The yaw ring assembly fits in a machined groove in the nacelle main frame casting.
Several studs are inserted to locate the ring as it is lowered into the groove.
The ring is lifted and carefully lowered into position.
The remaining studs are inserted and run down.
Spacers are added, then nuts are installed and checked with a gage to be sure that enough threads are exposed for tensioning.
An index mark is added to verify the rotation of the nut during the tensioning process.
In order to apply the loads evenly, bolt tensioning requires three people to set the tensions, and one hydraulic operator
The tensioners are screwed down on the studs, then hydraulic pressure is applied to stretch them. Notice the puller moving up as pressure builds, and how the nuts can be easily tightened. Next, hydraulic pressure is released, and the process is repeated before moving to the next stud.
Once all bolts are tensioned, a black index mark is added.
Video: Wind Turbine Yaw Ring Assembly
Highland Community College as part of WindTechTV.org