Usage and Features of Stream Extraction Check Valves

Usage of stream extraction check valves

Stream extraction check valves are mainly used for stream extraction system in power plants or thermal power plants. The vales are also used for non-corrosive media such as steam and water. Stream extraction check valves prevent fatality that pressure inside turbine drop suddenly when turbine throwing off load. Steam in extraction steam pipe and other heaters backflows into turbine, breaking vanes and destroying electric generator. The valves also stop pipes in heater from leaking so that water enters into turbine from stream extraction pipes and results in water hammer, ensuring safe operation of turbine. As device for preventing countercurrent of media, the valve can close tightly within 0.5 seconds, ensuring that pneumatic device separates turbine rapidly and provide the maximum protection to turbine or stream extraction system after receiving countercurrent signal of fluid when water level in feed water heater is ultrahigh. Check valves are generally appropriate for clean media. They are suitable for media containing solid particles and having high viscosity. 

 

Air source comes from compressed air (air source pressure 0.4~0.6Mpa). Compressed air enters into two-position three-way solenoid valve, entering into inlet of cylinder through extraction valves. Then, check valves open. Hand directional valve is used to test flexibility of check valves during operation.

 

When check valves closing, solenoid valve closes due to outage, cutting off air source. Then, extraction valve launches to drain air inside inferior vena of cylinder. Check valves turn off rapidly.  

 

Features of stream extraction check valves

1. Sealing face is bead welded with stainless steel or cobalt based cemented carbide, having good wearing resistance and reliable sealing. 

2. When media flowing forward, air enters into inferior vena of cylinder, interacting with counter weight. Disc is located at the full open position evenly. When media flowing contra, inferior vena of cylinder decompresses rapidly. The disc closes within 0.5 seconds.   

3. Counter weight is applied on pin roll through lengthening bar and shifting fork, used for balancing gravitational torque, in case of water hammer. When media flowing forward, counter weight contributes to opening valves, remaining steady of valves and reducing vibration during operation.