基于远场涡流的碳钢管道弯头缺陷外检测方法研究

发布时间：2018-11-12 10:15

【摘要】：金属管道广泛应用于各行各业,在长期的服役过程中,由于管材老化、所处环境苛刻或工况恶劣等原因,其壁面上会产生裂纹、腐蚀、凹坑等损伤。特别是管道弯头部位,因内部介质冲刷和撞击而造成的腐蚀失效更易发生,成为整体管道的薄弱环节。管道损伤的积累最终会引发泄漏或爆炸事故,给安全生产带来隐患。因此,对在役管道进行定期的无损检测,以便及时发现问题并进行维护,显得尤为必要。远场涡流检测技术对内外壁缺陷有相同的灵敏度,而且对传感器的提离不敏感,在金属管道的无损检测中备受重视。但是,常规的远场涡流传感器为内通过式,在实际应用时往往需要设备停机,以便将传感器放入管内。为满足压力管道在役检测的需求,本学位论文针对其易腐蚀的管道弯头部位,设计了一种在管外放置的远场涡流传感器。主要研究如下:1.基于有限元仿真,以实现激励磁场两次穿透管壁的远场涡流现象作为目标,研究了激励线圈放置方式、磁屏蔽、激励单元个数等因素对激励磁场穿透效果的影响,确定了以矩形线圈为激励线圈、外加磁屏蔽罩、夹角为120度的双激励单元作为外置式远场涡流传感器的结构形式,仿真表明采用这种传感器不仅可缩短远场区的周向距离,还能增强远场区的磁场信号。2.利用有限元软件建立了弯头缺陷外置式远场涡流检测仿真模型,研究了传感器信号的幅值和相位与内、外壁缺陷深度的定量关系,以及传感器对不同取向外壁缺陷的检测性能。结果表明传感器信号的相位随缺陷深度线性变化,可用于弯头缺陷深度的定量,但由于传感器对内、外壁缺陷检测灵敏度不同,尚不能对内、外壁缺陷都存在时的缺陷深度进行定量;周向缺陷引起的传感器响应比轴向缺陷响应显著减弱,但两者引起的相位变化相差较小。3.根据仿真设计结果,研制了外置式远场涡流传感器,搭建了远场涡流检测系统硬件平台;并基于LabVIEW设计了锁相放大器,实现检测信号相位和幅值的提取;利用该系统在Q235管道弯头、45钢阶梯管等试件上进行了试验。试验信号特征的变化规律与仿真结果一致,验证了所设计探头的有效性和实用性。与常规远场涡流传感器相比,本文所提出的外置式传感器具有结构紧凑、无需设备停机等优势。因此,研究结果可为压力管道在役检测提供可借鉴的新思路和方法。
[Abstract]:Metal pipes are widely used in various industries. In the long service process, due to the aging of pipes, harsh environment or harsh working conditions, cracks, corrosion, pits and other damage will occur on the wall. Especially, the corrosion failure caused by internal media scour and impact is more likely to occur in the bend of pipeline, which becomes the weak link of the whole pipeline. The accumulation of pipeline damage will eventually lead to leakage or explosion accident, and bring hidden danger to safety production. Therefore, it is necessary to carry out regular nondestructive testing to detect problems and maintain them in time. The far field eddy current testing technology has the same sensitivity to the inner and outer wall defects, and is not sensitive to the lifting of the sensor, so it has attracted much attention in the nondestructive testing of metal pipes. However, the conventional far field eddy current sensor is an internal passage type, which often requires the equipment to stop in order to put the sensor into the pipe. In order to meet the need of in-service inspection of pressure pipes, a far-field eddy current sensor is designed for the corrosion prone pipe elbows. The main research is as follows: 1. Based on finite element simulation, the effect of excitation coil placement, magnetic shielding and the number of excitation units on the penetration effect of excitation magnetic field is studied. The rectangular coil is used as the exciting coil, the magnetic shield is applied and the double excitation element with an angle of 120 degrees is used as the structure of the external far-field eddy current sensor. The simulation results show that this kind of sensor can not only shorten the circumferential distance in the far field. Can also enhance the far-field magnetic field signal. 2. The simulation model of the far field eddy current detection of elbow defects is established by using the finite element software. The quantitative relationship between the amplitude and phase of the sensor signal and the depth of the inner and outer wall defects, as well as the detection performance of the sensor for the outer wall defects with different orientations are studied. The results show that the phase of the sensor signal varies linearly with the depth of the defect, and can be used to quantify the depth of the defect in the elbow. The depth of defects in the outer wall is quantified when there are defects in the outer wall. The response of the sensor caused by circumferential defect is much weaker than that of axial defect, but the phase change caused by them is smaller than that caused by axial defect. According to the simulation design results, the external far-field eddy current sensor is developed, the hardware platform of the far-field eddy current detection system is built, and the phase-locked amplifier is designed based on LabVIEW, which can extract the phase and amplitude of the detection signal. The system was used to test the Q235 pipe elbows and 45 steel ladder pipes. The characteristics of the test signal are consistent with the simulation results, and the validity and practicability of the designed probe are verified. Compared with the conventional far field eddy current sensor, the external sensor presented in this paper has the advantages of compact structure and no equipment shutdown. Therefore, the results of the study can provide a new idea and method for the in-service inspection of pressure pipelines.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115.28

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