Case – Vibration Measurement 

The customer noticed a strange sound near one of the bottom-type coolers. Vibration 
measurements revealed the cause of the sound.

Observation during the measurements:

Analysis of the vibration measurements on bottom-type cooler A shows damage to the 
engine bearings. The measurements reveal advanced damage and we clearly see faulty 
frequencies at the beginning of the spectrum.

That peakvue also shows us damage to the bearings and a highly elevated level of friction.

Further examination of the machine shows that the belts are fairly deep in their pulleys.

Advice:

Replace the engine bearings and check the belts for signs of wear. If necessary, replace 
them as well. 

Damage analysis:

Outer ring

Bearing balls

We can see that 120° of the outer ring is polished clean. That shiny surface is the result of insufficient grease between the outer ring and the bearing balls, causing the balls to slide across the outer ring. The rest of the outer ring is heavily damaged. That area is probably affected by the tension of the belt. Subsequently the balls start to bounce in the bearing, causing increased load on the bearing and the roller pitch. Metal fatigue will occur in the affected zone. That fatigue will have its effects on other components of the bearing. The balls clearly show signs of crumbling and local heating. All symptoms are reducible to a lubrication problem. The single lubrication in the closed ball bearings had reached the end of its service life.

Conclusion

By conducting vibration measurements the cause of the strange sound quickly emerged. Analysis of the measurements showed that the bearing was in need of replacement. Analysis of the damage reveals the exact cause of the wear. 
In the cooling bank this was an isolated case of wear after a respectable service life. Therefore no further course of action is advised.