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Although in rare cases expansion is due to over-pressurization in line segments, it is primarily related to a type of low-strength steel that was used to manufacture high pressure gas pipelines between 2007 and 2009.

The problem of pipes expanding during operation was first identified when pipeline owners and operators recorded pressure drops during hydrostatic testing to validate maximum operating pressure (MOP). Investigation into the cause uncovered weaknesses in the pipe materials.

TDW has inspected thousands of miles of larger diameter pipe for this anomaly and can help Gas Transmission operators detect and size expansions to maintain the integrity of their systems. TDW services include:

  • Cleaning to prepare pipelines for inline inspection (ILI).
  • Identifying expansion and prioritizing repair to address locations before pipeline failure can occur.



Cleaning pigs prepare pipelines for evaluation with inline inspection (ILI) tools, helping to improve data capture and accuracy ensuring Gas Transmission operators acquire the most valuable information possible. 

Pigs for pre-ILI cleaning

  • 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.
  • WCK cleaning pig – Removes contaminants and deposits that increase resistance to flow.
  • REDSKIN™ foam pig – Used for light cleaning. Able to negotiate short radius elbows, miter bends, and major diameter reductions.
  • OptionAll™ cleaning pig – Features Formula SI™ polyurethane for superior abrasion resistance.
  • 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.


Sensitive, accurate, and verifiable, our high-resolution inline inspection (ILI) technology detects and locates pipeline anomalies, including pipe expansion, enabling Gas Transmission operators to improve system integrity. TDW pipe expansion analysis procedures were developed directly with a major pipeline operator.

ILI technologies for detecting and characterizing pipe expansion

  • Deformation (DEF) – High resolution tool that efficiently detects expansions prior to pipeline commissioning or after it has been placed in service.
  • Multiple Dataset (MDS) platform – Combines multiple technologies to generate comprehensive, critical information in a single tool run.
  • XYZ mapping (XYZ) – Supplies highly accurate location information about every defect reported by pairing global positioning system (GPS) coordinates with inertial mapping.


In the Gas Transmission market, where pipeline shutdown may not be an option, hot tapping and plugging (HT&P) technology allows operators to expand lines, make connections and tie-ins, launch new services, and upgrade capacity – all while their line is in service. TDW HT&P solutions protect operators’ revenue stream while minimizing risk and are available for a wide spectrum of pipelines, environments, and products. 

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 requires work has been safely isolated and evacuated, the line modification can be performed. 

The full suite of isolation solutions offered by TDW plays a critical role in this process. The TDW STOPPLE® Train isolation system, for example, uses double block and bleed technology to help increase efficiency and safety during pipeline modification. The system – 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 bypassing the first seal is contained and evacuated through the bleed port, which creates a safe zone in high-consequence areas.

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

Whether operators purchase equipment to perform their own HT&P jobs or turn to TDW to execute the service for them, they can rely on the broad line of equipment and consumables from TDW. The company engineers and manufactures nearly every component needed for an HT&P project, and TDW tapping and plugging machines are considered the industry standard.

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.