（4） It is very important to maintain the positive pressure value of the clean room in the purification air conditioning system. The positive pressure value of the clean room can be effectively guaranteed by setting the air volume valve in the exhaust or air supply and exhaust system. The positive pressure of the operating room shall be maintained when the operation in the clean operating room is in progress or not. When the gate valve operation is in progress, the fresh air volume shall be the fresh air volume required to ensure the positive pressure plus the fresh air volume required by the personnel. When the operation is not in progress, the fresh air volume shall be the fresh air volume required to ensure the positive pressure only. Therefore, the double position constant air volume valve shall be set on the fresh air pipe.

After a brief understanding of the working principle of the electric butterfly valve, we will talk about its various characteristics. Because it is a flow control device, it will correspond to different valve types for different use environments. At present, butterfly valves are mainly used in chemical, gas, petroleum and other industrial fields. Of course, they can also be seen in the cooling water system of thermal power plants. Generally speaking, they are more suitable for making large diameter valves.