GREASES
Revolutionising open gear lubrication in mills with novel anti-wear additives
Dr Sergei Mamykin, Tribologist, copper filming technology developer, at NEOL Copper Technologies and Rafe Britton, Lubrication specialist and consultant at Lubrication Expert.
Lubrication is critical in ensuring the optimal performance of mills worldwide. The key area that poses a significant challenge is lubricating the open gear sets that drive ball mills, grinding mills, kilns and dryers. Large, exposed mill gears are often found in cement, power generation, and mining industries and are essential components that demand meticulous care and maintenance thanks to the significant loads placed upon the gear teeth. The asset’s value and the importance of uptime make open gearing a critical lubricant application.
Lubrication challenges in open gear sets Open gear sets in mills present unique challenges due to their size, exposure to harsh environmental conditions, and the significant load they carry. Unlike enclosed gears, open gears are subject to more severe contamination with dust, water, and debris, which can accelerate wear and tear. The sheer size of these gears also requires the lubricant to have excellent adhesion properties to remain effective over the entire gear face, despite the centrifugal forces and varying speeds encountered during operation.
Misalignment issues are a common problem in mill operations and can lead to uneven distribution of loads across the gear teeth. This uneven load distribution results in excessive heat generation, further stressing the lubricant and leading to an uneven film thickness across the face of the gear. An effective lubricant must protect against wear and possess properties that mitigate these thermal challenges.
Choosing between open gear greases and lubricants Many products have been developed over the years to cope with the challenges described. The two main product groups are semi-fluid greases, and liquid lubricants (although these can be further differentiated into asphaltic, polymers, and high viscosity synthetics). The decision to use either an open gear grease or an open gear lubricant hinge on several factors. Open gear greases typically provide a robust protective layer and are adept at sealing out contaminants. Their consistency and tackiness can provide better adhesion, and they can be beneficial in scenarios where environmental contamination is a significant concern.
On the other hand, open gear lubricants, which are usually more fluid, offer the advantage of more straightforward application and better penetration, especially in high-speed or heavily loaded gears. They are designed to form a thin, protective film that ensures consistent coverage and reduced friction, essential for gears operating under high load conditions.
Challenges for the industry
The challenges faced by the industry in open gear lubrication are multifaceted. Environmental contamination, misalignment issues, and the need for consistent thermal performance create a complex scenario where conventional lubricants often fall short. Traditional approaches struggle to address the evolving demands of modern mill operations,
Continued on page 22 LUBE MAGAZINE NO.180 APRIL 2024 21
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