Types and Selection of Pneumatic Control Valves in Power Industry
1. Feed water valve Main and auxiliary boiler feed water valves, composite feed water regulating valve: control requirements: control boiler water inlet, maintain boiler liquid level and steam flow. Working condition requirements: when the boiler is started, the valve pressure difference can reach 100-300 kg, and the flow is small. When the boiler is in normal operation, the pressure difference is small, and the flow is large. The flow adjustable ratio is 75:1-100:1. Requirements for valves: the valve body material is WCB/WC9. For the startup valve in the double valve system, it is required to be cavitation resistant and Class V closed. For the composite feed water valve, it is required to use the characteristic valve trim to meet the needs of boiler startup and normal operation at the same time. Generally, the valve is fault closed (it should be noted that in order to eliminate dissolved oxygen in general water supply, hydrazine will be added for treatment, which will cause adverse reaction to SATELLITE No. 6 alloy or other similar alloys, so 316 STELLITE surfacing is not used to treat the valve internals, and 416 stainless steel can be directly used).

The domestic electric butterfly valve, as a component used to realize the on-off and flow control of the pipeline system, has been widely used in many fields. In the known butterfly valve technology research, its sealing form mostly adopts sealing structure, and the sealing materials are rubber, polytetrafluoroethylene, etc. Due to the limitation of structural characteristics, it is not suitable for high temperature, high pressure, corrosion resistance, wear resistance and other industries.