Oil and gas transmission pipelines are critical items of infrastructure in providing energy sources to regions and countries. Steel pipes are commonly used which can be subject to both internal and external corrosion. This paper presents an advanced nondestructive inspection technique for detection of oil-gas pipeline corrosion defect. The Pulsed Eddy Current (PEC) method has been successfully applied in corrosion detection of unburied gas pipeline without removing the insulation. First, the principles of pulse eddy current method is pointed out then, the pulsed eddy current test on a pipe is simulated by Maxwell software to obtain optimum test parameters. To test the new technique, some artificial defects are fabricated on the inner surface of a gas pipe to simulate different corrosions phenomena in practice. Three isolation layers are applied to the pipe in order to show the efficiency of PEC in the detection of wall thinning areas without removing the insulation. پرونده مقاله

This paper presents a new methodology for the automated inspection of pipes. Standard inspection systems are based on closed-circuit television cameras which are mounted on remotely controlled robots and connected to remote video recording devices. The main problems of such camera-based inspection systems are: 1) the lack of visibility in the interior of the pipes and 2) the poor quality of the obtained images because of difficult lighting conditions. The focus of this research is the automated detection and location of defects in the internal surface of pipes. The proposed optical system is an assembly of a CCD camera and a laser diode to create a ring-shaped pattern. The camera obtains images of the light projections on the pipe wall. A novel method for extracting and analyzing intensity variations in the obtained images is described. The image data analysis is based on image processing algorithms. Finally, an image of the pipe wall is generated by extracting the intensity information existing in the pipe pictures. Defects and anomalies can be detected using this extracted image. پرونده مقاله

Stress and residual stress are the main problems in the operating performance of materials. They are the principal causes of material failure and can affect life time of component. However measurement or predictions of them are typically difficult. Two common non-destructive methods, X-ray diffraction and ultrasound are not reliable methods for subsurface residual stress measurements and destructive hole-drilling method is not absolutely precise and safe. In this study, the PEC method was applied to the qualitative and quantitative measurements of stress in aluminum alloy specimens. PEC is a high performance non-destructive testing technique but its application in stress and residual measurement is unknown. In this study a qualitative and quantitative approach for measuring residual stress by PEC technique was developed. Results indicated that pulsed eddy current responses are sensitive to stress and showed PEC method is capable of residual stress measurements. پرونده مقاله

Magnetic Flux Leakage (MFL) is an indirect measurement technique. Therefore, calibration curves are generally used to estimate the depths of the defects from the measured MFL signals. This has been shown to give good results on varying degrees of the single defects. However due to the interaction between the leakage fluxes, nearby pittings can-not be discriminated and properly assessed using the conventional MFL technique. In order to ensure reliable measurement for this case, the MFL technique is combined with the optical inspection technique. The main contributions of this study are to develop a new calibration method based on the defect depth, defect area as well as the amplitude of the corresponding MFL signal and propose a novel combined approach for detection and identification of the nearby pittings. MFL and optical inspection techniques are applied to a test specimen containing the nearby pittings. The results obtained from the experimental tests demonstrate the efficacy of the proposed approach. پرونده مقاله