The structure of diaphragm valve is very different from that of general valve. It is a new type of valve and a special type of block valve. Its opening and closing part is a diaphragm made of soft material, which separates the inner cavity of the valve body from the inner cavity of the valve cover and the driving parts. It is widely used in various fields. The commonly used diaphragm valves are rubber lined diaphragm valve, fluorine lined diaphragm valve, unlined diaphragm valve and plastic diaphragm valve. The valve core assembly is replaced by a corrosion-resistant lined valve body and a corrosion-resistant diaphragm, which uses the movement of the diaphragm to play a regulating role. The valve body material of diaphragm valve is cast iron, cast steel or cast stainless steel, and lined with various corrosion-resistant or wear-resistant materials, diaphragm material rubber and polytetrafluoroethylene. The lining diaphragm has strong corrosion resistance and is suitable for adjustment of strong corrosive media such as strong acid and alkali.
Pneumatic diaphragm valve
Advantages of diaphragm valve
1. The structure of diaphragm valve is simple, the fluid resistance is small, and the flow capacity is larger than other types of valves of the same specification;
2. Suitable for corrosive, viscous and slurry media.
3. The valve is easy to be disassembled and maintained quickly, and the diaphragm can be replaced on site and in a short time.
4. No leakage, it can be used to adjust the medium with high viscosity and suspended particles. The diaphragm separates the medium from the upper chamber of the valve stem, so the medium without packing will not leak out.
5. The flow characteristic of the diaphragm valve is close to the quick opening characteristic, which is approximately linear before 60% stroke, and the flow rate changes little after 60%.
6. Pneumatic diaphragm valve can also be equipped with feedback signal, limiter and positioner to meet the needs of automatic control, program control or flow regulation.
7. The feedback signal of pneumatic diaphragm valve adopts contactless sensing technology. The product uses membrane type propulsion cylinder instead of piston cylinder, which eliminates the defects of piston ring easily damaged, resulting in leakage and unable to push the valve to open and close. When the air source fails, the hand wheel can be operated to open and close the valve.
Disadvantages of diaphragm valve
1. Can not be used in high pressure situation.
2. Due to the limitation of diaphragm and lining material, its pressure resistance and temperature resistance are poor. It is generally only applicable to 1.6Mpa nominal pressure and below 150 ℃.
Common materials for valves (1) Cast iron 1. Gray cast iron, such as HT200, HT lung 0, etc., is suitable