A 22-inch onshore natural gas transmission pipeline experienced an in-service rupture on January 2018. The rupture was caused by an axial crack that occurred 150 Km (93 miles) downstream of the closest compression station.

While the root cause analysis investigation of the rupture was in progress, the pipeline operator carried out excavations starting approximately 42 km (26 miles) downstream of the rupture with the purpose of investigating indications reported by a Hard Spot In-Line Inspection (ILI). These excavations discovered predominantly circumferential crack colonies, with a number of the excavation locations leaking.

The pipeline section was constructed in 1960 in the Buenos Aires Province, Argentina, with API 5L X52 steel, with a nominal diameter of 22 inches (558.8 mm) and a nominal thickness of 0.250 inches (6.35 mm). The pipes were fabricated by A.O. Smith (USA), the first 118 Km (74 mi) with longitudinal Electric Flash Welded (EFW) seam weld, the remaining 34 Km (21 mi) with seamless pipe, in both cases with asphaltic coating. The design pressure of the section and the MAOP coincides in 59.8 Kg/cm2 (850 psi, 72% of the SMYS).

Transportadora de Gas del Norte (TGN) engaged Blade Energy Partners, Ltd. (Blade) to conduct the root cause analysis investigation, which concluded that the axial and circumferential external cracks found are neither related to high pH SCC, near-neutral pH SCC nor fatigue, that the characteristics of the fracture morphology are consistent with hydrogen cracking, and that the hydrogen is generated by the impressed-current cathodic protection system operated near the -1200 mV pipe-to-soil recommended potential limit.

TGN implemented a series of preventive and corrective tasks that included pressure testing, cathodic protection improvement, coating rehabilitation programs and In Line Inspection programs among others.

This paper discusses the background and approach used in the root cause investigation, summarizes the methodology, results and findings of the root cause analysis, and discusses their implications in the management of the Pipeline Integrity of the affected pipeline section and of the rest of the pipeline system operated by TGN.


An Onshore Pipeline Failure Produced by Cathodic-Protection-Induced Hydrogen Cracking \u2013 Case Study

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

IPC2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.