its operations to achieve the highest levels of effi ciency. “To ensure productivity and profi tability in the future, we decided to develop a preventive maintenance improvement programme, which is comprised of a master plan to maximise availability and minimise bottlenecks, through a long-term and sustainable approach. Its objective is to detect potential problems in advance and maximise the performance and availability of existing equipment,” explains Dalibor Dragicevic, vice president for processes at Collahuasi. In addition to the VPA fi lters, Collahuasi also has other equipment from Metso, such as semi-autogenous (SAG) grinding mills, ball mills and and Vertimills.

Ageing equipment poses a challenge T anks to the collaborative relationship between Collahuasi and Metso, a joint diagnostic meeting was held to review the main needs and potential improvement to the fi ltrate- concentrate level, which was related to the requirements of its VPA vertical fi lters to increase their production capacity while also increasing the overall reliability of the system. Due to the high productivity

requirements and over 20 years of use since installation, the fi lters were showing a high degree of wear and misalignment, which reduced their availability due to the extra maintenance required by the fi lters and considerable unplanned downtime. During the review stage of the

overhaul, a joint decision was made to make improvements and upgrade the control systems, lubrication and structure of the equipment to achieve higher levels of availability. T e challenge for Metso resulted in upgrading the control systems to

the latest technology, achieving values of over 92% availability and 100% of design capability. T is involved reinstalling and upgrading equipment in less than 20 days to minimise lost production. T e engineering coordination, parts procurement and planning activities began six months earlier to ensure the complete compatibility and successful outcome of this upgrade.

Comprehensive technological solution T e extensive upgrade of the equipment involved multiple steps. T e Metso team fi rst proposed improving the original design capacity by updating components and systems to produce some important benefi ts. For this, they focused on the main problems that were causing the structural misalignment of the fi lters. To solve the structural problems, the fi lter was completely disassembled and over 80% of its parts were replaced with new parts using a nanocoating technology for corrosive environments. Using this approach would double the lifespan of the key parts and components and reduce potential downtime. To achieve the optimal selection of fabric, a pilot fi lter was implemented at the worksite to take samples of concentrate. T e samples were then used to help defi ne the proper fabric for the fi ltering process given the specifi c mineral conditions that Collahuasi was processing. In many situations, these types of tests involve using Metso laboratories located in Brazil and Finland. However, with the pilot fi lter on site, it was possible to perform all the tests in situ with the client, improving the selection and making it easier and quicker to get the results.

Another technological improvement introduced was the implementation

OCS-4D, an advanced process control solution. T is assisted in determining the optimal control modes through analysing the interplay between the selection of fabrics and maintenance events. Finally, the chute was also examined for possible improvement opportunities. As the VPA fi lters discharge the fi ltered material (cake) into the chute, it was subjected to high rates of wear, causing a reduction in performance. Various designs and options were examined to improve ease of maintenance and thus reduce downtime. “Searching for a design that

improved maintainability, we implemented new, modular design upgrades to the chute so that it could receive maintenance section by section. T us, when a specifi c part shows signs of wear, we can disassemble that part and change it quickly. T is is also an improvement that was tailored for the client, given that with the original design we had to disassemble the entire equipment to be able to change some parts,” says Alejandro Bravo, manager of Minerals Process Equipment.

Expansion of the project to all VPA fi lters Given the success of the project, Minera Doña Inés de Collahuasi is evaluating the implementation of the same upgrade concept in other VPA fi lters as part of its asset management plan. “With this solution, we have been able to meet some of the availability goals we set for 2017. T e fi lter works according to the plans drawn up with Metso, which helps us to continue operating effi ciently,” says Cristián Barros, senior engineer for Symptomatic Process at Collahuasi. ● 25

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