Wind-turbine blades pose a unique set of inspection challenges: from very thick and attentive spar-cap structures to porous bond lines, varying core material, and a multitude of manufacturing defects of interest. The need for viable, accurate, nondestructive inspection (NDI) technology becomes more important as the cost per blade—and lost revenue from downtime—grows. Under its Blade Reliability Collaborative program, Sandia is quantitatively assessing the performance of a wide range of NDI methods that are currently deployed, as well as new NDI candidates for wind-blade inspections.
Custom wind-turbine blade test specimens, containing engineered defects, are being used to determine critical aspects of NDI performance including sensitivity, accuracy, repeatability, speed of inspection coverage, and ease of equipment deployment. Wind-turbine blade flaw detection experiments are being conducted to quantify the flaw detection performance of NDI in composite wind-turbine blades. This experiment seeks to determine a probability-of-detection curve for the wind-turbine blade industry. In general, inspectors are asked to locate and size hidden flaws in the test specimens, which mimic the construction and include damage types found in today’s wind-turbine blades.
Several Sandians traveled to Denmark in May to conduct the wind-turbine blade flaw detection experiments with Siemens Wind Power and Force Technology inspectors. The experiment with Siemens was hosted by Aalborg University, Aalborg. Force Technology hosted the experiment at their Brondby facility, just outside Copenhagen.
Denmark will be combined with those acquired from inspectors from a wide range of blade manufacturers and wind-blade inspection support companies to produce a baseline of how well the wind industry is currently able to detect flaws or damage in their blades. This baseline from the wind-turbine blade flaw detection experiments will then be compared with results from advanced NDI methods to determine the degree of improvement possible through applying more sophisticated inspection devices.
Ultimately, the proper combination of several inspection methods may be required to produce the best inspection sensitivity and reliability for both near-surface and deep, subsurface damage. Detecting fabrication defects helps enhance plant reliability and increase blade life while improved inspection of operating blades can result in efficient blade maintenance, facilitate repairs before critical damage levels are reached, and minimize turbine downtime.