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Robust Welding Repair Technology for Oil/Gas Pipelines
Project Number
FWP-FEAA139
Last Reviewed Dated
Goal

The goal of this project is to refine and optimize Oak Ridge National Laboratory’s (ORNL) innovative low-temperature phase transformation weld wire/consumables to eliminate hydrogen-induced corrosion and improve the fracture and fatigue properties of the repaired weld region of oil/gas steel pipelines.

Performer

Oak Ridge National Laboratory (ORNL)

Background

Welding repair is one of the widely used technologies to ensure the structural integrity and extend the service life of oil/gas pipelines. Compared to original pipeline construction welding, on-site or in-field repair welding is generally much more challenging in many aspects. For example, accessibility and equipment setup can be impaired or difficult to accomplish due to space and location constraints. Pre-heat and/or post-weld heat treatment (PWHT) that are routine and mandatory in the welding of original structures may be impossible or compromised. Furthermore, welding materials with lower strength may have to be used to overcome hydrogen-induced cracking (HIC) due to the inability of pre-heating or PWHT. HIC would be of particular concern for old pipelines made of steels of high carbon equivalent due to steel production technologies prior to 1970. HIC is also a major concern for high-strength steel pipelines (such as X80 or higher strength steels) that have been installed in the past 20 years or so. For these reasons, welding, including repair welding of pipeline can be costly, and if not done properly, may compromise the safety margin of pipeline options, resulting in catastrophic failure of pipelines such as the 2010 incident in San Bruno, California, which destroyed 38 houses, damaged 120 houses, and killed 8 people.
The Materials Processing and Joining group at ORNL has a long history of developing practical joining solutions for structural materials for a broad range of industry sectors including automotive, fossil power plants, oil/gas, petrochemical, and nuclear energy.  Research topics range from fundamental welding science projects to welding technology development intended to solve specific industry problems.
 

Impact

The analytics to be developed will enable earlier detection of degradation in operating pipelines to support decisions about where to focus inspections, enhance situational awareness about the scope of inspections to be performed, allow monitor trending between inspections, and inform the timing of preventative maintenance. The research will reduce the repair cost and improve the structural integrity and reliability of repaired structures.

Accomplishments (most recent listed first)
  • Solved the low weld impact toughness issue of the first-round weld wires. Two of the weld wires in the second round produced welds with Charpy impact value of 259 J and 178 J respectively, much higher than the Charpy V-Notch impact test value (measure of material’s toughness under impact loading conditions) requirement for highest steel grade (X120) of 108 J per API Specification 5L.
  • Demonstrated three different low-temperature phase transformation weld wires to successfully weld X60 to 100 pipeline steels without HIC. All welds were without pre-heat and post-weld heat treatment and met or exceeded the strength and other requirements from industry partners for these pipeline steels.
  • Finalized specific target metrics for research based on both technology and business considerations.
     
Current Status

The next steps include a refinement of the weld wire chemistry to reduce the strength for better matching with X80-X100 pipelines, perform additional welding and testing on X65 and other pipeline steels with lean and rich chemistry, and perform an in-depth study of the microstructure of the partial melting region and microhardness. 

Project Start
Project End
DOE Contribution

$1,800,000.00

Performer Contribution

$0.00

Contact Information

Federal Project Manager – Eric Smistad (eric.smistad@netl.doe.gov or 281-494-2619)
HQ Program Manager – Christopher Freitas(christopher.freitas@hq.doe.gov or 202-586-1657)
Principal Investigator – Zhili Feng(fengz@ornl.gov) or 864-576-3797)
Team Supervisor – John Duda (john.duda@netl.doe.gov)
Technology Manager – Jared Ciferno (jared.ciferno@netl.doe.gov or 412-386-5862)