Figure 20 Structural fasteners, courtesy of Cooper & Turner.
Function
Fasteners (either bolts or studs) are used in a range of critical bolted joints, for example connecting rotor to main shaft, main bearing housings to nacelle bedplate and yaw bearing to the underside of nacelle bedplate.
What it costs*
The structural fasteners cost for a 15 MW wind turbine nacelle is about £70,000 (similar for rotor and included in total rotor cost).
Who supplies them
August Friedberg, Clyde Cooper & Turner, Fuchs & Sanders, Gexpro Services and Multifix.
Key facts
Fasteners for critical structural joints within large turbines are typically of size up to M72 and grade 10.9.
Often, the fasteners are specified to have threads rolled after heat treatment to improve fatigue properties.
Coatings provide corrosion protection.
All critical structural fasteners are preloaded either using hydraulic torque tooling or (in the case of studs) hydraulic tensioning. Increasingly, preload indicators or other visual checks on tightness are used.
What’s in it
- Bolts
- Studs
- Nuts