Many mills in the U.S. are more than 30 years old, and while they have years or decades of productive life ahead of them, operators often maintain them with outdated products or practices.

Modern production demands often require that today’s mills run above their original design parameters. The lubricants that were appropriate for yesterday’s operating conditions are no longer the best options for insuring continued production efficiency and component protection.

The lubricants that were appropriate for yesterday’s operating conditions are no longer the best options.

For years, asphaltic grease was the only option for open-gear lubrication at grinding mills (ball, rod and SAG) and kilns. Today, however, mill operators and others that use open-gear systems have more choices, many of which offer advantages that traditional asphaltic lubrication does not.

Because of their heavy nature, asphaltics require solvents or other additives to dilute the lubricant so it can be applied to the gear. Companies are paying for these solvents, which don’t contribute to lubricity or component protection. Asphaltics can be compromised by extreme temperatures and tend to create buildup in the root of gear teeth, which can lead to equipment damage.

The grease-type advantage

Grease-type lubricants can offer mill operators greater manageability and improved performance. They can be applied with the same spray systems as asphaltic lubricants, but grease-type lubricants provide better protection for the gear set, with less buildup in the gear teeth.

“If you can extend the life of the gear, you can save significantly on the cost of production,” says Greg Paluska, who leads Shell Lubricants’ team of LubeExperts, dedicated personnel for mining machinery. “You also can maintain or increase production efficiency and asset utilization.”

A key ingredient in the formulation of grease-type open gear lubricants is the solid additive matrix. This is typically some form of molybdenum disulphide (“moly”), graphite or a combination of both. These solid additives have significant advantages in reducing friction and increasing load carrying capability.

In theory, a reduction in friction results in a lower temperature and more efficient movement, ultimately putting less load on the motor. Grease-type lubricants also handle heavier loads better, which is critical to wear protection.

Grease-type lubricants may result in higher consumption rates depending on the type of mill and the operating conditions, but most operators find the slightly higher upfront costs are a small price to pay for improved gear life and lower maintenance costs in the long run.

The heavy synthetic option

As their name implies, synthetics don’t use a mineral oil base. Instead, they are built from base molecules to have a viscosity that rivals asphaltic lubricants. Unlike asphaltics, heavy synthetics are clear fluids with no solid additives, such as graphite or molybdenum. The load carrying capability and friction reducing properties come entirely from the viscosity of the lubricant.

With heavy synthetics, the load carrying capability and friction reducing properties come entirely from the viscosity of the lubricant.

“It’s relying on the viscosity to do all the work, whereas the grease-type lets some of the solid additives do the work,” Paluska says.

Because the molecules are purer, synthetics have a lower traction coefficient than asphaltics and grease-type lubricants. Their high viscosity, combined with performance additives that enhance their adhesiveness on gear surfaces, give these products excellent performance characteristics. In addition, the clear nature of synthetics can make gear inspection easier.

Synthetics are more expensive to produce than other open-gear lubricants, and as a result, they cost more. In addition, their high viscosity makes them difficult to pump in cold temperatures, and in some cases existing spray systems may need to be modified.

Understanding the latest advances in lubrication technology can save hundreds of thousands of dollars in repairs, avoid thousands of dollars an hour in downtime and reduce the frequency with which pinion gears must be replaced.

By considering lubricants that are better-suited to the demands of today’s operating environment, mill operators may find they can improve their operating efficiency, reduce maintenance expenses and enhance cost-effectiveness.

Greg Paluska, North America Technical Manager for Eastern US, has over nine years of experience in Shell Lubricants including experience with lubricant application and lubrication systems support for heavy machinery.

Visit lube-education.com/mining for the latest industry insights from Shell. Please direct all inquiries about Shell Lubricants to Cassie Hackstedt at Cassie.Hackstedt@shell.com.

Pit & Quarry Direct provides professionals in the aggregate mining industry with insights on timely innovations in equipment and technology. This newsletter was produced by North Coast Media’s content marketing staff in collaboration with Shell Lubricants.