Experimental Research On Infrared Thermal Imaging Detection Of Bonding Defects In Oil And Gas Pipeline Joints

The construction of oil and gas pipelines involves national energy security,people's lives and property safety,accidents caused by bonding defects at pipeline junctions account for a high proportion of oil and gas leakage and explosion accidents at home and abroad.The anti-corrosion layer of oil and gas pipeline is composed by polyethylene material,because of its large wall thickness and low thermal conductivity,ultrasonic,infiltration and other detection methods have low detecting efficiency.Infrared non-destructive testing technology has the advantages of non-contact,high efficiency and large detectable area.It is widely used in aerospace,mechatronics and medical and health fields.In this paper,based on active infrared non-destructive testing and image processing technology,a series of research on the bonding defects of oil and gas pipeline anti-corrosion layer are carried out.The main research contents are as follows:Based on the characteristics of large wall thickness and poor thermal conductivity of polyethylene anti-corrosion layer of oil and gas pipeline,the infrared radiation capability of different excitation sources is analyzed,multiple carbon fiber lamps are placed side by side as the excitation to rise the detecting depth.It has been found that the carbon fiber lamp would produce infrared light reflection on the surface of the tested sample while greatly improving the infrared effect,the reflection is reduced by studying the relationship of the angle that made by the thermal imager and the carbon fiber lamp and the intensity of the reflected light.In order to study the influence of excitation power,phase-locked frequency,defect depth and defect diameter on the signal-to-noise ratio of defects,an orthogonal test is designed to analyze the relationship between different test levels and signal-to-noise ratio of each test factor.The selection of parameters for infrared detection provides an experimental basis.In order to meet the testing requirements of engineering practice,it is necessary to improve the detectable depth of defects,and reconstruct the original heat wave signal by principal component analysis technology to further reduce the temperature non-uniformity of the surface of the tested sample and improve the signal-to-noise ratio of deep defects.Then,the image sequence processed by principal component analysis is processed by phase-locked infrared technology.By comparing the original infrared image,phase-locked infrared processing image and temperature gradient method,the phase-locked infrared technology based on principal component analysis can greatly improve the defect detectable depth.Based on the principle of phase-locked infrared detection,a prototype that can be used for onsite detection is designed and developed.An algorithm that can be used to process the original infrared image sequence is developed,and an image processing interface is designed to facilitate detection.