基于超声波衍射时差法(TOFD)检测原理和技术特点，在分析厚壁容器TOFD检测存在盲区的基础上，针对性提出采用分层检测以减小检测盲区的方法，结合理论计算和试块试验测试结果，提出和优化分层检测参数。根据参数优化的结果，指导厚度150 mm厚壁焊缝的检测。检测结果表明，超标缺陷检出率高，缺陷性质判断准确，缺陷尺寸测量精度高；该分层检测参数设计方法可以推广应用于相关的厚壁容器检测。

Based on TOFD technique detection principle and technical characteristics, and on the analysis of dead zones existing in thick-walled vessel TOFD inspection, this article proposed layered detection methods to reduce the dead zone of inspection. Combined with the theoretical calculations and experimental test results of test block, tiered testing parameters were proposed and optimized. Detection of 150 mm thick weld was guided according to the results of parameter optimization, and test results showed that excessive defect detection rate could be obtained and the nature of defects could be more accurately determined with high accuracy of defect size. So the layered detection parameters design method can be applied to the thick-walled vessel associated testing.