The style of a SAG mill liner is driven by the material of building and construction and also the application, as well as limited by casting, molding, and taking care of constraints. For huge mills with wide inlet trunnions, in excess of 1.5 m, liner handling types of equipment are currently in common usage, and also this has actually permitted the development of large integral liner blocks, considering as much as 1.5 t a piece, Figure 1. This holds
1. Solid Liners – These have an integral lifter and liner, as shown in following. These have fewer pieces and are easier to install, but tend to have a high scrap weight as once the lifter section is worn down liner performance drops and necessitates change out.
2.Removable lifter – The lifter can be changed rather than the complete liner, thereby maximizing liner life and assisting in manually relined mills. More pieces have to be installed and liners can move during relining and if not well secured against the backing liner the lifter can shift and work loose, this is especially a problem if the bolts begin to stretch.
3. Grid Liners .A system that appears to be unique to Southern Africa, is pocketed grid liners, where the grinding media packs in the grid structure and forms an integral part of the liner, Figure 3. Often the liners have a flat profile, suited to the high speeds (85% to 90% of critical) that most of the older mills operate at. These liners have been demonstrated to be economically unbeatable for highly abrasive ores in small to medium size
5. Integral wave blocks – These are commonly used in ball mills, and the profile of the liners has become sufficiently sophisticated to enable the liner profile to be maintained as the liner wears.
6. Uni-Direction Profiled Liners – The lifter has different leading and trailing profiles, Figure The profile can be better customised to suit mill speed and filling and therefore optimise performance, and it allows more material in the lifter for a given base width, but the mill must only run in one direction.
7. High–low double wave ball mill liners – These are a refinement of the wave liner, Figure 5. This was applied to Cadia Hill Gold Mine through evaluation of their existing wear profile and wear rate, and provided a more consistent wear profile through the liners working life. The correct wave face angle needs to be calculated and applied as an incorrect angle could lead to ball segregation and loss of grind.
An indication of our limited ability to accurately ‘design’ liner profiles is that few liners are optimal at original installation or in the post-commissioning set, and it is imperative as a user to vigorously pursue the improvement of the design, to get the most out of the liners. An indication of our limited ability to accurately ‘design’ liner profiles is that few liners are optimal at original installation or in the post-commissioning set, and it is imperative as a user to vigorously pursue the improvement of the design, to get the most out of the liners.