Guido Pfister No Comments

A work site with a view

It is not a secret anymore that our thread repair solutions excel in the most demanding applications and environments. It is therefore not surprising that our colleagues from Lock-N-Stitch were recently contacted for assistance in repairing damaged threads in the hub of a wind turbine operating in the American Mid-West. Our specialists quickly engineered a repair solution and brought it to life inside the 4.2 MW turbine’s nacelle, which sits 105 meters (345 feet) above ground.

Three out of 88 bolt holes that connect the rotor hub to the (low speed) rotor shaft had their threads stripped. Our solution was to machine these to over-size and to install Full-TorqueTM thread inserts. Unlike convential thread repair inserts, Full-TorqueTM thread inserts are equipped with the patented spiral-hook thread, which makes them the ideal for any application, where superior strength is required.

The three inserts that the Lock-N-Stitch specialists installed have an M48 x 5 internal thread that is 130 mm deep. They are also counter-sunk to a depth of 25 mm.

Inside view of the nacelle, towards the rotor, with the drive train components (gear box, generator, ...) removed.
Inside view of the nacelle, towards the rotor, with the drive train components (gear box, generator, ...) removed.

Our specialists locked the inserts in place with three bolts, to prevent them from ever rotating during any future loosening of the bolts.

A few days after we completed our work and after the drive train had been installed back, the customer reported that the alignment of our inserts had been found to be perfect.

Read more about Thread Repairs

 

Damaged bolt hole
One of the damaged M48 x 5 mm bolt holes
During drilling
During drilling
CAD drawing of the thread repair insert
2D drawing of the thread repair insert installed in the hub
Enlarging the bore to accomodate a Full-Torque insert
Enlarging the bore to accomodate a Full-Torque insert

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