lubricating rotary bearings

Easy Maintenance Tips for Your Rotary Bearings

Most production facilities have some kind of rotary bearings, and while they are working, no one gives them much thought. But as the saying goes, a little ounce of prevention can spare a huge pound of broken down machinery. That prevention always includes making sure your rotary bearings are well lubricated and within their life spans. The easiest, simplest method of knowing when to lubricate or replace your rotary bearings is to watch your bearings and keep good notes. Most bearing manufacturers provide information and instructions on bearing life spans and lubrication schedules – this is always a great place to start when you are developing a strategy. Of course, you can’t beat real world results when it comes to calculating when your bearings need lubrication, maintenance, or replacement.

However, if your equipment is older, if you can’t get manufacturer information, or if you can’t risk having a production line go down, you can still get some approximations for life span and lubrication. You will have to gather some information and dust off your calculator, but the process is pretty straightforward. For example, rotary bearing life is expressed in this equation:

Screen Shot 2014-05-27 at 12.25.40 PM where:

  • L: nominal life of the bearing in millions of revolutions
  • C: basic dynamic load rating (provided by the manufacturer, or find common values)
  • P: equivalent dynamic bearing load (how much load your bearing is supporting, specific to your situation)
  • a: exponent
    • a = 3 for ball bearings
    • a = 10/3 for cylindrical, needle, spherical, and tapered roller bearing

Filling in your information will give you an idea of when you should replace your rotary bearing. Make sure to watch your units on the loads – manufacturers might supply them in Newtons rather than in pounds. Now what about lubrication? The expected life span, of course, assumes that you are properly maintaining your rotary bearings with a good quality lithium or mineral oil grease. To get an estimate of when to pull out that grease gun and go hit the assembly line, use this equation: Screen Shot 2014-05-27 at 12.33.03 PM where:

  • t: lubrication time interval in hours of operation
  • K: bearing constant
    • K: 1 for spherical or tapered roller bearings
    • K: 5 for cylindrical or needle bearings
    • K: 10 for radial ball bearings
  • d: bearing bore diameter in millimeters (watch your units)
  • n: rotation speed in revolutions per minute

Just glancing at the equations can seem a little challenging, but breaking down the variables is actually pretty simple. Remember, always take good notes and document your work. It is not only good practice, but it also gives you a great resource to follow for future maintenance needs. Now you should have a good idea on both when your bearing should fail, and when you need to lubricate to prevent it from failing prematurely. So grab your tape measure, calculator, and favorite grease gun and get to work on maintaining those rotary bearings! If you have any further questions, Misumi is always happy to help. Please leave comments and questions below, or call 800-681-7475 to talk to one of our experts!

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