Inspecting the Uninspectable: Intero’s Approach to Short-Radius Pipeline Integrity
Intero Integrity Services demonstrates how advanced ultrasonic ILI technology can inspect short-radius, previously unpiggable pipelines, delivering critical integrity data for aging infrastructure.
KAREM AKCHA, Integrity Engineer, Intero Integrity Services, Tricht, The Netherlands
(P&GJ) — Across the global pipeline network, a significant share of operating lines were built before modern inline inspection (ILI) requirements existed. Short-radius elbows, absent launcher and receiver infrastructure, and decades of unrecorded operational history have left many of these assets without integrity data. A recent project completed by Intero Integrity Services at a French petroleum refinery illustrates what it takes to successfully inspect a pipeline that was never designed to be inspected.
The asset and its challenges. The pipeline in question is a 20-in. gasoline line installed at a major French refinery in the 1980s. Spanning 1,500 meters (m), the line had never been inspected and was the only route available for transferring product from the facility to its customers. Operational drawings were unreliable or absent. Excavations at known bend locations confirmed radii of 0.8 times–0.9 times the pipe diameter (D), and additional unknown geometries could not be ruled out.
The product itself introduced further risk. Gasoline, flammable and high-value, demanded that all inspection activities meet the highest safety and environmental standards. The pipeline’s sandy substrate, proximity to public roads and adjacency to a river added operational constraints throughout the project.
Engineering the solution. The company dispatched an engineering crew to the site to physically measure and record pipeline geometry, reproducing the data in software to establish a worst-case design baseline. That baseline, a bend radius confirmed at 0.74 D during subsequent testing, became the qualification target for tool development.
The solution was a purpose-modified version of the pipeline surveyor, a 20-in. ultrasonic ILI tool combining high-resolution corrosion detection with geometry inspection capability. The tool’s compact phased-array ultrasonic testing (UT) head uses a rotating focused sensor system to capture full circumferential wall thickness measurements. Raw ultrasonic data is transmitted via fiber-optic cable to an external data acquisition unit, where it is stored for post-run analysis. This approach preserves Amplitude-scan data for quality review, in contrast to tools that process data onboard, and allows the application of multiple analytical algorithms during assessment.
Tool qualification testing was conducted at the company’s Center of Excellence (CoE) in Tricht, Netherlands, prior to field mobilization.
Field execution. Mobilization required three days to transport equipment to site. Deployment and rig-up procedures took an additional three days. The piggability assessment, pipeline cleaning, gauging and inspection phases were completed in two days. Demobilization followed without incident, and the client resumed regular operations on schedule.
An inertial measurement unit (IMU) integrated into the pipeline surveyor confirmed pipeline positioning throughout the run, along with elbow count and bend radius values, providing geometry data the operator had never previously held.
Results and implications. The company’s data analysis team processed the inspection results and delivered a final integrity report within weeks of the field operation. The report documented all relevant features and gave the operator its first-ever baseline dataset on a line that had been in service for roughly 40 yrs. That data has since been integrated into the operator’s integrity management system, establishing the foundation for corrosion growth monitoring and long-term maintenance planning.
The project demonstrates that elbow radius constraints below 0.8 D, long considered a practical barrier to free-swimming ILI, are not a permanent obstacle to inspection. With rigorous feasibility engineering, purpose-built tooling, and disciplined field execution, pipelines previously classified as “unpiggable” can be inspected safely and cost-effectively. For operators managing aging infrastructure with no inspection history, the gap between what has been inspectable and what must be inspected continues to close.
This article is based on “Adapting ILI Technology to the Most Challenging Pipelines,” by Karem Akcha, Intero Integrity Services, presented at the 21st Pipeline Technology Conference, April 27-30, 2026, Berlin.
To access the full report, visit: https://www.intero-integrity.com/downloads?fileid=58835&conversion_group=Inspection_UT&conversion_title=Avoiding_Modification_Costs_and_Downtime_when_Inspectinge_Refinery_Heater_Coils_with_oversized_Common_Headers