In-Field Verification of Internal Corrosion
Combined MFL-A and -C inspection for internal corrosion detection
ROSEN performed a combined MFL-A and -C inspection on a large pipeline network for a client in the Middle East. The customer requested support from ROSEN’s integrity team because the in-line inspection identified accelerated internal corrosion due to changes in the pipeline’s operating parameters. The integrity team recommended the use of special corrosion inhibitors to slow or stop the growth of internal corrosion.
Following the application of the corrosion inhibitor, the customer contracted a local NDT company to measure and monitor peak internal corrosion levels. The inspection showed significant growth, which called into question not only the effectiveness of the corrosion inhibitor but also the original sizing accuracy of ROSEN’s ILI tools.
Our Solution
Due to the severity of the in-field depth sizing and the potential damage to the reputation of ROSEN tools, the ROSEN field verification team was brought in to review the reports and quality of the third-party on-site inspection and to provide a second opinion.
Due to some discrepancies in the 3rd party reports, ROSEN was mobilized to perform detailed corrosion mapping of some complex internal morphology on critical infrastructure.
During the inspection period, multiple sites were investigated using the robust ROSEN encoded PAUT procedure. This procedure was developed and qualified against known defects, taking into account the minimum detectable flaw size and sizing accuracy on various feature morphologies.
At all sites studied, the performance of the ROSEN tool was validated by investigation of key target features.
The ROSEN in-field data did not show significant growth (within the combined tolerances of the tool and field measurement procedures per API 1163), which was inconsistent with previous field reports.
Due to the detailed data collection method, the data clarity and the openness to sharing raw field data, the customer was happy with the quality of the data, which made the customer confident that:
- The corrosion inhibition was working correctly
- The 3rd party in-field results were not reliable
- The in-line inspection tool was performing within its specification
The customer’s substandard field data gave the impression that there was still a significant problem with internal corrosion in this pipeline. Had the customer known the inspectors’ competency in evaluating this type of feature prior to the field visit, this impression would not have been confirmed. Guidance on understanding the competence of field verification technicians is detailed in ROSEN’s “Field Verification Requirements” document.
Your Benefit
Understanding technician competency in field verification is critical, especially when it comes to validating ILI performance. A small sample of field measurements is extrapolated to justify potentially thousands of ILI decisions, so high accuracy is critical.
If low-quality data or data of unknown quality is collected to validate ILI tools, it jeopardizes not only the performance of the ILI tool, but also the potential integrity of the pipelines.
ROSEN field verification technicians are trained to collect the highest-quality data and can be utilized to support ILI validation campaigns, especially for customers facing new problems and those with little experience validating specific feature types.