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    What are the advantages of eccentric hemisphere valves?

    Release time:2019-12-25 Author:fzy667 Source:Xingda Valve

    What are the advantages of eccentric hemisphere valves? In many industrial fields nowadays, everyone can see the eccentric hemisphere valve, which is also very popular. So what are the advantages of eccentric hemisphere valve? The following editors summarize it for everyone.


    1. Unique design and novel structure.
    Second, the structure adopts the principle of eccentricity-wedge tightening.
        The center of rotation of the valve body and spool (that is, the axis of the valve stem) is offset from the geometric center of the sealing spherical surface of the spool by a radial dimension. Contact with metal-metal external force, the valve relies on two eccentricity to achieve self-locking closing. The reasonable selection of eccentricity makes the self-locking angle smaller than the friction angle. Too small a self-locking angle is easy to close, it is very difficult to open, and the angle is too large. Although the opening force is small, the closing torque increases rapidly. Repeated tests on the test bench determine that two reasonable eccentricities are essential. The reliable self-locking performance ensures its tight seal. This is the core technology of the hemisphere valve. From the structural principle to achieve the best seal through manufacturing methods, ball valves, butterfly valves, gate valves, globe valves, etc. are indeed inferior.
    Third, it is easy to achieve and maintain zero leakage for a long time.
        The seal between the valve core and the valve seat is a spherical line contact, and self-locking is achieved by eccentricity. The sealing pair hardly contacts during the entire opening and closing process. Only at the moment of opening and closing, it will contact and lock to achieve zero leakage, ensuring dynamic and static sealing. There are no leaks anywhere. Fouling or other deposits on the valve seat, the valve core has a strong ability to remove scale during the process of contacting the valve seat. During the frequent reciprocating movements of the sealing surface of the gate valve, mixed-flow medium deposits in the cavity at the lower part of the valve body. The shut-off valve completely relies on positive pressure to achieve sealing. The scaling on the valve seat has no cleaning ability. Frequent wear and tear can easily cause internal leakage and leakage of gate valves and globe valves. Ball valve seal is based on the valve seat being squeezed on the ball surface for a long time. It is definitely faster to wear than the half ball valve. The butterfly valve seal is rubber-mediated. It has a far worse performance than the metal hard seal of the half ball valve, ball valve and gate valve. After long-term use of the hemisphere valve, the valve seat will also generate a small amount of wear. It can be continued to use by adjustment. The valve stem and packing only need to rotate 90 ° during the opening and closing process. When there is a sign of leakage, then the packing gland is compressed. A small number of bolts can achieve no leakage at the packing, while other valves are still used with small leaks, and large leaks can be replaced. Fourth, the operation is extremely light. During the whole process of opening and closing the hemisphere valve, the sealing pair is almost in the non-damping idling state. The external force is only detached or compressed at the moment of opening and closing, and the valve stem only needs to rotate 90 ° to be light and fast, and of course, it is easy to operate. The ball valve is operated under the clamping force of the valve seat at both ends during opening and closing. It is larger than the opening and closing torque of the hemisphere valve. The larger the nominal diameter is, the more obvious the opening and closing torque is. The opening and closing of the butterfly valve is to overcome the deformation of the rubber. To achieve, the torque is greater. Gate valves and shut-off valves are long and laborious to operate.
    5. Long service life.
        The sealing pair is a bimetal, and the alloy used for different purposes is superimposed on the mother body. After special heat treatment, its mechanical properties and physical and chemical indicators reach the best state to meet different working conditions (strong wear, rapid erosion, severe corrosion, etc.) As required, the hardness of the valve seat is slightly lower than that of the valve core, and the materials and heat treatment processes are different. When needed, the hardness of the sealing pair can reach HRC53 or higher, and it can withstand high temperatures of 560 ° C. Practice has proved that its anti-corrosion and anti-seizure capabilities are 6 times that of stainless steel sealing pairs, and the valve can be opened and closed tens of thousands of times without failure, which prolongs the service life.
    6. Wide application range.
        Our company's multi-series varieties of hemisphere valves are widely used in non-ferrous metallurgy, gas and natural gas, pulverized coal injection and dust removal of steel, power slag transportation, harmful gases (hydrogen sulfide, phosgene, etc.) and oil products (heavy oil, crude oil, residue oil) Etc.) Smelting and transportation. The reason why it has a wide range of applications is mainly because the sealing pair is separately welded with different alloys to make it bimetal. The main parts such as valve body and valve stem use the required materials to meet different working conditions and constitute a variety of products of our company. series.
    The above is the introduction of six advantages of eccentric hemisphere valve.

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