Generator dovetail slot examinations

KEMA applies these examinations to any generator field that is deemed suspect to produce stray high-energy currents

In high aspect ratio machines (> 5:1) a fretting condition can develop at the butt joints between the coil retaining wedges. This form of damage may act as a sole initiator or as an accelerant to defects initiated by the fretting process. In many cases the examinations have been referred to as TIL-1292 examinations. The examinations offered by KEMA can be applied to any generator field that is deemed suspect or has experienced a negative sequence event or other operational condition that may produce stray high-energy currents.

• Ultrasonics: in cases where the retaining rings and wedges are not removed
• Visual and Eddy Current: the retaining rings and wedges are removed and the coils remain in place
• Magnetic Particle: where the coils are also removed
• Liquid Penetrant and Ammonium Persulfate: where repairs have been performed

It has been demonstrated that situations exist such as plastic flow at the test site that can mask conditions from being detected by other stand-alone examinations. A structured approach enhances the probability of successful analysis.