On August 25, 2007, the collapse of a wind turbine tower at the Klondike III Wind Farm near Wasco, Ore., killed one worker and injured another. As a result of the incident, the Oregon Department of Consumer and Business Services, Occupational Safety and Health Division (Oregon OSHA), Salem, Ore., has fined the manufacturer a total of $10,500 for safety violations.

According to a press release issued by Oregon OSHA, three technicians were performing maintenance on a wind turbine tower. After applying a service brake to stop the blades from moving, one of the workers entered the hub of the turbine. He then positioned all three blades to the maximum wind resistance position and closed all three energy isolation devices on the blades. The devices are designed to control the mechanism that direct the blade pitch so workers don't get injured while they are working in the hub. Prior to leaving the confined space, the worker did not return the energy isolation devices to the operational position. Therefore, when he released the service brake, wind energy on the out-of-position blades caused an “overspeed” condition, causing one of the blades to strike the tower and the tower to collapse, the Oregon OSHA investigation found.

The technician working at the top of the tower died in the collapse. The worker who was on his way down a ladder in the tower when it collapsed was injured, while the third worker, who was outside the tower, was unharmed.

During its investigation, Oregon OSHA found no structural problems with the tower. However, several violations of safety rules were discovered, including:

  • Workers were not properly instructed and supervised in the safe operation of machinery, tools, equipment, process, or practice they were authorized to use or apply. The technicians working on the turbine each had less than two months of experience, and no supervisor was present on site. The workers were unaware of the potential for catastrophic failure of the turbine that could occur as a result of not restoring energy isolation devices to the operational position.

  • The company's procedures for controlling potentially hazardous energy during service or maintenance activities did not fully comply with Oregon OSHA regulations. Oregon OSHA requirements include developing, documenting, and using detailed procedures and applying lockout or tagout devices to secure hazardous energy in a “safe” or “off” position during service or maintenance. Several energy isolation devices in the towers, such as valves and lock pins, were not designed to hold a lockout device, and energy control procedures in place at the time of the accident did not include the application and removal of tagout devices.

  • Employees who were required to enter the hub (a permit-required confined space) or act as attendants to employees entering the hub had not been trained in emergency rescue procedures from the hub.

According to Michael Wood, Oregon OSHA administrator, the manufacturer “has made changes to the tower's engineering controls to ensure it does not happen again.”

The manufacturer appealed the findings on March 21. On April 16, the company met with Oregon regulators to defend its safety procedures that were in place at the time of the incident. The meeting was closed to the media and public.