BX-Coated Bearings for Driven Shaft Pinion Support in SAG & Ball Mills

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We are pleased to share a milestone engineering project recently implemented by Atlantic Bearing Services (ABS) in close collaboration with SKM Industrial at one of Chile’s major copper concentrators.

This initiative marks the pioneering application of BX (Black Oxide) coated spherical roller bearings in a critical driven shaft pinion support configuration within a high-demand SAG and ball mill drive system.

Developed through the integrated capabilities of ABS and its brands ACB Custom Bearings and MGS Gears, the solution was delivered during a record production cycle, without interrupting operations, reinforcing operational stability in a mission-critical grinding environment.

Beyond this installation, the engineering model applied here is directly transferable to other industries operating under severe mechanical and reliability constraints.

Front view of BX-coated spherical roller bearing engineered for driven shaft pinion support in SAG and ball mill drive systems.

• Sector: Mining-Cooper
• Equipment: SAG & Ball Mill grinding systems
• Country: Chile
• Criticality: High dynamic gear mesh loading, Misalignment and shaft deflection under load, Severe lubrication regime (mixed rolling–sliding conditions).

Large-scale copper concentrators operate SAG and ball mill grinding circuits under continuous duty and severe mechanical loading. In these systems, the driven shaft pinion support plays a critical role in drivetrain stability and overall process availability.

In this installation — with more than 30 years of service — load fluctuations, transient operating conditions, and lubrication regime variations increased the risk of surface distress and premature support degradation.

ABS supported the replacement and upgrade of the driven shaft pinion support system for Lines 1 and 2 without interrupting operations during the 2024–2025 production cycle. The intervention was executed during a record production period, highlighting the operational criticality of maintaining stable grinding circuit performance.

SAG and ball mill grinding circuit operating within a large-scale copper concentrator.

Schematic representation of the SAG and ball mill grinding circuit, illustrating material flow, mill drives, and auxiliary systems within a copper concentrator.

The project involved replacing the driven shaft pinion support system in a SAG/ball mill circuit with more than 30 years of service, while maintaining continuous operation under high dynamic loads and strict availability targets. Conventional bearing arrangements showed sensitivity to misalignment and load fluctuations in the pinion drive, leading to localized load concentrations (edge loading) and increased surface distress under mixed rolling–sliding conditions. Shaft and housing deflection under operating loads further amplified these effects, accelerating wear and reducing support stability. No operational precedent existed for applying BX-coated spherical roller bearings in this specific driven shaft pinion configuration, requiring rigorous, risk-controlled engineering validation prior to implementation.

The implemented solution consisted of integrating a BX-coated spherical roller bearing as the core element of the driven pinion shaft support system, replacing the existing bearing arrangement within the shaft–pinion assembly.

Applied in the non-locating support position, the bearing provides stable radial load capacity and misalignment tolerance under continuous operation, helping to reduce constraint-induced load concentrations within the assembly.

The solution was engineered to match actual grinding circuit conditions, including mechanical loads, thermal behavior, and alignment constraints, ensuring long-term reliability in a demanding mining environment. The final configuration was implemented as a direct replacement without altering the overall drive architecture, resulting in improved functional stability and performance of the driven pinion shaft system.

3D exploded view of the custom driven shaft pinion assembly featuring an integrated BX-coated spherical roller bearing support, engineered for high-load ball mill pinion drive applications.

1. ACB Bearing Housing for Driven Shaft Pinion Support

2. MGS Gears Shaft & Pinion

3. ACB Black Oxide–Coated Spherical Roller Bearing

ABS delivered a BX-coated spherical roller bearing solution that reduced delivery lead time from 40 to 26 weeks, optimized the driven shaf pinion support arrangement, and enhanced reliability in a critical grinding operation where each hour of mill downtime can exceed USD 150,000.

The non-locating support arrangement improved misalignment compliance, minimizing internal constraint forces and helping maintain stable load zones and alignment under continuous high-load operation. These improvements reduced the potential for premature surface distress and increased overall operational robustness in a critical grinding application. The solution supports sustained equipment availability and long-term reliability in environments where unplanned mill downtime carries significant operational and economic consequences.

In Chile, ABS has positioned itself as a reliable alternative for SAG and ball mill drive system applications at one of the world’s largest copper mining operations, where production reached approximately 1.305 million tons (100% basis) in 2025.

Beyond this installation, the combined capabilities ABS, ACB, and MGS Gears are directly transferable to other critical rotating equipment and industrial sectors facing similar challenges in support stability, load distribution, and long-term reliability under demanding operating conditions.