Inspection and repair on SCOLARI RM72 gearbox

This client from Belgium came to us with this SCOLARI RM72. We inspected the gearbox and performed a repair. After a succesful testrun we shipped the gearbox back to the client.

The state of the main drive can be considered as acceptable, no major damage has been observed. However, indications of developing bearing damage have been observed and a small amount of metal particles was found in the oil filter.

Comparison to last inspection:

- On some of the pinions micropitting has developed locally or in the dedendum of the tooth
- Some bearings show signs of degradation of the surface of the rolling elements, having progressed since the last inspection.

When metal to metal contact takes place, particles break out of the affected surfaces. These particles stick to the rolling elements, are smeared out over the surface and break loose again, speeding up the process. The damage is usually not limited to one bearing due to transportation of particles in the oil. The duration of the process of bearing degradation is hard to predict but can be slowed down by oil filtration and good quality oil.

Micropitting is a phenomenon which can occur in hardened gears. Multiple factors can be of influence such as surface roughness, lubrication and gear mesh. This failure mode can be recognized by a local dull and grey appearance of the tooth as a result of surface fatigue and micro cracks. Micropitting can exist in a stabilized form or have a progressive nature, in the last case it can develop into pitting, spalling and possibly tooth breakage.

Recommendations are:

- To continue annual visual inspections and biannual oil sample analysis
- To monitor the condition of the bearings closely during the next inspection considering the criticality of this machine to factory operations.