Dependence of Magnetisation near Saturation on Alloying Content in Ferromagnetic Steel

This paper shows that there is strong dependence of saturation magnetization on the alloying content in ferromagnetic steels. This dependence was used to determine the cross-sectional areas of the commercial non-oriented and grain-oriented silicon-iron steels. The relation between magnetization near saturation and the contents of silicon and aluminum for a large number of steel samples was experimentally obtained using an air-cored magnetizing system. The influence of the approach to magnetic saturation and its use in the determination of the cross-sectional area of electrical steel strips using the saturation magnetization method was estimated. Standard deviation (SD) of cross-sectional area obtained using the saturation magnetization method was on the order of 0.14%. SD for using conventional technique was also on the similar order of ~0.11%

Development of an On-Line System for Precision Dimensional Measurements in Electrical Steels using Approach to Ferromagnetic Saturation

A system based on a measurement technique magnetisation near saturation is presented that allows high precision measurement of dimensional parameters of iron alloys. Extensive measurements in electrical steel laminations show high accuracy in measurement of cross section area of the strips. The technique uses approach to saturation magnetisation which has previously been shown to be dependent on alloying content of the materials. This system is proposed for on-line measurement of cross sectional area and thickness of electrical steels, and other types of ferromagnetic strip metals

Computation of Rectifier Transformers employed in Railway Networks

Many rail transport providers operate and maintain a medium voltage distribution network providing power to trains, signalling equipment and stations. Transformers form an important part of the distribution network stepping voltage up and down. Rectifier transformers are used to provide DC for traction, usually stepping down from medium voltage levels. Mineral oil is essential for optimised performance of large transformers, providing the much needed cooling at high power operation and elevated core and winding temperatures. A representative rectifier transformer has been modelled for a realistic analysis of the 3D model constructed using exact manufacturer’s data for the geometry and coil arrangements. The results are seen to be in good agreement with the actual tests carried out during the commissioning of the transformer

Climbing robot design for NDT inspection

Wall climbing robots are extremely useful for deployment in hazardous environments and operation at great heights and other hard to reach space. However, these robots usually require large and heavy suction pads and associated cylinders for supporting the payload and effectual movement during climbing and inspection process and are very difficult to miniaturise. A new type of robot mechanism has been developed where movements are powered by electric motors and hence can be made on a much smaller scale and with the promise of high speed of operation

Enhanced TDR Technique for Fault Detection in Electrical Wires and Cables

Degradation and failure of aircraft wiring insulation is of particular interest which could lead to smoke and fire due to arcing. With two recent major air accidents and hundreds of major incidents over the past twenty years, health monitoring and sustainment of wiring, particularly for aging aircraft is a major concern. The results of a technique based on TDR, using trains of successive pulses is presented in this paper for detection of partial damage to insulation in electrical wires and cables

Thickness Evaluation for Steel Sheets Using Saturation Magnetization

A method based on characterisation of ferromagnetic steels under saturation magnetization has been developed, which allows precision evaluation of their thickness. A comparative study of the results obtained using this method, to those achieved using a γ- ray scattering technique shows remarkable accuracy

Reliability Improvement of Magnetic Corrosion Monitor for Long-Term Applications

Electromagnetic techniques are widely employed for corrosion detection, and their performance for inspection of corrosion is well established. However, limited work is carried out on the development and reliability of smart corrosion monitoring devices for tracking internal or buried thickness loss due to corrosion remotely. A novel smart magnetic corrosion transducer is developed for long-term monitoring of thickness loss due to corrosion at critical locations. The reliability of the transducer is enhanced by using a dissimilar active redundancy approach. The improved corrosion monitor has been tested in the ambient environment for seven months to evaluate the stability against environmental factors and degradation. The monitor is found to show great sensitivity to detect defects due to corrosion. Detection of anomalous patterns in the time series data received from the monitors is accomplished by using Pearson’s correlation coefficient. The critical component of the monitor is identified at the end of the test. Research findings reveal that, compared to the existing corrosion monitoring techniques in the industry, the detection and isolation of faulty sensor features introduced in this study can contribute to reliable monitoring of thickness loss due to corrosion in ferromagnetic structures over an extended period of tim

Development of Permanently Installed Magnetic Eddy Current Sensor for Corrosion Monitoring of Ferromagnetic Pipelines

Permanently installed sensors are a cost-effective solution for corrosion monitoring due to their advantages, such as less human interference and continuous data acquisition. Some of the most widely used permanently installed corrosion sensors are ultrasonic thickness (UT) gauges. However, UT sensors are limited by the need for coupling agents between pipe surfaces and sensors. The magnetic eddy current (MEC) method, on the other hand, does not require couplant and can be used over insulations. With the development of powerful rare earth magnets, MEC sensors with low power consumption are possible, and there is the prospect of using them as permanently installed sensors. A novel wireless magnetic eddy current sensor has been designed and optimized using finite element simulation. Sensitivity studies of the sensors reveal that the excitation frequency is a critical parameter for the detection of corrosion defects. An in-depth explanation of the relationship between the sensitivity of the sensor and the excitation frequency is presented in this paper. The results of an accelerated corrosion test, conducted to simulate the service environment of the sensor, are also discussed. It was observed that the sensor signals are very sensitive to corrosion defects and show no subtle differences due to temperature and humidity changes

Parameter analysis of pulsed eddy current sensor using principal component analysis

Pulsed eddy current (PEC) technique provides a means to inspect structures without surface contact. It is particularly useful when the structure’s surface is rough or inaccessible, such as insulated pipes in pipeline. Probe parameters of a PEC system, especially the sensing and excitation coil diameters, can significantly affect the PEC system’s performance. Thus, detailed analysis of these parameters is paramount in developing a PEC system. Currently, this is accomplished by establishing the trend of features with respect to the analyzed variables, e.g. sample thicknesses. However, prior to extracting these features, a number of configuration parameters have to be determined. For this reason, analyzing PEC performance over a range of coil diameter values is rather time-consuming as both the sensing and excitation coil diameters significantly affect the received signals. Principal component analysis (PCA) is proposed as an alternative to the feature extraction. The work here analyzes the trends contributed by the PCA scores for different values of sensing and excitation coil parameters. Results from both numerical simulations and experiments suggest that the sensitivity of the PEC probe is highly correlated with the excitation coil diameter, while the excitation-sensing coil distance is not significant in determining the sensitivity of the PEC probe. These findings are consistent with those reported in the literature, suggesting the potential of adopting PCA for an automated PEC performance analysis process

Development of an MFL Coil Sensor for Testing Pipes in Extreme Temperature Conditions

This paper aims to design a coil sensor for corrosion monitoring of industrial pipes that could detect variations in thickness using the MFL (Magnetic Flux Leakage) technique. An MFL coil sensor is designed and tested with pipe sample thicknesses of 2, 4, 6, and 8 mm based on the magnetic field effect of ferrite cores. Moreover, a measurement setup for analysing pipe samples up to a temperature of 200° Celsius is suggested. Experimental results reveal that the MFL coil sensor can fulfil the requirements for MFL testing of pipes in high temperature conditions, and that the precision of MFL monitoring of pipes to detect corrosion at high temperatures can be improved significantly