Research On Large Oil Storage Top Corrosion Detection Technology Based On Ultrasonic Guided Wave

With the rapid development of the national economy and the implementation of energy strategies,storage tanks have become an important infrastructure for domestic oil and chemical raw material reserves.As the capacity of stored liquids increases,their structural defects could lead to great danger,such as fire and explosion accidents,causing serious negative impacts on enterprises and society.Therefore,it is crucial to detect and evaluate the structural defects of storage tanks.At present,the defect detection of petroleum storage tanks is concentrated in the bottom and the wall of the tank or other parts of the tank that can be in direct contact with the storage medium.However,the top of the tank,which is not in direct contact with the storage medium,has not yet attracted sufficient attention.The top of the tank with its complex structure and special working environment is prone to corrosion,which can cause serious fire and other major safety accidents.Therefore,during the regular inspection of storage tanks,corrosion defect detection on the tank top is particularly important.At present,there are mainly the following difficulties for tank top inspection: 1)conventional detection methods aimed at tanks with large area are inefficient.2)existing detection techniques cannot rapidly position and quantitatively assess the corrosion defects of the tank top.To address the above problems,based on the key R&D project of CNPC,this dissertation focuses on the theoretical derivation of elastic waves,defect signal feature expression and quantitative assessment methods,and research work of detection technology and experimental analysis and validation with ultrasonic guided wave-based non-destructive structural health monitoring technology as the research direction.The main research work and the contributions of this dissertation are as follows:(1)The basic principles of guided wave propagation in the plate are analyzed and studied.According to the features of the tank top,the appropriate mode and frequency of the guided wave for tank top plate detection are determined by analyzing the attenuation characteristics of the guided wave modes propagating in the tank top plate at different frequencies.The transmissive wave is adopted instead of the traditional reflected wave for detection,and the feasibility of the transmissive guided wave in large-scale tank top plate inspection applications is analyzed.(2)A dual-element reference-free corrosion imaging localization technique based on probabilistic damage imaging is proposed and studied.The variability of the received signal waveform of the dual element sensor induced by corrosion defects is investigated by analyzing the mechanism of the modulation effect of corrosion defects on defects.A theoretical expression for the identification of dual element reference-free corrosion defects is derived by combining the Pearson coefficient method to characterize the waveform difference values.The waveform difference value is used as the damage factor,and the damage probability imaging algorithm is combined to realize the corrosion defect localization detection of the tank top plate,and verified by experimental tests.(3)The quantitative assessment technique of corrosion defects based on the amplitude ratio coefficient of ultrasonic guided waves was proposed and studied.By analyzing the modulation mechanism of corrosion defects on the guided wave,the relationship between the corrosion depth and the amplitude of the reflected and transmitted wave signals is studied,and then the theoretical expression of the amplitude ratio coefficient considering the attenuation factor is derived.Finite element analysis and electrochemical corrosion depth experiments are conducted to verify the relationship between corrosion depth and amplitude ratio coefficient.The algorithm optimization and applicability study of the amplitude ratio coefficient method is conducted considering the effect of the tank top plate welds.Combined with finite element analysis and experimental studies,the applicability of the amplitude ratio coefficient corrosion depth assessment under the influence of the weld is verified.(4)An integrated explosion-proof wireless ultrasonic guided wave detection device for quantitative assessment of structural corrosion defects on the top of large storage tanks is developed,mainly including an explosion-proof high-power output signal exciter and an intrinsically safe multi-channel wireless data collector.(1)Output signal exciter design:with FPGA as the central processing unit,waveform data and control commands are transmitted to the central processing unit through a Zig Bee wireless communication to output pulse clock signal,and then through the DAC circuit and power amplifier circuit to achieve higher voltage signal excitation to meet the demand of wide range detection.(2)multi-channel data collector design: FPGA as the central control unit,the received signal through the ADC module for data acquisition,and then the converted data is wirelessly sent to the host computer via a Wi-Fi module.The whole device has been tested in laboratories and on-site,showing that the device can meet the demand for on-site detection of the top plate of large storage tanks.