What is the function of the vacuum breaker in a steam turbine?

• A. To reduce noise
• B. To achieve a faster coast down cycle
• C. To prevent vacuum formation
• D. To increase energy efficiency

Answer: (B)

The vacuum breaker’s job is to prevent dangerous vacuum levels in the steam-turbine condenser system by admitting air when the pressure drops too low. When the condenser is operating, it creates a vacuum to improve exhaust-steam condensation and overall efficiency. If that vacuum becomes too strong, the breaker opens and lets air in, breaking the vacuum to protect piping, valves, and the turbine from damage and to reduce the risk of water hammer during shutdown or cooling. This function is about maintaining safe pressure conditions, not about reducing noise, speeding up the turbine’s coast-down, or boosting energy efficiency.