Case 3: Visible and virtually invisible damage to wind turbines. Experience saves the day.

Different finishes

A wind turbine suffers damage in its gearbox: pitting and fretting on the gearwheels and bits breaking off. The park holds 60 more wind turbines.

Inspection reveals 4 more turbines with the same problem. Costs per repair: approx. 150.000 euros, loss of profits included. Inspection also reveals that several turbines have a different finishing in terms of tooth tips. At first, this is identified as the cause of the damage.

Arntz investigates why the finishing is different in some turbines. It turns out the supplier hadn’t been able to cope with such a large order and had purchased a number of gearwheels from another supplier, who operated on his own set of finishing criteria.


The real cause?

With the help of a material research lab, Arntz learns that the finishing may be different, but the gearwheels’ functionality and quality are not affected. Tooth shape, curve, hardness etc. are completely identical.

Arntz proposes a closer look at the other undamaged wind turbines, paying particular attention to micro fretting on the tooth flanks. All turbines turn out to show the same fretting, though to a lesser degree and not quite visible to the naked eye.

Further investigation by Arntz reveals that the 4 seriously damaged turbines had been put in place 3 months before the others, though all turbines were put into operation at the same time.

Experience saves the day

From his vast experience with wind turbine damages, Arntz investigates the construction and installation procedure and comes to the conclusion that the damage was not incurred during operation but during standstill!

The turbine brake, applied when the vanes are in idle position, is located behind the gearbox. Taking into account the highly variable winds in this region, all vibrations from the idle blades are directly transmitted into the gearbox. Result: micro vibrations and fretting on the idle gearwheel teeth.

The supplier agrees to modify his construction to solve this problem. No more damages were incurred.

The actual damage is limited to the 4 turbines and further damage is prevented. Modification costs are not included in the insurance, but the insurer is willing to cover part of the loss of profits as a courtesy.

Case 1:

Arntz exposes a design error and prevents further mishap.
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Case 2:

Engine damage... or attempted fraud? Arntz uncovers the true events and saves insurance heaps of money.
Read more >>