What's with extraction non-return valve?

The check valve is also known as reflux valve, non-return valve, back pressure valve, check valve. This type of valve is to rely on the force created by the flow of the medium itself in the line of open and close automatically, belongs to a kind of automatic valve. Extraction non-return valve applications: extraction non-return valve used in thermal power plant power plant or extraction system, or other system of steam and the non corrosive medium such as water pipes, to prevent the steam turbine unit in the pressure inside the turbine load rejection suddenly suddenly, extraction tube and each heater in steam flow back into the steam turbine turbine blade broken, destroy malignant accident of the steam turbine generator, and prevent the pipeline leak drain water heater system from the extraction steam pipe into the steam turbine and water hammer accident, in order to protect the safe operation of the steam turbine. 5 seconds quickly close close, ensure the feed water heater water level high, pneumatic device parts after receiving liquid flow signal, to separate the steam turbine quickly, to steam turbine or extraction system to protect. Check valve generally applies to clean medium, should not be used for medium containing solid particles and viscosity is bigger.