A few years ago, the Kinross Paracatu mill was experiencing a high recurrence of unscheduled shutdowns due to failures with its lubrication system. The semi-autogenous grinding (SAG) mill is the main production line in the concentrator plant for Kinross, which is a gold mine operation located in Minas Gerais, Brazil. Cash flow losses of more than $2 million were reported in 2013, with at least 79 events identified as lubrication failures.
The lubrication system is characterized by three idler pumps, two high-flow idler pumps, four gear pumps, two axial piston pumps and four flow dividers. An initial analysis determined the failures were the result of oil contamination, incorrect drum storage, a corroded return pipe, low-performing heat exchangers, water in the pumps, worn flow dividers, inappropriately designed filters and slurry ore leakage.
To solve the lubrication failures, a number of actions would be necessary. New routes were created for inspection and oil analysis, with seven new points for oil sample collection and a new calibration standard for the system. Heat exchangers and damaged hoses were replaced. Pressure filters and filter elements were redesigned. A new valve was used to control the oil temperature. New flow dividers were specified, and a new drainage pipeline was installed. An air blower, quick coupler and breather were also added to the reservoir. The trunnion's protective seal was changed, and ore slurry leakage was prevented in the discharge cover. An oil level digital sensor was installed along with a relative humidity sensor with the alarm set at 60 percent. For quality control, an oil purifier and a particle counter were purchased. The investment cost for all of these actions was approximately $200,000.
After implementing the improvements, the mill was able to reduce the level of oil contamination from an ISO code of 24/23/21 to 17/15/11. In 2014, production losses decreased to $950,000, with 39 lubrication failure events. For 2015, the reported losses dropped to nearly $350,000, with only seven lubrication failure events. Revenue also increased by $2.8 million for the two years.
In addition, a cultural change took place at the mill. Plant personnel recognized the importance of lubrication, and there was an increase in morale for the lube technicians. The reliability of the mill's lubrication system also improved from 4.58 to 55.51 percent per month, making the company's relatively small investment well worthwhile.