Generator Dovetail Slots Inspections TIL 1292
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 3angles 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.
On the forging, fretting occurs on the upper surface of the dovetail slot, most pronounced within the outer two-thirds of the surface. The eddy current testing offered by 3angles uses probes specially designed to target the critical area along the length of the dovetails when properly placed into the dovetail slots.
In most cases, a penetrant and/or magnetic particle inspection is performed as an additional inspection to the visual and eddy current examinations.