Airfoil Replacement Repair offers 100 percent yield
Engine Parts and Accessories Repair (EPAR)
Scrapping completely avoided
After engine disassembly in the shop for overhaul, high pressure turbine nozzles often show damage beyond conventional repair. A new cost-efficient OEM repair method available from Lufthansa Technik EPAR for CFM56-5A and CF6-80C2 turbofans delivers practically 100 percent yield, completely avoiding scrapping.
Expanded OEM repair method – ARF
Standard repair methods for damaged HPT nozzles of the CFM56-5A include welding, brazing and partitioned alloy component healing (PACH). Components showing nozzle damage exceeding the limits however had to be send to OEM for repair. To offer an improved solution, Lufthansa Technik's Engine Parts and Accessories Repair division (EPAR) has expanded on its OEM repair method termed Airfoil Replacement Repair (AFR).
Process of the ARF
The entire repair process is highly critical, as the HPT nozzle is one of the most highly-stressed parts in the engine and the geometry of the vanes has direct influence on engine performance data such as EGT margin. Therefore AFR is a rather complex repair. The procedure begins with a small part of the HPT nozzle inner platform being cut off. The remaining piece, the forward inner platform, now serves as the basis for the build-up of a new HPT nozzle. Next, OEM-provided Spads are clustered to give a so-called "shroil", which is then attached to the old part using high-temperature brazing. After machining of all surfaces to the final contour and drilling the cooling holes, the process is concluded by coating the nozzles with a protective layer of vapor phase aluminizing as well ceramics on the convex surfaces.
The same repair method has been available for the CFM56-3 HPT nozzle from Lufthansa Technik Turbine Shannon (LTTS) and is now also available for the first stage of the CF6-80C2 HPT vane, underlining the performance of Lufthansa Technik's EPAR division. For all intents and purposes the yield achieved is 100 percent, as virtually every HPT nozzle can be repaired now. Thus a substantial reduction in overhaul costs is possible, as the cost of the repair is only about one third of a replacement part. And since part of the new nozzle is now a monocrystal material, the repaired nozzle can be expected to show a superior service life.