Abstract
In this paper, an optical fiber sensor is designed by using optical Faraday effect. It is composed of fiber collimator, polarizer, magneto-optical crystal and mirror. Based on the magnetic flux leakage (MFL) theory, The optical fiber sensor was placed between two permanent magnets with the N-pole. Therefore, the optical fiber sensing system was built to detect the defective ferromagnetic objects. Theoretical and experimental studies shown that the system can identify a little defects, such as irons’ blind hole (diameter φ = 3mm , depth t = 4mm ), irons’ grooves (length l= 30mm , width ω = 10mm ), hole (φ = 3mm ) and crackle etc. The system has the characteristics of small size, high sensitivity, fast signal response and high resolution. In terms of the defective oil and gas pipelines detection, The optical fiber sensing system is used in non-destructive testing, which will be valuable and meaningful.
Highlights
In the field of non-destructive testing, especially in oil and gas pipelines, there are five commonly used non-destructive testing technologies: Radiographic Testing (RT), Ultrasonic Testing (UT), Magnetic powder Testing (MT), Penetration Testing (PT), Eddy Current Testing (ECT)
Based on the magnetic flux leakage (MFL) theory, The optical fiber sensor was placed between two permanent magnets with the N-pole
Through the theoretical and experimental analysis of the leakage magnetic field on the ferromagnetic plate, it was proved that the optical fiber sensing system can correctly detect the defects on the metal surface
Summary
In the field of non-destructive testing, especially in oil and gas pipelines, there are five commonly used non-destructive testing technologies: Radiographic Testing (RT), Ultrasonic Testing (UT), Magnetic powder Testing (MT), Penetration Testing (PT), Eddy Current Testing (ECT). They have their own advantages and disadvantages. Ultrasonic testing (UT) technology [1] and Magnetic Flux Leakage Testing (MFLT) technology [2] are the most mature and widely used in pipeline and plate inspection. The electromagnetic eddy current testing (ECT) method [3] has been rapidly developed in the field of internal detection, due to its non-contact detection, test instrument assembly and simple operation. Because the eddy current method relies on the skin effect of metal conductor, the defect depth of objects and the interference of electromagnetic wave will bring difficulties to the signal identification
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