When designing and calculating a fully welded trunnion ball valve, first determine the channel diameter of the valve body to serve as the basis for calculation of other parts. The minimum diameter of the ball through to the bottom must comply with the corresponding standards. When designing the national standard all-welded fixed ball valve, the minimum diameter of the full-bore ball valve shall comply with GB/T 19672-2005 "Technical Conditions of Pipeline Valves" or GB/T20173-2006 "Petroleum, Natural Gas Industry - Pipeline Transportation System - Pipeline Valves" standard regulation. When designing the American standard all-welded fixed ball valve, the minimum diameter of the full-bore ball valve shall comply with the API6D-2008/ISO14313:2007 "Petroleum, Natural Gas Industry - Pipeline Transportation System - Pipeline Valve" standard. For all welded reduced diameter fixed ball valves, the standard specifies for ball valves with nominal size ≤ DN300 (NPS12). The nominal size of the ball valve is reduced by one specification and the inner diameter is specified according to the standard. For ball valves with nominal sizes DN350 (NPS14) to DN600 (NPS24) The nominal size of the ball valve is reduced by two specifications, according to the standard inner diameter; for ball valves with nominal size > DN600 (NPS24), it should be agreed with the user. For all-welded ball valves without standard regulations, the cross-sectional area of the ball passage should not be less than 60% of the rated cross-sectional area of the pipe. It is designed to be reduced in diameter, which can reduce the structure of the ball valve, reduce the weight, and reduce the sealing surface of the seat. The force and opening and closing torque. Generally, the ratio of the nominal size of the ball valve DN to the diameter of the ball passage is equal to 0.78. At this point, the resistance of the ball valve will not be too large.
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