Air close type: the action direction is exactly opposite to that of air open type. When the air pressure increases, the valve acts in the closing direction. When the air pressure decreases or does not exist, the valve acts in the opening direction until it is fully opened, so it is sometimes called fail to open FO. Air opening or air closing of pneumatic control valve is usually realized by different assembly methods of valve body internal structure and actuator.

First, let's understand the lining of the electromagnetic flowmeter sensor
One of the basic conditions for the operation of the electromagnetic flowmeter is that the normal current of the inner wall of the measuring pipe is zero except at the electrode. This requires measuring the pipe wall insulation, which can protect the induced aerodynamic force from being short circuited by the metal pipe. Therefore, the inner wall of the conductive metal measuring pipe and the end face of the flange are lined with insulating linings. At the same time, the insulating lining also enables it to have corrosion resistance, wear resistance and other properties, Here, polytetrafluoroethylene is used as the insulating lining material. Generally, the lining materials include polytetrafluoroethylene, rubber, PVC, polyurethane rubber, industrial ceramics, etc. The polytetrafluoroethylene used here has very stable chemical properties and is resistant to boiling hydrochloric acid, sulfuric acid, aqua regia and concentrated alkali.