December 19, 2008
by Paul Michalicka
Properly lubricating rolling bearings in rotating equipment involves delivering the right lubricant, in the right quantity, to the right location. Advanced lubricant dispensing technologies such as automatic lubricators, lube selection and calculation software, and precision metering devices make this task easier.
More than one-third of all bearing failures can be traced to lubrication-related errors. For example, under greasing bearings leads to metal-on-metal contact between components that causes wear and then failure. Over greasing causes lubricant churning, which increases bearing operating temperatures and results in a loss of viscosity; but you’re also paying for the excess grease and its disposal, which harms your plant’s sustainability efforts.
General-purpose grease was once routinely used for all rotating-equipment applications, but a single grease doesn’t offer optimal performance in every instance. A better practice is to select the lubricants best suited for specific applications.
Special software programs, available from many lubricant and bearing manufacturers, make the selection process easier. They identify a grease or oil based on application variables such as speed, load, ambient temperature and contamination.
And automatic lubricators ensure the lubricant is delivered in the right amount to the right location, improving precision and reducing the guesswork that’s generally required during manual application. Depending on facility size and the number of machine points requiring lubrication, you can use single-point automatic lubricators, multi-point automatic lubricators, or custom-designed lubrication systems.
Single-point lubricators are self-contained units that attach to a bearing housing or machine point and dispense at a preset rate for a period of up to one year and require only periodic visual inspection. These units are used in fans and blowers, pumps, cranes and conveyors, but are especially useful in hard-to-access locations.
Although spring-activated lubricators are still in use, the trend is toward gas-activated.
Higher-capacity single-point lubricators, currently in development, will have capacities of more than 200 millilitres of lubricant, and will be put to use in heavy-duty applications such as mining.
Multipoint automatic lubricators, using a high-pressure pump powered by an electric motor, supply grease through multiple feed lines emanating from a centralized, refillable cartridge. Larger systems supply up to 20 separate lubrication points.