Eccentric hemispherical valves for transportation in the petroleum industry

Eccentric hemispherical valves for transportation in the petroleum industry

working principle

Eccentric hemispherical valves control fluids through eccentric design and have multiple working modes. One approach is to use an eccentric crankshaft design, where the centerline of the ball crown deviates from the centerline of the valve passage by an eccentric distance. When the valve is opened, the crankshaft rotates a small angle and the ball crown leaves the valve seat; When closed, the ball crown only comes into contact with the valve seat at the moment of closure, ensuring sealing and usage time. There is also an electric eccentric hemispherical valve, which drives the valve stem through an electric actuator to rotate the hemispherical valve core around the eccentric axis. Upon receiving the opening signal, the electric actuator drives the valve stem to rotate the eccentric ball around the eccentric axis. The ball first lifts upwards and disengages from the valve seat, then continues to rotate to open the valve and allow the medium to flow; Upon receiving the shutdown signal, the sphere rotates in the opposite direction, first approaching the valve seat position, and then pressing down on the valve seat to achieve sealing and prevent the flow of the medium.

Eccentric hemispherical valves are generally composed of a valve body, a valve cover, a valve ball, and a valve stem. There is a hemispherical flow channel on the valve body, and the valve ball and stem are used to control the opening and closing of the valve.

When the valve stem rotates, the valve ball rotates accordingly, and the spherical surface of the valve ball always maintains a certain distance from the inner wall of the valve body, forming an eccentric space. The valve opening degree is adjusted by controlling the rotation angle of the valve ball.

When the sphere tends to move away from the valve seat, the fluid in the pipeline passes uniformly along the sealing surface of the sphere at a 360 ° angle, which can wash away the accumulated substances on the sealing surface and achieve self-cleaning.

Adopting a wedge-shaped sealing structure, relying on the mechanical force provided by the valve stem to press the ball wedge onto the valve seat to achieve sealing, ensuring reliable sealing performance under various working conditions. The sealing pair of the partially eccentric hemispherical valve is a metal ring hard surface contact seal. The double eccentric structure has a large flow cross-section when the valve core is located in the ball storage chamber during opening, and the valve core is not flushed. When the valve core is closed, it is also not flushed. When the valve core is opened, the spherical surface of the valve core gradually moves along the valve seat, which can effectively remove scaling obstacles and achieve reliable sealing.