Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/136253
to determine if the estimated oil drain intervals are acceptable. • Implement the optimized oil drain interval after testing. Fleet profiles describe the equipment, service severity, operating conditions and maintenance practices. Different engine models contaminate engine oil at different rates. The same engine may have a different oil volume in different equipment. Fuel and oil consumption rates vary for different equipment and service severities. The capability of the oil and the engines must be considered to properly estimate oil drain intervals. Studies show that a liter of fleet oil possesses the ability to neutralize and suspend the contamination generated by burning 300 liters of fuel. High-quality premium oils have the ability to neutralize and suspend the contamination generated by burning 500 liters of fuel. Case Study: Sishen Mine Situated in the Northern Cape of South Africa, the Sishen ironore mine is an open-pit operation with the deepest area of the mine about 492 feet deep. The hematite iron ore at Sishen is extremely abrasive, and repairing and circumventing wear is the major cost component of maintenance. Tests were run on the mine's haul trucks to extend service intervals, reduce maintenance costs through high-efficiency filtration and increase production by better availability. The goal was to increase the service intervals from 500 hours to 1,000 hours. The biggest barrier to overcome was the life of the hydraulic oil and filters. To achieve the target of 1,000-hour service intervals, the mine considered the factors that have an influence on the life of lubricants and filters, as well as reliability and safety risks. Oil analysis was used to determine the oil condition. Samples were taken and analyzed weekly by the in-house lab. The 500-hour wear limits were taken as the target for 1,000-hour service intervals. As could be expected, Figure 1 shows iron exceeding the limit of 28 ppm at about 600 hours. Test results showed that the mineral oil was still fit for use after 1,000 hours. The main problem was the increasing of wear metals after about 650 hours. Full-flow filters in the engines were replaced with advanced Venturi combo full-flow bypass filters. The bypass media was developed for organic contamination (oil sludge) separation. An additional depth-style bypass filter was also added. It allowed a certain amount of oil to flow from the main gallery of the engine oil line, and by means of the element depth, filter out the impurities to 1-micron size. The cartridge used was made of densely wound, pure coniferous, long-fiber wood pulp paper. It works both by absorption and adsorption in a continuously recycling process. The long fibers of the paper absorb water formed by either the combustion process or by condensation. As the oil passes through the cartridge, minute carbon, wear metals and silicon particles are extracted from the oil by adsorption. The removing of Installing bypass filters was key in water inhibits the production of extending the service intervals on the haul trucks at the Sishen mine. acids that both degrade the oil and cause excessive wear. The simultaneous removal of minute contaminants as they occur enables the oil life to be extended. After the filter modification, a test was run on the same haul truck. The 1,000-hour target was achieved within the set wear limits of 28 ppm iron. Figure 2 shows results from a second test in which the iron limit was exceeded after 1,195 hours. Several tests were performed on three other haul trucks, and the same results were achieved. Figure 2. Analysis of wear limits in mineral oil after bypass filter installation Figure 1. Analysis of increasing wear metals in mineral oils before installing bypass filters In October 2007, the haul truck fleet's service intervals were increased to 750 hours, and every truck was monitored closely by using oil analysis. No problems have been experienced so far, but the haul truck availability immediately increased by 4 percent. In conclusion, it has been shown how extended service intervals can lead to enormous savings. By using oil analysis and setting target cleanliness levels along with proactive maintenance, a significant downward trend in lubricant consumption and maintenance costs can be achieved. The availability of equipment also will increase, allowing for more production, higher revenue and increased utilization of equipment. www.machinerylubrication.com | May - June 2013 | 13