NRV IN EXTRACTION LINES

• Non return valves has been installed on the non regulated extraction lines to prevent racing of TG set by reverse flow of steam at the time of tripping or shut down.
• These valve are force closed whenever the emergency stop valve are closed or the generator is isolated from the grid.
• For this purpose each non return valve is provided with hydraulic servomotor which acts by air lines guided by solenoid valves.
• The solenoid receive impulse from limits switches installed on the emergency stop valves servomotors and from generator circuit barkers.

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