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The basic structure and working principle of ball valve piping
Nov 28, 2017

1. The basic structure

General gas pipeline valve is mainly composed of the valve body, seat, ball, stem and transmission components. The main function of the ball valve is to connect and cut off the passage of the fluid in the pipe. The ball valve is used to make the ball rotate 90 ° through the transmission to realize the on and off functions.

 Commonly used natural gas pipeline valve ball floating ball structure and the main structure of the two major categories.

① floating ball valve ball is floating, under the effect of natural gas pressure, the ball will be pressed firmly to the outlet side of the ring, which will form a single seal, the valve seat seal can not be guaranteed. This structure of the ball valve is characterized by simple structure, good unilateral sealing performance, but the sealing surface to withstand greater pressure, so the opening and closing torque.

② The fixed structure of the ball valve with the upper and lower shaft, the lower shaft is fixed to the lower part of the bearing body, the upper stem connected. The ball can rotate along the axis perpendicular to the valve passage, and can not be moved laterally as the floating structure ball valve. Therefore, the fixed ball valve work, the pressure before the valve fluid is only passed to the bearing and the stem, will not cause pressure on the seat, so the fixed valve torque is small, valve seat deformation is small, stable sealing performance, long service life. Fixed ball valve seat is floating, floating valve seat seat with the spring pressure and natural gas pressure on the ball, in order to achieve the seal.

2. Ball valve seat structure

(1) ordinary seat

Normal seat is generally used in the ball valve diameter equal to less than 200mm floating seat [1]. Normal seat is mainly in the pre-tightening force or fluid pressure, the valve seat and the ball compression, and plastic deformation of the seat material to achieve a seal, the sealing effect depends on the valve seat in the fluid under the action or pre-tightening Under the action of force, it can compensate the degree of non-roundness and surface micro-roughness of the sphere. This valve seat structure is simple, easy processing, application is more common.

(2) flexible seat

There are a lot of flexible seat forms, but commonly used in natural gas lines are the coil spring seat and the disc spring seat. Both of these seat seats push the seat to the ball body by the elastic force of the spring and the pressure of the fluid Reached seal. These two seats have good bi-directional sealing ability and good elasticity compensation capability, but for the coil spring seat, the stiffness of each spring is difficult to be consistent, resulting in uneven seat pressure, the impact Valve sealing performance. In contrast, the disc spring structure is simple, compact, easy processing, and force evenly. Therefore, a wide range of applications.

(3) Rotary valve seat

Ball valve opening moment or closing before the ball and the valve seat to form a narrow crescent-shaped channel, so natural gas was thrown into the high-speed turbulent turbulent flow, often resulting in erosion of the valve seat and internal leakage occurred. The main feature of the rotary valve seat is the valve during opening and closing, the valve seat can be made along the axis of the channel for rotational movement through the valve to rotate the valve seat, the valve seat can be evenly wear along the circumferential direction to improve the working conditions and prolong the service life .