Glue not UFO caused turbine blade failure

Published on Saturday 17 April 2010 20:59

ENGINEERS have discovered that the giant turbine blade which plunged to the ground at a Scottish wind farm last month snapped off because of freak problems with the glue used to coat it – scotching theories it may have been hit by lightning or, as some even suggested, an unidentified flying object.

The catastrophic failure of the 150ft-long, 14-tonne blade at the Whitelees site near Eaglesham sparked global concerns about the safety of wind farm equipment.

But manufacturers Siemens, the German engineering company, said the blade broke off due to what it described as a one-off manufacturing fault in its outer coating.

Spokesman Oliver Loenker said: "We will carry out further investigations but we think there was a manufacturing defect in the laminate that covers the blade, a weak spot which caused it to break and fall off."

The blade is made of balsa – the ultra-light tropical wood beloved by model-makers – but covered, to give it strength, first with glass fibre and then with a laminate of Epoxy resin.

Engineers believe that this sticky liquid – which dries and hardens into a laminate coating – was not applied correctly at the Siemens factory in the Danish city of Aalborg.

At some stage, the weakened laminate cracked and the blade fell off under its own weight.

Loenker said it was thought the problem had emerged in a single blade after "an adjustment" in manufacturing procedures.

"This is the first time this has ever happened since we started making the blades in 2000," he said.

"We checked all the other blades that were made after the adjustment and were happy to find they were OK. We don't expect any more defects."

The Scottish accident prompted a massive international check of wind turbine blades.

Whitelees owner ScottishPower had to check the other 139 already up at the site, an expensive process that took a week. The firm also had to check similar structures elsewhere.

The accident was spotted as soon as it happened thanks to the 24-hour system monitoring Whitelees. The blade was found five yards from the huge wind turbine tower.

A spokesman for ScottishPower Renewables said their investigation was now over. He said: "As the investigation is now focused on the manufacture of an individual turbine blade, the process is being led by the manufacturer Siemens."

The 300m Whitelees windfarm starting coming on line in 2008 and was opened in May last year by First Minister Alex Salmond. By 2012, when the farm is completed, there will be 215 turbines covering an area of around 50 square miles.