During teardown, what criteria determine whether a turbine blade is unrepairable and must be replaced?

• A. Cracks, chipping, bending, excessive root or airfoil wear, corrosion, or coating damage exceed OEM repair limits.
• B. If the blade is older than a specified service life.
• C. If the blade weight exceeds a threshold.
• D. If the blade has any minor surface blemish.

Answer: (A)

When deciding if a turbine blade must be replaced, the check is whether damage exceeds the OEM repair limits. Cracks, chipping, bending, excessive root or airfoil wear, corrosion, or coating damage beyond what the manufacturer's repair criteria allow means the blade can’t be safely repaired and must be replaced. OEM limits are set to ensure structural integrity and aerodynamic performance; if damage stays within those limits, repairs or rework can be performed. Other factors like service life or weight thresholds aren’t by themselves deciding factors, and minor surface blemishes aren’t grounds for replacement.