What are the structural forms of eccentric hemispherical valves, and what are their characteristics?

Eccentric hemispherical valve and flange gate valve are the same type of valves, the difference is that its closing part is a ball, and the ball rotates around the center line of the valve body to achieve opening and closing.

Ball valves are mainly used in pipelines to cut off, distribute and change the flow direction of the medium. The two-piece ball valve and the three-piece ball valve are a new type of valves that have been widely used in recent years.

1. Structural form:

Eccentric hemispherical valves are divided into two types in terms of appearance and structure

Body-mounted type: Mainly for the medium with very serious erosion and wear, the replacement and maintenance of the damaged opening and closing parts of the body-mounted structure is very convenient, and there is no need to remove the whole valve from the pipeline, which greatly saves maintenance time and cost.

Side-mounted type: The side-mounted type has a compact structure and light valve weight, which is suitable for occasions where the installation space of the valve is required.

Eccentric hemispherical valves are single-seat designs. It eliminates the problem that the medium in the cavity of the valve affects the safety of use due to abnormal pressure increase.

Low torque design. The valve stem with special structure design can be easily opened and closed with only a small handle valve.

Frictionless opening and closing. This function completely solves the problem of traditional valves affecting the seal due to the friction between the sealing surfaces.

Wedge-shaped seal construction. The valve is sealed by the mechanical force provided by the valve stem to press the ball wedge to the valve seat, so that the sealing of the valve is not affected by the change of pipeline pressure, and the sealing performance is reliably guaranteed under various working conditions.

Self-cleaning structure of the sealing surface of the eccentric hemispherical valve. When the ball is tilted away from the valve seat, the fluid in the pipeline passes evenly along the sealing surface of the ball at 360°, which not only eliminates the local scouring of the valve seat by the high-speed fluid, but also washes away the accumulation on the sealing surface to achieve the purpose of self-cleaning.

Here are some of the well-known brands recognized in the valve industry, which are widely recognized and have a high reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following influential first-line brands of water system valves and industrial valves can be used as a reference, but for reference only: Suzhou Neway Valve, Shanghai Guanlong Valve, Shanghai Qizhong Valve, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

<> with the continuous development of the industry, the demand for ball valves, especially ball valves under high temperature and high pressure harsh working conditions, is increasing, and ball valves are required to have higher performance such as wear resistance, erosion resistance, high temperature resistance, and corrosion resistance. However, although the traditional full-bore ball valve and valve seat are surface hardened by surfacing welding and spraying technology, their service life, cost and performance still cannot meet the requirements of use, such as industrial silicon, coal chemical industry, blast furnace gas, gas and other harsh working conditions. The double eccentric hemispherical valve is a new product developed by absorbing the advantages of ball valves, V-shaped valves and orbital ball valves with different structures.

The ball valve adopts double eccentric sealing structure, which has low wear, small torque, good sealing performance and long service life. The valve seat and hemisphere are treated with a special hardening process, which is especially suitable for the requirements of wear resistance, erosion resistance, corrosion resistance and high temperature resistance under harsh working conditions.

2. Structural characteristics.

Hemispherical body The hemispherical body of the double eccentric hemisphere valve adopts double eccentric design, which has reliable sealing effect, instant disengagement, small torque and long service life. It can be used in harsh working conditions for conveying particulate media. Its structural principle is that the center line of the hemisphere and the center line of the valve stem offset size a, and the center line offset size b of the valve seat, when fully opened, the ball and the valve seat are completely disengaged, and there is a certain gap, the radius of rotation is divided into long radius and short radius, the tangent of the long radius rotation trajectory will form an angle with the sealing surface of the valve seat, when the valve is opened and closed, the hemisphere has a fade out of the valve seat surface (as shown in the figure when the opening is 10 °, the core has been completely detached) and the effect of gradual extrusion, As a result, the mechanical wear and abrasion between the seat and the hemisphere during opening and closing is reduced, and the service life is improved.

1.The biggest difference between eccentric hemispherical valve and other ball valves is that it adopts a triple eccentric design structure.

The mounting center of the ball plate is designed with a strict eccentricity from the center of rotation. When the valve is open 10 or even fully open, the valve seat sealing surface of the eccentric hemispherical valve is in a non-contact state with the ball plate, and when it is closed, the ball plate rotates with the valve stem and deflects into the valve seat sealing surface to make it sealed. Therefore, the service life of the valve is prolonged due to less and no wear in the opening and closing process.

2.The seat of the eccentric hemispherical valve is combined into a seal by an embedded O-ring rubber ring or fluoroplastic gasket. Therefore, it has the function of self-compensation for temperature difference and wear, etc., to ensure that the eccentric hemispherical valve is tightly sealed.

3.When the fluid pressure of the eccentric hemispherical valve pipeline is transmitted into the valve seat sealing groove, due to the principle of force component, the resultant force generated by the sealing part and the O-ring expansion force when the pipeline pressure is applied will squeeze the valve seat sealing surface to the ball plate. This unique sealing structure creates a greater sealing force as the line pressure increases.

4.The seat of this eccentric hemispherical valve can be fine-tuned. After a certain period of service life of the eccentric hemispherical valve, when the sealing ring wears out and leaks, the sealing pressure ring can be fine-tuned to the required size by the adjusting screw in the direction of the ball plate without disassembling the valve, which can be compensated and have the same sealing performance as the new valve.

5.In the fully open position, the thickness of the ball plate is the only resistance to the flow of the medium through the valve body, so the pressure drop generated through the valve is very small, so it has good flow control characteristics. There are two types of sealing types for eccentric hemispherical valves: elastic seal and metal seal.

Elastomeric seal valves, the sealing ring can be embedded in the valve body or attached to the perimeter of the ball plate.

1, its structure using the principle of eccentric tightening, through the transmission mechanism to achieve the purpose of tightening, adjusting, closing, sealing pair is a metal surface ring with hard surface contact seal, double eccentric structure in the opening of the valve core is located in the hidden ball room, the flow section is large, and the valve is not washed, the valve core is not washed out when closed, the spherical surface of the valve core is gradually along the valve seat when opening, effectively remove the scaling obstacle, and achieve reliable sealing. It is particularly effective for the mixed-flow transport of two-phase mixed-flow solids that are prone to fouling.

2. The hemisphere of the valve is made of bimetal, and different alloys are welded on the base metal, and the valve seat is also welded accordingly after special treatment, and the sealing surface is combined into various types such as anti-corrosion, wear-resistant, high-strength, etc., to meet the needs of different occasions.

3. Tight sealing, zero leakage of harmful gases.

4. The valve core of the sealing pair is left with a compensation amount, and when the valve is worn, it is rotated a little when it is closed, so that it can be reliably sealed and prolong the service life. In addition, the user unscrews the compression nut, and the valve seat is still available after adjustment or replacement, which avoids the drawbacks of the whole scrapping after the valve seal fails.

1) Small pressure loss: the water loss is zero when fully opened, the flow channel is completely unblocked, and the medium will not be deposited in the cavity of the valve body;

2) Resistant to particle wear: the ball crown of the V-shaped opening has a shear effect between the metal valve seat, in the closing process, only at the last moment the ball crown leans against the valve seat, does not form friction, and the valve seat is made of wear-resistant nickel alloy, which is not easy to be washed and worn, so it is suitable for fiber-containing, tiny solid particles, slurry, etc.;

3) Suitable for high flow rate medium: straight flow channel, strong eccentric crankshaft makes it suitable for high flow rate with no vibration;

4) Long life: no vulnerable parts, due to eccentricity, there is no friction between the sealing surfaces when the valve is opened and closed, and the service life is long;

5) Convenient maintenance: the valve does not need to be removed from the pipeline during maintenance, as long as the valve cover is opened, it can be repaired;

6) Widely used in water, sewage, particles containing fine solids, water, steam, gas, natural gas, oil, etc.