When designing and calculating a fully welded fixed 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 meet the requirements of 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 valve" standard regulation. When designing the American standard all-welded fixed ball valve, the minimum diameter of the full-bore ball valve shall comply with API6D-2008 / ISO14313:2007 "Petroleum, Natural Gas Industry - Pipeline Transportation System - Pipeline Valve" standard for all welded reduced diameter fixed ball valve The standard stipulates that for ball valves with nominal size â‰¤ DN300 (NPS12), the diameter of the nominal size of the ball valve is reduced by one specification, and the inner diameter is specified according to the standard; for the ball valve of nominal size DN350 (NPS14) to DN600 (NPS24), the nominal size of the ball valve is reduced. Two specifications, according to the standard inner diameter size; for nominal size > DN600 (NPS24) ball valve, should be agreed with the user for all welded ball valves without standard requirements, usually the cross-sectional area of the ball channel should not be less than 60 of the rated cross-sectional area of the pipe %, designed to reduce the diameter, which can reduce the structure of the ball valve, reduce the weight, reduce the force on the sealing surface of the seat and the closing 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.