The safety valve plays a safety protection role in the system. When the system pressure exceeds the specified value, the safety valve opens and releases a portion of the gas in the system into the atmosphere, ensuring that the system pressure does not exceed the allowable value, thereby ensuring that accidents do not occur due to excessive pressure. Safety valve, also known as relief valve. The diagram shows several typical structural forms of safety valves. Figure a shows a piston type safety valve with a flat valve core. The air source pressure acts on piston A. When the pressure exceeds the safety value determined by the spring force, piston A is pushed open, and a portion of compressed air is discharged into the atmosphere from the valve port; When the pressure of the air source is lower than the safe value, the spring drives the piston to move downwards and closes the valve port.

Figures b and c show ball valve and diaphragm type safety valves, respectively, with the same working principle as piston type. These three types of safety valves are all controlled by springs. By adjusting the pre tension force of the spring, the safety value can be changed, so they are called direct acting safety valves.

Figure d shows a pilot operated safety valve, which provides control pressure on the diaphragm through a small direct acting valve. The hard core on the diaphragm is the valve core, which is pressed against the valve seat. When the air source pressure A exceeds the safety pressure, the valve core opens and compressed air is discharged into the atmosphere from the left output hole. Diaphragm type safety valves and pilot type safety valves have good pressure characteristics and sensitive actions; But the maximum opening force is relatively small, indicating poor flow characteristics. In practical applications, the type of safety valve should be selected according to actual needs, and its diameter should be selected based on the maximum exhaust volume.