Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1032074
ML taking place at the surface level. It is caused by combus- tion byproducts, hydrogen sulfide, bacteria, salts and other factors. is type of wear can appear on many different components and applications, depending on the environmental surroundings. Surface fatigue also acts as a supplier to particle contamination. is undesired evolution is the result of repeated loading over time, which leads to pitting and flaking of the component surface. Surface or contact fatigue is most prevalent on the mesh point of gear teeth as well as other rolling friction surfaces. In addition, particle contamination can affect the rate of additive depletion. Additives become a limited resource for protection, as they are designed to be sacrificial in nature while adhering to surfaces or contaminant particles. As the additive count begins to diminish, fewer particles can be eliminated, and component surfaces are inadequately shielded. Contam- ination then becomes a greater threat. Particle Contamination Elimination Strategies Among the strategies for eliminating or minimizing particle contamination, hardware modifications and component modifications are two available options. Modifying lubrication hardware can have an immediate impact on particle contamination and often comes in the form of breathers and filters. When selecting a filter, several factors should be taken into account, such as the location, configuration, operating pressure, beta ratio, micron size and flow rate. Breathers present another form of protection if properly outfitted. When choosing a breather, consider the pressure in the housing or reser- voir, fill port clearance and exposure to the environment. Component modif ications can also minimize particle contamination. Several elements should be evaluated, including the reservoir access points, system pressure and bearing type. While reservoirs are ideal for visually inspecting the lubricant on a large scale, seals and hatches are often left open, allowing external parti- cles to gain access to the system. Ensuring that hatches are properly sealed and modifying existing access points that have a poor design configuration can dramatically reduce particle ingression. It also is important to assess the system pressure, as positive pressure on a tank or reservoir can serve as a deterrent against airborne particles. Another option would be the addition of magnetic or electrostatic sepa- rators to remove ferrous and opposite-charged particles. One final consideration is the bearing and motor selection. Utilizing sealed or shielded bearings and enclosed motors can help to minimize particle contami- nation in certain applications. Temperature Dispersing heat is a primary function of a lubricant. erefore, temperature plays a critical role in a lubricant's physical characteristics. Lubricants that must cope with substantial temperature fluctuations over time tend to have a reduced life cycle. When lubricants function at the edge of their operating temperature range, several issues may arise. e most prominent complications are thermal degradation, oxidation, varnish and film strength depri- vation. On the high end of the temperature spectrum, viscosity will be affected with a thinning of the base oil. is can also lead to acidic accumulation, sludge and varnish through weak oxidation stability. ese issues can result in flow restriction or starvation along with restricted component movement. Lower temperatures impact viscosity as well, negatively altering the flow rate properties of certain lubricants. Temperature Moderation Strategies To limit temperature-related issues in a lubrication system, it is best to evaluate your lubricant options and component modifications. Re-examine the current oil or grease in systems that have concerns of recurring failures. Ensure the viscosity of the oil or consistency of the grease is appropriate for the system. e correct oil level or lubricant amount is key as well. Reservoirs with oil level indicators that are out of range or bear- ings with too little or too much grease often operate with temperature anomalies. is information can be checked through sight glasses and level gauges for oil www . machinerylubrication.com | September - October 2018 | 47 33% of lubrication professionals say premature lubricant failure is a problem at their plant, based on a recent poll at MachineryLubrication.com