ACCEPTANCE OF EMAT BASED IN-LINE INSPECTION TECHNOLOGY FOR THE ASSESSMENT OF STRESS CORROSION CRACKING AND OTHER FORMS OF CRACKING IN PIPELINES

摘要

Posing a major integrity threat, the phenomenon of Stress Corrosion Cracking (SCC) has been investigated and discussed intensively since the 1970's. On the basis of a deeper understanding of this threat today, integrity management programs have been developed further in the recent past.The detection of SCC with conventional liquid coupled ultrasonic technology is well accepted within the pipeline industry. Part of this acceptance is the successful application of such assessment standards as API 579. It has been shown that the conventional ultrasonic technology is sensitive and accurate enough to meet the needs of the standard. Recently, another form of ultrasonic technology has been recognized as a competitive alternative for in-line inspection tools. The electromagnetic acoustic transducer (EMAT) based ultrasonic technology does not require a liquid coupling making it cost effective for use in gas pipelines. In recent years, a newer generation of Electro-Magnetic Acoustic Technology tools has been made available and a process is on the way to establish this technology as a future option for gas pipeline operators [1,2]. In this paper results from the inspection of several gas pipelines and a series of pull-tests are used to show that EMAT technology is sufficiently sensitive and accurate to meet industry standards like API 579, making it a viable option for pipeline operators, especially for transportation of gaseous media.