The wind sector remains under pressure to boost productivity while reducing costs, calling on parts suppliers to tackle all new design requirements. SKF takes this responsibility seriously with a deep understanding of turbine gearboxes and the challenges that face SKF bearings.
As Australia accelerates its renewable energy transition, wind turbines are becoming increasingly sophisticated, demanding precision engineering at every turn. It’s here that SKF’s deep expertise keeps this ever-evolving industry supported.
SKF Application Engineer, Global Competence Center Wind, Pawel Gwadera, explains how SKF has evolved to accommodate the wind sector’s growing need for different wind turbine configurations.
“High-speed turbines need a high-speed gearbox and this is a design constraint that SKF constantly helps to overcome,” he said.
The high-speed drive trains in these turbines – which operate at up to 7.5 megawatt (MW) – can be required to turn at 1200 to 1800 revolutions per minute (RPM). These larger turbines operate at slower input speeds of just 8 to 10.5 RPM but require extremely high gear ratios of 110 to 190.
“The complexity increases with integrated designs where the generator rotor is fixed on the gearbox output shaft, requiring bearings to support both generator and high-speed shaft components,” Gwadera said.
Common bearing failures
On top of the immense output speeds and gear ratios, wind turbine gearbox bearings face some of the most demanding operating conditions in industrial applications, with variable wind loads, temperature extremes and 20-year operational life requirements.
One of the most common failures is micro-pitting, which Gwadera describes as “progressive removal of material” caused primarily by poor lubrication conditions. This phenomenon is particularly problematic for cylindrical roller bearings on high-speed shafts where variable wind conditions create rapid changes in speed and torque.
Perhaps more challenging is smearing, also known as adhesive wear – a type of lubricant-related damage that occurs between two surfaces sliding relative to each other.
“The smearing itself exists when the bearings are losing their load,” Gwadera explained.
“Once they lose the load conditions, they start to feel more freedom and acceleration, creating this smearing phenomenon. At this point, the rollers start to rotate faster, break the film, and create metal-to-metal contact.”
A modern challenge plaguing the wind industry, these cracks are symptoms of high stresses or material degradation. While not root causes, they propagate rapidly once they begin, particularly in high-speed stages with roller slip conditions.
Several factors significantly impact a bearing’s performance and can mitigate the likelihood of these three challenges occurring. Lubrication, temperature management and load conditions are all manageable, but common issues SKF recognises and helps alleviate in the wind sector.
Engineering beyond the bearing
SKF’s approach to the challenges of bearings in wind turbines goes beyond manufacturing standard bearings. One of the company’s most significant innovations has been the widespread adoption of black oxide coating for wind applications. This solution has been found to greatly reduce material degradation.
Additionally, black oxidised versions present a strong aftermarket solution to replace individual Full Complement CRB bearings – a model that SKF ceased installing in new machines from 2018. The treatment provides crucial protection against smearing and micro-pitting while offering enhanced protection against white etching cracks. For high-speed shaft applications, black oxide coating has become highly recommended – virtually mandatory.
SKF’s DuraPro bearing technology is another significant tool in the fight against wind turbine bearing failure. The solution represents an unprecedented leap in performance, thanks to its thermo-chemical, heat-treated manufacturing process. This process enriches and strengthens the bearing’s surface by reordering the material’s microstructure. A complex-sounding solution to a simple problem.
“This bearing gives you a product lifetime of more than 10 times the usual standard,” Gwadera says. “The DuraPro works perfectly against white etching cracks – and it’s not only theoretical. We run our bearings under extreme testing conditions, and we can see significant improvement.”
DuraPro allows for either smaller bearing sizes or dramatically extended life when maintaining existing dimensions – crucial for retrofitting existing turbines and achieving the 20-year lifespan of these renewable energy machines.
SKF’s global expertise
Behind each innovation is the advantage of scale. SKF maintains a comprehensive database of gearbox types across the global wind industry, giving its engineers a deep knowledge base to draw from.
“In our database we have an overview of 300 to 400 different gearboxes assigned to different turbines,” Gwadera explains. “This knowledge helps us prepare customers for service activities in advance.”
This global view also allows SKF to connect insights across markets.
“From a global perspective, we are building connections,” Gwadera said.
“If there’s a problem in one market, the same problem will also exist in another.
“So, for any problem that you can see in the field which you cannot solve with just redesign and standardised solutions, we strongly recommend contacting our team to guide you through intelligently engineered SKF solutions.”
To view recent and upcoming SKF Wind Energy webinars, click here.