What Are the Characteristics and Classification of Diaphragm Valve?

The structure of the diaphragm valve is very different from the general valve. It is a special type of stop valve, which relies on a soft rubber mold or plastic film to control fluid movement. 

1. Sealing Principle of Diaphragm Valve

The sealing principle of diaphragm valve is to press down the diaphragm assembly by the downward movement of the operating mechanism to close with the channel of weir type lining valve body or through type lining valve body, so as to achieve sealing. The specific pressure of the seal depends on the downward pressure of the closing member. Because the valve body can be lined with various soft materials, such as rubber or polytetrafluoroethylene, etc. The diaphragm is also made of soft materials, such as rubber or synthetic rubber lined polytetrafluoroethylene, so it can be achieved a complete seal with very little force. 

The diaphragm valve has only three main components: body, diaphragm and bonnet assembly. The diaphragm separates the inner cavity of the lower valve body and the inner cavity of the upper valve cover, so that the valve rod, stem nut, valve disc, pneumatic control mechanism, electric control mechanism and other parts above the diaphragm do not contact with the medium, and do not produce the medium leakage, thus eliminating the sealing structure of the stuffing box. 

2. Application of Diaphragm Valve

Diaphragm valve is a special form of stop 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 limitation of valve body lining process and diaphragm manufacturing process, it is difficult to manufacture large valve body lining and diaphragm. Therefore, diaphragm valve is not suitable for large pipe diameter, and it is generally used in pipelines under DN200. 

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 ℃. Because the diaphragm valve has good anti-corrosion performance, it is generally used in devices and pipelines with corrosive media. 

3. Characteristics of Diaphragm Valve

(1) The fluid resistance is small.

(2) It can be used for medium containing hard suspended solids. Because the medium only contacts with the valve body and diaphragm, there is no need for packing box, and there is no possibility of corrosion to the valve stem.

(3) It is suitable for corrosive, viscous and slurry media.

(4) It can not be used in high pressure situations.

4. Classification of Diaphragm Valves

(1) Right Angle Diaphragm Valve

Right angle diaphragm valve is the most basic one commonly used code G41. Diaphragm valve body lining is to better play its corrosion resistance.

(2) Ridge Diaphragm Valve

The ridge diaphragm valve has larger fluid resistance than the right-angle diaphragm valve. And it has a large sealing area and good sealing performance, which can be applied to pipelines with high vacuum.

(3) Gate Type Diaphragm Valve

The gate type diaphragm valve has the smallest fluid resistance and is suitable for conveying viscous materials. Diaphragm materials commonly used natural rubber, neoprene, butyl rubber, NBR, isobutylene rubber, fluorinated rubber and polyfluoroethylene propylene plastic (F46), etc. The disadvantage of the gate type diaphragm valve is that the pressure resistance is not high, generally within 6kgf/cm2 (0.6MPa). The temperature resistance performance is also limited by the diaphragm, generally it can only withstand 60 ~ 80 ℃, and the maximum is not more than 180 ℃. 

Diaphragm valves are popular in a wide variety of industries, including agriculture, chemical processing, medicine and so on.