If you are changing the bearings on a skateboard, you can do it in your garage with a pair of tweezers. For many applications though, the process of relubrication requires precision, expertise and sophisticated technology. Here, Chris Johnson, director of bearing relubrication specialist SMB Bearings, examines some of the specialist equipment you might find in a bearing relubrication facility.
As a specialist bearing supplier, we used to receive requests for bearings with non-standard lubricants, or for relubrication. Over the years, our expertise in this area and our collection of specialist equipment has grown. If you want to know more about bearing relubrication, here are five key elements, plus one that is so secret I can’t really tell you too much about it!
For precision applications, process of relubrication must take place in a contamination-free environment. Particles far smaller than the naked eye can see could easily compromise a bearing if they enter and contaminate the lubricant.
A good relubrication facility requires filtered air. Although most applications don’t require a certified cleanroom, many customers should expect a facility that can offer a highly controlled environment, free from sources of contamination and akin to a cleanroom environment.
In some applications, the quantity of grease is just as important as the type of grease. For example, while a standard fill might be 30 per cent, for certain low torque applications this would be too stiff, and a ten percent fill would be more suitable. When dealing with miniature bearings and quantities on this scale, precision is key. A job like this requires specialised, ultrasensitive scales capable of providing the necessary level of precision.
Ultrasonic cleaning equipment
Degreasing bearings is just as important as adding in fresh lubricant. If degreasing is not done in the right way, traces of the old grease can remain and cause problems. In addition to special solvents and chemicals, relubrication specialists might use ultrasonic cleaning technology. Ultrasonic waves cause cavitation, releasing tiny bubbles that provide a gentle scrubbing effect on the surfaces.
Standard greases can become combustible in high oxygen environments. This highlights the importance of degreasing properly, with the right chemicals and equipment, to avoid potentially explosive consequences. Bearings used in oxygen systems should not have any hydrocarbon-based oil in the lubricant, due to the risk of spontaneous combustion. Making sure the bearing is properly cleaned out is therefore essential. Having cleaned a bearing, a specialist can use ultraviolet light to ensure no traces of potentially combustible material remains, as hydrocarbons will fluoresce under this light.
Relubrication specialists are often called for because of the need for a specialist lubricant. Often, a problem could be easily resolved with the correct lubrication. One interesting area here is dry lubricants. The inner surfaces of a bearing can be coated in dry coatings, such as molybdenum disulphide, which will help prevent micro-welding between steel surfaces in vacuum environments. If you need dry lubricants to be burnished or sputtered on to the balls or raceways of a bearing, this is something that requires specialist expertise, particularly in precision applications such as vacuum environments.
Some relubrication facility equipment is so sophisticated that full details of its operation cannot be disclosed. For example, we have proprietary technology that allows us to relubricate bearings without removing the shields. Customers who need a specialist service like this can inspect the facility to see the equipment in action, but they must sign non-disclosure agreements to make sure the secrets stay with the experts.
From ultrasonic cleaning devices to secretive technology that can degrease a bearing without removing the shields, a modern relubrication facility has an impressive array of equipment. If you don’t have the expertise or access to the right equipment, stay clear of botched DIY jobs and rely on the experts.
SMB Bearings is a specialist supplier of miniature bearings with its own inhouse relubrication facility. To find out more, visit smbbearings.com.