Skipper NDT

Inspection and mapping of buried pipelines
When it is embedded on a drone, the Skipper NDT magnetic inspection solution provides high performance speed, enables access to hard-to-reach areas and protects the safety of operators in the field.

With support from Cetim throughout the development and validation of its solution, this start-up devised a system to inspect buried metal pipelines from the surface using magnetic technology. The system can be embedded onto a UAV for the high-precision mapping of buried pipelines within a centimetre.

Skipper NDT, a company founded in 2006, develops contactless solutions to inspect the integrity of buried oil and gas pipelines. The goal is to identify damage to the metal such as dents or corrosion, which may ultimately result in incidents. Through partnerships with several research laboratories, the start-up has been able to qualify the impact of various parameters that influence the performance of the technology in the different operational configurations. Today, Skipper NDT, which currently employs 9 people, including 3 PhD holders and several engineers, is taking things a step further as its solution can now be installed on a drone to map buried networks. The start-up called on Cetim’s expertise throughout the whole process of developing and validating its solution.

A simple physical principle

Skipper NDT relies on a simple physical principle: the mechanical stress in a metal pipeline causes a change in the magnetic field which helps to identify damaged areas. Once the physical principle was validated, next came the hard part of designing the measurement system and developing the appropriate signal processing algorithms to successfully use the system. The company drew on Cetim’s expertise in non-destructive testing, numerical simulation and tests to design the magnetic inspection system. Its R&D team focused on improving the signal processing algorithms serving to detect and identify potential anomalies. It then turned its efforts to broadening the range of applications for its solution. Accordingly, in addition to detecting damage to buried pipelines as validated by many inspections on the networks of pipeline operators, the solution can now detect thickness losses caused by corrosion.

Inspection and geolocation of networks

Lastly, the young company continued its work as a means of addressing another stated need of pipeline operators, namely the centimetric geolocation of their networks in order to prevent third-party damage (in connection with the anti-damage reform). The required equipment is embedded on a drone to provide high performance speed, enable access to hard-to-reach areas and protect the safety of operators in the field. The drone is fitted with a carbon fibre bar that features five 3‑axis magnetometers, a topography GPS and a high-accuracy inertial measurement unit. It carries out magnetic mapping and geo-referencing of all types of water, oil and gas pipelines. In addition to detecting the position and depth of the pipelines, this solution also provides information about the magnetic environment (pipelines running side by side, metal objects within the vicinity, third-party work, etc.).

Importance of numerical simulation

Numerical simulation plays a predominant role in designing the inspection solution and improving its performance. Nothing was left to chance especially as the development cycle went in hand with numerical simulation, measurements on test benches and validation of performance in the field.

As part of applying the detection of defects in the metal, Skipper NDT sought to ascertain, in particular, if its technology was able to identify the dents of varying levels of severity, which are a common cause of pipeline failure. Therefore, the company had to determine the pipeline crushing process so as to reproduce the tube distortion and dent defects. Accordingly, it had to specify the mechanical force to be applied, size the actuator tasked with crushing the pipeline and characterise the resulting mechanical stresses, amongst other factors. The tubes were crushed by a press under the thus defined conditions to obtain the various types of defects which were then detected by the magnetic inspection system installed on a 20-metre long test bench at Cetim. The Skipper NDT teams used these magnetic measurements combined with the simulation data (strains, stresses, displacement) during the virtual crushing process to correlate the changes in the magnetic fields to the denting variations and fine-tune their numerical models. This experiment led to a scientific publication in connection with the Pipeline Technology Conference held in Berlin in 2020.

Magnetic measurements of the various types of defects were carried out on the 20m-long test bench installed at Cetim.

We took advantage of Cetim’s expertise and the valuable technical support provided by its specialist teams in non-destructive inspection, numerical simulation, measurements and testing as well as their knowledge of metallic corrosion phenomena. Our results were scientifically proven by a combination of simulation and laboratory tests. These results were validated under real conditions of use in the field.

Luigi Kassir, co-founder and chief operations officer of Skipper NDT

Thickness loss due to corrosion

Once it had validated the ability to detect the various dent defects on metal pipelines, Skipper NDT then focused its attention on determining whether its solution could detect another type of defect: pipe thickness losses due to corrosion. The company asked Cetim’s metallurgy experts to devise a method to create representative defects of pipeline corrosion. Machining processes could not be used to reduce the thickness of the pipelines as these operations would have modified their magnetic signature. Therefore chemical etching was carried out on the metallic samples with the aim of creating charts to reproduce the thickness loss caused by corrosion. The development of this process helped to create defect gauges of varying depths over areas of approximately 25 m2, located at different points of the pipeline. “Based on the numerical modelling of the corrosion defects carried out by Cetim, we were able to determine their magnetic signature and check the quality of our numerical models. We then inspected the tubes on which these corrosion defects were made and which were calibrated on our test bench. As such, we validated the consistency of our measurements”, explained Hamza Bennani, who holds a doctorate in mechanical engineering, and who is responsible for the corrosion research programme at Skipper NDT.

Besides the testing equipment provided by Cetim, Skipper NDT took advantage of Cetim’s expertise in non-destructive testing to enhance its understanding of various technical issues and to calibrate its technology. The thickness of the pipelines was measured with ultrasonic techniques both before and after the defects were made on the tubes and the corrosion defects were created by chemical etching. This process provided the precise dimensional properties making it possible to assess the detection performance of the magnetic inspection system.

Other partnerships on the horizon

The magnetic inspection system for the mapping of buried networks and the detection of defects is now fully operational. However, Skipper NDT has no intention of stopping there. It intends to continue working with Cetim in two main areas: mass production of its field measurement solution so that it can be embedded on a ground-based solution or a UAV and the development of a real-time embedded processing unit. Although this data is automatically interpreted, this operation is still carried out through post-processing immediately after the inspection campaign. YB

Contact: Pascal Souquet

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