Solutions Engine

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 Gas Transmission operators minimize the risks associated with SSWC, including detection, anomaly characterization, and mitigation.




Pigging programs help Gas Transmission 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.


TDW has developed an inline inspection (ILI) procedure that distinguishes selective seam weld corrosion (SSWC) from corrosion crossing the long seam (CCLS). This enables Gas Transmission 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.


Non-destructive Evaluation (NDE)

TDW provides non-destructive in-ditch assessment of selective seam weld corrosion (SSWC), from localized areas up to entire joint lengths. Combining the Gas Transmission operator’s interaction rules with TDW corrosion mapping capabilities provides highly accurate and useful information to help address pressing corrosion issues before they become critical.

  • Phased array ultrasound – An advanced non-destructive evaluation enhances the sensitivity and efficiency of ultrasonic inspections. The shear wave phased array ultrasonic method is used to detect and size planar anomalies, including cracks, crack-like features, and other weld defects. This evaluation allows for permanent documentation of acquired data for anomaly growth monitoring.
  • Conventional shear wave ultrasound – This technology detects and sizes planar anomalies that are perpendicular to the pipe wall.
  • Magnetic particle inspection – A combination of two non-destructive evaluation methods – magnetic flux leakage (MFL) testing and visual inspection – is used to check exposed pipe for surface anomalies.


In the Gas Transmission market, where pipeline shutdown often is not an option, TDW offers safe and efficient hot tapping and plugging (HT&P) solutions for a wide array of pipeline defects and maintenance challenges, from dents to corrosion to valve failure.

The HT&P 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 a temporary bypass allows work to be performed without the need to stop product flow. The TDW STOPPLE® Train isolation system, for example, uses double block and bleed technology to help increase efficiency and safety during pipeline modification. This approach to line isolation, which only requires a single pipeline tap, 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 helps operators better protect people and the environment.

Because double block and bleed plays such a large role in protecting people, the environment, and communities that a number of regulators in Canada now require it for HT&P repairs. American regulators are likewise moving in that direction.

Whether operators purchase equipment to perform their own HT&P jobs or turn to TDW to execute the service, they can rely on the company’s broad line of equipment and consumables. TDW engineers and manufactures nearly every component needed for an HT&P project, and the company’s tapping and plugging machines are considered the industry standard. To meet regional needs quickly and efficiently, TDW maintains equipment and consumables in service centers around the globe.

TDW can also partner with operators before the work begins, providing consulting services to help them make optimum use of TDW products and services. TDW application engineers are recognized industry experts, ready to assist operators through each project phase – from start to finish. 

TDW also offers RES-Q® Wrap and Steel Repair Sleeves, quick, simple solutions that allow operators to keep their pipeline operational and within code.

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