Top loaded ball valve is widely used in oil and gas pipelines, and oil, oil refining, petrochemical, chemical, chemical fiber, metallurgy, electricity, nuclear power, food and paper and other devices. Top-mounted ball valve in the pipeline demolition is simple and quick, easy maintenance. When the valve fails in the pipeline to be repaired, there is no need to disassemble the valve from the pipeline. Just remove the middle flange bolt and nut, remove the valve cover and the stem assembly together with the valve body, and then remove the ball and valve Seat assembly. The ball and seat can be repaired online. This maintenance saves time and minimizes production losses. Top loaded ball valve is divided into floating ball valve and fixed ball valve. Float mounted ball valve nominal size ≤ DN200. The sphere exerts a compression spring, the role of the compression spring is to exert preload on the ball so that the valve seat sealing surface in all cases are in close contact, good sealing performance. Seat and body contact surface wedge angle of 10 °, the valve seat to self-locking in the direction of the pipeline, when the valve seat subjected to greater pressure, the valve seat will not produce any displacement. Therefore, the structure of the valve has the characteristics of both the valve and the ball valve advantages. In the maintenance inspection found that the valve body and seat prone to leakage, if you increase the spring preload, it is bound to increase the ball valve closing torque. In order not to increase the closing torque of the ball valve, a rubber O-ring is added on the back of the valve seat sealing surface to solve the leakage problem of the back surface of the valve seat sealing surface. The drawback of the fixed ball valve is the spring preload can not be adjusted and controlled, and the spring assembly when a large amount of compression, assembly difficulties. In order to solve this problem, ANSI 302 is used instead of 304 as the spring material. ANSI 302 spring stiffness, corrosion resistance and 304 similar. In addition, an increase of spring seat and adjusting nut, outside the seat and spring seat on the outer thread respectively, with the adjusting nut spring will be pressed into the spring seat, the valve seat assembly into the body. Since the spring is compressed before the ball is installed, it is convenient to install the ball. When the ball is assembled, the adjusting nut will be withdrawn from the spring seat. At this moment, the spring preloads the ball less. If you want to increase the preload, adjust the nut can be used to adjust. Search Keyword: More Valve Technical Articles
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