Potential Vertimill® issues and their causes: Screw liners

Metso Outotec Vertimills^® provide various advantages over traditional ball mills, such as energy efficiency, reduced media consumption, smaller footprint and longer wear life. With their sustainability advantages, many customers are exploring the possibility of integrating stirred mills into their flowsheets, in both greenfield and brownfield projects. For plants that need extra milling or want to ensure a finer grind in their circuit, Vertimills can be an attractive option and their installed base has seen a rapid rise over the last several years.

Pushing the limits

In today’s competitive marketplace, operators may stretch the limits of equipment components to increase uptime and enhance production. But when screw liners and other wear parts are used to the limit of their useful life, they can cause damage to non-wear parts, including the body liner and screw shaft. Damage to these components can not only cause mill stoppage, but also carry a high price tag and long lead time for repair or replacement. In extreme cases, a worn screw liner may break, causing damage to the mill body or potential catastrophic mill failure.

An ounce of prevention – the benefits of frequent inspections

Ideally, Vertimill^® operators should initiate a regular maintenance routine early in the mill’s operating life. New operators are recommended to open the mill after 90 days of operation to perform screw liner wear inspection and inspect the mill afterward according to wear rates observed on the initial inspection. Operators should watch for screw and end liner wear, potential liner breakage, and shaft damage, and replace parts and maintain regular service to keep the mill performing at its best. This and subsequent inspections should include equipment service professionals who can

Experienced mill operators may overlook the value of including service professionals during inspections. However, service professionals can assess existing conditions together with historical relining trends, media addition rates, power draw during wear life cycle, media charge depth and the remaining wear life of liners replaced during maintenance shutdowns to provide a full picture of your mill and its maintenance health.

Where Vertimill^® technology fits in to your grinding operations, be sure to practice proper screw liner monitoring and maintenance and consult Metso Outotec’s trained service professionals to sustain your mill’s uptime and productivity and make the most of your investment. Our comprehensive service portfolio ranges from spares and wears to advanced lifecycle services. As the preferred services provider for our industry, our ambition is to deliver the best-in-class total cost of ownership.