对管道焊缝抽样射线探伤检验数量的探讨

Discussion on Detecting Quantity of Sampling Radiography

针对GB50235-97《工业金属管道工程施工及验收规范》中,管道焊缝抽样射线探伤检验采用百分比抽样方案和补充探伤时仅增做不合格数的两倍探伤的规定提出异议。用概率统计方法分析接收概率的变化,认为百分比抽样方案不科学,存在“大批严,小批宽”的问题;而补充探伤的规定客观上使业主接收不合格焊缝的概率明显增大。建议在采用百分比抽样方案时把焊缝批数量选大一些,在做补充探伤时应按抽检数量的两倍数探伤,以便减小业主风险。

In GB50235-97“The Construction and Acceptance Code on Industrial Metal Pipeline Engineering”,the sampling radiographic detection of pipeline welding seams applies percent sampling method,and only doubles the detection quantity of unqualified welding seams in supplementary detec-tion.The author raises an objection against above stipulation.The percent sampling is not a scientific method according to permutation and combination rule to analyze the change of acceptable probability.There is a problem of“too strict for large amount of batches and too loose for small amount of batches”.The stipulation of supplementary detection will increase objectively the probability of accepting unqualified welding seams by user.The author suggests that the batch quantity should be larger in percent sampling and should double the sampling quantity in supplementary detection in order to reduce user's risk.