Which method is used to prevent water hammer during valve operations?

• A. Quick full closure
• B. Opening both ends to relieve pressure
• C. Abruptly closing and reopening the valve
• D. A controlled closing of valves to prevent water hammer and sudden pressure surges

Answer: (D)

Water hammer occurs when moving water is suddenly stopped or its flow is abruptly changed, creating a pressure surge that can damage pipes and fittings. The best way to prevent this during valve operations is to close valves in a controlled, gradual manner, throttling the valve so the flow decreases slowly. This steady deceleration limits the magnitude of the pressure rise and protects the system from shocks from sudden changes in flow. Opening both ends to relieve pressure isn’t a standard protective technique for controlling surge because it doesn’t provide a controlled deceleration of flow and can create unpredictable conditions. Abruptly closing and reopening the valve would generate a severe surge, making it worse. So, controlled valve closure to prevent water hammer and sudden pressure surges is the correct approach.