One of the key maintenance activities undertaken at a mineral processing site is relining of grinding mills. This process requires lengthy shutdowns of the grinding mills, costing vast sums of money through lost productivity. Undertaken twice a year on average, a typical reline process can take between 50 and 100 hours, with each hour of lost production costing between A$50,000 and A$200,000 in revenue. Reducing the time required to reline by one day can recover millions of dollars in revenue lost through inefficient processes and under-used or inappropriate equipment.
As part of their commitment to improve the performance of their customers’ mineral processing concentrators, Russell Mineral Equipment (RME) has invested in the optimisation of the overall relining process as part of their service offering. “By looking beyond just the equipment they supply and taking a holistic view of their customers’ relining process, RME are able to demonstrate how the relining activities could be best organised and complimented with appropriate products and services, resulting in greatly enhanced productivity and significant cost reductions for customers.”
All RME customers are slightly different to one another, however the relining process commonly uses similar sophisticated and rapid transport systems to extract worn liners and install new ones, including advanced 7 or 8 axis placement machines and various bolt removal and fixing devices. The execution is constrained by the limited points of entry into the mill and the configuration of the working platforms around it.
Operators attempting to optimise the relining process are faced with a major challenge due to the high degree of variability for each element of the process. While estimations are the most common means of reline planning, they cannot evaluate, demonstrate or predict the effects on reline time of the introduction of new technology, additional labour, additional equipment, site modifications, or the natural variations inherent in a complex process.
“RME’s engineers have often been asked to predict the effect on relining times, of changing mill liner and reline variables. Aware of the optimisation challenge faced by mineral concentrator operators, RME investigated methods of modelling the reline process and observed how modern manufacturing environments used predictive simulation to optimise productivity and resources.” By integrating WITNESS into their approach and MILL RELINE DIRECTOR product, RME says it is able to extend its simulation capability to its customers, “thereby allowing customers to build a solid business case for investing in appropriate relining products and services while optimising relining processes at the same time.”
A model developed on Lanner’s WITNESS simulation platform is used to analyse the current reline operation at a customer site, providing statistically accurate, configurable, and dynamic simulation of their mill relining process. The data used in the evaluations is crucial to the validity and confidence to be had in the results and recommendations. RME addressed this by developing a database of numerous mill relining projects and using this as the basis for future predictions. All new projects are adding continually to this knowledge base. To manage the unique constraints for each mill, new data is obtained through the use of customised, long memory, rugged video cameras which capture the entire relining process. This footage is then analysed to identify individual process steps and the time required for each individual reline activity. RME then use these data points to construct statistical distributions that are used to create a ‘Reference Reline’, a virtual snapshot of a customer’s reline situation, and is the basis for evaluating options for each customer.
Using the constraints of the local environment, each customer’s budget and RME’s vast experience in mill relining, RME develops a series of alternative scenarios which are simulated and analysed. Each alternative scenario is then compared to the Reference Reline to assess the effectiveness of the proposed changes, the impact on overall reline time, equipment utilisation and individual reline activity efficiency. The model itself contains several hundred elements, each imparted with behavioural data drawn out of many hours of actual reline video footage. RME analysed the footage second by second to produce around 50,000 discrete reline activities along with associated meta-data for inclusion within the reline model. These outputs were then evaluated to ensure that the behaviour of the reline model was consistent with real world observations and reline practices.
“MILL RELINE DIRECTOR is a hugely valuable solution to provide to our customers – whether they are looking to optimise an existing process or design a new facility,” comments Geoff O’Shannassy, MILL RELINE DIRECTOR Engineer, RME. “For individual relining facilities at existing operations, RME starts with either video capture and other plant data, or completion of a detailed Data Sheet. For mills using the Data Sheet approach, typical values derived from a database of actual relines are used. And for new facilities, the model quantifies good plant design in order to inform and quantify investment decisions, as it provides reliable ‘real world’ times for typical equipment, processes and solutions, thus enabling mills to optimise practices from the outset.”
