Experimental Study On Corrosion Immersion Acoustic Detection Method For Large Tank Bottom Plate

Storage tanks are the main equipment for crude oil reserves in the petrochemical industry.In recent years,with the rapid development of the petrochemical industry and the increasing demand for energy in various industries,the number of storage tanks has increased dramatically,and the size of storage tanks has become larger.Directional design.Due to the overall structure of the tank and the working environment,the tank bottom plate is most prone to corrosion damage,and once the oil storage tank is exposed due to corrosion,perforation,crack propagation and cracking of the bottom plate,accidents such as leakage or explosion will cause huge accidents.Economic losses and safety hazards.However,the existing tank wall type acoustic emission detection method has a detection dead zone for the detection of large storage tanks.Therefore,in order to accurately know the corrosion severity of the tank bottom plate,it is of great significance to design a mobile full coverage acoustic emission detection method that can detect the entire area of the large tank floor.The main research contents of this paper are summarized as follows:(1)This paper reviews the research status of acoustic detection technology of tank bottom corrosion in in-service storage tanks,and discusses in detail the detection principle,technical advantages and existing problems of acoustic emission detection technology for the bottom plate corrosion detection of in-service storage tanks.The experimental conditions,techniques and schemes determine the feasibility of the content of the paper,formulate the research content of the paper,and clarify the research route of the paper;(2)Feasibility study on the immersion acoustic detection method of the tank bottom plate,comprehensively grasp the tank floor by studying the causes and mechanism analysis of the tank floor corrosion,the acoustic signal characteristics of the tank bottom corrosion and the sound signal transmission path of the tank bottom corrosion.Corrosive environmental conditions and characteristics of corrosive acoustic signals.The experiment of simulating the acoustic signal of the tank bottom plate in different propagation paths is carried out.It is known from the experimental results that the acoustic emission signal propagated only through the medium in the tank is less attenuated and the sound source characteristics are retained more.The immersion acoustic detection of the corrosion of the large tank bottom plate in service has high accuracy and feasibility;(3)This paper proposes a cross-type small matrix plane localization algorithm based on time delay estimation.Then the theoretical derivation and comparative analysis of the sound source localization methods based on the quaternary cross array and the five-element cross array are made respectively,and the factors affecting the azimuth estimation and the accuracy of the ranging estimation are analyzed.The analysis finds that when the variance,array spacing and sound velocity are constant,the ranging variance of the quaternary cross-location algorithm is related to the ranging r and the azimuth angle ?,respectively,and the azimuth variance is only related to the azimuth angle ?,and the ranging r Nothing.The ranging variance of the five-element cross-location algorithm is only related to the ranging r and the azimuth angle ?,and the azimuth variance is independent of the azimuth angle ? and the ranging r;(4)Four-element cross and Five-element cross arrays are used to test the location of sound source on tank floor.The test results show that the performance of four-element cross algorithm is lower than that of five-element cross algorithm in terms of ranging accuracy,and it will be affected by the angle of sound source.Especially at 45 degrees,the four-element cross algorithm is not suitable for the location of sound source.Bit algorithms all have high direction finding accuracy,but the direction finding accuracy of quaternion cross algorithm will be affected by the angle of sound source.The experimental results are consistent with the mathematical analysis results of location algorithm errors,so the five-element cross algorithm is chosen as the immersion source location algorithm;(5)In order to solve the problem of detecting dead zone in large tank bottom plate,a method for detecting the corrosion immersion mobile acoustic field of large tank floor is proposed.In order to realize the method,an immersed automatic acoustic detector is designed.The overall structure of the detector is mainly divided into four parts: the body structure,the motion mechanism,the detection mechanism and the recovery device,in order to ensure the safety of the in-service storage tank.The detector has also been designed with an explosion-proof seal as a whole.