Rotor Slot Dovetail Repair (TIL-1292)

MD&A provides a permanent and economical solution for addressing the potential fretting or cracking of generator rotor slot dovetail surfaces.  The inspection and repairs can be conducted either at your plant or in our centrally located Turbine-Generator Repair Facility in St. Louis, Missouri.

Crack indications located along the wedge loading surfaces are the result of a combination of factors. These include fretting created at the butt-ends of the field wedges, excessive starts / stops, and cyclic stresses resulting from rotor “bending” while on turning gear. Negative sequence current events have also been found to aggravate the effects.

Engineered Repair Alternatives
MD&A provides economic alternatives for addressing issues associated with generator rotor dovetail load surface cracking. MD&A’s methods meet all OEM requirements and include testing of critical regions which may be susceptible to cracking.

Recommendations for addressing these issues may vary depending on a variety of factors. The objectives of MD&A’s recommendations are:

• To provide reliable alternative repairs for our customers
• To meet or exceed OEM recommendations
• To provide inspection and repairs that are cost-effective, reliable, and meet the operating needs of the owner

MD&A Inspection Scope and Repair Options Include:

• Work can be performed at the owner’s site or in our St. Louis repair facility
• Remove retaining rings and slot wedges, as needed
• Visual inspection of all rotor dovetail surfaces and wedges
• NDE of wedge slot dovetail load surfaces using Eddy Current Testing
• Replacement of steel wedges with newly designed aluminum wedges which incorporate larger end radii
• Redesign of wedge lengths when appropriate to move the location where fretting can occur
• Machining of the affected load surface areas to remove indications, if any, and/or provide increased reliability when appropriate

Read our case study example:

Field Rewind with a Rotor Slot Dovetail Repair

Learn more about the other Generator Repairs that MD&A offers.