What Causes Bearing Noise?

September 12, 2018

Among a cluster of synchronized, quietly rotating mechanical parts, one shaft is emitting a bone-rattling squealing noise. Off the top of the maintenance engineer’s head, the bearing is probably running dry. The lubricating film is breaking down. That’s a good guess, one that might even hit the mark, but that supposition can’t be confirmed until the bearing is inspected, especially when we know there are other causal factors in play.

Tainted By Contamination 

This is a big problem in dusty and dirty environments. Bearings are loaded with rolling elements, after all, but there’s no room inside that tightly assembled device for foreign materials. Like a circular runway, packed with spinning parts, which run in circles between those two closely aligned rings, bearings rely on absolutely clean inner workings. If even a single grain of sand or a few loose particles of dust contaminate those workings, then the interfering grit will cause bearing noise.

Dry Running Episodes

Even perfect material geometries and super-dense microcrystalline surfaces aren’t enough to battle the energy loss phenomena known as friction. Essentially, in opposition to the previous scenario, this time the device is making a racket because it’s missing a key operational constituent. The bearing is dry. It needs oil, grease, or wax as lubrication. If a shaft is producing waves of heat, plus a squealing racket of epic proportions, it needs a lubricating agent.

Eliminating Manufacturing Hiccups 

Again, bearings are finely fabricated devices. Their rolling elements are consistently shaped and polished. Likewise, the slender channels within their rings provide a mirror-like finish for those burnished balls to skate upon. Unfortunately, perhaps because of poor heat treatment or a substandard alloy, manufacturing errors can introduce coarse surfaces, which become even rougher as a bearing’s service life is put to the test.

Mounting Mistakes and Sealing Flaws 

Misalignment errors produce bearing noise when angular discrepancies introduce thrust force. The bearing is fighting conflicting energies, as applied by a heavy, side-introduced load. Generating noise, the problem isn’t going to go away until the misaligned shaft is adjusted. Elsewhere, the shield or seal on an environment-capable component has failed. With the seal broken, contaminants penetrate the rolling parts again.

After the fact, there are failure analysis tests to conduct. Far better, however, is a preventative planned maintenance program. Planned maintenance technicians carry their logbooks, keep oil levels high, and take note of strange noises. Then, upon recording the data, bearing noise prevention strategies are formed, simply by detecting a worrying trend and eliminating that problem before it permanently damages the shaft mount and its friction-reducing assembly.

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