Working Principle and Composition of Diaphragm Valves
Release Date:
2023-02-15
Diaphragm valves replace the valve plug assembly with a corrosion-resistant lined valve body and a corrosion-resistant diaphragm, with the diaphragm’s movement providing the regulating function. The valve body is typically made of cast iron, cast steel, or cast stainless steel, lined with various corrosion-resistant or wear-resistant materials, while the diaphragm is made of rubber or polytetrafluoroethylene. The lined diaphragm exhibits excellent corrosion resistance, making it suitable for regulating highly corrosive media such as strong acids and strong bases.
Diaphragm valves replace the valve plug assembly with a corrosion-resistant lined valve body and a corrosion-resistant diaphragm, with the diaphragm’s movement providing the regulating function. The valve body is typically made of cast iron, cast steel, or cast stainless steel, lined with various corrosion-resistant or wear-resistant materials, while the diaphragm is made of rubber or polytetrafluoroethylene. The lined diaphragm exhibits excellent corrosion resistance, making it suitable for regulating highly corrosive media such as strong acids and strong bases.
Diaphragm valves feature a simple structure, low fluid resistance, and greater flow capacity than other valve types of the same size; they are leak-free and suitable for regulating highly viscous media and media containing suspended particles. The diaphragm isolates the process fluid from the upper chamber of the valve stem, eliminating the need for packing and preventing external leakage. However, due to limitations in diaphragm and lining materials, their pressure and temperature ratings are relatively low, typically limited to a nominal pressure of 1.6 MPa and a maximum operating temperature of 150°C.
The flow characteristic of a diaphragm valve is close to quick-opening; prior to 60% of the stroke, it approximates linearity, while beyond 60% the flow change is relatively small. Pneumatically actuated diaphragm valves can also be equipped with feedback signals, limit switches, and positioners to meet the requirements of automatic control, program control, or flow regulation. The feedback signal for pneumatic diaphragm valves employs contactless sensing technology. This product utilizes a diaphragm-type actuating cylinder instead of a piston cylinder, thereby eliminating the drawback of piston rings being prone to damage, which can lead to leakage and prevent the valve from being opened or closed. In the event of an air supply failure, the valve can still be manually operated via a handwheel to open or close it.
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