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Difficult to Pig

A variety of conditions can make it difficult for Liquids Transmission operators to pig their pipeline systems for cleaning, maintenance, or inline inspection (ILI). However, with expanding regulatory requirements for inline inspection – and the fact that pigging can contribute to pipeline productivity and profitability – making pipelines piggable is becoming a necessity.

Pigging is often impeded by pipeline design characteristics – including tight, mitred , or forged bends; certain types of welds and connections; and dual- and multi-diameter pipe sections. Some valves, particularly older gate valves, obstruct pig passage. And of course, systems without pig launchers and receivers cannot be pigged at all.

Pigging challenges are also caused by conditions inside the pipeline – such as internal damage and the build-up of debris, sediment, and other flow-restricting materials. Low flow rates may cause stopping and starting, preventing the pig from performing effectively. Conversely, pigs running in high velocity product streams can also be less effective.

TDW will assist pipeline owners and operators in the Liquids Transmission market to:

  • Make a pipeline piggable.
  • Allow works to be completed while the pipeline is live.
  • Provide cleaning tools that can: Increase pipeline flow efficiency; Provide better corrosion control; Allow for batching.
  • Provide ILI services to ensure the integrity of the pipeline.



TDW provides Liquids Transmission operators a variety of solutions to improve piggability and enable inspection of difficult-to-pig pipelines, including launchers and receivers for pigging access and cleaning pigs to clear pipelines of deposits and debris.

Launchers and receivers

Cleaning pigs

  • REDSKIN™ foam pig – Available with bristle stripes that allow the pigs to easily clean the pipeline with a low probability of becoming lodged or stuck. REDSKIN pigs are well designed for unknown bend designs, low flow, and low-pressure operating systems.
  • OptionAll™ cleaning pig – A versatile pig available in multiple configurations. Blades and brushes are easily added for pipeline cleaning and maintenance.    
  • X-Pig® multi-purpose utility tool – A truly all-urethane pig that provides the flexibility needed for tight pipeline turns in cleaning, batching, and displacement operations.
  • VANTAGE® + pig – Used for batching and displacement; extremely flexible in tight bend pipelines and can traverse a 20 percent reduction in interior pipe diameter.  
  • WCK and WCK DD (dual diameter) cleaning pigs – Designed to clean pipelines that have hard deposits and multiple inside diameters. A spring center enables tight radius bend clearance.           

For pipelines with severe internal build-up, TDW can deliver a customized progressive pigging program where a series of increasingly aggressive pigs is sent through the pipeline to break up and eliminate wax, solids, and other dirt and debris.

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


Technological advances in inline inspection (ILI) are enabling better inspection of difficult-to-pig pipeline systems. As a result, Liquids Transmission owners and operators know more than ever about the condition of pipelines previously thought to be “unpiggable.”

TDW provides the following services for inspection of difficult-to-pig pipelines:                                                                           

  • Deformation (DEF) technology – Our high resolution DEF tool detects minute bore reductions — including dents, ovalities, wrinkles, and misalignments — down to the slightest change in a pipeline’s internal diameter.
  • Magnetic Flux Leakage (MFL) technology – Provides accurate detection and sizing of internal and external metal loss. Sizes include 4-inch and 6-inch diameters proven to improve speed profiles in low pressure/low flow pipelines, as well as sizing of dents, internal and external metal loss, and dents with metal loss.
  • Speed Control (SPC) technology – Patented active speed control solution allows inspection tools to produce precise data about metal loss and geometry in high-flow gas lines.


In the Liquids Transmission market, where pipeline shutdown may not be an option, hot tapping and plugging (HT&P) technology allows operators to complete pipeline replacements and modifications – from making lines piggable to line lowering and relocations – with minimal flow interruption. TDW HT&P solutions protect customers’ 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 fitting, valve, tapping machine, and isolation technology – 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. 

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 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 for them, they can rely on the broad line of TDW equipment and consumables. The company engineers and manufactures nearly every component needed for an HT&P project, and TDW tapping and isolation equipment is 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.