SWET repair saves nozzle

Lufthansa Technik Turbine Shannon (LTTS)
Increasing the service life

CF6-80C2: Lufthansa Technik Turbine Shannon (LTTS) has expanded its range of repairs to include a new procedure for repairing low-pressure turbine nozzles. The SWET procedure enables even heavily worn parts to be repaired, thus reducing the scrap rate. During inspection of the low-pressure turbine nozzles on the CF6-80C2 when carried out as part of an engine overhaul, it is normal to identify two to five parts per nozzle set that have exceeded the relevant wear limit. Wear conditions on these parts exceed the criteria for a braze repair so the part has to be scrapped. However, the Superalloy Welding at Elevated Temperatures (SWET) procedure offers an alternative. 

Strategy of the repair

This entails heating the nozzles to over 1000°C in a precisely controlled inert gas atmosphere before the welding operation begins, filling in the material defects using material introduced by the welder. The SWET procedure reduces considerably the stresses introduced during welding and the result is a stable and lasting repair.                                                                                 However, the SWET procedure is extremely demanding not just in terms of the equipment required. In particular, the skills of the welder are critical to the quality of the weld. To complete its capacity for the repair of turbine nozzles, LTTS has now introduced a SWET repair for CF6-80C2 LPT nozzles. The procedure takes the form of an optional step in the overall nozzle repair process and thus is applied after consultation with the customer as an extra step inserted into the normal overhaul sequence. Once the repair has been carried out, the nozzles then go through the remaining process steps, such as heat treatment and coating. 

Customers benefit

The introduction of the SWET repair at Lufthansa Technik Turbine Shannon offers customers considerable cost savings by returning the part to service, a saving of more than 20,000 US dollars per unit compared with the cost of a new replacement part. With the new, OEM approved repair, customers can be confident that if a part can be repaired, LTTS will fix it.