基于变频交流场指纹法的金属管道点蚀在线监测技术研究

Pipeline corrosion is an important factor leading to safety accidents in petrochemical industry while pitting corrosion, with very small corrosion area and very deep corrosion depth, can easily lead to oil and gas pipeline perforation leakage accident. However, the commonly used technical means in China at present, such as electrical resistance probe or corrosion coupon, can hardly detect pitting corrosion. Even relatively advanced Field Signature Method (FSM) is unable to accurately monitor pitting due to that the small amount of measured information and monitoring signal of FSM is easily affected by instrument drift. Multi-frequency Alternative Current Field Signature Method (MACFSM) is proposed in this project based on years of research on direct current FSM. Previous studies show that a large number of effective measurement signals, which can reflect such as number, depth, size and position of pitting, can be obtained by MACFSM when applying multi frequency AC excitation to the measured pipeline, and that lays the foundation for the accurate monitoring of pitting corrosion. Besides, MACFSM uses the derivative of the signal to solve pitting, which can overcome the adverse effects caused by the drift of the instrument system. This project will focus on researching the effect of pitting on the distribution of the current field in the metal pipeline at different frequencies, and the study of eliminating the drag effect of multiple pitting is also an important research content. The ultimate goal of the project is to propose analytical function of pitting corrosion and develop principle prototype to provide theoretical and technical basis for developing a new type of on-line monitoring technology for pitting corrosion of metal pipes.

管道腐蚀是引发石化企业安全事故的重要因素，而点蚀由于腐蚀面积很小、深度深，更是频繁地引发管道穿孔泄漏事故。然而电阻探针、腐蚀挂片等目前国内常用的技术手段只能检测均匀腐蚀，无法检测点蚀，包括相对先进的直流场指纹法在线腐蚀监测技术，由于测量获得的信息量偏少、监测信号易受仪器漂移干扰等原因，其点蚀监测精度也很低。本项目在多年研究直流场指纹技术的基础上，提出了一种多频交流场指纹技术（MACFSM），前期研究表明，MACFSM利用多频率交流激励，可以获得大量包含点蚀数量、深度、大小、位置等信息的有效测量信号，为准确监测点蚀奠定了基础，而且MACFSM利用信号的导数求解点蚀缺陷，可以克服仪器漂移所造成的不利影响。本项目拟以点蚀在不同频率下对金属管道电流场分布的影响为重点研究对象，消除多点蚀情况下的牵扯效应，提出点蚀解析函数，进而开发原理样机，为最终开发新型的金属管道点蚀在线监测技术奠定理论和技术基础。

随着油气管道服役年限增加，管道发生各种缺陷的风险急剧增加，而点蚀由于发生位置随机、腐蚀面积小、但往往深度很深，因此极难被有效检测到，极易引发管道穿孔泄漏，因此是最危险的缺陷类型之一。场指纹技术（Field Signature Method，FSM）由于检测面积大、且属于在线监测技术，非常适合管道缺陷检测，但其坑蚀的检测能力较差。本项目开展基于变频交流场指纹法的金属管道点蚀在线监测技术研究，建立了点蚀电流场模型，分析了点蚀的各项参数对测试信号的作用机理，研究了不同缺陷分类识别的方法，设计了基于多频交流场指纹缺陷检测样机，并进行了相关的测试实验。本项目具体开展了以下几方面的工作：1、分析并整理了本团队前期研究的相关理论研究成果，提出了一种基于零相位（Zero Phase）求解点蚀缺陷深度的方法，解决了电压导数极值求解点蚀深度所引起的不可识别问题；2、对缺陷类型的识别方法进行了研究；3、提出了裂纹的求解算法，裂纹同属于最危险的缺陷类型之一；4、研发了多频交流场指纹原理样机，并进行了相关实验测试。本项目的研发，提升了坑蚀检测的能力和精度，同时也为缺陷分类、裂纹检测等奠定了基础，对预防油气管道泄漏、保护人员和资源安全、减少环境破坏等有着重要作用和意义。