Basic composition and working principle of pipeline ball valve
Basic structure composition
Generally, the ball valve for natural gas pipeline is mainly composed of a valve body, a valve seat, a ball body, a valve stem and a actuator device. The main function of the ball valve is to open and close the passage of the fluid in the pipe. The ball valve realizes the opening and closing function by rotating the ball by 90° through the actuator. Commonly used natural gas pipeline ball valves mainly have two types: floating ball structure and fixed ball structure.
① The ball of the floating ball valve can floate. Under the action of natural gas pressure, the ball will be tightly pressed to the seal ring on the outlet side. This will form a single seal, and the sealing of the valve seat before the valve cannot be guaranteed. The ball valve of this structure is characterized by simple structure and good single-side sealing performance, but the sealing surface bears a large pressure, so the opening and closing torque is large.
② The ball of the fixed ball valve has upper and lower rotating shafts, and the lower rotating shaft is fixed on the bearing at the lower part of the valve body, and the upper part is connected with the valve stem. The ball can rotate along an axis perpendicular to the valve passage, and the ball cannot move laterally like a floating structural ball valve. Therefore, when the fixed ball valve is working, the pressure of the fluid before the valve is transmitted only to the bearing and the valve stem, and no pressure is applied to the valve seat, so the fixed ball valve has small torque, small deformation of the valve seat, stable sealing performance and long service life. The seat of the fixed ball valve is floating, and the floating seat is pressed against the ball by the pressure of the spring behind the seat and the pressure of the natural gas, thereby achieving sealing.
The most common seat structure has the following forms:
(1) Ordinary valve seat
Ordinary valve seats are generally used on floating seated ball valves with a diameter equal to or less than 200 mm. Under the action of preload or fluid pressure, the valve seat is pressed against the ball and the seat material is plastically deformed to achieve sealing. The sealing effect depends on the valve seat under the action of the fluid or the preloading force. It can compensate for the degree of ball out-of-roundness and surface micro-levelness. The valve seat has the advantages of simple structure, convenient processing And manufacture, and is widely used.
(2) Elastic valve seat
The elastic valve seats have relatively more forms. However, the coil spring valve seats and disc spring valve seats are commonly used on natural gas pipelines. Both of these seats are held against the ball by the spring force and the pressure of the fluid to achieve sealing The two valve seats have good two-way sealing ability and good elastic compensation ability, but for the coil spring group valve seat, the rigidity of each spring is difficult to be consistent, so that the valve seat is unevenly stressed, which affects the The contrasting of the valve. In contrast, the disc spring has a simple and compact structure, is easy to process, and can be evenly stressed, so the application is quite extensive.
(3) Rotating valve seat
Before the ball valve is opened or closed, a narrow channel with a crescent shape is formed between the ball and the valve seat, so that the natural gas is throttled and has a high-speed turbulent flow state, which often causes the valve seat to The main feature of the rotary valve seat is that the valve seat can rotate along the axis of the channel during the opening and closing process. The valve seat can be rotated by opening and closing the valve, so that The valve seat can wear evenly in the circumferential direction, improving the working condition and prolonging the service life.
Basic structure composition
Generally, the ball valve for natural gas pipeline is mainly composed of a valve body, a valve seat, a ball body, a valve stem and a actuator device. The main function of the ball valve is to open and close the passage of the fluid in the pipe. The ball valve realizes the opening and closing function by rotating the ball by 90° through the actuator. Commonly used natural gas pipeline ball valves mainly have two types: floating ball structure and fixed ball structure.
① The ball of the floating ball valve can floate. Under the action of natural gas pressure, the ball will be tightly pressed to the seal ring on the outlet side. This will form a single seal, and the sealing of the valve seat before the valve cannot be guaranteed. The ball valve of this structure is characterized by simple structure and good single-side sealing performance, but the sealing surface bears a large pressure, so the opening and closing torque is large.
② The ball of the fixed ball valve has upper and lower rotating shafts, and the lower rotating shaft is fixed on the bearing at the lower part of the valve body, and the upper part is connected with the valve stem. The ball can rotate along an axis perpendicular to the valve passage, and the ball cannot move laterally like a floating structural ball valve. Therefore, when the fixed ball valve is working, the pressure of the fluid before the valve is transmitted only to the bearing and the valve stem, and no pressure is applied to the valve seat, so the fixed ball valve has small torque, small deformation of the valve seat, stable sealing performance and long service life. The seat of the fixed ball valve is floating, and the floating seat is pressed against the ball by the pressure of the spring behind the seat and the pressure of the natural gas, thereby achieving sealing.
The most common seat structure has the following forms:
(1) Ordinary valve seat
Ordinary valve seats are generally used on floating seated ball valves with a diameter equal to or less than 200 mm. Under the action of preload or fluid pressure, the valve seat is pressed against the ball and the seat material is plastically deformed to achieve sealing. The sealing effect depends on the valve seat under the action of the fluid or the preloading force. It can compensate for the degree of ball out-of-roundness and surface micro-levelness. The valve seat has the advantages of simple structure, convenient processing And manufacture, and is widely used.
(2) Elastic valve seat
The elastic valve seats have relatively more forms. However, the coil spring valve seats and disc spring valve seats are commonly used on natural gas pipelines. Both of these seats are held against the ball by the spring force and the pressure of the fluid to achieve sealing The two valve seats have good two-way sealing ability and good elastic compensation ability, but for the coil spring group valve seat, the rigidity of each spring is difficult to be consistent, so that the valve seat is unevenly stressed, which affects the The contrasting of the valve. In contrast, the disc spring has a simple and compact structure, is easy to process, and can be evenly stressed, so the application is quite extensive.
(3) Rotating valve seat
Before the ball valve is opened or closed, a narrow channel with a crescent shape is formed between the ball and the valve seat, so that the natural gas is throttled and has a high-speed turbulent flow state, which often causes the valve seat to The main feature of the rotary valve seat is that the valve seat can rotate along the axis of the channel during the opening and closing process. The valve seat can be rotated by opening and closing the valve, so that The valve seat can wear evenly in the circumferential direction, improving the working condition and prolonging the service life.
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