Bearings vary widely in their maintenance requirements. While numerous bearings demand periodic maintenance to avert premature failure, a significant number need minimal upkeep. The latter category encompasses diverse polymer, fluid, and magnetic bearings, along with rolling – element bearings like sealed bearings and those labeled “sealed for life.” These are equipped with seals that keep out dirt and retain grease, enabling maintenance – free operation in numerous applications. However, not all applications can effectively utilize them.
Non – sealed bearings typically feature a grease fitting for periodic lubrication using a grease gun or an oil cup for intermittent oil refills. Prior to the 1970s, sealed bearings were rarely found on most machinery, and oiling and greasing were more common practices than they are today. For instance, automotive chassis once required “lube jobs” almost as frequently as engine oil changes, but modern car chassis are mostly designed to be maintenance – free for their lifespan. From the late 1700s to the mid – 1900s, industry relied on numerous workers known as oilers who regularly lubricated machinery using oil cans.
Today’s factory machines generally incorporate lubrication systems. In these systems, a central pump delivers periodic charges of oil or grease from a reservoir, distributing it through lubrication lines to various lubrication points on the machine, such as bearing surfaces, bearing journals, and pillow blocks. The timing and frequency of these lubrication cycles are regulated by the machine’s computerized controls, like PLC (Programmable Logic Controller) or CNC (Computer Numerical Control), with manual override capabilities available when necessary. This automated approach is how all modern CNC machine tools and many other contemporary factory machines are lubricated. Similar lubrication systems are also employed on non – automated machines, where a hand pump is used. For machines in continuous use, the machine operator is expected to pump it daily, or weekly for less frequently used machines. These are referred to as one – shot systems, named for their main advantage: a single pull of a handle lubricates the entire machine, eliminating the need for multiple pumps with an alemite gun or oil can at numerous different locations around the machine.
The oiling system within a modern automotive or truck engine is conceptually similar to the lubrication systems described above, with the key difference being that oil is pumped continuously. A large portion of this oil flows through passages drilled or cast into the engine block and cylinder heads, emerging from ports directly onto bearings and spraying elsewhere to create an oil bath. The oil pump operates constantly, and any excess oil is continuously diverted back into the sump through a relief valve.
In high – cycle industrial operations, many bearings require regular lubrication and cleaning, and some need occasional adjustment, such as pre – load adjustment, to mitigate the effects of wear.
Maintaining a clean and well – lubricated bearing significantly extends its lifespan. However, effective maintenance can be challenging in many applications. For example, bearings in a rock crusher’s conveyor are constantly exposed to hard abrasive particles. Cleaning is often ineffective as it is costly, and the bearing becomes re – contaminated as soon as the conveyor restarts. Therefore, an appropriate maintenance plan might involve frequent lubrication without disassembly for cleaning. Frequent lubrication inherently provides a limited cleaning effect as fresh lubricant displaces older, grit – filled oil or grease, which then accumulates grit until the next lubrication cycle. Another example is bearings in wind turbines. Maintenance is difficult because the nacelle is located high in the air in areas with strong winds. Additionally, turbines do not operate continuously and exhibit different behaviors in varying weather conditions, posing challenges for proper lubrication.