Do You Really Understand The Working Principle Of Pilot Operated Safety Valve
Mar 19, 2022
Pilot operated safety valve (also known as pulse safety valve) is a safety valve that drives or controls the main valve by discharging medium from the pilot valve. The pilot valve itself is a standard spring-loaded safety valve. Safety valves are automatic valves, which are mainly used in boilers, pressure vessels and pipelines. The control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation. According to the opening height of the safety valve disc, it can be divided into micro open safety valve and full open safety valve.
When the protected system is in normal operation. The slide valve in the pilot valve chamber is open, and the system pressure is transmitted from the main valve inlet to the air chamber above the main valve disc (piston) through the lower conduit, pilot valve chamber and upper conduit. At this time, the gas pressure in the upper air chamber is equal to the system pressure at the main valve inlet. The sealing surface of the pilot valve is in a sealed state to ensure that the gas in the air chamber above the main valve cannot be discharged from the discharge port of the pilot valve. As the piston area is larger than the sealing surface area of the valve disc, the system pressure produces a downward resultant force on the main valve disc, so that the main valve is closed and sealed.
When the system pressure rises to the set pressure, the gas pushes up the valve core of the pilot valve at the sealing surface of the pilot valve to make the sealing surface open. At the same time, the slide valve in the pilot valve chamber moves upward to close the air passage in the pilot valve chamber. The medium in the air chamber above the main valve disc is discharged through the sealing surface of the open pilot valve, reducing the pressure above the main valve disc. The main valve disc opens under the push of inlet pressure to relieve the pressure of the system.
When the system pressure drops to a certain value, the pilot valve core returns to its seat under the action of the spring, the sealing surface of the pilot valve is closed, the slide valve in the pilot valve chamber is opened, and the valve chamber is unblocked. The system pressure is transmitted to the air chamber above the main valve disc through the pilot valve chamber again, and the main valve disc is pushed to close.
