Which two valves are self-actuated?

• A. Check and relief
• B. Ball valve
• C. Globe valve
• D. Gate valve

Answer: (A)

The idea is automatic operation driven by the fluid itself, without needing external power or manual control. A check valve and a relief valve fit this behavior.

A check valve automatically opens when fluid flows in the intended direction and closes to prevent backflow when flow reverses. It doesn’t need any external actuation to do this; the flow itself drives the movement.

A relief valve automatically opens when system pressure exceeds its set limit to relieve pressure, then reseats when pressure drops back down. It responds directly to the fluid pressure.

In contrast, a ball valve, globe valve, and gate valve typically require manual operation (turning a handle or using an actuator) to open or close, so they are not inherently self-actuated.