A wind turbine was being erected as part of a small wind energy park. The wind turbine tower and the nacelle housing the generator were successfully installed. The three-bladed rotor assembly was installed and connected to the nacelle as the last major component of the wind turbine.
The rotor assembly was secured against rotation by taglines connected to two of the rotor blade tips as it was being installed.
A rotor locking pin provided additional protection against rotation once the rotor assembly was installed. The rotor locking pin was released at the end of the work day so that the rotor assembly could be rotated enough to release the taglines from the rotor blades.
The rotor blades were inadvertently turned to the ‘power’ position rather than the ‘feathered’ position that would provide little or no wind driven rotation of the rotor assembly with the rotor lock disengaged. Additionally, the assembly step to install the rotor brake had not been completed so there was no rotor braking mechanism.
The rotor assembly began to turn at increasing speeds after the rotor lock was released. Personnel were evacuated from the site as the rotor speed exceeded safe levels. The rotor assembly turned at increasing speeds for several hours, shaking to the point that the rotor and nacelle eventually broke free and fell to the ground.
An investigation found that the personnel who were erecting the wind turbine were inexperienced with this type of wind turbine and had skipped many of the steps in the erection checklist. The failure to follow proper installation procedures for the wind turbine, by the erection crew, was the cause of the incident.
John Phillips, senior consulting engineer at Warren, has more than 30 years of crane and heavy equipment experience and more than 17 years of experience in forensic engineering. A licensed professional engineer in South Carolina, North Carolina, Georgia, Louisiana and Ohio, he’s NCEES registered both as a model engineer and with The United States Council for International Engineering Practice, USCIEP. John has designed crane systems, supervised installation, tested and certified lifting equipment even serving as a project engineer for maintenance and certification of nuclear weapon lifting and handling systems. John is a certified fire and explosion investigator and fire and explosion investigator instructor by the National Association of Fire Investigators. John is a member of the American Society of Materials and American Society of Testing and Materials, as well as a voting member of ASTM Ships & Marine Forensic Sciences, Forensic Engineering, and Performance of Buildings committees.