What triggers NGV replacement during overhaul?

• A. Cracks or deep wear.
• B. Minor surface scratches that can be repaired.
• C. Coating wear only.
• D. Random test results.

Answer: (A)

Cracks or deep wear on the nozzle guide vanes indicate structural damage that cannot be reliably repaired to safe, in-spec limits. The NGV faces high temperatures and stresses, so a crack can grow with turbine cycling and lead to failure or imbalance, while deep wear reduces thickness and alters sealing and aerodynamic performance. Minor surface scratches and coating wear are typically repairable or within allowable limits when properly addressed (polishing, recoating, or similar methods). Random test results don’t by themselves mandate replacement; they must be evaluated against established acceptance criteria and confirm actual defects.