Non-ferromagnetic Tubing Research Articles

Artificial Intelligence for Assisted Analysis of Eddy Current Data from Heat Exchangers with Non-Ferromagnetic Tubes

Oil & Gas and petrochemical industries need regular inspection of shell and tube heat exchangers to maintain performance. NDT inspection service providers are required to complete the data collection and analysis in the shortest possible time frame, but manual analysis for defects like corrosion or pitting is time-consuming and prone to errors. This leads to safety risks and unexpected downtime, and there's a shortage of experienced ECT level II/III certified analysts globally. The industry needs tools to simplify data interpretation and increase analysis efficiency while maintaining a consistent and repeatable level of confidence. While assisted analysis for tube ECT testing has existed for several years, most solutions have been developed for the nuclear industry and employ methods that become quickly limited when the test conditions are not well controlled or when the tube bundle information is incomplete These situations are very common outside the nuclear industry, and they often contribute to reducing the efficiency and reliability of data interpretation. This communication outlines the use of AI in various tasks of tube data analysis, from landmark localization to indication detection, to improve efficiency and confidence in the analysis process. A complete analysis system has been implemented and field data results demonstrate the system's value. Robustness to suboptimal data quality is also discussed.

Simulation on Influence of Wall Thickness and Probe Channel Numbers on the Examination Rate of Oxides Blocking Ratio in non-Ferromagnetic Tubes

Oxides accumulated in the inner bend of austenite heating tubes of super critical units may cause overheat and bursting. Traditional methods could not examine oxides blocking ratio. A magnetic field simulation of the boiler tube’s oxide skin blockage model has been set up in this paper. The influence of different wall thickness and different accumulation of oxide on the distribution of magnetic field was analyzed. It was demonstrated that the blockage oxide scale could be quantitatively measured by the amplitude and distribution of magnetic field.

Discussion on Roundness of Non-Ferromagnetic Tube by Interior Magnetic Abrasive Finishing Using a Magnetic Machining Jig

In this study, mainly researching the improvement of roundness of thick SUS304 stainless steel tube by interior magnetic abrasive finishing using a magnetic machining jig. The influence of reciprocating velocity of magnetic pole unit on the improvement of roundness of interior surface was studied by establishing the dynamic equation of magnetic machining jig. Experimental results showed that low reciprocating velocity of magnetic pole unit is conducive to the improvement of interior roundness of the thick SUS304 stainless steel tube. The reason is that the low reciprocating velocity of magnetic pole unit reduces the pitch of the helical motion and can produce greater finishing force of the magnetic machining jig.

Bobbin pulsed eddy current array probe for detection and classification of defects in nonferromagnetic tubes

The pulsed eddy current technique has received a great deal of attention in recent decades. To improve its performance and applicability, several kinds of probes, such as rectangular and gradient field probes for plate detection and encircling probes for tube detection, have been proposed. However, few bobbin-type pulsed eddy current probes have been proposed. This study proposes a bobbin pulsed eddy current array probe to simultaneously detect, classify and evaluate inner and outer surface defects in nonferromagnetic tubes. The probe contains double exciting coils and 20 sensors. The double exciting coils could generate stronger and more uniform induced eddy current in tube. The 20-sensors array could measure the complete circumferential magnetic signals above tube inner surface. Using the Br curves drawn by peak value and post peak value, inner and outer surface defects can be classified without beforehand training or the usage of complex process. Meanwhile, the maximum value in Br curve can be used to measure the defect depth and residual depth accurately.

Magnetic compression effect for the enhancement of crack response signals in non-ferromagnetic conductive tubes

Magnetic compression effect for the enhancement of crack response signals in non-ferromagnetic conductive tubes

Real time groove characterization combining partial least squares and SVR strategies: application to eddy current testing

A quasi real-time inversion strategy is presented for groove characterization of a conductive non-ferromagnetic tube structure by exploiting eddy current testing (ECT) signal. Inversion problem has been formulated by non-iterative Learning-by-Examples (LBE) strategy. Within the framework of LBE, an efficient training strategy has been adopted with the combination of feature extraction and a customized version of output space filling (OSF) adaptive sampling in order to get optimal training set during offline phase. Partial Least Squares (PLS) and Support Vector Regression (SVR) have been exploited for feature extraction and prediction technique respectively to have robust and accurate real time inversion during online phase.

Transient eddy current method for the characterization of magnetic permeability and conductivity

Recent analytical solutions, that correctly describe transient eddy current signals in voltage-controlled driver-pickup circuits, are applied for the case of a coaxial probe encircling a long ferromagnetic conducting tube. Experimental results, obtained for the case of a square wave excitation, are in excellent agreement with the predicted driver and pickup responses. Using the forward solutions, a novel inverse method, that enables simultaneous and accurate characterization of magnetic permeability and electrical conductivity, has been developed. Specifically, the method considers computed areas under scaled transient eddy current signal curves. In the generalized case, multiple parameters of interest can be extracted from a single transient signal by taking advantage of the frequency domain differentiation property of the Laplace transform. Preliminary experiments show that permeability and conductivity values, calculated for a variety of ferromagnetic and non-ferromagnetic tubes, agree well with published values (permeability) and with values obtained by four point measurement (conductivity). The inverse method introduced in this work may be straightforwardly extended to consider other parameters, such as lift-off and material thickness, and to consider other geometries, such as conducting plates.

Study on Internal Magnetic Field Assisted Finishing Process Using a Magnetic Machining Jig for Thick Non-Ferromagnetic Tube

This paper describes an internal finishing process for thick non-ferromagnetic tube (10~20 mm in thickness) by the application of a magnetic field-assisted machining process using a magnetic machining jig (permanent magnet tool). In this study, a new automatic inner surface finishing system was developed, and to achieve smooth surface roughness and high form accuracy, a multiple-stage machining which contains of rough machining and precision finishing was carried out. Especially, in order to improve the form accuracy the rough processing time was made longer compared with the research in the past. The experiments were performed for a thick SUS304 stainless steel tube 10 mm in thickness. The results showed that surface-roughness and form accuracy were able to be improved greatly, the initial surface roughness of 4.9μmRa can be improved to 0.01 μmRa and the roundness of inside tube can be improved from 206 μm to13μm.

Nondestructive Inspection Using Rotating Magnetic Field Eddy-Current Probe

Rotating magnetic field eddy-current (RoFEC) probe for nondestructive evaluation of steam generator tubes in a nuclear power plant offers an alternate method that has compact configuration and higher speed compared to traditional bobbin coil, rotating probe coils, and array probes. This paper investigates the feasibility of the proposed RoFEC eddy-current probe which is composed of three windings excited by three-phase ac current and does not require mechanical rotation of probe. Results of finite-element modeling using reduced magnetic vector potential (RMVP) formulation are presented for modeling the inspection of ferromagnetic and nonferromagnetic tubes. Design parameters of the excitation coils and GMR pick-up sensor are optimized by means of a parametric study.

Measurement of electrical conductivity in nonferromagnetic tubes and rods at low frequencies

We present a simple and precise method to measure the azimuthal electrical conductivity in nonferromagnetic tubes and rods at low frequencies. The results are readily obtained by analyzing the eddy currents in the sample when it is subjected to an axial harmonic magnetic field. The information about the eddy currents can be obtained from a measurement of the phase of the induced voltage in a short probe coil located inside the tube or around the rod when the sample is axially excited by a long primary coil. At low frequencies, the eddy currents are distributed over the full depth of the sample and any irregularities can be detected when the probe coil is moved along the sample axis.

A New Internal Magnetic Field Assisted Machining Process Using a Magnetic Machining Jig-Machining Characteristics of Inside Finishing of a SUS304 Stainless Steel Tube

This paper proposes a new magnetic field assisted machining process using a magnetic machining jig (permanent magnet tool) to finish the internal surface of thick tubing 5~30 mm in thickness. Because the magnetic machining jig consists of permanent magnets, it can generate a higher magnetic force (finishing force) than conventional magnetic abrasives, and makes possible the internal finishing of thick non-ferromagnetic tubing. First, the principle and the feature of this process were examined. It was compared that the difference of the mechanism of using the conventional magnetic abrasives and magnetic machining jig (magnet tool) was clarified. Next, a processing unit and magnetic machining jig were made, and the processing unit was set on a lathe machine. An experiment was performed on a thick SUS304 stainless steel tubing 5 mm in thickness. In this study, it was clarified that this processing method can improve the roundness of the inside tubing while improving the surface roughness. The results showed that the initial surface roughness of 6.5 μm Ra can be improved to 0.06 μm Ra, and the roundness of the inside tubing can be improved from 187 μm to 89 μm.

Mechanism of a Magnetic Field Assisted Finishing Process Using a Magnet Tool and Magnetic Particles

This paper describes a new efficient internal finishing process for a thick tubing (10~30mm in thickness), by the application of a magnetic field-assisted machining process using a magnet tool. Because a stronger magnetic force can be generated than conventional magnetic abrasives, it makes the internal finishing of thick non-ferromagnetic tubing possible. Moreover, in order to obtain a high-quality surface, this process method was developed using magnetic particles magnetically attracted on the magnet surface. This paper characterizes the processing principle and advantages of this process. Then, the mechanism of this finishing process was examined by a plane model experiment. It was clarified that the magnetism and shape of a magnetic particle influence realization possibility of this processing method, and it also influence the finishing characteristics.

Superconducting pipes and levitating magnets

Motivated by a beautiful demonstration of the Faraday and the Lenz laws in which a small neodymium magnet falls slowly through a conducting nonferromagnetic tube, we consider the dynamics of a magnet falling coaxially through a superconducting pipe. Unlike the case of normal conducting pipes, in which the magnet quickly reaches the terminal velocity, inside a superconducting tube the magnet falls freely. On the other hand, to enter the pipe the magnet must overcome a large electromagnetic energy barrier. For sufficiently strong magnets, the barrier is so large that the magnet will not be able to penetrate it and will be levitated over the mouth of the pipe. We calculate the work that must done to force the magnet to enter a superconducting tube. The calculations show that superconducting pipes are very efficient at screening magnetic fields. For example, the magnetic field of a dipole at the center of a short pipe of radius a and length L approximately > a decays, in the axial direction, with a characteristic length xi approximately 0.26a. The efficient screening of the magnetic field might be useful for shielding highly sensitive superconducting quantum interference devices. Finally, the motion of the magnet through a superconducting pipe is compared and contrasted to the flow of ions through a trans-membrane channel.

Magnetic Abrasive Finishing of Non-Ferromagnetic Tube

Magnetic Abrasive Finishing of Non-Ferromagnetic Tube

Remote field eddy current inspection

The Remote Field Eddy Current (RFEC) technique uses an internal probe to inspect conducting tubes nondestructively. A coaxial solenoidal exciter, energized with low frequency AC, and detector coils near the inside of the pipe wall are separated by about two pipe diameters to obtain through wall transmission and equal sensitivity to defects on the outside or inside of the pipe wall. Calculation methods are outlined and the voltage plane polar plot signal representation for defect measurement is described. Slit defect interactions in ferromagnetic and non-ferromagnetic tubes are discussed. Defect-induced anomalous fields are interpreted in terms of anomalous source eddy current and missing magnetization defect models. The use of computer animations to represent the time variations of high resolution field measurements and calculations is described.

Study on a New Internal Finishing Process by the Application of Magnetic Abrasive Machining : Internal Finishing of Stainless Steel Tube and Clean Gas Bomb

In magnetic machining, the internal finishing of a nonferromagnetic tube is performed by means of the magnetic force generated between magnetic and the N-S magnetic poles. In this experiment, magnetic abrasive are applied to finish the internal surface of a tube, in which large iron particles, generating a high finishing pressure, are mixed with magnetic resulting in finishing. By this new process using the mixed-type magnetic abrasive, the finishing efficiency is increased markedly. In this paper we describe the effects of both the size and the mixed weight percentage of iron particles on the surface roughness of a stainless steel tube. We also describe the application of the new process to the internal finishing of the bottom of a clean gas bomb for practical use. As a result, the surface roughness before finishing, 7 μm Rmax, was reduced to 0.2 μm Rmax over the entire inner surface of the bottom.

Remote field eddy current technique: Phantom exciter model calculations

High resolution results of finite element calculations for remote field eddy current “phantom exciter” simulations of slit defect interactions using single through wall transit are presented. These show that fine circumferential slits cause almost no field perturbations in the case of nonferromagnetic tubes but big perturbations in ferromagnetic tubes where high magnetic H fields occur in the slits. Defect-induced magnetic field perturbations must therefore be considered in addition to eddy current perturbations when ferromagnetic materials are inspected, particularly in the case of fine slits orthogonal to the magnetic field direction. Additional details seen are the funnelling of energy into slits in ferromagnetic pipes and precursor disturbances of fields approaching defects. It is suggested that these are due to the reflection of the electromagnetic waves dictates by boundary conditions at the near side defect boundary.

非磁性円管内面の磁気援用研磨法に関する研究 永久磁石を利用したユニット型研磨装置の開発

A new unit type magnetic finishing apparatus composed of ferrite permanent magnets is developed to finish precisely the internal surface of a non-ferromagnetic tubing, as a substitute for the previous finishing apparatus with large and heavy electromagnetic coils. This new finishing unit is installed easily on the carriage of a conventional lathe. The finishing jig composed of rare earth permanent magnets is also developed by which the powerful finishing pressure is generated by a magnetic force. This paper described the new unit type finishing apparatus, the finishing jig and their internal finishing performances for cleaning stainless steel tubings.

回転磁界を利用した非磁性円管内面の平滑加工法 実用研磨装置の開発とその研磨性能

A new internal finishing process is investigated of a non-ferromagnetic tubing applying a rotating magnetic field generated by electromagnetic coils. To finish the inner surfaces of long or vent clean tubings, a new type finishing equipment is made for practical use. This equipment has conically shaped magnetic coils and magnetic cores consisted of laminated thin electric pure iron plates, so that this equipment is able to be applied to the tubings with the wide range outer diameter from 25 to 150 mm and the temperature rise generated by iron loss of the cores were prevented in lower level. Using this equipment, the finishing experiments were carried out to examine the influences of various factors, especially, finishing tool size, tool weight, tool contact curvature and magnetic field strength, on the maximum adulating revolution of the finishing tool. As the result, the suitable finishing conditions were made clear. Then, from the experiment applying this new process to the internal finishing of a stainless steel elbow tubing which could not be rotated, it was clarified that the surface roughness of 15 μmRmax before finishing was improved to 0.4μmRmax after finishing.

Pulsed eddy-current inspection of thin-walled stainless steel tubing : Oak Ridge national laboratory, Oak Ridge, Tennessee (United States), DE88-001492, 118 pp. (Sep. 1987)

A pulsed eddy-current system has been developed for production inspection of small, thin-wall, non-ferromagnetic tubing. To detect and accurately size both outer and bore-side flaws required an operating frequency higher than available from present commercial equipment. A pulsed eddy-current instrument was designed and constructed that used 3.2 MHz square waves, with a bandwidth of 20 MHz. The system is able to reliably detect flaws as small as 0.015 mm (0.6 mils) on either the inner or outer surface of the tube. A computer controls the scanning of the tube, as recording, analyzing, and plotting the data. The computer programs and instrument details are given in the report.