| Pipelines usually transport inflammable and explosive petroleum and natural gas and other energy materials.The existence of pipeline deformation defects will lead to the decrease of transportation efficiency and even the occurrence of pipeline rupture.Therefore,regular inspection of in-service pipelines is of great significance for the normal operation of pipelines.Based on the eddy current detection technology applied to the deformation detection of small-diameter oil and gas pipelines,this paper conducts theoretical analysis,structural design,simulation and experimental research.(1)The development status of pulsed eddy current detection technology at home and abroad is summarized,the shortcomings of traditional contact-type pipeline deformation detection are analyzed,the composite technology of contact-type deformation detection and eddy current deformation detection is proposed,and the eddy current detection is theoretically analyzed.(2)This paper designs the overall structure of the eddy current pipeline deformation detector.According to the maximum deformation of the inner detector and the pipe,the number of output channels of the probe,the scheme design of the inner detection framework,the collection system,and the arrangement scheme of the wheelset.The overall size of the eddy current pipeline deformation detector is determined,and the mechanical framework,circuit system and torsion spring of the eddy current detector are designed and calculated.The finite element simulation method is used to analyze the curve passing property of the simplified inner detector model,and the results show that the designed rigid structure of the detector can pass the limit condition of 1.5d ×90° elbow.(3)In this paper,using the finite element analysis software Maxwell,to simplify the probe,the specimen model electromagnetic simulation analysis,obtained array excitation coil,to solve the peak point of magnetic induction intensity and lift-off value nonlinear change trend,showing a negative correlation between two adjacent coil spacing respectively: a = 0.1 mm,2.5 mm,5 mm,to solve the peak point of magnetic induction strength with the lift-off value variation is respectively: 1m T/mm,0.7m T/mm,0.5m T/mm,shows that the existence of the adjacent coil has a positive influence to improve the sensitivity of eddy current sensor.At the same time,the excitation parameters such as excitation frequency,excitation voltage amplitude,duty cycle and the inner diameter of the excitation coil were changed to study the influence of the above parameters on eddy current deformation detection.(4)Finally,the eddy current distance detection probe developed by the author is used to build an eddy current detection test bed for experimental research.The results show that when the amplitude of the excitation voltage is increased,the amplitude of the voltage signal output by the sensor increases.When other parameters are fixed and the lift off value is increased,the amplitude of the voltage signal output by the sensor shows a nonlinear change law of negative correlation.When the double coil is excited,the range of the sensor and the sensitivity to the change of the lift off value are improved,indicating that the presence of adjacent coils improves the sensor’s ability to detect the distance.The experimental results verify the conclusion of finite element analysis,and show that eddy current deformation detection is feasible.The analysis of the collected experimental data shows that under the experimental conditions,the eddy current deformation detection probe designed in this paper can realize the deformation detection at the minimum of 1mm and the measuring range can reach to the maximum of 8mm.The research work of this paper provides a reference for the eddy current deformation detection method and the design of eddy current detection probe of small-diameter oil and gas pipeline,which has good theoretical significance and engineering application value. |
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