What indicators would signal a need for turbine blade inspection or replacement?

• A. Excessive vibration.
• B. Abnormal bearing temperatures.
• C. Acoustic anomalies.
• D. Excessive vibration, abnormal bearing temperatures, acoustic anomalies, blade root cracks on borescope inspection, or performance decline.

Answer: (D)

Turbine blade health is assessed by watching for signs that reflect mechanical, aerodynamic, and structural issues. Excessive vibration points to imbalances or damage in the rotating parts that alter the blade loading, which can lead to further wear or failure if not addressed. Abnormal bearing temperatures signal increased friction or lubrication problems in the rotor train, which can stress blades indirectly through misalignment or higher loads. Acoustic anomalies reveal changes in the flow or contact issues such as rubbing or cavitation, offering an early hint of blade or housing problems. Blade root cracks found during a borescope inspection are direct, critical evidence of structural damage where cracks can propagate under load. A noticeable performance decline ties everything together by indicating the overall degradation of aerodynamic efficiency and mechanical condition, which often accompanies blade damage or wear.

Because each indicator can have other causes, seeing several of these signs together provides a clear, reliable reason to inspect or replace blades. The combination covers both indirect symptoms and direct visual evidence, giving a comprehensive basis for maintenance decisions.