To distinguish between welded ball valves and flanged ball valves, it depends on the working conditions on site. The maintenance of welded ball valves is definitely not as convenient as the maintenance of flanged ball valves, but sometimes the pipeline can only be welded on site.
Technical characteristics of welded ball valve:
1. The valve body structure is integrally welded, so there will be no external leakage.
2. The valve seat is composed of PTFE sealing ring and spring. It has strong adaptability to changes in pressure and temperature, and will not produce any leakage within the scope of use.
3. The anti-leakage structure of the valve stem. There is a PTFE self-sealing gasket and an O-ring at the bottom of the valve stem. There are 2 O-rings and two PTFE gaskets on the top to ensure no leakage.
4. The material of the valve body is the same as that of the pipeline, so there will be no uneven stress, and no extrusion deformation due to earthquakes and vehicles passing the ground.
5. The valve body is light and easy to keep warm.
6. The direct-buried ball valve can be directly buried in the ground, instead of building tall and large valve wells, it only needs to set up small shallow wells on the ground, which greatly saves construction costs and engineering time.
7. The length of the valve body and the height of the valve stem can be adjusted according to the construction and design requirements of the pipeline.
8. The machining accuracy of the sphere is very precise and easy to operate without bad interference.
10. There are two connection methods of welding and flange.
11. Operation mode: handle, gear (vertical/horizontal)
The structure of welded ball valve:
1. The integral welded ball valve is formed by pressing carbon steel seamless steel pipe.
2. The valve stem is made of AISI303 stainless steel, and the valve body is made of AISI304 stainless steel, which is made by fine machining and grinding, and has excellent sealing performance and corrosion resistance.
3. The seal adopts the carbon-reinforced PTFE slope elastic sealing ring with negative pressure on the spherical surface, so that the seal can achieve zero leakage and long service life.
4. Connection method: There are welding, thread, flange, etc. for users to choose. Transmission mode: use handle, turbine, pneumatic, electric and other transmission structures, and the switch is flexible and light.
5. Compact structure, light weight, easy to keep warm, easy to install. This valve is generally installed horizontally.
6. Widely used in long-distance pipeline fields such as natural gas, petroleum, heat supply, chemical industry and thermoelectric pipeline network.
Advantages of flanged ball valves:
1. The fluid resistance is small, and its resistance coefficient is equal to that of a pipe section of the same length.
2. Simple structure, small size and light weight.
3. Tight and reliable, the sealing surface material of the ball valve is widely used in plastics, which has good sealing performance and has been widely used in vacuum systems.
4. It is easy to operate and open and close quickly. It only needs to rotate 90° from fully open to fully closed, which is convenient for long-distance control.
5. It is easy to maintain, the structure of the ball valve is simple, and the sealing ring is generally movable, so it is more convenient to disassemble and replace.
6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and when the medium passes through, it will not cause erosion of the valve sealing surface.
7. It has a wide range of applications, with diameters as small as a few millimeters and as large as several meters, and can be used from high vacuum to high pressure. This type of valve should generally be installed horizontally in the pipeline.
Structural classification of flanged ball valves:
The ball of the ball valve is floating. Under the action of medium pressure, the ball can produce a certain displacement and press tightly on the sealing surface of the outlet end to ensure the seal of the outlet end. The floating ball valve has a simple structure and good sealing performance, but the load of the working medium on the ball is completely transmitted to the outlet sealing ring, so it is necessary to consider whether the material of the sealing ring can withstand the working load of the ball medium. This structure is widely used in medium and low pressure ball valves.
2. Fixed ball valve
The ball of the ball valve is fixed and does not move after being pressurized. Fixed ball and ball valves are equipped with floating valve seats. After being subjected to medium pressure, the valve seat moves, so that the sealing ring is pressed tightly on the ball to ensure the sealing. Usually, bearings are installed on the upper and lower shafts with the ball, and the operating torque is small, which is suitable for high pressure and large diameter valves. In order to reduce the operating torque of the ball valve and increase the reliability of the seal, an oil-sealed ball valve has appeared in recent years, which not only injects special lubricating oil between the sealing surfaces to form an oil film, which enhances the sealing performance but also reduces the operating torque. , more suitable for high-pressure large-diameter ball valves.
3. Elastic ball valve
The ball of the ball valve is elastic. Both the ball and the sealing ring of the valve seat are made of metal materials, and the sealing specific pressure is very high. The pressure of the medium itself cannot meet the sealing requirements, and an external force must be applied. This valve is suitable for high temperature and high pressure medium. The elastic sphere obtains elasticity by opening an elastic groove at the lower end of the inner wall of the sphere. When closing the channel, use the wedge-shaped head of the valve stem to expand the ball and press the valve seat to achieve sealing. Before turning the ball first release wedge-shaped head, and the ball along with restoration of the original prototype, so that small gap, sealing surface can reduce friction and operating torque between the ball and valve seat.