PURPOSE: To prevent a serious system confusion and any trouble such as leakage from valve seat, by combining advantages of ON-OFF control with those of continuous control.
CONSTITUTION: A recirculation conduit 5 having its one end connected with a deaerator 1 branches out downstream of a feed water pump 3. The conduit 5 is equipped with an ON-OFF valve 12 and downstream the valve a continuous flow control valve 13. When the actual flow exeeds a preset flow level the ON-OFF valve 12 and the flow control valve 13 are full opend trough a relay 14 and regulator 15.The valve 12 thus shuts off the conduit in order not to exert ex- cessive differential pressure on the valve 13 and cause any leak from a valve seat. When the actual flow is smaller than or equal to the preset level, the ON-OFF valve 12 is full open to keep the flow valve 13 under continuous control for preventing quick fluctuation
KISHIDA KENJI
TAKAHASHI MASAHIKO
