Air to open type: when the air pressure on the diaphragm head increases, the valve acts in the direction of increasing opening. When the upper limit of input air pressure is reached, the valve is fully open. Conversely, when the air pressure decreases, the valve acts in the closing direction. When no air is input, the valve is fully closed. Therefore, sometimes air to open valves are also called fail to close FC.

How to weld pneumatic butterfly valve?
Welding method? It is widely used in machinery, chemical industry, petroleum, metallurgy, food and other industries. Pneumatic butterfly valves are generally welded during connection. How should they be welded? Next, I will introduce you to the five steps of welding. You can also read the first step of the welding process site: when welding the pipe orifice size, you should first measure the length of the pipe, and then use the pipe knife to cut the pipe size.
Step 2: Clean the pipeline. Because the pipeline is metal, some waste slag will be generated in the pipeline due to oxidation, and some waste slag will affect the welding effect. Therefore, before welding, we should use emery cloth or paper to grind away the waste slag in the pipe.
Step 3: Use the pipe brush to clean the fittings. Cleaning the fittings can ensure that the welding hoses are clean and tinned.
Step 4: Control the welding time. Generally speaking, the length of weld bead you need depends on the length of solder.
Step 5: The use of flare heat pipe in line with the flare heat pipe is mainly to ensure that the weld of the pipe is evenly heated. It is worth noting that when using the torch, ensure that the flame is close enough to cover the diameter of the entire pipeline.