油气管道聚乙烯层粘接缺陷的红外热成像检测方法和信号增强技术研究

Research on infrared thermal imaging detection method and signal enhancement technology for bonding defects of polyethylene layer in oil and gas pipeline

为降低油气管道聚乙烯层粘接处的脱粘、粘接缝隙等面积型缺陷造成的安全事故发生概率,通过主动式红外热成像技术以及对不同深度的聚乙烯材料缺陷进行检测,采用主成分分析法和锁相技术对获取的原始红外图像进行处理,实现深度在5 mm处的粘接缺陷定量检测,该深度为油气管道聚乙烯层的标准尺寸大小。通过实验确定锁相频率与图像信噪比的关系,可为提高锁相检测效果提供依据。研究表明:激励频率在0.005~0.006 Hz范围内,锁相检测可以满足在役油气管道5 mm深的粘接缺陷检测,主成分分析法可以有效解决激励导致的温度分布不均匀带来的噪声干扰,弥补锁相检测方法的不足,提升缺陷可检测深度,该方法可以将原始温度分布图像的信噪比均值由0.637 dB提升至8.033 dB。

In order to reduce the probability of safety accidents caused by area defects such as debonding and bonding gaps in the polyethylene layer of oil and gas pipelines,active infrared thermal imaging technology and detection of polyethylene bonding defects at different depths are detected.The original infrared thermal images obtained are processed by the principal component analysis method and the phase-locking technique to realize the quantitative detection of the bonding defect at a depth of 5 mm,which is the standard size of the polyethylene layer of the oil and gas pipeline.The relationship between phase-locked frequency and image signal-to-noise ratio is determined by experiments,which provides a basis for improving the phase-locking detection effect.The research shows that if the excitation frequency was in the range of 0.005 Hz-0.006 Hz,the phase-locking detection can meet the 5 mm deep bonding defect detection of the in-service oil and gas pipeline.The principal component analysis method can effectively solve the noise interference caused by the uneven temperature distribution and make up for the deficiency of the phase-locked detection method,improving the detectable depth of the defect.The method can raise the signal-to-noise ratio of the original temperature distribution image from 0.637 dB to 8.033 dB.