Which scenario best describes the use of a check valve?

• A. Prevent backflow in a pipeline carrying process fluid
• B. Increase pressure in a vessel
• C. Monitor ambient temperature
• D. Act as an emergency shutdown device

Answer: (A)

Check valves are one-way devices that open when fluid moves in the intended direction and close if flow reverses. This behavior prevents backflow in a pipeline carrying process fluid, protecting pumps, vessels, and downstream equipment from reverse flow, contamination, or siphoning. They’re passive components that don’t require power or external signals, and they don’t add energy to the system. That’s why they aren’t used to increase pressure, monitor temperature, or act as emergency shutdown devices, which rely on active control or sensing rather than a simple one-way seal.