the vortex finder and apex are at the location of maximum shear stress, they are the areas most prone to wearing.
Premature wear in these essential areas occurs mainly because of the constant and rapid impact of the abrasive particles. As shown by the scientific investigations, increasing the roughness of the surface caused by corrosion, localized wear or particle deposition considerably changes the tangential velocity and the pressure drop in the vessel (Kaya et al., 2011). With the continuous alteration of geometry because of friction, the flow pattern changes significantly. Thus, in case of wear at the vortex finder, its dimensions increase, and coarse slurry can pass without undergoing classification, and the wear at the apex disrupts the centrifugal force necessary for exact separation.
Apart from regular wear caused by the interaction with abrasives, the operational mistakes often increase the rate of premature wear of hydrocyclones. One of them is the so-called “roping” effect. Under optimal conditions, the hydrocyclone should eject the solids in the shape of an umbrella from the apex, but excessive feed density or overflow causes ejection in the form of a thick stream called roping. It causes very fast erosion of the apex and vortex finder.
Both material changes and operational processes need to be implemented to enhance service life of the components. First of all, standard metallic components have to be replaced with components made of very durable materials such as engineered ceramics, high alumina tiles, or polyurethane liners in order to greatly reduce the rate of abrasions. In terms of operation, it is vital to control feed pressures and concentration to avoid extreme pressure variation that will wear components very quickly (Kanyemba et al., 2023). Regular physical measurements will also play an important role in determining whether components are within the operational tolerance.
In summary, it should be stated that the wear of vortex finders and apexes occurs as a result of mechanical abrasion, changes in surface roughness, and poor operational control of components. Since these components influence the dynamics of the flows inside the system, the wear affects their functioning. It is possible to prevent premature wear if operators acknowledge high abrasiveness of process feeds and overload situations such as roping.
References
Kanyemba, A., Dzinomwa, G., & Sony, M. (2023). Application of lean Six Sigma to improve the dense medium separation performance at a diamond processing plant in Namibia. Cogent Engineering, 10. https://doi.org/10.1080/23311916.2023.2165216
Kaya, F., Karagoz, I., & Avci, A. (2011). Effects of Surface Roughness on the Performance of Tangential Inlet Cyclone Separators. Aerosol Science and Technology, 45(8), 988–995. https://doi.org/10.1080/02786826.2011.574174
