V2500 fuel nozzle guide repair

Slashing the scrap rate
Restoring and saving

The combustion chamber fuel nozzle guide of the V2500 engines (versions A1, A5) is constantly exposed to severe heat stress. To prevent early deterioration with cracking and oxidation of the outer ring, Lufthansa Technik has developed a special repair method to restore the damaged nozzle guide, avoiding the cost of a complete fuel nozzle guide replacement.
Exposed to severe thermal stress during operation, the combustion chamber fuel nozzle guide may exhibit cracking and severe oxidation. If the protective thermal barrier coating bursts or spalls, the nozzle guide may sustain heat damage. The OEM manual offers no repair procedure for this situation, thus the entire nozzle guide has to be replaced.

The repair method

To avoid scrapping – which is one of the basics of Lufthansa Technik's philosophy – EPAR engineers have developed a special repair method to restore the damaged nozzle guide. The damaged segment of the nozzle guide is removed and replaced by a new SPAD ring using Electron Beam (EB) or Plasma Arc Welding (PAW), yielding a repaired nozzle guide which has the material properties of a new part in the process. 

The net effect

But the EPAR engineers did not stop here. In order to enhance the original design of the outer ring and to improve long term reliability of the part, multiple saw cuts in the ring prevent future heat cracks from occuring. For optimum precision, Lufthansa Technik employs laser cutting in this step. In a subsequent step, an improved thermal barrier coating is applied. The net effect: A thermal protection of the repaired nozzle guide that is more comprehensive than the OEM coating.
The new repair not only slashed the scrap rate from 90 percent to 30 percent, it also substantially extended the service life of the component beyond that of a new part.