Vacuum negative pressure safety valves are divided into two categories: spring type and rod type. In addition, there are impulse safety valves, pilot safety valves, safety switching valves, safety pressure relief valves, static weight safety valves, etc. Spring-type safety valves mainly rely on the force of the spring to work. There are closed and unclosed spring-type safety valves. Generally, flammable, explosive or toxic media should be closed, and steam or inert gas can be unclosed. There are also spring-type safety valves with wrenches and without wrenches. The function of the wrench is mainly to check the flexibility of the valve disc, and sometimes it can also be used for manual emergency pressure relief.
Working principle:
The safety valve plays a safety protection role in the system. When the system pressure exceeds the specified value, the safety valve opens and discharges part of the gas in the system into the atmosphere, so that the system pressure does not exceed the allowable value, thereby ensuring that the system does not cause accidents due to excessive pressure. Safety valves are also called overflow valves. The figure shows several typical structural forms of safety valves. Figure a is a piston safety valve, and the valve core is a flat plate. 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 part of the compressed air is discharged into the atmosphere from the valve port. When the air source pressure is lower than the safety value, the spring drives the piston downward to close the valve port.