A relief valve is a safety device used in various systems to control pressure. It automatically opens to release excess pressure when it exceeds a predetermined limit, preventing potential damage or failure of equipment. Relief valves are commonly found in systems like boilers, pipelines, and hydraulic machinery. These valves are designed to return to a closed position once the pressure drops back to a safe level. By doing so, they help maintain the integrity of the system and ensure safe operation. Proper maintenance of relief valves is essential to ensure they function correctly when needed, protecting both equipment and personnel.