Abstract: Because the pulse repetition frequency of pipeline ultrasonic inner inspection is very high, the echo data amount generated is very large, automatic acquisition of wall thickness information is the core problem. At the same time, the working condition of the actual pipeline is very complex, the useful echo signal is mixed with varied noise and uncertain disturbance, which requires the automatic wall thickness conversion algorithm with a strong adaptability. But the accuracy of second-order statistics method commonly used for the automatic wall thickness conversion is lower, the misdiagnosis rate and the miss rate is higher, and so on. Aiming at this problem, the echo signal was processed using 1.5-dimension spectrum of higher-order statistics. And according to the frequency range of wall thickness and the periodic characteristics of spectral lines, the spectrum data were intercepted and transformed again, and the improved 1.5-dimension spectrum was obtained. The transit time of the wall thickness was acquired, and then the wall thickness was obtained. Experimental results show that the inspection precision of the algorithm is very high and much better than the second-order statistics method, which is suitable for the corrosion inner inspection on long-distance oil pipeline.

Key words: pipeline, ultrasonic inner inspection, higher-order statistics, 1.5-dimension spectrum, automatic wall thickness conversion

摘要： 管道超声内检测脉冲重复频率很高,产生的回波数据量很大,壁厚信息的自动获取是其核心问题.同时实际管道工况复杂,有用回波信号混杂多种噪声及不确定性干扰,这就要求自动壁厚转换算法有很强的适应性.但常用的二阶统计量方法用于自动壁厚转换时精度较低,存在误判率与漏检率较高等情况.针对这一问题, 提出采用高阶统计量中的1.5维谱处理回波信号,并根据壁厚频率范围和谱线的周期性特点,截取频谱数据做二次变换,得到改进的1.5维谱,获取壁厚的渡越时间,得出壁厚.实验结果表明该算法检测精度很高, 大大优于二阶统计量方法,适用于长距离输油管道腐蚀内检测.

关键词: 管道, 超声内检测, 高阶统计量, 1.5维谱, 自动壁厚转换