What must operators monitor to prevent damage when a turbine may approach critical speed?

• A. Turbine will overheat
• B. Turbine will vibrate violently
• C. Turbine will stall
• D. Turbine will accelerate uncontrollably

Answer: (B)

When a turbine gets close to its critical speed, resonance can drive large vibrations in the rotor system. Operators monitor vibration levels because those strong vibrations are the clearest early warning that the machine is near that resonance and at risk of bearing, shaft, or support damage if not adjusted. By keeping an eye on how much and how the vibration changes, they can take corrective actions—such as reducing speed, retuning balance, or adding damping—to prevent damage. Other problems like overheating, stalling, or runaway acceleration involve different failure modes and are not the primary indicators of nearing critical speed, so they don’t serve as the best signal in this specific scenario.