Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/793941
T ypically, when mine operators are asked what they are doing for their lubrication program, the response is generally along the lines of scheduled preventive maintenance (PM) and used oil analysis provided by the equipment manu- facturer. Unfortunately, these activities alone do not constitute an effective program. This article will explore lubrication strategies for "big iron," which includes large earthmovers such as rope shovels, hydraulic shovels, drag - lines and bucket-wheel excavators. FAILING GEARCASES ON ROPE SHOVELS A pair of rope shovels working the central Appalachian coal region had planetary gear- cases on the propel drives (i.e., the tracks). On average, one of four planetary propel gearcases in service would fail every six to eight months. In a matter of two years, it was conceivable that all four gearboxes would be replaced. A single gearcase cost approximately $400,000, and lead times were increasing to six months. To further complicate the situation, most failures were catastrophic, and the gearcases could not be rebuilt. So what was causing the gearcases to fail? Lube changes were being conducted approxi- mately every six months on regularly scheduled PMs, and oil samples were being taken nearly every three months, but these tasks alone were not detecting failures. Consequently, there was little belief from the maintenance team that used oil analysis was effective. Part of the problem was the lack of new oil sample analysis with which to compare the used oil. Lubricants for "big iron" typi- cally have high viscosities (approximately 1,000 centistokes) and unique additive packages. The only way to know if you have lost your additive package in your used oil is to have a new oil reference. Another problem was the test slate being performed on used oil at the laboratory. As with most used oil analysis, labs sell a basic test package that costs $15 to $20 per sample. Typically, this includes a 19-element atomic emission spectroscopy (AES) report, a viscosity test and an indication of moisture content, which is usually determined by a crackle test on a hot plate. With "big iron," www.machinerylubrication.com | March - April 2017 | 7