Characteristics, Classification And Application Environment Of Sanitary Valves

Sanitary Valve Features, classification and application environment

Sanitary valves are simple flapper valves that are not tightly closed, usually used in water pipeline systems for flow regulation and damping. In the past decade, the manufacturing technology of sanitary valves has developed rapidly. They are widely used in developed countries such as the United States, Japan, Germany, and France. Their varieties are also expanding, and they are developing in the direction of high temperature, high pressure, large diameter, high sealing, long life, excellent adjustability and multi-function of one valve. Their sealing and safety reliability have reached a high level, and they have partially replaced stop valves, gate valves and ball valves. The traditional sanitary valves no longer exist. Therefore, sanitary valves are widely used in water supply, oil, gas and other pipelines.

Sanitary valves are classified by connection method

1. Flange sanitary valves

2. Wafer sanitary valves

3. Welded sanitary valves

4. Clamp sanitary valves

5. Threaded sanitary valves

The structural characteristics of American standard sanitary valves eliminate the shortcomings of other types of sanitary valves that cannot be sealed due to over-opening, and can be used normally at high temperatures, overcoming the shortcomings of other types of valves that are prone to leakage due to thermal expansion when used at high temperatures. The sanitary valve uses different sealing surface materials according to the medium requirements to ensure that the sealing surface is wear-resistant, corrosion-resistant, and has a long service life. The structural features of American standard sanitary valves are as follows:

① The unique design of three-way eccentricity enables frictionless transmission between sealing surfaces, extending the service life of the valve;

② Elastic seal is generated by torque;

③ The clever wedge design enables the valve to have an automatic sealing function that becomes tighter and tighter, and the sealing surfaces are compensatory and leak-free;

④ Small size, light weight, easy operation, and easy installation;

⑤ Pneumatic and electric devices can be configured according to user requirements to meet the needs of remote control and program control;

⑥ The material of replacement parts can be applied to various media, and lining anti-corrosion (lining F46, GXPP, PO, etc.);

⑦ Continuous structure diversification: clamping, flange, butt welding.

Precautions for sanitary valves:

1. Since the multi-layer soft stacking seal ring is fixed on the valve plate, when the valve plate is normally open, the medium forms a positive scouring on its sealing surface, and the scouring directly affects the sealing performance.

2. Due to the limitation of structural conditions, this structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate is too thick and the flow resistance is large.

Product use of sanitary valves:

D371F46 wafer-type fluorine-lined sanitary valves are suitable for various concentrations of aqua regia, sulfuric acid, hydrochloric acid, hydrofluoric acid and various organic acids, strong acids, and strong oxidants at -50℃ to 150℃. FEP is also suitable for use on pipelines of various concentrations of strong alkali organic solvents and other corrosive gases and liquid media.

Features of sanitary valves:

When in the countercurrent state, the seal between the valve plate and the valve seat is pressed against the valve seat by the torque of the drive device. As the pressure of the reverse medium increases, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored in the spring of the adjusting ring after being loaded compensates for the tight pressure of the valve plate and the valve seat sealing surface and plays an automatic compensation role. Therefore, unlike the existing technology, the utility model does not install a soft and hard multi-layer sealing ring on the valve plate, but directly installs it on the valve body. Adding an adjustment ring between the pressure plate and the valve seat is a very ideal two-way hard sealing method. It will replace gate valves and ball valves.

The disadvantage of rubber-sealed sanitary valves is that when used for conservation, cavitation will occur due to improper use, causing the rubber seat to peel off and be damaged. For this reason, metal-sealed sanitary valves are now developed internationally. The cavitation zone is weakened. Generally, the life of the sealing seat is 15-20 years for rubber and 80-90 years for metal under normal circumstances. But how to choose correctly depends on the working conditions. 

The relationship between the opening and flow of sanitary valves is basically linear. If it is used to control flow, its flow characteristics are also closely related to the flow resistance of the piping. If the valves installed on two pipelines are of different diameters and forms, and the pipeline loss coefficients are different, the flow differences of the valves will also be very large. 

When the sanitary valve is in the middle opening, the opening shape formed by the valve body and the front end of the butterfly plate is centered on the valve shaft, and the two sides form a complete divergence. The front end of the butterfly plate on one side moves in the direction of the water flow, and the other side moves against the direction of the water flow. Therefore, the valve body and the valve plate on one side form a nozzle-shaped opening, and the other side is similar to a throttling hole-shaped opening. The flow rate on the nozzle side is much faster than that on the throttling side, and negative pressure will occur under the valve on the throttling side, which often causes the rubber seal to fall off.