Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/136253
COVER STORY The timing of an oil and filter change is important, but even more important is the strategy to proactively improve conditions that extend oil life. When applied correctly, proactive maintenance strategies can double or triple lubricant and filter life. This is achieved by reducing the conditions that stress the oil and filter. The following is a list of factors that influence the life of a lubricant: Contamination Contamination control is indispensable in preserving the integrity of all material in power and motion systems. Without it, few if any systems could ever achieve their intended purpose, let alone their expected service lives. Contamination control offers the assurance needed to achieve efficient, reliable and economical production of the "necessities" and "amenities" of our modern civilization. Knowing the potential and probable sources of contaminants helps to establish an effective exclusion program. Generally, three fundamental modes contribute to contamination: 1. Those injected by people (implanted during manufacturing or induced in the field during maintenance, repair or overhaul operations). Effects of Particle Size on Roller Bearing and Pump Life In a recent case study, contaminant particle size was controlled by the use of filtration. The study concluded that there was a dramatic increase in bearing and pump life when the majority of particles of 3 to 5 microns and larger were removed from the lubricating oil. While several factors cause rapid deterioration in service life, two of the main reasons are: • Abrasion caused by particles greater than 3 microns bridging the dynamic clearances provided by the oil film. • Large concentrations of small particles rolling through the oil film under pressure. This eventually leads to surface fatigue of the metal, causing pitting and ultimately bearing and pump failure. The study showed that bearing and pump life should increase significantly with lower particle concentration. 2. Those generated by the systems (created tribologically, chemically or by desorption). 3.Those ingested by the machine (introduced by inhalation of dust, air and water; encroachment of energy; and migration of microbes from the environment). The control of contamination in machinery is pointless if contaminated or below-specification lubricants are used, or if clean lubricant is being handled so carelessly that it enters machines in a contaminated state. Much work should be done in close cooperation with the lubricant suppliers to ensure that clean lubricants of the right specification are used in a particular application. High Fuel Consumption Inefficient engines contaminate by combustion byproducts including soot, fuel and fuel residuals, sulfur, acids and water. These contaminants distress the quality of the lubricant, resulting in filters going into bypass very quickly. Blow-by Worn engines, timing/injector problems, lugging, incorrect rack settings, excessive idling, cold operating conditions and high elevations can all contribute to increase blow-by. This adds soot, fuel and other contaminants that distress even the most robust lubricants. Coolant Leaks Glycol and water sharply disrupt dispersancy and contribute to a host of other problems such as corrosion, deposits, filter plugging, etc. Fuel Dilution and Fuel Quality Fuel dilutes additives and introduces sulfur and aromatics into crankcase oils, which will affect viscosity. Lubricant and filter life is influenced by the quality of diesel fuel and natural gas, especially relating to sulfur levels. Air Cleaners Blocked air filters result in the engine being starved. This causes overfuelling, leading to higher levels of soot entering the crankcase oil. Running Conditions Lugging, stop-and-go driving, intermittent service, cold ambient temperatures, idling, etc., all influence the life of the crankcase oil. Oil Level After 28,000 hours of operation, this crankshaft (left) and camshaft (right) from a haul truck only needed polishing before being reused. 10 | May - June 2013 | www.machinerylubrication.com Low oil levels concentrate heat, contaminants and catalytic wear