小径管内壁缺陷的涡流热成像定量检测

管道内壁腐蚀对化工企业的安全生产造成重大隐患,因此对于内壁腐蚀缺陷深度的预估极其重要。本文采用涡流热成像技术对内壁不同深度的腐蚀缺陷进行检测与评估。利用COMSOL建立不同深度缺陷的3维有限元模型,提取不同深度缺陷在冷却阶段温度信号,并进行数据归一化处理,分析缺陷深度对于热传导影响。同时,通过实验对数值模拟分析结果进行验证,并提出以瞬态温度衰减信号的积分值为特征量预估腐蚀缺陷的深度。结果表明:缺陷深度越深,冷却阶段温度衰减速率越快,瞬态温度衰减信号的积分值越小。对于壁厚4 mm的小径管,可以从原始热图像中可识别直径6 mm,最小深度为1.5 mm腐蚀缺陷。

Quantitative detection of inner defects of small diameter tube by eddy current thermal imaging

The inner wall corrosion of pipeline causes great serious problems to the safety production of chemical enterprises,so it is very important to estimate the inner wall corrosion defect depth.Eddy current thermal imaging technology is used to detect and evaluate the corrosion defects in different depths of the inner wall.COMSOL was used to establish 3D finite element models of defects with different depths,and temperature signals of defects with different depths were extracted during the cooling stage.Through data normalization method,the influence of defect depth on heat conduction was analyzed.At the same time,the numerical simulation results were verified by eddy current thermal imaging experiment,and the depth of corrosion defects was estimated by using the integral value of transient temperature attenuation signal as the characteristic quantity.The results show that the deeper the defect depth,the faster the temperature attenuation rate in cooling stage and the smaller the integral value of temperature attenuation signal in transient state.At the same time,for the 4 mm pipe with a wall thickness,the corrosion defect with a diameter of 6 mm and a minimum depth of 1.5 mm can be identified from the original thermal image.