Abstract: A ball valve is a device with good sealing performance, long service life and economical safety that has been widely used in pipelines transporting natural gas. However, in the actual installation construction and post-maintenance, a small mistake will lead to leakages, and the impact will be very great. At this time, it is necessary to do a good job in the maintenance and troubleshooting of ball valves, and apply efficient and feasible technical methods to ensure the safety and smooth operation of pipelines. With rapid economic development, the demand for energy is also increasing. Natural gas has the characteristics of high performance and no pollution, so the natural gas pipeline business has also developed well. Ball valves are widely used in natural gas pipelines and also play a good role. Compared with other shut-off valves, the ball valve has more advantages, such as simple structure, low fluid resistance and longer service life, so its utilization rate is very high. In order to further promote the development of the natural gas pipeline business, it is necessary to carry out a detailed and in-depth analysis for the faults existing in the ball valve, and finally propose a practical solution strategy.
1. Structural characteristics and working principles of pipeline ball valves
1.1 Basic structure
The ball valve is mainly composed of valve bodies, upper cavities, valve seats, lower cavities, balls and other components. Figure 1 shows the structure of the ball valve. Commonly used ball valves can be divided into trunnion ball valves and floating ball valves. Both kinds of ball valves evolved from a cock. The opening and closing part of the ball valve is a sphere with a circular channel and is rotated at an angle of 90 around the axis of the valve stem to achieve the purpose of opening and closing.
Figure 1 The structure of the ball valve
1.2 Working principles
Taking the trunnion ball valve as an example, the sphere has an upper and lower shaft and is fixed in the bearing of the sphere. The great liquid pressure cannot make it move, but the fluid pressure is transmitted to the bearing through the force generated by the sphere. However, the valve seat is floating, and it is pressed against the ball by means of spring and fluid thrust to establish the initial sealing pressure. The first seal is established between the metal seat and the valve ball, and also ensures the sealing in the event of a fire; the soft seal is tightly fitted with the seat to establish the second sealing to ensure zero leakage.
2. Maintenance technology of natural gas pipeline ball valves
2.1 Maintenance during construction
During the construction of natural gas pipelines, it is necessary to do a good job in the maintenance and management of ball valves in order to ensure the rationality, efficiency and safety of ball valves, speed up construction progress, reduce construction costs and improve construction quality. The following maintenance should be paid attention to: First, the purchase contract of valves must be signed by professionals after an in-depth understanding of the building materials market. During transportation, the valve should also be packed tightly to prevent damage caused by collision. After being transported to the construction site, professional quality inspectors are required to conduct quality, specification, performance and other inspections, and only qualified valves can be used for construction. Place the valve neatly on the sleepers to prevent damage and loss. Second, the valve installation process requires manual and mechanical cooperation. Therefore, when hoisting, you must operate carefully and check repeatedly; hang the steel wire rope on the hook, and gently lift the tail to prevent the valve from being damaged. Third, before the valve leaves the factory, the blind plates at both ends must be installed to prevent dust, water and impurities from entering the valve cavity and affecting the sealing performance of the valve. Fourth, before installation, grease injection is required. Check the tightness and smoothness of the valve while injecting grease to avoid damage caused by high temperatures. In the whole installation process, the valve must be fully opened. Fifth, whether it is the welding process or the hydrostatic test process, grease needs to be injected to prevent impurities from entering the interior. Sixth, before running, a hydrostatic test is also required. During the hydrostatic test, the water inside the valve cavity needs to be drained to prevent corrosion.
1. Structural characteristics and working principles of pipeline ball valves
1.1 Basic structure
The ball valve is mainly composed of valve bodies, upper cavities, valve seats, lower cavities, balls and other components. Figure 1 shows the structure of the ball valve. Commonly used ball valves can be divided into trunnion ball valves and floating ball valves. Both kinds of ball valves evolved from a cock. The opening and closing part of the ball valve is a sphere with a circular channel and is rotated at an angle of 90 around the axis of the valve stem to achieve the purpose of opening and closing.
Figure 1 The structure of the ball valve
1.2 Working principles
Taking the trunnion ball valve as an example, the sphere has an upper and lower shaft and is fixed in the bearing of the sphere. The great liquid pressure cannot make it move, but the fluid pressure is transmitted to the bearing through the force generated by the sphere. However, the valve seat is floating, and it is pressed against the ball by means of spring and fluid thrust to establish the initial sealing pressure. The first seal is established between the metal seat and the valve ball, and also ensures the sealing in the event of a fire; the soft seal is tightly fitted with the seat to establish the second sealing to ensure zero leakage.
2. Maintenance technology of natural gas pipeline ball valves
2.1 Maintenance during construction
During the construction of natural gas pipelines, it is necessary to do a good job in the maintenance and management of ball valves in order to ensure the rationality, efficiency and safety of ball valves, speed up construction progress, reduce construction costs and improve construction quality. The following maintenance should be paid attention to: First, the purchase contract of valves must be signed by professionals after an in-depth understanding of the building materials market. During transportation, the valve should also be packed tightly to prevent damage caused by collision. After being transported to the construction site, professional quality inspectors are required to conduct quality, specification, performance and other inspections, and only qualified valves can be used for construction. Place the valve neatly on the sleepers to prevent damage and loss. Second, the valve installation process requires manual and mechanical cooperation. Therefore, when hoisting, you must operate carefully and check repeatedly; hang the steel wire rope on the hook, and gently lift the tail to prevent the valve from being damaged. Third, before the valve leaves the factory, the blind plates at both ends must be installed to prevent dust, water and impurities from entering the valve cavity and affecting the sealing performance of the valve. Fourth, before installation, grease injection is required. Check the tightness and smoothness of the valve while injecting grease to avoid damage caused by high temperatures. In the whole installation process, the valve must be fully opened. Fifth, whether it is the welding process or the hydrostatic test process, grease needs to be injected to prevent impurities from entering the interior. Sixth, before running, a hydrostatic test is also required. During the hydrostatic test, the water inside the valve cavity needs to be drained to prevent corrosion.
Next: Maintenance of Ball Valves in Pipelines Transporting Natural Gas (Part Two)