Metallic debris and varnish residues removed

The challenge 

A Bonus 300 kW wind turbine gearbox with over 10 years of operation showed persistent oil discolouration and internal contamination, even after repeated oil changes and flushing. New oil was observed to degrade rapidly, indicating legacy varnish and debris within the gearbox that conventional maintenance could not remove.  

Customer savings & impact 

After installing Delta-Xero offline filtration and operating the turbine under normal conditions: 

• Oil condition improved significantly within 51 days, confirmed by micropatch analysis 

• Metallic debris and varnish residues removed, leaving visibly cleaner oil and internal surfaces 

• Extended gearbox protection achieved, reducing the need for repeated oil changes and flushing 

The full case study shows before-and-after micropatch images, how contamination persisted without filtration, and why continuous off-line filtration is critical for ageing wind turbine gearboxes.  

Download the complete wind turbine gearbox long-term cleanliness case study, including inspection images, micropatch evidence, and timeline results. 

Why routine particle counts missed this: your oil passed ISO 4406, so why is the gearbox still failing?