Earlier this year, two E40 units failed as a result of sub standard kingpins, with the nacelles crashing to the ground (Windpower Monthly, May 1999). Enercon's owner, Aloys Wobben, has now officially confirmed the details of retrofits on other E40 turbines. He declines, however, to say whether the E40 units affected are only those in Germany, or are all of the more than 1600 worldwide.
With the use of new "inductive sensors," Enercon says, changes of less than 0.25 millimetres in the gap between the nacelle and the kingpin can be detected. The software, which has been approved by Germanischer Lloyd, is designed to shut down a turbine before a break can occur. Enercon states that the use of such sensors on its larger 1.5 MW E66 machines is not necessary because the nacelle is connected to the tower by an azimuth bearing, not a kingpin.
Wobben continues to avoid public mention of an additional retrofit completed on E40 machines-a mechanical safety system developed to secure the nacelle on the tower in the event of a kingpin failure. This is work that several wind plant operators in Germany and Austria confirm is being completed. According to the Enercon marketing office in Marne, mechanical retrofits are being carried out on more than 220 E40 units in Schleswig-Holstein.
Wobben is critical of the press for reporting on Enercon failures and retrofits before the company had issued public statements. These recently appeared in company newsletter Windblatt. Enercon, he says, needed time to analyse the damage to the kingpins and come up with the correct reason for failure before being required to answer questions. The company says it is suing the German news magazine Focus over a story that reported that six-not two-E40 nacelles had crashed to the ground.