What Is a Diaphragm Valve?
The diaphragm valve is a shut-off valve that uses a diaphragm as an opening and closing member to close the flow channel, cut off the fluid, and separate the inner cavity of the valve body from the inner cavity of the valve cover. The diaphragm is usually made of elastic, corrosion-resistant and impermeable materials such as rubber and plastic. The valve body is mostly made of plastic, glass fiber reinforced plastic, ceramic or metal rubber lining material. Simple structure, good sealing and anti-corrosion performance, and low fluid resistance. For low pressure, low temperature, strong corrosive and suspended substance-containing media. According to the structure, there are roof type, cut-off type and gate type. According to the driving mode, there are manual, pneumatic and electric. [1]
- The structure of the diaphragm valve is very different from the general valve. It is a new type of valve and a special form of valve.
- Diaphragm valves use a corrosion-resistant lined valve body and a corrosion-resistant diaphragm instead of the spool assembly, and use the movement of the diaphragm to adjust. The valve body material of the 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 the adjustment of strong corrosive media such as strong acids and alkalis.
- Diaphragm valve has simple structure, low fluid resistance, and larger flow capacity than other types of valves of the same specification. It has no leakage and can be used for the regulation of high viscosity and suspended particulate media. The diaphragm isolates the medium from the upper cavity of the valve stem, so there is no leakage of medium without packing. However, due to the limitations of the diaphragm and lining materials, the pressure resistance and temperature resistance are poor, and generally only applicable to a nominal pressure of 1.6MPa and below 150 ° C.
- The flow characteristic of the diaphragm valve is close to the fast opening characteristic, and is approximately linear before 60% of the stroke, and the flow change after 60% is not large. Pneumatic diaphragm valve can still be equipped with feedback signals, limiters and positioners, etc., to meet the needs of self-control, program control or flow adjustment. The feedback signal of the pneumatic diaphragm valve uses non-contact sensing technology. This product uses a film-type propulsion cylinder instead of a piston cylinder, eliminating the disadvantages of easy damage to the piston ring, which can cause the valve to open and close due to leakage. When the air source fails, you can still operate the handwheel to open and close the valve.
- The sealing principle of the diaphragm valve is that the diaphragm or the diaphragm assembly is pressed against the channel of the weir-type lined valve body or the straight-line lined valve body by the downward movement of the operating mechanism to achieve sealing. The specific pressure of the seal is achieved by the downward pressure of the closing member. Since the valve body can be lined with various soft materials, such as rubber or Teflon; the diaphragm is also made of soft materials, such as polytetrafluoroethylene lined with rubber or synthetic rubber, so it can be achieved with a small sealing force Fully sealed. [2]
- Diaphragm valve is a special form of cut-off valve. Its opening and closing piece is a diaphragm made of soft material, which separates the inner cavity of the valve body from the inner cavity of the valve cover.
- Due to the limitations of the valve body lining process and the diaphragm manufacturing process, both the larger valve body lining and the larger diaphragm manufacturing process are difficult. Therefore, the diaphragm valve should not be used for larger pipe diameters. On the way.
- Due to the limitation of the diaphragm material, the diaphragm valve is suitable for occasions with low pressure and low temperature. Generally do not exceed 180 ° C. Because the diaphragm valve has good anti-corrosion performance, it is generally used in devices and pipelines with corrosive media. Due to the operating temperature of the diaphragm valve, the applicable medium is limited by the diaphragm valve body lining material and the diaphragm material.
- (1) The fluid resistance is small.
- (2) Can be used for the medium containing hard suspended matter; because the medium only contacts the valve body and the diaphragm, there is no need for stuffing box, there is no leakage of stuffing box, and there is no possibility of corrosion on the valve stem.
- (3) Suitable for corrosive, viscous, slurry media.
- (4) Can not be used in high pressure situations.
- Diaphragm valve can be divided into: house type, DC type, cut-off type, straight type, gate type and
- Before installing the diaphragm valve, carefully check whether the operating conditions of the pipeline are consistent with the scope of use specified by this valve, and clean the inner cavity to prevent dirt from blocking or damaging the sealing parts.
- Do not paint grease-like items on the rubber lining and the surface of the rubber diaphragm to prevent the rubber from swelling and affecting the service life of the diaphragm valve.
- The hand wheel or transmission mechanism is not allowed to be used for lifting, and collision is strictly prohibited.
- When manually operating the diaphragm valve, do not use the auxiliary lever to prevent excessive torque from damaging the driving parts or sealing parts.
- Diaphragm valves should be stored in a dry and ventilated room. Stacking is strictly prohibited. Both ends of the inventory diaphragm valves must be sealed, and the opening and closing parts should be slightly opened.
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