ABSTRACT

High-Frequency Electric Resistance Welded pipe (HF-ERW) has been around for more than 40 years with a reputation of high toughness and fewer seam weld defects than Low Frequency (LF) ERW pre- 1970s. However, both HF-ERW pre-1980s and LF-ERW pre-1970s are susceptible, under the right conditions, to develop selective seam weld corrosion (SSWC) and hook cracks due to a high content of sulfur in the pre-1980s steel. This paper describes a supplemental screening process that operators can perform as part of their due diligence. The process uses ultrasonic detection data and ILI vendor display software to identify and prioritize potential longitudinal seam weld anomalies, specifically focusing on SSWC to differentiate it from general corrosion located across or adjacent to the longitudinal seam weld. The process ranks anomalies to help operators prioritize integrity management efforts and resources.

INTRODUCTION

On July 8th, 1986, an 8-inch pipeline transporting gasoline ruptured in Mounds View, Minnesota. Vaporized gasoline combined with air and liquid gasoline flowed along neighborhood streets. Approximately 30 minutes later, a vehicle entered the area igniting the gasoline vapor. Two people were severely burned and later died. Jones and Laughlin Steel Co. manufactured the low-frequency electric resistance welding (LF-ERW) pipes. The pipeline failed at 1434 psig but had been hydrostatically pressure tested to 1900 psig just 2 years before this incident. The National Transportation Safety Board (NTSB), in its Pipeline Accident Report [1] determined that the susceptibility of the pipe to selective seam weld seam corrosion (SSWC) contributed to the incident. As a result of the investigation, the NTSB made several safety recommendations to the Department of Transportation (DOT), including the review of all pertinent data such as leak, and failure reports submitted by liquid pipeline carriers to determine if longitudinal weld failures constitute a recurrent safety problem, and take appropriate regulatory action if they do.

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