Solutions Engine

Unpiggable System

A variety of conditions can make it difficult for Offshore Pipeline operators to pig their pipelines for cleaning, maintenance, or inline inspection (ILI), leading them to believe that their system is unpiggable. The truth is, any pipeline system can be modified and made piggable. And with expanding regulatory requirements for inline inspection – and the fact that pigging can contribute to pipeline productivity and profitability – improving piggability is essential and may be required. 

Pigging is often impeded by pipeline design characteristics – tight, mitered, or forged bends, certain types of welds and connections, back to back bends and tees, dual- and multi-diameter pipe sections, etc. Some valves, particularly older globe body gate and check valves, obstruct pig passage; in fact, valves are the leading cause of stuck pigs and other pigging performance problems.

In the case of pipeline acquisitions, absent or incomplete records can lead to piggability concerns. And of course, systems without pig launchers and receivers cannot be pigged at all.

Conditions inside the gas pipelines – such as internal damage and the build-up of debris, sediment, and other flow-restricting materials – also cause pigging challenges. Because pigs are pushed along by product pressure inside the pipeline, 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. Liquid pipelines tend to have low flow for better operational control.

TDW helps operators improve piggability for:

  • Increased pipeline flow efficiency.
  • Corrosion control.
  • Batching and liquids displacement.
  • Internal inspection.
  • Increase service life for the pipeline as an asset.



Although the definition of “piggability” varies widely, by providing Offshore Pipeline operators with a comprehensive review of pressurized piping systems, TDW can help facilitate a better understanding of piggability challenges.

In addition to offering consultation with piggability subject matter experts, TDW provides cleaning pigs to prepare lines for necessary modifications, remove liquids and debris, and enable more reliable inline inspections of difficult-to-pig pipelines. TDW pigging solutions also include launchers and receivers that allow pigging access.

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. 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 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. With a spring center to enable tight radius bend clearance.

 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, Offshore Pipeline 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) – 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) – Provides accurate detection and sizing of internal and external metal loss. Solutions include a 6-inch tool proven to successfully inspect low pressure/low flow pipelines with pressures as low as 120 psi (8.3 bar). Can be combined with DEF technology for full inspection of bore and pipe wall thickness in a single run.
  • Active speed control (SPC) technology – Patented active speed control solution allows inspection tools to produce precise data about metal loss and geometry in high-flow natural gas lines.


In the Offshore Pipeline market, safety is of the utmost importance. During planned shutdowns, hot tapping and plugging (HT&P) technology allows operators to complete topside pipeline replacements and modifications – from making lines piggable to line lowering and relocations – with minimal flow interruption.

The HT&P process incorporates a high pressure pipeline fittingvalvetapping 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.

The full suite of isolation solutions by TDW plays a critical role in this process. The STOPPLE® Train Isolation System, for example, uses double block and bleed technology to help increase efficiency and safety during pipeline maintenance and repair. This approach to line isolation, which can 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 captured and evacuated through the bleed port, which creates a safe zone within 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 company’s 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.

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