Characteristics of Variable Frequency Valve:
1. High efficiency, energy conservation and low noise
2. With flexible closure and reliable operation accuracy, its service life is 5 times as many as that of ordinary regulating valve.
3. Valve opening and closing time is regulated quickly; valve can be opened/closed within 3 seconds.
4. Realize partition running speed and wide flow regulation range.
5. Powerful protection function and reliable operation.
6. Operation data failure is traceable and convenient for use.
Butterfly valve, also known as flap valve, is a regulating valve with simple structure, which is used to control the opening and closing of media in low-pressure pipelines. Its closing member (valve flap or butterfly plate) is a disc; it rotates around valve shaft to realize opening and closing. This valve is used to control the flow of all kinds of fluids, such as air, water, steam, all corrosive media, slurry, oil, liquid metal and radioactive media. On the pipelines, it mainly cuts off fluids and realizes throttling action. Opening and closing member of butterfly valve is a disc butterfly plate, which rotates around its own axis in valve body, in order to open, close or regulate the fluids.
Advantages
1. Opening and closing is convenient, quick and easy, with small fluid resistance, so it can be operated frequently. 
2. It applies to large-caliber valves due to simple structure, small boundary dimension, short structure length, small size and light weight.
3. It can delivery slurry; the least liquid accumulates at pipeline inlets and outlets.
4. Realize good seal under low pressure.
5. Good regulation performance.
6. At full open position, valve seat channel owns large effective flow area and small fluid resistance.
7. Opening and closing torque is small. Since butterfly plates beside the spindle are equally affected by media, and torque direction is contrary, it is easy to open and close.
8. Sealing face is usually made of rubber and plastic, so low-pressure sealing performance is good.
9. Convenient installation.
10. Flexible and easy operation. Manual, electric, pneumatic and hydraulic types are available.