What restricts flow and prevents pressure build up in the system?

• A. Relief valve
• B. Orifice plates
• C. Gate valve
• D. Check valve

Answer: (B)

Orifice plates act as a fixed throttle in a pipe, introducing a controlled restriction that limits how much fluid can pass for a given upstream pressure. This creates a pressure drop across the plate, so the flow rate is reduced and the system is less prone to pressure spikes downstream. The device is passive and predictable, making it effective at preventing unintended pressure buildup by throttling the flow rather than actively venting or blocking flow.

Relief valves actively vent excess pressure to prevent overpressure, so they aren’t just restricting flow. Gate valves and check valves mainly open, close, or prevent backflow rather than providing a steady, fixed restriction to control pressure rise.