Internal and External Defects Discrimination of Pipelines Using Composite Magnetic Flux Leakage Detection

Abstract

Leakage failure risks of oil and natural gas pipelines caused by internal and external defects are different. In the magnetic flux leakage (MFL) detection, different quantification algorithms for internal and external defects are required to obtain more accurate defect quantification. However, MFL detection can not distinguish internal and external defects well. To address this problem, this paper proposed an eccentric magnetic circuit branch structure suitable for MFL detection. Based on the magnetic circuit branch structure, this paper developed a magnetic concentrating testing (MCT) method to identify internal defects. Moreover, this paper put forward a magnetic circuit isomagnetic potential point method to pinpoint the optimal MFL sensor point. Combining MFL and MCT detection, this paper presented a composite MFL detection method to discriminate between internal and external defects in the pipelines. The results of the simulation demonstrated the effectiveness of the composite MFL detection method.