ILI Verification drone underwater.

ILI Verification

Pipelines are often inspected by In-Line Inspection (ILI) using intelligent pigging tools. These tools provide valuable information on pipeline conditions but given the challenges of inspection from the inside of pipelines, the accuracy of measurements can be limited. This can affect decisions on the integrity and remaining life of pipelines, the outcomes of which can be expensive, e.g. replacement or repair of a line.

Consequently, pipeline operators will often choose to verify the wall thickness and extent of degradation features identified during an ILI run. This is most often done using externally applied inspection tools with enhanced accuracy.

Verification and Inspection Techniques

In the case of ILI verification, Sonomatic has a wide range of tools and techniques capable of performing high accuracy verification of any defects. Sonomatic tooling is deployable by divers or ROVs. Inspection tools and techniques are provided to be able to inspect through-coating inspections, piggyback solutions, weld inspection and field joint inspections.

Regardless of the defect location, Sonomatic can provide the technique and tooling best suited to provide the inspection requirement. Sonomatic can pair our in-field inspection capability with our integrity services team to make better use of the data collected. With this, we can “re-calibrate” ILI datasets, further interrogate ILI data analysis, target locations for verification and many more services.

Subsea ILI Verification techniques.
Key Subsea Inspection Applications:
  • Through Coating Inspection
  • Piggyback Solutions
  • Weld Inspection
  • Field Joint Inspection
  • Internal and External Defect Solutions

Key Subsea Inspection Techniques

Ultrasonic Corrosion Mapping

Ultrasonic corrosion mapping involves scanning the pipeline to determine the minimum remaining thickness for each position and can be achieved using conventional UT probe or a PAUT probe. The systems deployed produce comprehensive, high-quality data that can be displayed in different views to easily identify and/or verify any areas of concern. Sonomatic Inspection Management Software (SIMS) is used to generate 2D and 3D thickness map composites to improve efficiency in data management during the collection phase, and assists in semi-autonomous data analysis and reporting.

Time of Flight Diffraction

TOFD is an industry norm for pipeline weld inspection. This ultrasonic technique is the best method for defect detection and accurately sizing & monitoring the through-wall height of weld defects.

Phased Array inclusive of Full Matrix Capture (FMC/TFM)

Full matrix capture (FMC) is a data acquisition strategy that allows for the capture of every possible transmit-receive combination for a given ultrasonic phased array transducer.

Pulsed Eddy Current

PEC is a comparative technique whereby advanced processing of the eddy current signal decay and comparison with a reference signal, allows for the determination of the average wall thickness (AWT). This fast-screening method allows for the assessment of the general condition of structural steel and is best suited for general corrosion type defects in subsea pipelines. A major benefit of PEC is its ability to inspect through challenging coatings and marine growth.

Dynamic Response Spectroscopy

DRS is a proprietary technology developed by Sonomatic using frequency-based ultrasonic wall thickness measurements. It is a corrosion mapping technique that applies a broad range of low ultrasonic frequencies (<1 MHz) to penetrate challenging coatings such as composite repairs, PE and Neoprene, and excites the natural frequencies of vibration of the underlying steel. The DRS probe raster scans over an area of interest and collects response signals. Advanced signal processing algorithms have been developed to extract the vibration frequencies and map the wall thickness profile.

Automated Shear Wave Pulse Echo

Angle shear wave methods are widely used in NDT and in most applications the probe is manually manipulated. There are, however, significant benefits to automating the process, both in terms of probe manipulation and data collection. The benefits include the following:

  • Consistent performance with minimised human factors effects
  • Substantially improved probability of detection (POD)
  • Improved sizing capability
  • Accurate positional control
  • Accurate position information for each scan
  • Full recording of all data for more detailed analysis
  • Reliable repeat comparisons

Automated shear wave pulse echo is used for a variety of applications, some examples are listed below:

  • Inspection of welds to detect and size planar flaws.
  • Inspection of corrosion-resistant alloys for stress corrosion cracking.
  • Inspection of corrosion-resistant alloys for chloride pitting.
  • Inspection of materials in wet H2S service for vertical cracking elements.

InspeCT (Computerized Tomography)

InspeCT™ is Sonomatic’s proprietary subsea computed tomography system designed to eliminate the requirement to remove protective pipeline coatings, specifically concrete weight coating, to evaluate common pipeline integrity challenges including corrosion under insulation/coating, internal pitting & corrosion, degradation of internal linings & corrosion-resistant alloys, and detection & sizing of internal build-up of deposits and scale.

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