Pipeline Inspection (In-line)

Dacon has been involved with in-line pipeline inspection services since 1976 and has performed successful Inspections for many of the worlds largest multinational oil and gas companies around the globe.

In-line inspection (ILI) tools, sometimes referred to as "intelligent" or "smart" pigs, are used to inspect pipelines for evidence of internal or external corrosion, deformations, laminations, cracks, or other defects.

Selecting the correct tool is typically based on the perceived threats to the pipeline integrity as well as the pipeline's physical and operational characteristics. Dacon can help you to evaluate the types of defects the pipe might be subject to (such as internal corrosion, external corrosion, weld cracks, stress corrosion cracks) and the risk presented to the pipeline section being inspected.

Magnetic Flux Leakage (MFL) and Ultrasonic Testing (UT) are the two primary methods for in-line inspection of pipelines and each have their own strengths and weaknesses. Whilst Dacon provides both techniques our recommended method where the pipeline parameters permit is to use UT Intelligent Pigging for its higher accuracy and easier mobilization.

UT tools are well suited for heavy walled pipe. UT tools do require a liquid couplant through which ultrasonic pulses can travel to and from the pipe wall. The presence of any gas between sensors and pipe wall will interfere with the inspection but gas pipelines can still be inspected using ultrasonic techniques by running the tool in a liquid slug between two high-sealing pigs.

MFL tools have difficulty magnetizing heavy walled pipe to saturation meaning they have an upper wall thickness limit ranging from 12.7 to 25.4 mm (0.5 to 1.0 inches depending on the specific tools.

Both types of intelligent pig require a clean pipeline to function correctly and a pipeline cleaning program should be carried out before the intelligent pig is run through the line. In addition Dacon uses a Progressive Pigging system which combines cleaning pigs and gauge pigs to ensure there is no debris or obstruction in the line that could lead to a stuck Pig.

Dacon has the experience and expertise needed to ensure safe and obstruction free pipeline inspection runs and you can have every confidence that Dacon will successfully complete any inspections of your most prized asset.

Considerations For In-line Inspection

Prior to any pipeline inspection Dacon will conduct a thorough examination of the physical and operational characteristics of a pipeline in order to assess piggability and recommend the best solutions.
A number of items need to be considered in every pipeline assessment and the major factors are summarized below:

Pig Launchers and Receivers

Pig launchers and receivers are required for pipeline pigging operations however temporary launchers and receivers can be built and installed as needed.

pipeline inspection

Typical Launcher/Receiver


Most in-line inspection tools and hard body utility pigs are designed to negotiate bends with a radius of 3D or greater, all of Dacon’s UT Intelligent Pigs can pass 1.5D bends.

Internal Coating

Internal coatings can potentially interfere with data collection by some in-line inspection tools and a correct understanding of the coating material and bonding method needs to be established.

Wall Thickness

In-line inspection tools have a range of pipe wall thicknesses for which they are capable of inspecting for metal loss. MFL is not suitable for heavy wall thickness whereas UT is suitable for almost any wall thickness.

Internal Diameter (Bore)

Dual diameter pipelines are problematic for in-line inspection due to the risk of the pig stalling at the diameter change. Dacon has successfully pigged dual diameter pipelines with a 15% change in pipe ID but each case needs to assessed individually.

In-line Valves

All in-line valves should be full bore to facilitate pigging operations. Dacon will physically check all mainline valves to be sure they are fully open prior to any pig runs to avoid pig or valve damage. For check valves flappers may need to be removed or locked in the open position.


Branch connections to the pipeline should be barred to prevent the front of a pig from becoming lodged. Special tool nose cones can overcome unbarred tees in some cases.


Wyes can be a major obstacle for pigs and inspection tools to navigate. However, Dacon has designed, built and tested ILI tools that can negotiate Wyes.

Flexible Risers

Flexible risers consist of several layers of metallic and elastomeric materials. Whilst no tools currently exist that can inspect all layers of a flexible riser Dacon's tools have passed successfully through flexible risers and into the FPSO turret (without taking data measurements).

Pig Speed

Flow rates must be monitored and controlled to allow for optimum pipeline inspection results. Typically UT intelligent pigs require lower flow rates whereas MFL pigs can accommodate much higher flow rates.


Intelligent pigs have a specific temperature range in which they can function properly due to onboard electronic equipment. The upper limit of this temperature range is generally less than 40 °C, but Dacon’s UT Pigs can operate in temperatures as high as 65 °C.

Pressure Limitations

Intelligent pigs do have maximum pressure limitations typically somewhere between 90 to 150 bars.

For more information and a full assessment of your pipeline inspection needs please do not hesitate to contact us at info@dacon-inspection.com