Bearings: Causes of failure (1/2)

Today, bearings are used in almost every imaginable application and in a factory I think they are one of the most essential element to focus and ensure the reability of your machines.

operario de mantenimiento

The most important reasons why they fall are, briefly:

  • LUBRICATION FAILURE

More than 90% of bearing failures are caused by improper lubrication (insufficient lubrication, use of improper lubricants or excessive temperatures that degrade the lubricant)

It’s very important to look for discolored rolling elements (diferents tones of brown) and rolling-element tracks as well as overheating or excessive wear in the bearing.

And PLEASE, use the appropriate type and correct amount of lubricant, avoid grease loss, and follow appropriate relubrication intervals. Take care also with the contamination of the lubricants and the corrosion.

  • IMPROPER MOUNTING

In most instances, bearings should be mounted with an especific press fit on the rotating ring.

A number of conditions can cause cracked rings, denting, wear, high operating temperatures, early fatigue of bearings. These include mounting bearings on shafts by applying pressure or blows to the outer race, mounting bearings into a housing by pressing on the inner ring, loose shaft fits, loose housing fits, excessively tight fits, out-of-round housings and a poor finish on the bearing seat.

The way to solve this is follow proper mounting instructions and provide training to ensure all employees understand the difference between a properly and improperly installed mounting.

I usually follow this checklist from SKF supplier:

1º Work only with clean tools, clean hands and clean surroundings to avoid damage to the bearing.
2º Shaft seat and housing bore should be clean, smooth, with the correct dimensions.
3º Leave bearings in the package until ready for assembly. Do not wash off the lubricant covering them.
4º Lubricate the race being press-fit, and shaft or housing seat on which it will sit.
5º Start the bearing on the shaft with the rounded corner of the race going on first.
6º Apply even, driving pressure directly only to the race being press-fit. Be sure that pressure is straight and square.
7º Never hammer directly on races or rollers. Do not use a wooden or soft metal mallet, as chips or splinters may enter the bearing.
8º Use smart, quick taps rather than heavy ones.
9º Be sure all driving accessories and fixtures have straight, square ends.
10º Drive races solidly up against the shoulder of the shaft and housing.
11º Pre-lube bearing prior to installation.

In next posts, we continue talking about the reason why bearings fail.

Nevertheless, if you want to know more about bearings, perhaps you would like to read these guides. For me, they’s been very useful.

Link1: Bearing faulures from schaeffler
Link2: Bearing investigation from SKF
Link3: Bearing Guide from SKF

 

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