Turbine air cooler condensate discharge valve

If the valve air supply fails, the FC valve closes and the FO valve opens. Note: The air supply failures mentioned below all refer to faults in the air supply of individual valves; if there is a loss of pressure in the IA system across the entire plant (although this is unlikely), it is a different matter. The condensate outlet valve is designed as FO, and the return valve is designed as FC, both to prevent a high liquid level in the heat well of the surface cooler in the event of a failure in the air supply for the valves; a high liquid level can trigger an interlocked shutdown. Imagine that, if the unit is operating normally but there is a fault in the air supply for the condensate discharge valve, and it is designed as FC, then the discharge will be shut off and the condensate will not be able to be discharged outside. As a result, the level of liquid in the hot well rises, causing the backup pump to start up; yet the level in the hot well continues to rise until the unit shuts down. The actual delivery valve is designed as FO; in the event of a failure in its air supply, it opens fully. As the liquid level drops, the return valve opens wider. If the liquid level continues to drop, an alarm is triggered indicating a low liquid level, but this does not cause the system to stop operating. Imagine that the check valve is designed as FO; if there is a failure in the air supply for the valve, the check valve will open fully. Although the opening degree of the export valve increases gradually due to LT regulation, the level of liquid in the hot well will inevitably rise slowly until the backup pump starts automatically.

Thank you for your thorough explanation; I’ve learned a lot!