It is feasible for Sunnyvale double eccentric hemi

2022-10-12
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Feasibility of Neville double eccentric hemispherical ball valve replacing gate valve and globe valve

feasibility of double eccentric hemispherical ball valve replacing gate valve and globe valve

ball valve is the fastest growing valve type in China in recent years. In addition to hard seal ball valve, double eccentric hemispherical ball valve has also achieved rapid development. Double eccentric hemispherical ball valve is a domestic product developed by introducing German hemispherical valve products on the premise of carefully weighing the advantages and disadvantages of various valves such as ball valve, butterfly valve and gate valve. The appraisal conclusion points out that it is better than the equivalent products of gate valve, globe valve and ball valve in some aspects, and can be widely used in petroleum, chemical industry, electric power and metallurgy industries. The double eccentric hemispherical ball valve has unique design and novel structure, The range of orders continues to expand. Indeed, it has replaced ball valves, butterfly valves, gate valves and other valves on different occasions. The structural advantages of double eccentric hemispherical ball valves are as follows:

first, the structure of hemispherical ball valves adopts the wedge eccentric principle

the rotation center of the valve body and valve core (i.e. the axis of the valve stem) is offset by a radial dimension from the geometric center of the sealing spherical surface of the valve core, and also has an offset dimension with the sealing surface of the valve seat on the axis of the valve channel. The sealing pair is in contact with metal under the action of external force. The valve relies on two eccentric centers to realize self-locking closure. The reasonable selection of eccentricity makes the self-locking angle smaller than the friction angle. The self-locking angle is too small to be selected, which makes it easy to close and difficult to open, The angle is larger. Although the opening force is small, the closing torque increases rapidly. After repeated tests on the test bench, it is very important to determine the reasonable eccentricity of the two collocations, and the reliable self-locking performance ensures its tight sealing. This is the core technology of eccentric hemispherical valve. In terms of structural principle and manufacturing means to achieve the best seal, ball valves, butterfly valves, gate valves, globe valves and so on are inferior

second, the hemispherical valve is very easy to realize and maintain zero leakage for a long time

the sealing between the valve core and the valve seat is spherical line contact, which realizes self-locking by eccentricity. The sealing pair hardly contacts during the whole process of opening and closing. Only at the moment of opening and closing, it contacts and locks tightly to achieve zero leakage, ensuring that there are no leakage points at the dynamic and static seals. During the process of contacting the valve seat, the valve core has the ability to strongly remove the scaling or other deposits on the valve seat. During the frequent reciprocating motion of the opening and closing of the sealing surface of the gate valve, the mixed flow medium scales and precipitates in the lower cavity of the valve body. The stop valve completely relies on positive pressure to seal, and the scale on the valve seat has no cleaning ability. The development of the second extruder industry still has a large market space. The frequent repeated wear of the packing is easy to cause the internal leakage and external leakage of the gate valve and stop valve. The sealing of ball valve depends on the long-term extrusion of the valve seat on the spherical surface. It must wear faster than the hemispherical valve. The sealing of butterfly valve is mediated by rubber, which is far from the metal hard sealing performance of hemispherical valve, ball valve and gate valve. After long-term use of the hemispherical valve, the valve seat will also produce slight wear, which can be used continuously through adjustment. During the opening and closing process of the valve rod and packing, the valve rod only needs to rotate 90. When there is a sign of leakage, press a few bolts of the packing gland to achieve no leakage at the packing. However, other valves are still reluctantly used with small leakage, and the valve can be replaced with large leakage

III. The double eccentric hemispherical ball valve is extremely light to operate

experts in the double eccentric industry pointed out that during the whole process of opening and closing the hemispherical ball valve, the sealing pair is almost in the undamped idling state, and the external force is only disengaged or compressed at the moment of opening and closing, while the valve rod only needs to rotate 90, which is light and fast, of course, the operation is light. In the process of opening and closing, the ball valve operates under the holding force of the valve seats at both ends. Its opening and closing torque is larger than that of the hemispherical valve. The larger the nominal diameter is, the more obvious the difference between the opening and closing torque is. The opening and closing of the butterfly valve is realized by overcoming the deformation of the rubber, and the torque is larger. The operation time of gate valve and stop valve is long and laborious

IV. long service life of double eccentric hemisphere valve

the sealing pair is a kind of bimetal, which is overlaid with alloys for different purposes on the matrix. After special heat treatment, the mechanical properties and physical and chemical indexes of the sealing pair reach the best state to meet the needs of different working conditions (strong wear, rapid scouring, serious corrosion and other media). The hardness of the valve seat is slightly lower than that of the valve core, with different materials and heat treatment processes. When necessary, the hardness of the sealing pair can reach more than hrc53, and it can also withstand 560 ℃ high temperature. Practice has proved that its anti-corrosion and anti seizure ability is 6 times that of stainless steel sealing pair. The valve can be opened and closed for tens of thousands of times without failure, extending its service life

v. double eccentric hemispherical ball valve has a wide range of applications

side mounted eccentric hemispherical valve series are widely used in non-ferrous smelting, coal injection and dust removal of gas and natural gas, steel and iron, electric slag transportation, Coal Pulverization and transportation system, smelting and transportation of harmful gases (hydrogen sulfide, phosgene, etc.) and oil products (heavy oil, crude oil, residue, etc.). However, the objects of utilization are still small and medium-sized projects. The reason why hemispherical valves are widely used is that the sealing pair can be overlaid with different alloys to make them bimetallic. The main parts such as valve body and valve rod adopt the materials required by the new sand fixation net and new sand fixation technology developed by the Northwest Institute of ecological environment and resources, Chinese Academy of Sciences to meet the needs of different working conditions

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