TANK WATER LEVEL CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To secure the NPSH (Net Positive Suction Head) of a pump during water level control of a drain tank connected to a steam system of a power generation plant. SOLUTION: This tank water level control system includes: a tank 1 for storing condensation water obtained by condensing main steam or turbine bleed air; the pump 3 for discharging water stored in the tank 1; a water amount control valve 4 provided downstream of the pump 3 and controlling the amount of water to be discharged; a water level detector 5 for detecting the water level within the tank 1; and a water level controller 7 for controlling a valve opening of the water amount control valve 4 so that the detected water level becomes a predetermined water level within the tank 1. The tank water level control system further includes: a pressure detector 6 for detecting suction pressure of the pump 3; and a pressure controller 8 for controlling the valve opening of the water amount control valve 4 so that the detected pressure exceeds set pressure necessary for securing the NPSH of the pump 3. When the detected pressure becomes lower than a pressure threshold value which is the set pressure+α, control by the water level controller 7 is switched to control by the pressure controller 8. COPYRIGHT: (C)2010,JPO&INPIT