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What are the working principles of pneumatic diaphragm valve

    What are the working principles of pneumatic and electric diaphragm valves?
 
    Diaphragm valve is a special form of cut-off valve, which appeared in the 1920s. Its opening and closing part is a diaphragm made of soft material, which separates the inner chamber of the valve body from the inner chamber of the valve cover and the driving parts, so it is called diaphragm valve.
 
    The characteristics of the diaphragm valve are as follows:
 
    The prominent feature is that the diaphragm separates the inner chamber of the lower valve body from the inner chamber of the upper valve cover, so that the parts such as the stem and disc above the diaphragm are not corroded by the medium, thus eliminating the packing sealing structure and producing no leakage of the medium.
 
    1. The diaphragm made of soft seals such as rubber or plastics has good sealability. Because the diaphragm is fragile, it should be replaced periodically depending on the characteristics of the medium.
    
    2. Due to the limitation of diaphragm material, diaphragm valves are suitable for low pressure and relatively low temperature situations.
 
    3. Diaphragm valves can be divided into six types according to their structural forms: roof type, direct current type, cut-off type, straight-through type, gate type and right angle type; connection type is usually flange connection; according to the driving mode, it can be divided into manual, electric and pneumatic three types, among which pneumatic driving can be divided into three types: normal open type, normal closed type and reciprocating type.
 
    4. Generally, it is not suitable to use pneumatic diaphragm valves in pipelines with temperatures higher than 60 degrees and conveying organic solvents and strong oxidizing media, or in pipelines with high pressure.
 
    Pneumatic and electrical means the way the valve is driven.
 
    This is the principle of pneumatic actuator, which simply means that compressed gas makes the piston move to drive the valve stem.
 
    Electric simply means replacing manual operation with motor.
 
    Diaphragm valves are valves used to open or block airflow in a 1.3 *10-5~2.5X106 Pa fluid system.
 
    Main performance:
 
    Leakage rate: <1.3*10-5Pa. L / S
 
    Materials: 304, 316L;
 
    Working medium: gas, water, oil;
 
    Working temperature: fluororubber - 30 +150;
 
    Principles and characteristics:
 
    Principle: The drive screw is driven by compressed air, which makes the valve core move up and down, and pulls the diaphragm up and down to close and open.  Features: compact structure, simple, small size, beautiful appearance; directed switch, smooth movement; small closing moment, long service life, > 300,000 times; diaphragm compression can be automatically adjusted, pressure uniformity, reliable sealing; diaphragm loading valve core adopts push-in type, easy replacement;
 
    Electric diaphragm valve:
 
    1. The valve is composed of body, cover, stem, disc, diaphragm, electric device and other driving parts.
 
    The opening and closing of the valve is driven by the connecting shaft of the electric device to drive the stem nut, which drives the disc to rise and fall when the stem moves axially.
 
    3. When the power supply breaks down and the valve is in urgent need of opening and closing, the "hand-to-electric switch handle" should be first converted to the position engraved with manual marks, and then the flash door can be opened and closed by rotating the handwheel. When rotating clockwise, the valve closes; otherwise, it opens.
 
    When the electric operation needs to be restored, the "switch handle" can be converted to the position engraved with the electric mark before the electric operation can be carried out.