Determining Bearing Damage and Fatigue

February 28, 2018

Down on the factory floor, damaged bearings are causing unforgivable energy losses. Picture the machinery. It’s still spinning, but it’s throwing out those losses. Expressed as heat and noise, the spinning shaft is well on its way to a catastrophic failure. What’s needed here is a way to locate the damage. Before the equipment is crippled, let’s quickly find out where the mechanical distress is taking place.

Narrow Down the Fault 

If a circuit breaker is constantly tripping, there’s a potential loading problem occurring inside the equipment housing. Granted that the issue could be due to short-circuit, but then there’s still a mechanical culprit to consider. Bearing damage and fatigue slows the velocity of a spinning rotor. The equipment attempts to compensate for the speed drop, at which point the consumed electrical output spikes. More current zips down the wires, so the breaker trips. Meanwhile, the maintenance operative is feeling the heat, hearing the noise, and smelling the burning lubricant.

Weighing the Causative Factors 

Mechanical bearings are built to last. However, they rarely operate stress-free. Thrust loads push the rolling elements laterally. Outside, beyond the equipment housing, the environment is loaded with dirt and grime, which somehow finds its way inside the machine’s moving parts. Poorly installed components are next. An ill-adjusted component is enough to unbalance a machine and undermine its smoothly running rolling elements until the twin races exhibit a banded groove. Grooves or scratches, micro-welds or fractures, the ball and ring assembly will break down if these issues are left untended.

Fatigue and Damage Symptoms 

Dry bearings, those that are starved of oil, seize with a convulsive lurch. There’s noise beforehand because the rolling elements are flying over the surface of a cracked and worn race surface. Copious quantities of heat typically accompany the noise. Then there’s corrosion, an incident that’s seen as a brown/orange stain. The tarnished parts generate noise, that noise increases, then the equipment begins to vibrate. Somehow, perhaps because of a fluid leak, the alloy parts are oxidizing. Stop the machinery, find the leak and plug it, then address the bearing. Similarly, particle contaminants cause component wear. The fine dust works its way into the rings, then the charging rolling elements crush that particulate matter. The result is more noise.

It’s difficult to diagnose the movement-crippling effect. If further analysis is required, we can pull the bearing and deconstruct the parts. Orange/brown coatings and chemical blemishes indicate an obvious leak. Is there pitting on the balls and rings? Without question, there’s a contaminant finding its way into the equipment. Replace the damaged bearing if the cause of the failure is known. If there’s no obvious clue, have the part dismantled so that the above troubleshooting procedure can be followed.

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