Preventing Major Asset Failures – How to Protect the Heart of your Mine (Grinding Mills) *D.A. Bordi1 1Metso (*Presenting author: damon.bordi@metso.com) ABSTRACT As global ore grades continue to decline, mining operations are increasingly reliant on larger and more powerful grinding mills to maintain productivity and profitability. These mills are the heart of the concentrator, operating nearly continuously to process vast quantities of material. However, if not properly managed, the growing scale and complexity of grinding equipment heightens the consequence of major asset failures, which can result in significant downtime and costly production losses. This paper examines several critical mill failure modes, including fatigue-induced structural damage, trunnion bearing failures, and drive train reliability. Drawing on industry experience and recent technological advancements, it explores design, manufacturing, and installation strategies that can eliminate or minimise these risks from the outset. By combining sound engineering design with proactive maintenance and targeted upgrades, mining operations can safeguard their grinding mills against catastrophic failures. The insights provided aim to guide both new projects and ongoing operations in specifying, operating, and maintaining these vital assets, ensuring long-term reliability and productivity. KEYWORDS Grinding mill, SAG mill, ball mill, mill drive, finite element analysis, hydrostatic bearings, hydrodynamic bearings, asset health, gearbox, system analysis, modal analysis, harmonic response analysis 1. Introduction Grinding mills are the heart of most minerals processing plants. They are typically specified and purchased very early in the plant development schedule because they sit on the project’s critical path from a lead-time perspective and represent a significant portion of the overall equipment budget. Once the crushing and grinding circuits are defined, the remainder of the plant configuration follows. Selecting the correct mill type, size, design specification, and technology level is therefore essential, as these decisions directly influence plant performance for the entire life of the operation. Grinding duties are arduous. Due to their significant size, cost and complexity, mills are almost always specified to operate 365 days a year, 24 hours a day, with availability exceeding 95%. During that time the mills will run at, or close to, maximum load and power. The scale and expense of the equipment also make redundancy impractical, meaning that unplanned downtime
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