Which condition is usually not acceptable to any extent in turbine blades?

Which condition is usually not acceptable to any extent in turbine blades?

• A. Pits
• B. Cracks
• C. Dents
• D. Corrosion

Answer: (B)

Cracks in turbine blades are usually not acceptable because they create a concentrated stress point that can grow rapidly under the combined effects of high rotational speed, temperature, and fatigue cycling. Once a crack exists, it acts as a path for further fracture, and even a small one can propagate until the blade fails, risking rotor imbalance, engine damage, or a catastrophic shutdown. Other surface issues like pits, dents, or corrosion can often be repaired or kept within prescribed limits during overhaul if they don’t affect critical load paths, but cracks present an immediate and high-risk failure mode, so they demand decisive action.

Cracks in turbine blades are usually not acceptable because they create a concentrated stress point that can grow rapidly under the combined effects of high rotational speed, temperature, and fatigue cycling. Once a crack exists, it acts as a path for further fracture, and even a small one can propagate until the blade fails, risking rotor imbalance, engine damage, or a catastrophic shutdown. Other surface issues like pits, dents, or corrosion can often be repaired or kept within prescribed limits during overhaul if they don’t affect critical load paths, but cracks present an immediate and high-risk failure mode, so they demand decisive action.