Case: transition pieces and monopiles

Prevent damage and delay by proper procurement procedures as well as proper quality control of the procured materials/goods


During the construction of a German windmill park, something goes wrong during the installation of the transition pieces and monopiles: the M72 nuts start snapping. Though seemingly impossible, it does happen. In the end, 70% of the nuts prove to have snapped, causing the operations of two installation vessels to come to a halt. The underlying cause of this situation, is what needs to be determined.


Inspecto Visio investigates the situation. It turns outs that though the used bolts are self-produced by the supplier (a highly regarded company), the used nuts were procured by the supplier.

These nuts prove to have been produced by a punch press with insufficient capacity, which make multiple pressings necessary. Between pressings the steal cools off, causing it to be of mixed strength and consequently of sub-standard quality.


After identifying the cause of the problem, the production of the nuts is transferred to another manufacturer. The use of these new high quality nuts proves to solve the problem.

Take away

The damage and delay could have been avoided if the client had supervised the procurement procedures more strictly, enforcing a more strict quality control regarding the procured materials/ goods.

Therefore, never rely blindly on a supply company, even if its services/products are highly regarded.

Always pre-check on location, whether the production process is up to standard. This may, if appropriate, also be done by an independent NDT inspector.


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