Precision shaft alignment of wind turbine generators mounted on adjustable chocks is as straightforward as when aligning rotating machinery mounted on chocks down at ground level.
In the case of a recent NXA Training Class in a Vestas V82 we knew before going up-tower that one revolution of the adjustable chocks equals 1mm. Also, as there are 6 holes in the chocks, we calculated that the hole to hole adjustment equals 0.17mm (1mm ÷ 6 = 0.166).
The as found measurement results indicated a vertical and horizontal correction were needed to bring the generator into tolerance.
The shimming screen showed the rear feet of the generator needed to come up 3.70mm which translated to 3 full turns of each rear chock plus 4 holes. (.70mm ÷ 0.17mm = 4.12 holes). The front generator feet needed to be raised 2.25mm which equaled 2 full turns of each front chock plus 1.5 holes (.25mm ÷ .17mm = 1.47 holes).
After preforming the vertical correction, the technicians made the horizontal correction then torqued down the generator hold down bolts and remeasured.
One Verti-Zontal move and done! Time from as found (before) to final (after) was 59 minutes.
One of the keys when performing alignments with multiple technicians adjusting the chocks is to make sure all are on “the same page” before making chock adjustments.
The wind technicians performing this alignment had great precise communication before adjusting the chocks, so each knew exactly what to do when the adjustments were made.