Quantitative Research on Signal of Pipeline Coating Defect Detection Based on HHT
Coating is a very important way to ensure the integrity of the pipeline. However, due to environmental or external factors, the coating will has some defects such as peeling defects, holes and so on. This paper is concentrated on axial stripping defects and holes of buried pipeline coated with anti-corrosion coating, using ultrasonic guided wave detection technology to obtain the coating detection signal to do the study of quantification, it provides a feasible method to study the level quantitative description of the anticorrosive layer peeling defects.Doing time-frequency analysis to the operating status of the coating, we will have a conclusion that when the coating has peeling defects, the waveform of the detection signal will has a nonlinear characteristic signal. According to the analysis of time-frequency distribution, we can find out that when the signal has nonlinear characteristic signal, the time-frequency distribution will have a "concave" type frequency distribution, it is the basis to judge the junction of the coating peeling defects. According to the judgment, and obtain the relative length of the coating stripping defect, it will finally obtain the degree of damage caused by peeling defects.Therefore, this paper is a post-treatment method for pipeline coating detection, providing feasible and effective signal processing methods and quantitative research methods for the engineering application of the detection technology of non-linear ultrasonic pipeline coating peeling defects.
Signal processing and defect analysis of pipeline inspection applying magnetic flux leakage methods
Corrosion, stresses and mechanical damage of oil and gas pipelines can result in catastrophic failures, so pipeline safety evaluation is an important problem of oil and gas transmission. To evaluate the pipeline safety, this paper described a novel magnetic flux leakage (MFL) inspection device, and the designing MFL intelligent inspection pig was used to multi-radius pipelines and variational work condition. At the same time, because signal processing and defect recognition technique is one of the most important techniques in offshore pipeline inspection MFL system, the paper also discussed its signal processing procedure. Time-frequency analysis, median and adaptive filter, and interpolation processing are adopted to preprocess MFL inspection signal. In order to obtain high sensitivity and precision, we adopted multi-sensor data fusion technique. A wavelet basis function neural network was used to recognize defect parameters. The main contribution of the article is that we presented a novel method to evaluate and predict oil pipelines’ condition through combining neural network, data fusion and expert system techniques, and through constructing a knowledge-based off-line inspection expert system, the system improved its defect recognition capability greatly.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.