The principle and characteristics of diaphragm valve

The principle of diaphragm valve :

The diaphragm valve uses a corrosion-resistant lining body and a corrosion-resistant diaphragm instead of the valve core assembly, and the movement of the diaphragm is used for adjustment. The body material of the diaphragm valve is cast iron, cast steel, or cast stainless steel, and is lined with various corrosion-resistant or abrasive 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 acid and strong alkali.

The diaphragm valve has a simple structure , low fluid resistance, and a larger flow capacity than other types of valves of the same specification; it has no leakage and can be used for the adjustment of high viscosity and suspended particulate media. The diaphragm isolates the medium from the upper cavity of the valve stem, so there is no packing medium and no leakage. However, due to the limitation of the diaphragm and lining materials, the pressure resistance and temperature resistance are poor, and it is generally only applicable to the nominal pressure of 1.6MPa and below 150°C.

The flow characteristic of the diaphragm valve is close to the quick opening characteristic, which is approximately linear before 60% of the stroke, and the flow after 60% does not change much. Pneumatic diaphragm valves can also be equipped with feedback signals, limiters and positioners to meet the needs of automatic control, program control or flow adjustment. The feedback signal of the pneumatic diaphragm valve adopts non-contact sensing technology. The product adopts a membrane type propulsion cylinder instead of a piston cylinder, eliminating the disadvantage of easy damage to the piston ring, causing leakage and unable to push the valve to open and close. When the air source fails, the handwheel can still be operated to open and close the valve.

Features of diaphragm valve :

(1) The fluid resistance is small.

(2) It can be used for media containing hard suspended solids; since the media only contacts the valve body and diaphragm, there is no need for stuffing box, there is no stuffing box leakage problem, and there is no possibility of corrosion to the valve stem.

(3) Suitable for corrosive, viscous, and slurry media.

(4) Cannot be used in high pressure occasions.