Mill Liner Handlers Ensure Operational Uptime for Grinding Mills

Q: What are the characteristics of Mill Liner Handlers and why are they important to Mexican mining operations?

A: Many Mexican mining operations have grinding mills, which can be semi-autogenous grinding (SAG) or steel ball grinding mills. Other types exist but, in Mexico, these are the most common, particularly in newer operations where mills have large dimensions. The mills have internal steel, rubber or composite liners to elevate and tumble the mineral charge to create a grinding action. Another goal is to protect the structure of the mill: if the liners were absent, the impact and abrasion inside the mill would destroy it. Every so often, depending on metallurgical analysis and other tests that the mine performs, the liners are scheduled to be replaced. This can be done in segments on the side of the cylinder or on the lids of the mill. The operation is critical and key to the processing plant’s maintenance schedule. The duration of the operation varies depending on the mill and the sections in need of replacement, and it requires a complete mill shutdown to work inside and around it. Yet, more importantly, it is one of the riskiest operations in the mine in terms of personnel safety.

Q: How does IPEC’s solution regarding this system improve safety?

A: A combination of hazards are present during mill relines, including work in confined spaces, limited illumination, uneven and unstable ground because you are standing on top of the charge and balls, heat and humidity. The liners are heavy, weighing between 500 and 5,000kg, and have irregular shapes. The required task is to remove them from the mill and replace them in an awkward position, as the mill is curved on the inside. Therefore, workers must push it against the side of the mill, leading to a perfect combination of factors to make it a dangerous operation.

A key company that IPEC represents, McLellan Industries Inc., is a pioneer and leader in the manufacturing of machines called Mill Liner Handlers (MLH). These solutions are designed to perform this task efficiently and safely. It is a critical piece of equipment, though it is not used often, only every few months or when a faulty liner breaks. The department in charge of maintenance has special sensors in the mill, which can detect that a liner is missing. In that instance, the mill needs to be shut down and our MLH is brought inside the mill to remove the broken liner and replace it with a new one.

Even though the use of the machine is infrequent, it needs to be always ready and available because a mill shutdown can cost the mine tens or even hundreds of thousands of dollars. Most of the Mill Line Handlers in Mexico are McLellan machines. IPEC provides sales of new machines, parts, servicing, training and inspections, among other services.

Q: What do you do to reduce the risks for workers who operate mill line handlers?

A: Each machine is designed and built for the mill and liners that it will handle. We gather information of the mill and its operation, as well as the surrounding area. Then we analyze the different liner models and their weights to come up with the optimal solution for each customer.

Moreover, McLellan has over 50 years of experience, with many improvements to the design based on customer feedback and continuing engineering. We also implement innovative technologies as they emerge. An example is the crane structure at the front of the mill. This structure must rotate to place the liner. Previously, the rotation mechanism was based on a chain drive sprocket. To improve the precision of the movements inside the mill, 10 years ago we began implementing a precisely rotating slew drive. The more precise the system is, the safer the operation can be carried out. Even now, we constantly look for new components that make our machines tougher, safer and more efficient.

Q: How has energy efficiency been enhanced in these new solutions?
A: The newer machines can do the job in fewer hours:  for example, an operation that used to take 36 hours could be completed in 24 hours, which is a 33 percent reduction in time spent running heavy machinery. Nevertheless, its power consumption is not highly significant, considering it is a hydraulic power unit with an electric motor of 30 to 50 hp.

Q: What technologies have you encountered in other countries that could be implemented in Mexico?

A: Since McLellan is a global company, we are aware of the best practices in mining operations in various jurisdictions. One innovation we wish to implement in Mexico is the usage of custom elevation platforms outside the mill to use in conjunction with our Bolt Buster, a specifically designed hydraulic hammer to eliminate the use of sledgehammers and battering rams still used by some operations, to remove the bolts that hold the liners in place. This solution could drastically reduce the number of inching or precise positioning operations of the mill to remove bolts by three, thus cutting several hours of the complete reline operation, helping the mine save hundreds of thousands of dollars’ worth of downtime. Additionally, the improvements in safety and ergonomy could warrant the investment of these platforms with our Bolt Busters on their own.