Which valve prevents back flow into the compressor?

• A. Inlet valve
• B. Check valve
• C. Multi-turn valve
• D. Ball valve

Answer: (B)

Automatic backflow protection is essential in a compressor system to prevent reverse flow that can cause damage or loss of pressure. A check valve is designed for this purpose. It uses a movable element, like a disc or ball, that allows gas to flow in the intended direction but seats shut when flow attempts to reverse or when pressure on the downstream side is higher. This automatic closing stops backflow, protecting the compressor and helping maintain system pressure.

Other valves are not built to respond automatically to reverse flow. An inlet valve regulates gas entering the compressor, not backflow on the discharge side. A ball valve or a multi-turn valve can block flow when you manually close them, but they don’t automatically prevent reverse flow in operation.