Lambda Technologies, Cincinnati, reports that it has developed a low plasticity burnishing (LPB) process to extend the fatigue life of wind turbine bolts, providing significant cost savings and reduced downtime.
The turbine bolts, or tie rods, on these turbines are particularly susceptible to fretting fatigue at the edge contacts between the turbine rotors and the tie rod landings. Currently, plant operators perform frequent inspections of the bolts, replacing any that have signs of damage, and causing substantial down time.
The LPB process uses low plasticity burnishing to apply a deep, stable layer of engineered residual compression to regions of the bolts that are vulnerable to fatigue. By putting the edge of contact region in compression much deeper than the shallow shear cracks formed by fretting, the fatigue cracks are prevented from propagating through the compression and the chance of fracture is eliminated. Even when applied to a bolt with existing fretting fatigue damage, LPB claims a better than 500x life improvement.
LPB allows tie rod bolts to remain in service for the entire life of the turbine. Lambda reports that LPB has already saved operators approximately $16 million in replaced bolt sets, and approximately $40 million total in improved operating efficiency.
www.lambdatechs.com
