The primary purpose of a relief valve is to limit system pressure.

• A. Bleed
• B. Shut-off
• C. Check valve
• D. Relief

Answer: (D)

Relief valves protect the system by keeping pressure from exceeding safe limits. They stay closed during normal operation and then open when pressure reaches a preset level, venting fluid to a reservoir or back to a lower-pressure area. This action momentarily releases excess pressure and lowers the overall system pressure, then the valve closes again once the pressure drops below its opening range. The key idea is automatic protection against pressure spikes that could damage pumps, pipes, or components.

A bleed valve, by contrast, is used for small, controlled releases to de-pressurize a line or vent air, not as a protective overpressure device. A shut-off valve simply stops flow and doesn’t regulate pressure. A check valve prevents reverse flow but doesn’t relieve or limit pressure.