Research On The Application Of Marine Seawater Pipeline Corrosion Nondestructive Testing Technology

Corrosion is a damaging phenomenon caused by the interaction between materials and the environment.Corrosion will lead to structural damage,material failure,and function loss of equipment,and induce various accidents,with very serious direct and indirect losses.Seawater piping system is an important part of Marine equipment and Marine engineering,which is responsible for seawater transportation,cooling,fire fighting,and so on.Due to the comprehensive action of various corrosion factors,the Marine seawater pipeline leakage caused by corrosion in the process of use will be very serious.Therefore,it is very important to detect the corrosion problem of seawater piping systems timely and accurately.However,there is still a lack of research and application of Marine seawater pipeline corrosion nondestructive testing technology in China.Therefore,relevant research is urgently needed to fill the gap in the field of technical application and provide technical means for effectively preventing the corrosion of seawater pipeline system,reducing the corrosion failure rate and economic losses.In view of the technical needs of Marine seawater pipeline corrosion nondestructive testing,this paper studies and verifies the application scope,precision,and application scheme of the testing technology with the potential application through technical research and comparative analysis at home and abroad,laboratory and shipyard tests.The corrosion morphology and corrosion degree of seawater pipelines were compared and analyzed using micro testing and numerical simulation technology.The relevant research results can provide good technical support for the proposal of the application scheme of Marine seawater pipeline corrosion detection technology.The main research contents and results are as follows:1.According to the technical requirements for corrosion testing of Marine seawater pipelines,the principles and application status of different nondestructive testing technologies were investigated and analyzed,and the characteristics and environmental conditions of Marine seawater pipelines were combined to select the nondestructive testing technologies that could meet the corrosion testing requirements of Marine seawater pipelines.The simulation test of corrosion detection technology was carried out in the laboratory to verify the detection ability,detection range,and detection accuracy of different detection technologies.The test results show that the screened corrosion detection techniques have certain application feasibility in Marine seawater pipeline corrosion detection.Among them,ultrasonic thickness measurement can detect artificial defects of flat bottom holes with a diameter of ?3mm and above,and the thickness detection error is about 6%.Electromagnetic ultrasonic thickness measurement cannot detect small size artificial defects.Ultrasonic phased array can detect manual defects with a minimum diameter of 1mm.When the Angle between the inner wall of the pipeline and the probe is less than 17.5°,the signal intensity is 50%higher than the bottom wave intensity.When the Angle reaches 30°,the signal intensity is close to 0.When the wall thickness is less than 1mm,the ultrasonic phased array analyzes the actual wall thickness through the second wave and multiple waves.Eddy current testing can detect the remaining flat bottom hole with wall thickness less than or equal to 0.5mm and diameter?1mm;The remaining flat bottom hole with a wall thickness of less than or equal to 1.25mm and a diameter of ?3mm;The remaining flat bottom hole with a wall thickness of less than or equal to 1.5mm and a diameter of 5mm.Eddy current testing has a good detection effect on defects with a large wall thickness change rate,which is greatly affected by coating thickness.Ultrasonic guided wave detection can be used to detect defective pipelines with the length of less than 1m,which has the potential of application in ship inspection.2.The corrosion detection ability of different nondestructive testing technologies in seawater pipelines on real ships was verified through corrosion detection tests.The results show that electromagnetic ultrasound can not detect small size defects and is not suitable for corrosion detection of Marine pipelines on real ships.Eddy's current testing is of great background noise and poor detection effect when the thickness of coatings on real ships is up to about 1mm.Piezoelectric ultrasonic thickness measurement can be used to measure the thickness of pipelines with a thickness of more than cp20mm and 2.2mm and can detect local corrosion pits.Ultrasonic phased array has a better detection effect on the erosion and corrosion of elbow parts,and the detection results can directly reflect the conditions of the inner wall of the pipeline.Ultrasonic guided wave detection technology can also carry out a wide range of pipeline screening,real ships detected the signal strength of 3%corrosion,corrosion detection has the initial detection ability.The corrosion test was verified by static immersion experiment of 3.5%NaCl solution for 0?7 days,macro and micromorphology observation,electrochemical test,and so on.The self-corrosion potential of B10 Cu-Ni alloy first decreased,and began to increase in 3 days.The self-corrosion potential of B10 Cu-Ni alloy on 7 days was-0.318V.According to the above research results and the inspection requirements and conditions of real seawater pipelines,the corrosion application scheme and specific operation methods of real seawater pipelines are formulated in different maintenance stages including onboard vessel,dock repair,minor repair,and medium repair.3.In order to further optimize the detection scheme and solve the problems of the short construction period and heavy workload of seawater pipeline corrosion detection,a scheme combining simulation technology with corrosion detection technology was proposed based on the completion of the corrosion detection scheme of real ship seawater pipeline.Under different seawater conditions and pipeline structures,including flow rate,second phase particles,elbow Angle,and pipeline diameter,the simulation results are consistent with the actual situation.K-Epsilon standard model was adopted,and the residual was 1×10-6.After a data analysis of the simulation results,the predicted corrosion degree of the seawater pipeline is provided for corrosion detection work.Using the computer numerical simulation technology can optimize the corrosion detection scheme of real ships,improve the efficiency and pertinence of corrosion detection,and further improve the safety of Marine seawater pipelines under the existing conditions.