In-Situ Wind Turbine Blade Inspection Using Ultrasonic Non-Destructive Testing

Abstract Offshore and onshore wind turbine blades present significant inspection, maintenance and repair challenges arising from location, economic drivers, environment and the specific blade architecture concerned. In-situ tasks have traditionally been undertaken by people abseiling from the tower or use of gantries. Harsh conditions associated with windy environs, along with pressures to limit downtime, have led to a range of new technologies becoming available. This paper presents results from the use of ultrasonic non-destructive testing (NDT) measurements of subsurface blade topography arising from in-situ and static blade inspection for a range of wind turbine types. The measurements have been enabled using a hexapod robot that can accommodate NDT scanners within its chassis and can, using pneumatic suction for the robot pedipulators, navigate the convex, concave and flexing form of in-situ wind turbine blades. The arising NDT tomographic scans provide detailed information on blade integrity, the presence or otherwise of bonding materials and local feature condition. Measurements, presented over a 600 mm traverse span, have confirmed the reliability of the robotic platform to deliver high quality, consistent and reliable data to be acquired with limited NDT experience and to allow subsurface inspections to be performed and analysed remotely. In addition to detailed measurement of subsurface blade features, the robot system has also demonstrated capacity to undertake functions such as lightning protection system verification.