Data-Driven SAG Mill Ramp-Up Lifted Cowal Throughput 14%

Evolution Mining’s Cowal Gold Operations in New South Wales lifted SAG mill throughput by approximately 14% during the post-reline ramp-up period by replacing conservative restart habits with a structured, data-driven strategy built on Molycop’s MillROC and MillSlicer monitoring tools. The result, achieved over the first four weeks after a major shutdown and relining campaign in March–April 2025, came without any abnormal liner damage.

Cowal runs a conventional comminution circuit — primary crushing followed by semi-autogenous grinding and ball milling — processing a blend of open pit and underground ore into downstream flotation and leaching. With a relatively coarse target grind of roughly 180–200 microns, the plant is not highly sensitive to grind size; its performance depends on maximising throughput from the installed milling capacity. That makes the post-reline window the critical moment. Traditional practice after relining is deliberately conservative to protect the new liners, but the cost is sub-optimal breakage, reduced power draw and an extended ramp-up during which gold production is lost. MillROC provided real-time monitoring of load, power and throughput with centralised trend analysis, while MillSlicer detailed liner strike distribution, charge behaviour and the conditions where slurry pooling was suspected. Ball charge was tracked with power-based estimation models and steel consumption rates, allowing proactive control of charge levels. Progressive increases in ball charge and mill load improved power utilisation, impact efficiency and steel-to-rock interaction, and impact levels stayed within acceptable limits throughout, with monitoring enabling intervention before liner stress became excessive.

The procurement lesson is that ramp-up performance is bought, not hoped for. A relining shutdown is a fixed cost — the mill earns nothing until it is back at steady state — so the four-week recovery curve directly converts into production revenue, and the instrumentation that shortens it deserves line-item treatment in the equipment budget rather than being treated as an aftermarket afterthought. Buyers specifying new grinding circuits, or any large rotating equipment with similar restart sensitivity, should ask vendors to quote monitoring and analytics packages with the machine: what sensors ship installed, what commissioning support is included for the first restart, and what reference sites can prove a shorter ramp-up rather than promise one. The same logic extends to the pump and slurry circuits downstream — instrumentation that exposes charge behaviour, pooling or load drift protects liners and impellers alike. Molycop’s own framing of ramp-up optimisation as an ongoing process, with ore-type refinement and analytics integration still ahead, is the honest version of a vendor story; buyers should weight suppliers who commit to measured post-installation improvement over those who stop selling at commissioning. In capital equipment, the cheapest throughput gain is often the one measured during the weeks right after the shutdown.