Lessons learned from quality control in Windmill Installation
Recent years have seen a dramatic growth in the wind power industry. Global installed wind power capacity has grown from 283 GW in 2012 to 487 GW in 2016, and is expected to grow to 540 GW by the end of this year. This growth has also resulted in higher numbers of accidents, many of which have proved fatal. One 2011 study by RenewableUK showed the United Kingdom’s wind turbine accident record reaching a rate of nearly one per day.
One crucial cause of potential accidents is from improper bolting. Like helicopters, wind turbines are fatigue machines, meaning they are always under tremendous vibration stress, which works towards loosening any fasteners. As wind towers get higher and use longer blades, the vibrations increase exponentially. A survey of accidents involving bolt failures over the past decade has revealed the following lessons learned:
Bolt choice is critical: Bolt failure can occur if bolts are used that do not exactly meet design standards. Furthermore, design standards do not always take sufficient account of the fact that windmill bolts will suffer from additional stress over time given a windmill’s expected life of 25 years. Bolts must be chosen using precise scientific methods and, in windmill assembly, must be followed exactly.
Bolting is a science: Bolt failure is easily caused by improper installation or maintenance. Tower fasteners must be installed and maintained using precise torque specifications employing perfectly calibrated equipment. Minor damage caused by tools, if in an area of stress, can cause failure over time. Torque control is extremely important and is measured by a k-factor, or the relationship between applied torque and the actual tension reached in a bolt. Bolting during windmill installation should only be done by top-notch trained professionals – several incidents in the UK show just how important proper bolting can be.
Failure of each bolt has disproportionate impact: The 2013 accident at the Taikoyama Wind Power Plant demonstrated that for each bolt that fails, the stress placed on the remaining bolts increases exponentially. The University of Tokyo study identified that once 17 of the total bolts installed were damaged, the stress on the system increased to three times the amount designed.
Bolts used in wind turbines must be vibration proof and windmill assembly must be conducted by trained professionals. Not only are the costs of windmill accidents high, but the potential for death and significant injury is extremely serious. Working with the pros who specialize in bolting and approach it as a science can save your company money, reduce your reputation risk, and keep your employees and clients safe. Contact the bolting specialists today at Aztec Bolting for your windmill assembly needs.