The Role of Robotic In-Line Inspection Today and Tomorrow

Robotic in-line inspection (ILI) technology is becoming increasingly important in the pipeline sector as it provides critical information, particularly for pipelines that cannot be inspected by conventional ILI methods. ROSEN’s Head of Challenging Diagnostics, Markus Ginten, discusses in more detail the specific advantages of robotic inspection tools that make them attractive for the overall assessment of pipelines and the role of these tools for the future of the industry.

Significance of in-line inspection

Various data sources are building the foundation of sound integrity engineering and management as key to safe pipeline operation. These are, for instance, direct assessment, above-ground measurement methods, and arguably the most conclusive, in-line inspection (ILI). Alternatives such as hydrostatic testing, where a pipeline is filled with water and pressured up to a pre-defined limit above the maximum operating pressure (MOP), often are less conclusive and/or cost-prohibitive.

Conventional in-line inspection technologies have been developed over decades, starting in the late 1960s/early 1970s, with what can be referred to as low-resolution tools for the detection and coarse classification of metal loss anomalies. With conventional or free-swimming, the industry refers to tools propelled by the pipeline product. The transported fluid, either gas or liquid, creates a differential pressure across the inspection tool’s sealing plane(s), resulting in its forward motion. Conventional ILI requires certain boundary conditions. These are, broadly speaking, the presence of launcher and receiver traps, suitable mechanical pipeline design, and operating conditions. Today, these ILI tools cannot only detect and accurately size defects such as deformations, metal loss corrosion, and cracks in the base material and weld areas but also characterize pipeline mechanical and material properties – all crucial information for integrity management programs.

Industry need for robotic ILI

Industry research estimates that approximately 40% of the world’s pipelines are unpiggable and cannot be inspected with conventional ILI tools. In the early 2000s, this led to the development of robotic (self-propelled) solutions. In the following years and decades, failures led to a further increase in demand for robotic pipeline inspections. In particular, failures caused by missing information and records to make the right integrity decisions prompted the Pipeline and Hazardous Materials Safety Administration (PHMSA) to revise the code and require pipeline information to be traceable, verifiable, and complete (TVC). Naturally, the information gap is more significant for older pipelines designed and constructed when documentation requirements were much lower and without conventional ILI in mind.

Advantages and path forward

Robotic tools exhibit various advantages over conventional ones, such as flexibility in insertion and extraction, maneuverability in challenging mechanical configurations, and independence of pipeline products as a means of propulsion. This makes them more versatile and applicable to many unpiggable pipelines.

Additional advantages that piggable pipelines could contribute from are the controlled speed and the ability to start, stop, and to move in any direction. The controlled speed generally contributes to higher data quality. At the same time, the other aspects allow for the collection of various perspectives and deeper insights, for example on complex features such as girth welds. Moreover, pipelines operated at high flow rates could be inspected without reducing product flow during inspection, maximizing pipeline operator profits.

After more than 20 years of development, the technology is still in its early stages, though today, we see a wide range of applications. Limitations in inspection range and pipeline inspection preparation are imminent challenges to overcome.

Inspection range: Today, a robotic tool is powered either via cable (tether) or batteries. Both solutions are somewhat limited in terms of the inspection range. A cable causes friction forces that, particularly in pipelines with a higher number of bends, accumulate. As power is needed for the sensors, tool electronics, and propulsion unit, battery capacity is only sufficient for shorter inspection ranges. Therefore, alternatives are required. Basic concepts for inspection range extension do exist but it will still take some time until they become a reality.

Pipeline preparation: Adequate pipeline cleanliness is a pre-condition for collecting high-quality data. Particularly unpiggable pipelines are often difficult to clean. While some basic measures are in place today, there are certainly improvement opportunities.

In today’s industry, tool operator-controlled systems are in use. It is conceivable that in the distant future, autonomous systems set up on a mission and making own decisions based on (machine learning) algorithms will be deployed. Such systems could remain in pipelines permanently for pipeline condition monitoring rather than 'snapshot' inspections. To exploit the full potential of robotic ILI, crucial factors are continuous inspection experience and partnerships with pipeline operators supporting our efforts. As Rodney Brooks, a Roboticist, once said, hands-on experience is the best way to learn about all the interdisciplinary aspects of robotics.

Markus Ginten, Head of Challenging Diagnostics, ROSEN Group

Role in the energy transition

On our path to net-zero emissions, a proportion of the pipeline infrastructure will be used to transport hydrogen (H₂) and carbon dioxide (CO₂). The inspection of such pipelines is associated with certain challenges that robotic ILI may overcome. Some examples:

Accurate inspection data on girth welds is required for repurposing existing pipeline infrastructure to transport hydrogen. A conventional inspection tool passes by each girth weld at a relatively high speed and has “one shot” to collect the data. Therefore, and due to the weld’s mechanical impact on the sensor carriers, the quality of girth weld data obtained from conventional ILI tools is rather limited. Robotic ILI tools, in contrast, can stop at each girth weld and scan the area with high precision.
Hydrogen has an extremely low density and, therefore, is highly compressible. Consequently, inspecting a hydrogen pipeline with a conventional ILI tool is likely associated with a rather dynamic speed profile, which can lead to degraded data quality. This is a well-known phenomenon from inspection in natural gas pipelines where boundary conditions have to be met, and measures be taken to ensure adequate speed profiles. Achieving adequate speed profiles in hydrogen will be an even more difficult task. However, robotic ILI tools propel themselves independently of pipeline products and will always move at optimum speed.
Pipelines transporting CO₂ are typically operated at predefined pressures and temperatures. It is essential that an ILI tool does not introduce any additional pressure or temperature changes outside the allowable range. In addition, cups and discs of conventional ILI tools experience high wear when inspecting CO₂ pipelines. While the inspection of CO₂ pipelines with conventional tools is generally possible, there are cases where robotic inspection tools will be the better choice.

Impact on workforce

The rise of robotic technology raises questions about the role of human workers in an increasingly automated world. While it is generally correct that robotic technology increases the degree of automation, in robotic ILI today, we see a higher degree of field technician interaction than conventional ILI. This will remain the case in the foreseeable future. Operating robotic ILI tools is associated with exciting opportunities for skilled labor in programming, control, maintenance, and (life/onsite data) analysis. In that sense, robotic ILI tools can instead be understood as collaborative robots – or simply cobots.

Conclusion

Robotic ILI is playing a significant role in the pipeline industry today. It delivers valuable information primarily for unpiggable pipelines that cannot be inspected with conventional ILI. Robotic tools exhibit certain advantages that make them attractive for pipeline inspection in general. Their abilities enable an enhanced power of data as a basis for better integrity management decisions.