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Selective Seam Weld Corrosion

Typically found in pre-1970s pipelines, selective seam weld corrosion (SSWC) is localized along the weld bondline of pipe manufactured using low-frequency electric resistance welding or electric flash welding. Because SSWC creates weak points that can lead to leaks and other failures, repair or replacement of the affected pipeline section is required.

TDW provides a variety of services that help Offshore Pipeline operators minimize the risks associated with SSWC, including detection, anomaly characterization, and mitigation.

 

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Pigging programs help Offshore Pipeline operators limit corrosion damage and enhance pipeline integrity by removing built-up liquids, contaminants, and deposits on the pipe wall. Pigging also facilitates the application of special coatings to protect pipelines from corrosive agents. In addition, using cleaning pigs to prepare pipelines for inline inspection (ILI) helps improve data capture and accuracy, providing the most valuable and useful information possible.

Cleaning, pre-ILI preparation, and corrosion control:

  • VANTAGE® V cleaning pig – Multi-use pig designed to remove both hard, crust-like and soft, gummy deposits, as well as ferrous materials.
  • PitBoss™ cleaning pig – Removes soft to medium-hard deposits from internal pits, which is essential to improving the effectiveness of corrosion inhibitors.
  • WCK cleaning pig – Removes contaminants and deposits that increase resistance to flow in smaller pipelines.
  • REDSKIN™ foam pig – Used for light cleaning to remove paraffin and other soft deposits that could lead to corrosion.
  • OptionAll™ batching pig – Designed for light cleaning, line filling and dewatering, batch separation, and liquid removal.
  • VANTAGE® V batching pig – Multi-use pig used for batching, displacing, and light cleaning.
  • Pencil brush pig – Rids pipelines of finely divided black powder that has accumulated as the result of corrosion on steel pipe walls as well as hard scale deposits.

Removing built-up liquids:

  • UNISPHERE™ pig – Provides heavy-duty removal of liquid hydrocarbons and water from pipelines and piping systems.

Technical assistance is available from TDW subject matter experts for special circumstances or if the path to a solution requires consultation.

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TDW has developed an inline inspection (ILI) procedure that distinguishes selective seam weld corrosion (SSWC) from corrosion crossing the long seam (CCLS). This enables Offshore Pipeline operators to prioritize mitigation, focusing immediately on the areas most susceptible to SSWC and scheduling other corrosion-related work to comply with required pipeline assessment and repair criteria.

  • Multiple Dataset (MDS) platform – Combines multiple technologies to generate comprehensive, critical information in a single tool run. Includes magnetic flux leakage (MFL) to detect corrosion and SpirALL® MFL (SMFL) to identify the crack-like nature of SSWC.
  • SpirALL® Electromagnetic Acoustic Transducer (EMAT) – Using a unique sensor/magnetizer configuration, guided ultrasonic (sound) waves are transmitted into the pipe wall through direct contact, allowing EMAT to inspect natural gas and liquids pipelines. Detects axial planar/crack-like defects that are below the detectable limits of SMFL.
  • XYZ mapping (XYZ) – Supplies highly accurate location information about every defect reported by pairing global positioning system (GPS) coordinates with inertial mapping.

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In the Offshore Pipeline market, risk reduction is of utmost importance. TDW offers safe, proven hot tapping and plugging (HT&P) solutions for a wide array of pipeline defects and maintenance challenges from dents to corrosion to valve failure.

TDW technicians, who have a long track record of successful offshore projects around the globe, ensure that the work entrusted to the company is done efficiently with minimal interruption to product flow.

Whether operators need an emergency pipeline intervention or topside maintenance during a planned shutdown, HT&P offers safe and proven solutions for getting the project completed. The process incorporates a high pressure pipeline fitting, valve, tapping machine, and isolation equipment – all working together to provide a safe and proven isolation solution. Once the area of pipeline that needs work has been safely isolated and evacuated, the line modification can be performed.

TDW isolation technology plays a critical role in this process, and when combined with temporary bypass, it allows repairs to be performed without the need to stop product flow. The STOPPLE® Train Plugging System, for example, uses double block and bleed technology to help increase efficiency and safety during pipeline maintenance and repair. The system – which is able to create a double block and bleed seal through a single fitting – reduces costs associated with fittings, valves, welding, and inspection services. The bleed port affixed on the line ensures that any product that bypasses the first seal is contained and evacuated through the bleed port, which creates a safe zone in high-consequence areas.

Whether operators are purchasing equipment to perform their own HT&P jobs or turning to TDW to execute the service, they can rely on the TDW line of equipment and consumables. The Subsea 1200RC tapping machine, for example, is a topside-driven hot tap machine that can be safely operated down to a depth of 3,000 meters (9842.5 feet). The machine has proven to be a highly reliable shallow and deep-water solution.

To prepare for future challenges, operators also have the option of creating an Emergency Pipeline Repair System (EPRS), which equips them to take a proactive approach to pipeline emergencies. By working with TDW to create a custom system, operators will have planning and resources in place to repair and recommission their pipelines — and restore product flow — in the shortest time possible.