Liner wear in grinding mills occurs primarily due to the harsh working conditions within the grinding mill itself, where liners are constantly subjected to impact wear, abrasive wear, and fatigue through collisions with both the ore and the grinding media. Additionally, liner wear may be enhanced by the inappropriate selection of liner material, which is characterized by low hardness and brittleness, poor heat treatment, or any defects introduced during manufacture that reduce strength. The effects of operating conditions such as overloading, excessive mill speed, and frequent impacts of grinding media can further increase the load on the liners, reducing their lifespan.
The first reason that leads to liner wear is impact wear. This process becomes more significant when coarse grinding takes place in combination with high lift. High energy impacts of ore lumps and grinding media will result in liner deformation and cracking. The other important reason is abrasion wear. Due to the constant friction with tiny particles of materials, as well as grinding media, the surface is abraded. Impact and friction can be the reasons why fatigue wear appears; there will be the development of microcracks leading to the surface breaking down.
Material is an important element that affects wear. If the metal of the liners is soft, then their erosion occurs very fast, and vice versa, if it is hard enough but does not possess high strength. It is clear that the material should match both the ore properties and the mill operation. Moreover, there are other factors that can result in liner degradation due to poor metallurgy. There can be defects of casting, inclusions, and unevenness of the structure, leading to stress concentration at certain points.
Liner life is greatly affected by the way the plant operates. Loading the mill with excess load makes the wear faster because of increased impact loading, and an inappropriate milling speed will create additional friction between the liners and the charge. According to RME, newly installed thick liners might alter the path of the charge in such a manner that operators would be compelled to run the mill at lower speeds to prevent throwing too much charge material against the liners.
The lifespan of liners can be extended by improved designs as well as proper profiling for the liners relative to the objective of the operation. Properly designed liners, correct lifter heights, and suitable thicknesses for the liners according to the duties will enhance the performance of the liners while minimizing unnecessary damage, bearing in mind that the liners’ design should consider the mineral hardness as well as the operating condition of the mills. Generally, the choice of the right liner design relative to its intended use is more favorable than a universal liner design.
Maintenance and good installation practices are the last ways to increase life span. Inspections will allow noticing any signs of loosening, cracks, or unusual wear prior to an eventual failure. Proper bolt torquing, using the right fasteners, and accurate fit-up will help decrease liner movement as well as secondary impacts on liners. Additionally, faster and more efficient re-lining methods and improved planning will prevent any delays in the replacement of liners.
