漏磁检测技术在管道检测中的应用

为了检测埋地管道的腐蚀状态,开发了管道漏磁检测技术。该检测技术通过对管道局部磁化,检测磁化管段的磁场分布,识别记录缺陷位置磁场的畸变来判断腐蚀缺陷。该检测技术在多条管线上进行应用,其检测结果准确可靠,根据检测结果可以及时修复损伤严重的部位,保证管道安全运行。根据管道修复情况可以确定管道下次检测日期。分析检测结果的误差产生的原因,确定了设备分辨率、调试状态、管道自身特性等若干影响检测结果因素,并对今后的改进工作指出了切入点。     

CNG储气井井筒腐蚀的漏磁检测探索

为了对CNG储气井安全隐患进行有效检测,根据漏磁检测原理,应用ANSYS对CNG储气井井筒漏磁磁场分布进行模拟.仿真结果表明,在合适的磁化参数下可以有效地检测出腐蚀状况.在此基础上,采用交变磁化方式,以锰锌铁氧体作为磁化材料,用霍尔元件阵列检测漏磁信号,加以计算机组成漏磁检测系统.实验结果表明.该系统能够检测出井筒的缺陷,但是精度还需进一步提高.     

漏磁检测技术在油罐底板检测中的应用

漏磁检测是近年来发展起来的一种无损检测技术,具有检测效率高、准确等优点。目前,该技术在油罐底板检测中得到了广泛的应用。本文在阐述漏磁检测技术原理的基础上,分析了影响漏磁检测的因素,并介绍了相关的罐底板漏磁检测设备,最后论述了漏磁检测技术的具体应用实例。     

钢管漏磁在线检测技术的研究

介绍了钢管漏磁检测的基本原理，对钢管在线漏磁检测系统进行总体设计。分析了漏磁场理论模型和讨论了影响缺陷漏磁信号的一些因素及补偿方法，针对该系统的特点设计了高速数据采集板，借助Windows系统平台，在所研制硬件的基础上，采用多线编程和虚拟设备驱动技术编制了数据采集、分析、状态显示、实时控制等面向对象、多功能模块化的软件，详细叙述了漏磁信号数据分析的方法和过程。这种系统具有检测速度快、数据吞吐量大、效率高、钢管缺陷分辨率高等特点。     

石化储罐缺陷的漏磁检测系统

首先分析了漏磁检测的原理和漏磁检测技术的适用范围,然后探讨了石化储罐漏磁检测系统总体结构及其漏磁检测程序,并对其广阔前景进行了展望。     

油气管道漏磁检测缺陷区域的分段识别方法

为解决油气管道漏磁检测数据量巨大所带来的处理难题,研究一种从漏磁检测数据中快速识别出待求解目标缺陷区域的检测方法。基于有限元仿真计算,对油气管道三维漏磁检测信号的特性进行研究,进而对检测数据进行分段阈值截取处理,并提出一种管道待求解缺陷区域的分段识别方法,可快速且准确地处理油气管道漏磁检测海量数据。基于实际油气管道的漏磁检测数据,对所提出的分段识别方法进行试验验证。试验结果表明:所提出的方法可准确识别出管道上的缺陷区域,既完整地包含缺陷及其附近区域,也不存在过量的无关区域,可有效地控制后续处理过程的数据量。     

磁记忆技术在管件裂纹检测中的应用

基于金属磁记忆效应的原理，本文研究了利用磁记忆技术检测管件裂纹，虚拟仪器系统和漏磁传感器是检测系统的核心。试验表明，运用该技术检测管件裂纹是完全可和和有效的。     

城镇燃气管道中漏磁检测技术的应用

在城镇化快速发展的背景下,城镇燃气管网辐射面积越来越广,极大地方便了人们的日常生产生活。城镇燃气管道在长期使用过程中会发生腐蚀,为防止腐蚀导致严重的事故,就需要做好燃气管道的日常腐蚀检测。目前燃气管道腐蚀检测中常用技术包括漏磁法、超声波法及激光法等,其中因漏磁法对应用环境要求低,适用于多种传输介质且对铁损失等管道缺陷检测效果显著,所以广泛应用于铁磁性燃气管道缺陷检测中。基于此,该文以城镇燃气管道为背景,从漏磁检测技术角度出发,分析了其原理,又结合实例项目进一步研究了漏磁检测技术的应用情况,以期可以为保障城镇燃气管网安全运行作出应有贡献。     

高速钢轨缺陷的漏磁检测及反演

为保障高速铁路行车安全,从铁磁性材料磁化的机理出发,分析漏磁检测的基本原理,介绍漏磁检测技术在钢轨缺陷检测中的应用研究,提出高速钢轨缺陷的漏磁检测方法。采用有限元法建立缺陷漏磁检测模型,分析缺陷漏磁场Bx、By和Bz分量的特点,并针对高速钢轨漏磁检测中缺陷提取相应的特征参数,运用人工神经网络的方法实现漏磁检测缺陷的反演,取得较好的反演结果。     

油气输运管道缺陷漏磁检测量化技术研究

通过实测得到油气输运管道缺陷漏磁(MFL)信号，分析了缺陷几何尺寸与信号特征量之间关系。采用特征提取和模式识别技术对缺陷进行量化分析。对缺陷的长、宽、深三个指标分别应用不同的特征量和相应的非线性方法进行定量识别。试验结果表明，缺陷长度、宽度和深度的预测准确度分别达到了100％、89％和77．8％。这里通过使用长宽比特征量描述方法，有效地提高了深度的估计精度，很好地解决了管道缺陷的量化识别问题。     

Influence of Slot Defect Length on Magnetic Flux Leakage

A key issue, which influences the applications of magnetic flux leakage testing, is defect quantification. There have been many research on the relationship between width, depth and magnetic flux leakage of slot defect. However, the length factor is often ignored. The relationship between characteristics of defect leakage field and defect length was investigated. The magnetic flux leakages of a series of plate specimens with the same width, same depth and different length slot defects were tested under the same magnetizing conditions. Testing results show that defect length is an important parameter needed to consider in quantifying defects.     

Factors Affecting Magnetic Flux Leakage Inspection of Tailor-Welded Blanks

The development of a laboratory-based tailor-welded blank (TWB) inspection system using the principles of magnetic flux leakage (MFL) is presented. The effects of variations in inspection system operating parameters are quantified to allow for optimized system performance. The parameters examined include the applied magnetic field strength, inspection scanning velocity, spatial resolution of acquired signals, specimen end effects, and pole piece liftoff. The results indicate that this inspection method is relatively insensitive to operating parameters and is therefore robust.     

Evaluation of Surface Cracks Using Magnetic Flux Leakage Testing

The magnetic field distribution characteristics of surface cracks with various widths are discussed based on finite element (FEM) results.The crack depth was 0.20 mm ,the width range was from 0.02 to 1.00mm .The results showed that crack width and lift-off( the distance between surface and sensor )will influence singals.Discussed in this paper is the influence of various lift-off parameters on the peak to peak values of the normal component in magnetic flux leakage testing .The effects can be applied to evaluate surface breaking cracks of different widths and depths.An idea is presented to smooth narrow, sharp crack tips using alternating current (AC) field magnetization.     

基于脉冲漏磁理论的管道腐蚀缺陷宽度定量技术

在带保温层管道腐蚀缺陷的定量检测中,缺陷的宽度定量是一项重要内容.提出了采用脉冲漏磁技术对带保温层管道的腐蚀缺陷进行检测.通过提取传感器峰值扫描波形中极值点的位置差△D作为特征量,分析了无保温层和带保温层情况下,△D随管壁腐蚀缺陷宽度的变化规律,从而得出了对管道腐蚀缺陷进行宽度定量的方法.实验结果证明了所采用方法的正确性和有效性.     

A Dynamics Study of a Magnetic Flux Leakage （MFL） Signal and its Application to Defect Location Discrimination in Steel Pipes MFL Testing Equipment

Difference processing was used to the direct current magnetic flux leakage(DC-MFL) signal,emanating from the defects machined artificially on the internal and external surfaces of a steel pipe.Consequently,the location discriminating index δ was provided to identify the defect whether it is on the internal surface or the external one.Three characteristics,shape,depth and orientation of the defect,were discussed through a series of experiments on the artificial defects,such as transverse notches,oblique notc...     

Magnetization Time Lag Caused by Eddy Currents and Its Influence on High-Speed Magnetic Flux Leakage Testing

In high-speed magnetic flux leakage (MFL) testing, the tested workpieces pass rapidly through magnetizers. Thus, the magnetization time for workpieces is short. Because of the eddy current effect, the magnetic field inside the workpieces cannot instantly reach equilibrium, and if the magnetizing time is insufficient for the field to reach equilibrium, the MFL signals will be changed because of incomplete magnetization. In this article, the magnetization time lag caused by eddy currents and the influence of this lag on high-speed MFL testing is investigated. The time required for magnetic field to reach equilibrium in specimens, including steel bars and pipes, is obtained by theoretical calculations, finite element simulations, and experiments. The results indicate that the time required for a magnetic field inside a specimen to reach equilibrium is in the range of 50–100 ms. Using conventional magnetizers, the defect signals at testing speed of 10 m/s change because the workpiece reaches the detection zone before the magnetic field inside reaches the stable state. A simple solution is to increase the axial length of the magnetizing coil. After this procedure, signals obtained at 0.1 m/s and 10 m/s are almost identical.     

高速漏磁检测的二维缺陷轮廓重构

针对高速漏磁检测缺陷可视化中的关键技术与难点,通过提升小波包的方法对缺陷漏磁信号进行预处理,根据电磁场基本理论,对高速漏磁检测过程中传感器速度对漏磁信号的影响作了理论分析,提出了基于正则化理论的径向基函数神经网络的补偿措施,通过网络的映射,得到了缺陷漏磁信号的速度不变响应,最后利用蚁群算法优化的径向基函数网络对缺陷漏磁信号进行二维反演,实现了缺陷的二维轮廓重构。     

高精度智能磁场测量仪的设计

设计了一种由微处理器控制的具有通信接口的高精度智能磁场测量仪,通过双只配对的集成霍尔传感器来获取磁感应强度的信号,采用压频变换器完成数据的采集,并对仪器进行了校准和实验．实验结果表明,所设计的磁场测量仪在整个量程范围内的测量精度达到了0.1mT．该仪器不但可进行磁场的精密测量,还可用于对无线通讯基站电磁辐射的网络化远程监测．     

三维磁场精密测量系统的研制

介绍了三维磁场精密测量系统的研制,利用差动方式连接的6个霍尔元件构成三维磁场传感器,通过压频变换器完成数据采集,并采用电压比测量法来补偿温度变化对霍尔元件输入电阻的影响．对系统进行了高精度的标定,消除了温度变化对霍尔元件灵敏度系数的影响．标定后的系统达到了0．5％的精度,并利用这一系统对高速磁悬浮列车的气隙磁场进行了测量．