A safety valve is used to protect the system against overpressure. Overpressure occurs when the pressure exceeds the Maximum Allowable Working Pressure or the pressure for which the system is designed. A safety valve begins from a set pressure; the valve first opens a little, after which it opens fully so that the unwanted pressure is removed from the system as quickly as possible.
The fundamental purpose of a safety valve is the protection of life, property, and the environment. A safety valve is designed to open and relieve excess pressure from vessels or equipment and reclose and prevent further release of fluid after normal conditions have been restored.
A safety valve is a safety device and, in many cases, the last line of defense. It is vital to ensure that the safety valve can operate at all times and under all circumstances. A safety valve is not a process valve or pressure regulator and should not be misused as such. It should have to operate for one purpose only: overpressure protection.
Safety valves are used to restrict pressure increases, leading to malfunctions, fire hazards, or explosions. Safety valves only have mechanical parts, so they are used when electronic or pneumatic safety devices fail. A safety valve is fully actuated by the system's media, keeping it working in a power failure.