1. Introduction of pneumatic globe valve
Pneumatic cut-off valve, widely used in the important system of mine and nuclear power plant, is an important key equipment to ensure the safety production of power plant. In the actual operation, many factors such as the setting of manual mechanism, packing failure, improper operation, insufficient air intake flow lead to many failures, which threaten the safe and stable operation of the power station. In this article, taking the pneumatic globe valve produced by SEREG as an example, analyze the working principle of typical pneumatic globe valve for power station, and describe the setting of neutral point in detail. It provides a basis for the operation and troubleshooting of SEREG pneumatic globe valve or similar pneumatic globe valve used in the power station.
2. Introduction to the working principle of pneumatic globe valve
Working principle of pneumatic globe valve: most of the valves which uses compressed air as power source adopt remote control. The main control room manually or automatically triggers the action command to make the intake and exhaust solenoid valve act to supply and exhaust compressed air to the actuator. Compressed air acts on the piston or diaphragm to overcome the friction of valve action and the spring force on the stem. Press down (Loss of air pressure, open the valve J ) or lift up (Loss of air pressure, open the valve F1) the valve rod, driving the valve core up and down to open or close the valve. When the air pressure is lost in the valve and the driving head compresses air, the valve will be in the safe position of full opening or full closing according to the requirements of the system. The air supply pressure of the service instrument is generally 4-9 bar. Before entering the valve, filter and purify the compressed air through the filter, and then reduce the pressure through the pressure reducing valve. The reading of the inlet pressure gauge is not more than 4bar. The adjustment can be realized by adjusting the adjusting screw installed on the top of the pressure reducing valve, and the protective cover shall be loosened before adjustment.
The four most common and widely used types of pneumatic globe valves are: the valve closed by air loss of handwheel, the valve opened by air loss of handwheel, the valve closed by air loss without handwheel, and the valve opened by air loss without handwheel.