Complex sentence: During summer 2010 Siemens decided to change the blade bearings on all 25 turbines as a preemtive measure after cracks were found in blade bearings found on other sites.
Split into simpler sentences: During summer 2010 Siemens decided to change the blade bearings on all 25 turbines. A preemtive measure due to cracks in blade bearings found on other sites.