The all-welded ball valve is a one-piece welded ball valve made of carbon steel seamless steel tube. Yongjia Zhenghong Valve Factory specializes in producing all-welded ball valves, high temperature and high pressure power station valves, non-standard valves and so on. This paper mainly describes the advantages and working principle of the all-welded ball valve.
1. All welded ball valve structure
The ball valve body is assembled by welding the 6-part forged shell. The structure is compact and the whole ball valve is integrated. At present, the large-diameter ball valves used in production in the day are mostly three-piece structures with separate parts, and bolts are connected between the parts. Compared to a three-piece ball valve, the wall thickness of the all-welded ball valve forging can be made thin at the same strength. The weight of the valve can be reduced by a quarter, while the resistance to bending and squeezing of the pipe is increased; the body flange and bolts are eliminated. The external dimensions are reduced. The same call also eliminates potential leaks. In addition, the internal curve of the body welding structure is smooth. The lubrication connection with the pipeline is maintained without dead angle, and the medium fluidity is good.
2, frame shaft fixed ball design
The ball valve can be divided into a fixed ball and a floating ball according to the spherical form. The floating ball structure generally adopted in domestic products, the ball is pressed against the sealing surface of the outlet end under the pressure of the medium, and the sealing surface is reached. Once the pressure difference between the inlet and the outlet of the valve body is large, the prisoner torque is large and often opens the field. difficult. The all-welded ball valve uses a high-strength satin steel stem that is supported by a stainless steel PTFE (polytetrafluoroethylene) bearing for smooth and precise rotation. Since the pivotally supported stem absorbs the thrust generated by the pressure of the line medium and reduces the friction between the ball and the seat, the torque of the operating recess is still low even at full differential pressure, and the ball valve is freely open. .
3, rotary valve seat design
When the ball valve is close to full or just open, the narrow position (9 o'clock position) between the ball and the valve seat is subjected to high-speed turbulence due to the throttling of natural gas into high-speed turbulence, which becomes the most severely worn seat seal. city. Finally caused a leak. The CAM300 (and above) CAMERON ball valve features a unique rotary seat. Every time the valve is opened or closed. The valve seat on the upstream and downstream is rotated by 15 degrees Celsius by the paddle on the valve ball, so that the entire seat sealing surface is subjected to natural gas flushing. After the valve is opened or closed 12 times, the same part is re-swept once, and the entire seat wear is evenly maintained. . The working life is greatly extended. The seat of a conventional ball valve is fixed, and the damaged part of the valve seat is also fixed after a long time of operation. on the other hand. After the pipeline runs for a period of time, some harmful deposits will accumulate on the seat ring, causing the conventional ball valve seat to be stuck or unable to seal properly, and the rotating valve seat can remove the foreign matter on the surface of the female seat ring when it is rotated.
4, valve stem and secondary valve seat emergency grease seal
The sealing material PTFE of the upper part of the valve stem is a low friction and aging resistant material with long service life. The DN50 (and above) full-welded ball valve stem is also equipped with a grease injection system. Once the valve seat is in contact with foreign objects and the sealing surface is damaged, the special sealant can still be injected through the secondary seat to maintain the seal. Conventional ball valves do not have a sealant injection structure. Once the sealing surface is damaged, internal leakage occurs. Only replace the entire ball valve.
5, automatic internal pressure of the valve cavity 泄 bleed and double partition medium cavity pressure
Although the ball valve adopts the upstream and downstream double seat block seal, the long-running valve seat is inevitably worn out; when the valve is closed, the upper seat may have a certain internal leakage, and the leaked medium enters the valve ball. Cavity. The special valve seat of the juice can effectively prevent the valve ball from overpressure in the ten chamber. Once the valve chamber pressure exceeds the downstream pressure by about 138KPa, the downstream reading frame will be pushed away from the sphere to release the pressure into the downstream pipeline. The ball valve is equipped with a pressure release pipe that communicates with the middle cavity, and the pressure release pipe is led out of the ground. Whether the valve is in the fully open or fully closed position, the valve cavity shutoff valve can be opened to release the pressure in the middle cavity. Seat sealing performance can also be checked by releasing the pressure in the middle chamber.
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