Reliability Engineering Snapshot TM

Illustrated Case Stuies in the Maintenance Reliability Engineering World of Failure Analysis, Predictive Maintenance, and Non Destructive Evaluation



Corrosion - Case Study No. 12: Outdoor Storage of Spare Rotating Equipment Caused Bearing Failure


Storing expensive critical eqipment in the outdoors, exposed to the elements, is asking for trouble. A heated warehouse is worth every penny spent to get it.

Corroded Out of Rebuilt Spare Gear BoxThis is what remains of the high speed bearing on a tank agitator gear box. The gear box was a spare unit and was normally stored outside. The high speed shaft on the agitator that was in service had failed. Instead of replacing the gearbox, which would have been labor intensive, the high speed shaft was removed from the spare unit and installed in the damaged gearbox. The repair went well, but during this non routine style of repair it came to light that the bearings which came off of the spare were in terrible condition. This comment seemed hard to believe except when the evidence was recovered.

If this spare agitator had been installed then there was good reason to believe that the unit would have failed prematurely. The trouble was that there was no way in which to predict when it would have failed. If it had failed quickly, then the mechanics would have been blamed. If it had failed within a couple of months, then the manufacturer, or the repair shop, would have been blamed. If it had taken a year or more to fail, then nobody would have ever questioned it at all.

Use the cursor to zoom in on the far right ball. The fish scale pattern on the ball is actually tiny etchings.

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Close Up View of Outer Raceway Close Up of Ball Bearing