headsUP: LM2500 turbine blades

Double the life of LM2500 HPT blades

LM2500 Row 1 and 2 turbine blades are limited to 50,000 service hours using conventional repair techniques. Standard service practice is to perform a strip and replacement of external airfoil coatings at 25,000 hours and then retire the blades at 50,000.
Technical reasons for retirement at 50K: The internal protective coating is exhausted at this point, and the blade alloy has weakened because of its long-term exposure to high temperatures.
   Lloyd Cooke told the editors and users visiting the Liburdi Turbine Services booth that his company had an “advanced repair” process unique in its ability to remove the exhausted internal coating. The metallurgist said the chemical process first removes the internal oxides and then the coating material.
   After both the internal and external coatings are stripped, he continued, the blades can be processed through high-temperature heat treatments—so called FSR™ or full-solution rejuvenation—that restore new-part properties and strength. Coatings then are applied to the internal and external airfoil surfaces and the parts are effectively “zero-houred” and prepared for a second 50,000-hr service interval.
   Cooke said that Liburdi’s advanced repair process has been used successfully for more than 15 years to extend the lives of HP blades for the LM1600 and the Rolls-Royce RB211. Experience with the latter includes reliable service of some blade sets for 100,000 to 120,000 hours. Think of the saving associated with a doubling of HP blade life.
   The full-solution repair, Cooke continued, also has enabled buckets on some GE frames to achieve 100,000-120,000 hours of service. The process is offered to owner/operators of LM2500s as an alternative to the “conventional” repair. It must be requested by the owner or operator at the time of overhaul. The advanced repair has been subcontracted to and installed by several overhaul services firms.

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