Semiautogenous mills, more conventionally known as SAG mills, are big machinery that mill through mined ore, which are broken down into fine particles from large boulders and rocks. SAG mills utilize milling balls so the ore can be ground down into fine particles, a process known as comminution. The ore turn and tumble in the mill, creating an environment of high heat and constant vibrations. Downtime and repairs for SAG mills can be costly and dangerous; therefore, finding preventative measures is critical.
Relining Minerals, a prominent distributor of industrial bolts found in mining equipment, was looking for a lubricant to protect their liner bolts found in SAG mills from high temperatures and constant vibrations during the mining process. With the assistance of an Australia-based company Mining Products and Services (MPS), Relining Minerals began looking into lubricants to determine what kind would protect the bolts from elongating over the minimum stress yield threshold, causing the bolt to deform and fail.
The two companies controlled three variables within the tests they ran: the type of lubricant used, the lubricant application method, and the correct operation of the torque tools. Relining Minerals is not only a distributor of industrial bolts; they also provide lubricants and technical support. They wanted a solution that they and their customers could consistently rely on—not just as a product they could recommend but as its own preferred solution.
Problem the Customer Faced
With large-scale ore-processing plants, there are large industrial demands. To meet those demands, finding a lubricant that would reduce the frequency of plant downtime due to bolt failures and control maintenance costs was highly sought after. The optimal lubricant would protect the bolts from dusty and abrasive byproducts from the comminution process.
Mill liner bolts (shown right) secure the protective liner to the inside of the mill. Proper lubrication is essential for converting the applied torque to elongation and claping force, minimizing the risk of tension loss and fatigue failure.
During bolt-tensioning trials, MPS brought in a pulp lifter liner configured with M48 liner bolts from a 36-foot SAG mill. The test jig was used to calibrate the actual torque/bolt load and, through proper lubrication, get it closer to the calculated torque/bolt loads to reduce the variation in the bolt loads achieved.