Siemens says two separate incidents in which a B53 rotor blade broke off were both caused by “adhesive bonding failure.” The 53 meter long blades are on SWT-2.3-108 turbines which are assembled in Hutchinson.

In April, a Siemens service technician discovered a B53 blade on the ground at the Eclipse wind farm in Adair county Iowa. A second blade broke off at Pattern Energy’s Ocotillo Wind in California’s Imperial Valley.

Following the incidents, Siemens launched a root-cause analysis and announced it was curtailing all turbines with the B53 blade type globally. Siemens says the fractures happened as a result of adhesive bonding failure between pre-cast root segments and the fiberglass laminate of the main blade. The adhesive bonding failure was caused by insufficient surface preparation of the root segments.”

All existing B53 blades have been inspected, and most turbines with the blade type have returned to operation.