4. Deaerator water level pneumatic control valve (DALC): control requirements: provide flow to maintain the normal water level of the deaerator, increase the water temperature by adding steam to eliminate dissolved gases in water. Working condition: the flow in the startup phase is small, and the pressure difference is large. Under normal conditions, the flow is large, and the pressure difference is small. The working condition is similar to that of the water supply valve. Valve requirements: effective cavitation resistance at low flow.

Main component 2: if the system needs to realize program control or two position control, the solenoid valve shall be used together. When selecting solenoid valve for pneumatic ball valve, on the one hand, consider DC or AC power supply, voltage and frequency, and on the other hand, pay attention to the relationship between solenoid valve and pneumatic ball valve. If it is required to increase the capacity of the solenoid valve, the way to shorten the action time is to use two solenoid valves or use the solenoid valve as a pilot valve and a ball valve together.