Control requirements: the boiler feed pump start and run safely, eliminating the flow is too small, increasing temperature, strong water cavitation pump damage. (The old power station has a minimum flow control valve that uses a switch type, along with an automatic circulation valve using a mechanical pump). Condition conditions: pressure drop of 160-350 kg, is the largest pressure drop in the power plant valve, the flow is generally 30% of normal flow. Valve requirements: anti-cavitation, anti-blocking structure, v-class seal, the pump starts and stops running continuously when the valve is working, the pump is normally closed after the next valve, the valve is usually open.