Engineering & Mining Journal

MAY 2018

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FUELS AND LUBES MAY 2018 • E&MJ; 41 www.e-mj.com asphaltic "blackjack" compounds to en- hanced formulations that have specific compositions ranging from light-viscosity oils with solid additives, heavy-viscosi- ty oils, to combination fluid grease and synthetic oils. Although the new products are easier on the environment, their com- position makes it a bit tricky to achieve the level of grease-film thickness and ad- hesion needed to provide optimum pro- tection. The approach suggested by most lubrication experts is to apply this type of grease in smaller quantities at more frequent intervals, and if possible, take frequent temperature readings on gear surfaces to confirm that the layer of lubri- cant is adequate and evenly distributed. When applied correctly, enhanced gear lubes can offer a number of attrac- tive advantages that include overall ma- terial and energy cost savings, a cleaner and safer work environment, and in some cases, the power to heal. The latter advantage was explained in a paper presented by authors from Texas, USA-based Lubrication Engineers Inc. at a 2015 conference sponsored by the South African Institute of Tribology. The prob- lem, they explained, is that when an open gear is damaged, the surface of the gear tooth contact area is roughened by scor- ing, pitting and spalling. Removal of the metal causes areas of higher stress and loading on the open gears, which over time increases the wear and damage to the gear teeth. However, use of a high-performance open-gear lubricant can help "heal" the gear surface, as the high film strength and film thickness of the lubricant redistrib- utes the load over the surface area. This redistribution of load ultimately evens out to a point of equilibrium and results in a "healed gear" appearance, and small pits often close up completely. Not all open-gear lubes are convention- al heavy greases. Bel-Ray, for example, re- cently introduced Molylube open gear and rope lubricant, an aerosol product suitable for use on general industrial open gears, pins and bushings, chains, wire ropes, cables, drive chains and sliding surfaces. The company describes it as a highly te- nacious lubricant that ensures adherence to the gear teeth, creating excellent resis- tance to throw-off and slinging and pro- viding anti-wear, water resistance and rust and corrosion protection associated with demanding mining and other heavy indus- try equipment applications. As electric motors increasingly become incorporated into various forms of mobile and stationary mining equipment, correct application and maintenance techniques for motor bearings will become more im- portant as well. In these applications, an overzealous or inattentive worker can cause major motor problems with just a few extra, unneeded squirts from a grease gun or by mixing incompatible grease formulations. Noria Corp., an Oklahoma, USA-based lubrication consulting, training and pub- lishing firm, noted the ways in which improper motor bearing lubrication can cause equipment failure. These include: Incorrect Lubricant – Most oil suppliers have grease that is specifically designed for electric motors, which is different from their multipurpose extreme purpose (EP) grease. Grease Incompatibility – Greases are made with different thickeners, such as lithium, calcium or polyurea. Unfortunately, not all greases are compatible with each other, even those with the same thickener type. Motor Casing Full of Grease – If the grease cavity is overfilled, and high pressure from the grease gun is applied, the ex- cess grease can find its way between the shaft and the inner bearing cap and press into the inside of the motor. This allows the grease to cover the end windings of the insulation system and can cause both winding insulation and bearing failures. Lubricant Starvation – There are sever- al possible causes of lubrication starva- tion. The first is insufficient grease being added during installation. The second is inappropriate, elongated relubrication in- tervals. The third involves the possibility that the oil has separated from the thick- ener base due to excessive heat. Overpressurization of the Bearing Hous- ing – Overpressurization of the bearing housing causes stress on parts that were not designed to handle the pressure. Keep in mind that the standard manual grease gun can produce pressures up to 15,000 psi. Overheating Due to Excess Grease – Too much volume will cause the rotating bear- ing elements to churn the grease, trying to push it out of the way. This results in parasitic energy losses and high operating temperatures, and increases the risk of oil separation and bearing failure. Klüber, a global supplier of specialty lubricants, recently introduced Kluber- sustain GW 0-460, an industrial gear lube that uses water as a functional constituent. It's the first product in what Klüber envi- sions as a family of water-based lubricants that can offer both environmental and per- formance benefits, and the company sees a good correlation between these future products and the mining industry trend towards electrification of power trains. E&MJ; asked Markus Burbach, Klüber Lubrication's head of marketing and ap- plication engineering-North America, for additional details about the hydro-based product line and its potential advantages for mining applications. "Klüber Lubrica- tion aims to develop a complete portfolio of Hydro Lubricants for a variety of industrial applications by 2025. Klubersustain GW 0 460 is the first available Hydro Lubricant for closed gears on the market. We are currently looking for development partners interested in jointly testing this specialty lubricant and working with us to further ad- vance its properties and determine for what applications it can be most advantageous. "This can include gearbox applications in the mining industry. The electrification of underground mining equipment could be a potential area of use. This is because of the lubricant's superior protection against electro-corrosion and the reduced risk of parts damage caused by electric arcs due to the excellent electric-conduc- tivity of Hydro Lubricants. Improved fire protection is another benefit of Hydro Lubricants, which can be of interest to OEMs and operators in the mining indus- try striving to increase workplace safety. "The main difference between Hydro Lubricants and conventional lubricants is that water rather than oil serves as base fluid," he explained. "Base fluid typically accounts for about 70-90% of a lubri- cant. Lubricants in which oil serves as base fluid can cause environmental pol- lution when discharged into soil or water. Replacing oil fully or partially by water reduces this risk. Additionally, Hydro Lu- bricants exhibit super low friction proper- ties and possess excellent cooling capac- ity which reduce operating temperatures, energy consumption and CO 2 emissions. "We will focus our development efforts on applications where Hydro Lubricants lead to equal or superior performance compared to conventional lubricants. Thus, we do not expect any significant tradeoffs to be necessary [in handling, storage or usage] for applications suitable for Hydro Lubricants," he concluded.

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