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. This is crucial in systems like boilers, pipelines, and hydraulic systems, where high pressure can lead to dangerous situations. Relief valves come in different types, including spring-loaded and pilot-operated designs. They are essential in industries such as oil and gas, manufacturing, and chemical processing, ensuring safe operation by maintaining pressure within safe limits and protecting both equipment and personnel.