为焊接接头组对后坡口的最大宽度，mm。 7.5.3  Requirements for quality of weld joint’s surface: a No crack, not fusional, bubble, slag, splash; b Surface of seam of pipeline with design temperature lower than -29℃, stainless steel pipeline and alloy steel pipeline with trend of harden quenching shall be free from undercut. Depth for undercut of weld joints of other pipelines can’t be larger than 0.5mm. Continuous length for undercut can’t be longer than 100mm. Total length for undercut at two sides of seam can’t exceed 10% of total length of the seam. c Surface of seam can’t be lower than

 that of pipeline. Excess weld metal Δh shall meet following requirements: 1 After 100% radial test for weld joints: Δh≦1+0.1b1, not larger than 2mm; 2 Other weld joints: Δh≦1+0.2b1, not larger than 3mm. Notes: b1 is max. width of groove after assembly of weld joints, mm. 7.5.4　管道焊接接头的无损检测应按JB 4730进行焊缝缺点等级鉴定，并契合下列需求： 　　a 射线检测时，射线透照质量等级不得低于AB级，焊接接头经射线检测后的合格等级应契合表10的规则； 　　b 超声波检测时，管道焊接接头经检测后的合格标准如下： 　　　 1 规则进行100%超声波检测的焊接接头I级合格； 　　　 2 部分进行超声波检测的焊接接头II级合格； 　　c 磁粉检测和浸透检测的焊接接头I级合格。 7.5.4 Results of nondestructive test for weld joints shall be graded according to JB 4730. Following requirements shall be met: a For radial test, quality grade of radial transillumination can’t be lower than Grade AB, and that of weld joints shall meet table 10; b For supersonic test, approval standard for weld joints are as follows: 1 For weld joints of 100% supersonic test, grade Ⅰ. 2 For weld joints of local supersonic test, grade Ⅱ. c For magnetic particle test and penetration test, grade Ⅰ. 7.5.5　每名焊工焊接的对接焊焊接接头的射线检测百分率应契合表10的规则，并在被检测的焊接接头中，固定焊的焊接接头不得少于检测数量的40%，且不少于1个焊接接头，射线检测百分率核算准则如下： 　　a 按规划文件给出的同管道等级、同检测份额、同资料种类的管线编号核算； 　　b 当管道公称直径小于500 mm时，按焊接接头数量核算； 　　c 当管道公称直径等于或大于500mm时，按每个焊接接头的焊缝长度核算。 7.5.5   Percentage of radial test for weld joints of butt welding operated by each welder shall meet table 10. Weld joints of stationary welding shall be not less than 40% of total tested joints and at least one weld joint of stationary welding shall be tested. Principle for percentage calculation of radial test is as follows: a According to numbers of pipelines of the same level, test proportion and material category specified in the design document. b According to quantity of weld joints when nominal diameter of pipeline is less than 500mm. c According to length of seam 

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