Fatigue issues may arise from insufficient fatigue strength in the original design, material washout, poor installation practices, or inadequate maintenance. The mill body undergoes one full stress cycle with every revolution. With typical operating speeds of around 10 to 12 rpm, and with mills expected to run continuously for the life of the mine, the rotating structure rapidly enters the realm of high-cycle fatigue. To ensure long-term durability, the structural components and their connections must be designed carefully for fatigue resistance. If the design is inadequate or if manufacturing quality is poor, the likelihood of bolt failures or cracking in the mill body increases significantly. To that end, mill longevity can be maximized by utilizing a combination of applied learnings from decades of grinding mill design and operation, along with intelligent adoption of modern design tools. This includes leveraging advances in computing that facilitated significant development in engineering best practice. These developments allow for more-accurate drafting, improved collaboration globally, more efficient work practices, and vastly increased capacity for mathematical computation. Of note, the increased simulation capacity can allow extremely detailed fatigue analysis practices. Which, if used correctly, can guide design changes that dramatically improve fatigue resistance. With modern access to Finite Element Analysis (FEA) hardware and software, conducting a rudimentary fatigue analysis for a grinding mill is now relatively straightforward. However, the accuracy of such analyses is highly dependent on the underlying assumptions. The analysis geometry should be suitability detailed, the setup must be carefully defined, and results must be thoroughly scrutinized. To mitigate the risk associated with assumptions and model simplifications, the best fatigue analysis methods are supported by, and developed with reference to, field-stress measurements of operating mills (Bordi & Green, 2023). Recent validation campaigns have shown that accurately reproducing in-service stresses requires adding significantly more detail within the simulation environment. Two-dimensional (2-D) simulation methods, which were considered state-of-the-art in the 1990s, have been superseded by far more detailed three-dimensional (3-D) analyses. At the SAG conference in 2015 Green et al. (2015) reported that the inclusion of non-axisymmetric geometry and loading details, together with explicitly modelling fasteners and frictional contact between flanges, reveals high stress regions which would have otherwise been underreported by as much as 50% in an equivalent 2-D analysis. Although there are practical limits to the level of detail that can be incorporated into a finite element model, modern computing capability continues to extend these limits, and there is now little justification for omitting stress inducing geometric features. By developing a model that accurately captures the true performance of a mill in operation, critical stress regions can be readily identified and optimised. These regions, which include radial and longitudinal split flanges, can be refined by blending geometric transitions, tuning the stiffness of surrounding geometry, and a range of related optimisation techniques (Green et al., 2015). To translate a highly fatigue resistant design into equipment with maximum availability and reliability, manufacturing and installation quality must be prioritised. The following aspects are particularly important when defining and conducting quality related
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