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"Which extreme operating condition most affects lubrication: high temperatures, low temperatures, excessive vibration, dusty environments, etc.?"
A lubrication system’s environment can play a significant role in its longevity. Temperature abnormalities, extremely wet or dusty surroundings and excess vibration can all have detrimental effects on lubrication. It is also quite common for machines to experience more than one of these conditions at a time. Therefore, always consider the equipment’s location and possible mitigation strategies when the machine is installed or at least when maintenance is performed to help minimize downtime and increase reliability. It is often stated that lubricants should be kept clean, cool and dry. These characteristics are influenced by certain conditions that have the most impact on lubrication.
Heavy dirt and dust-filled environments can weigh profoundly on a lubricant due to the high risk of particle contamination, which is the primary cause of equipment failures. This type of contamination most frequently takes place when airborne or stagnant particles gain access to the lubrication system through open ports and hatches, especially in systems with negative pressure. Studies have found that half of a bearing’s loss of usefulness can be attributed to mechanical wear. This wear, which occurs through surface abrasion, fatigue and adhesion, is often the result of particle contamination. This particle-induced wear makes up roughly 80 percent of all wear that happens over the equipment’s lifespan.
An elevated temperature is another environmental condition that is cause for concern. To properly gauge the effect of this type of condition, you must have a general understanding of a lubricant’s characteristics. Viscosity is the most important physical property of a lubricant. It can be defined as a lubricant’s resistance to flow and shear, and is typically influenced by a combination of temperature, moisture and contaminants. Of these factors, temperature frequently has the greatest impact. Remember the Arrhenius Rate Rule, which states that once a lubricant has exceeded its base activation temperature, it will degrade twice as fast for every 10 degrees C (18 degrees F) it increases in temperature.
Equipment that is subjected to wet conditions can also experience lubrication-related failures. When moisture appears in lubricants, it can take three different forms: emulsified, dissolved and free. The specific form will depend on the amount of moisture, the lubricant and the application. Over time, moisture can affect oxidation, lubricant film strength and load-carrying ability, among other parameters.
Excess vibration, low temperatures and other harsh environments can impair lubrication as well. However, it would be in your best interest to focus initially on keeping your equipment clean, cool and dry by addressing machines in dusty areas, at elevated temperatures and with the likelihood of moisture ingression, in this order. Of course, equipment criticality, severity and other factors should also be considered. Finally, ensure proper lubrication-related hardware is installed and accurately execute maintenance procedures to reduce the number of issues that may arise from machines operating in these types of environments.