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Pipeline Direct Assessment as an Alternative for Inline Inspection of Unpiggable or Difficult to Inspect Pipelines

22 Dec

Are you facing challenges in performing inline inspection (ILI) of your unpiggable pipeline or difficult to inspect pipelines? Does the difficulty and/or delay in performing pipeline inspection force you to operate your pipeline network with an unacceptably high risk?

Performing inline inspection can be a challenging and complex undertaking. Pipeline Direct Assessment (DA) is an alternative method which can be considered.

A well Implemented Pipeline Direct Assessment can be extremely effective as an alternative means to inline inspection for unpiggable or difficult to inspect pipelines.


The assessment needs to be performed by experienced and competent pipeline integrity engineers, in accordance with industry standard practices and guidelines (e.g. NACE SP0110, SP0116, SP0204, SP0206, SP0208, SP0502)

A four-step process is typically employed:

  • Pre-assessment: Stage 1 involves gathering relevant data (pipeline design, construction, corrosion control, environmental, operation etc.), assessing feasibility of the pipeline Direct Assessment and defining the DA regions.
  • Indirect inspection: Stage 2 identifies locations susceptible to corrosion (or cracking) along the length of the pipeline. A detailed and comprehensive review of historical corrosion control/operating data is performed:
    1. Specialist CP surveys like close interval potential surveys, direct current voltage gradient surveys, Pearson surveys etc. for external corrosion; or
    2. Flow modelling supported corrosion rate prediction for internal corrosion; see figure below.
  • Direct examination: Stage 3 involves field inspection surveys based on indirect inspection results, localised inspections (e.g.: UT, laser mapping, visual inspection etc.) are performed to verify and assess the extent of corrosion damage.
  • Post assessment: Stage 4 involves assessment of overall effectiveness of the Pipeline Direct Assessment, determining mitigation activities, and estimating reassessment interval.

AIE has extensive experience and track record in all aspects of Pipeline Direct Assessment. We can guide pipeline operators to acquire the relevant data and our subject matter experts can promptly assess the feasibility of a Pipeline Direct Assessment. Furthermore, we can perform or support indirect inspection, direct examination, and post assessment activities.

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