Structural characteristics of direct buried all welded ball valve

1.1 the valve body of all welded ball valve structure is welded after the assembly of 6 parts of forged shell The structure is compact and the whole ball valve is integrated At present, the large-diameter ball valves used in the production in China are mostly divided into three-piece structure, and the parts are connected by bolts Compared with three piece ball valve, the wall thickness of all welded ball valve forging can be very thin under the same strength The weight of the valve can be reduced by a quarter, while the resistance to bending and extrusion of the pipeline is enhanced; the valve body flange and bolt are eliminated Electrical reduction of boundary dimension It also eliminates potential leakage channels In addition, the inner curve of the welding structure is smooth, the lubrication connection with the pipeline is free of dead angle, and the medium fluidity is good 1.2 according to the ball form, the ball valve with fixed axis can be divided into fixed ball and floating ball The floating ball structure is generally used in domestic products Under the pressure of the medium, the ball is tightly pressed on the sealing surface at the outlet end to reach the sealing day Once the pressure difference between the inlet and outlet of the valve body is large, it is difficult to open the field due to large torque All welded ball valve adopts high-strength Satin steel stem, which is supported by PTFE (polytetrafluoroethylene) stainless steel bearing to rotate smoothly Since the valve rod supported by the pivot can absorb the thrust generated by the medium pressure of the pipeline and reduce the friction between the valve ball and the valve seat, even under the full pressure difference, the torque for operating the concave door is still very low, and the ball valve can be opened and closed freely 1.3 design of rotary valve seat when the ball valve is close to fully closed or just opened, the narrow point (9 o'clock position) between the ball valve and the valve seat is subject to high-speed scour due to the high-speed turbulence caused by the throttling of natural gas, which becomes a serious area of seat seal wear Zui and causes leakage The Cameron ball valve of DN300 (and above) adopts a unique rotary valve seat Each time the valve is opened or closed, the upstream and downstream valve seats are rotated 15 ℃ by the paddle on the valve ball, so that the whole sealing surface of the valve seat is scoured by natural gas in turn, and the same part is scoured again after the valve is opened or closed 12 times, and the wear of the whole valve seat remains uniform The working life is greatly extended The valve seat of conventional ball valve is fixed, and the damaged part of the valve seat after long-time operation is also fixed), which often causes internal leakage On the other hand, some harmful deposits will accumulate on the valve seat ring after the pipeline runs for a period of time, which will cause the valve seat of conventional ball valve to be stuck or unable to seal normally, while the rotating valve seat can remove the foreign matters on the surface of the female seat ring when rotating 1.4 the sealing material pffe for the upper part of stem and secondary valve seat emergency grease injection sealing is a low friction and aging resistant material with long service life The valve stem of DN50 (and above) all welded ball valve is also equipped with a sealing grease injection system Once foreign matters enter between the valve ball seats and damage the sealing surface, special sealing grease can still be injected into the secondary valve seat to maintain the sealing The conventional ball valve does not have sealing grease injection structure Once the sealing surface is damaged and internal leakage occurs, only the whole ball valve is replaced 1.5 automatic internal relief of valve chamber pressure and pressure relief of double partition middle chamber Although the ball valve adopts the upstream and downstream double valve seat partition seal, the long-term operation of the valve seat will inevitably wear; when the valve is in the closed state, the upper fly valve seat may have some internal leakage, and the internal leakage medium will enter the valve ball cavity The special downstream valve seat can effectively avoid the overpressure of ten chambers of the valve ball Once the pressure of the valve chamber exceeds the downstream pressure by about 138kpa, the downstream reading seat will be pushed away from the ball and the pressure will be discharged into the downstream pipeline The ball valve is equipped with a pressure relief pipe connected with the middle chamber, and the pressure relief pipe is led out to the ground Whether the valve is in the fully open or fully closed position, the valve chamber shut-off valve can be opened to release the middle chamber pressure The sealing performance of the valve seat can also be measured by releasing the middle chamber pressure Source: http://