Inspection solutions and their role in pipeline repurposing

Achieving ambitious climate policy goals will require significant investments in energy efficiency, renewables, new low-carbon technologies, and grid infrastructure. It will also necessitate the close integration of the electricity and gas sectors and their respective infrastructures. A decarbonised Europe will be based on an interplay between renewable electricity and renewable and low-carbon gases in an integrated energy system, all aimed at transporting, storing, and supplying all sectors with green energy to deliver a reliable and affordable transition to climate neutrality.

A number of studies have shown that the existing gas infrastructure and knowledge can support the transition to net zero in the most efficient manner. As the energy transition advances, the valuable pipeline system will provide efficient transportation and storage capacity for renewable energy in the form of molecular energy carriers, making the energy system more flexible and resilient. [1].

Figure 1: Sector coupling principle with different forms of energy in pipeline transport.

Energy systems

Over the past decades, energy systems around the world have grown to connect supply and demand. Countries and companies have built electrical power transmission lines and pipelines for oil and gas to enable economic growth and prosperity. With this growth, consumption of fossil fuels, and therefore greenhouse gas emissions, has increased. The current carbon-based energy system is undergoing profound changes driven by increased concerns over the longevity and security of fossil energy. Countries all around the world are looking for ways to transform their energy systems. Initiatives like the European Hydrogen Backbone illustrate the efforts to transform current European energy systems in order to lower their greenhouse gas emissions.[2].

Pipelines play a major role in the transformation of the energy system because of their ability to safely transport energy over long distances and act as storage at the same time. Compared to electrical power lines, pipelines can carry more energy and are directly connected to existing storage infrastructure, such as caverns. This integrated setup enables countries like Germany to integrate imported energy via pipeline from sources with lower energy production costs. Especially in light of international climate control  goals, the high energy density and the established and partly global transport infrastructure (e.g., pipeline connections from Scandinavia or the Mediterranean or new terminals to import LNG from overseas), it can be assumed that a global market for CO2 neutral gases (and fuels) will develop.[3].

Figure 2: Exemplary operational limit diagram to evaluate tool run behavior based on simulations
for a single specific tool.

A transformed energy landscape with significantly lower emissions will be based on the sector coupling principle, providing greater flexibility to the energy system so that decarbonisation can be achieved in a more cost-effective way.[4]. Figure 1 illustrates the different sources of energy on the left; the right side highlights the different forms of energy that could be transported by pipeline (including carbon sequestration).

With more focus on the pipelines in the energy sector, it can be seen that the energy is transported in different carriers, such as hydrogen, ammonia, oxygen and/or biomethane. These carriers are called future fuels. Purpose-built pipeline networks transporting these products are already in use today but in a significantly smaller volume than will be needed in the future. [2].

The potential exists that low-carbon gases and their associated products can reliably and efficiently be transported, stored, and distributed in our global existing and newly built pipeline network. Pipelines will also be used to facilitate carbon capture, utilisation, and storage (CCUS) projects by transporting carbon dioxide safely from emission locations to permanent storage or end use locations. The transportation of these fuels through pipelines will require general as well as specific integrity threats and damage mechanisms to be considered to ensure safe and efficient operation. These challenges can only be managed with a comprehensive integrity management system. [5].

Inspection technologies and necessary changes for future fuels

In-line inspection (ILI) technology can be of significant value in repurposing activities, as it is highly utilised in today’s pipeline integrity management. The support of integrity decisions with measurement data has improved over the last decades, and technological developments in other industries (telecommunication, defense, IT, etc.) will further enhance these capabilities. ILI tools can be classified by integrity threat type or technology principle; widely used principles are mechanical calipers, magnetics, eddy current, ultrasound and electromagnetic acoustics. Knowing the integrity threats for pipelines related to hydrogen or other future fuels, ROSEN acknowledges that different kinds of ILI technologies can support the integrity management of such pipelines. Those ILI technologies could be technologies for the detection of, for example, deformations, mapping or corrosion. Technologies could also include those particularly applicable to future fuels, such as those for the determination of material properties or the detection of cracks and crack-like anomalies in gas pipelines. [5].

Today’s diagnostic ILI portfolio delivers solutions from simple cleaning applications to high-resolution crack detection services to understand feature populations and deliver data

f or integrity decisions. It is important that all these applications are also available in future fuel assets. Table 1 summarises the applications and technologies available. ROSEN is creating solutions to adapt its fleet of inspection tools, getting them ready for future fuels. Initial inspections in smaller-diameter product lines for hydrogen, ammonia and carbon dioxide have already been conducted [5], and the lessons learned and use of the solutions in larger diameters and longer pipelines are under development.

Figure 3: EMAT principle.

The main outcome of these development efforts are solutions for safe and successful inspections in future fuel pipelines. Independent of the technologies, the three main working areas are material compatibility, operational success and safety.

The inspection tools need to withstand the environment, which can be very different compared to oil and natural gas. Products like ammonia, carbon dioxide and hydrogen pose specific challenges for the materials comprising the inspection tools, and intense upfront testing and an understanding of deterioration processes are key for inspection vendors to deliver high-quality services. ROSEN is utilising its own hydrogen laboratory to execute material testing on all components used to build tools within the ILI portfolio.

Another key aspect of ILI is the ability to gather a high-quality dataset under the harsh conditions in pipelines. Speed control valves as well as low-flow/low-pressure setups enable a constant flow velocity without speed excursions or tool stops. [6]. The lower density of hydrogen compared to natural gas will increase bypass rates while also changing the behaviour of existing speed control implementations. Tool run simulations are a standard deliverable for proper inspection preparation, and these simulations have now been extended to also allow simulations to understand the tool dynamics in a hydrogen environment. Besides tool friction properties in the specific pipeline, the dynamic behaviour of ILI tools in gas pipelines also depends on the density and compressibility of the fluid. In order to classify the behaviour of tools in different pressures, velocities and fluids, operational limits diagrams as shown in Figure 2 can be used.

In order to generate the diagrams, several simulations of the specific ILI tool in a pipeline are performed at different pressures and the results evaluated. Based on availability, bypass information from a pump test in water is integrated to specify a minimum gas velocity for future inspections.

The safety requirements for the operation of ILI solutions may change with the introduction of hydrogen into pipeline networks. Existing ATEX certificates might need to be updated to ensure proper consideration of the lighter hydrogen in on-site safety procedures. ROSEN is covering this aspect in current developments to implement a suitable solution for customers worldwide.

The damage mechanism of hydrogen embrittlement, and therefore the potential initiation or propagation of cracks in pipeline steel, is one of the big uncertainties in repurposing activities. Understanding the population of planar flaws is as critical to estimating remaining life as it is to making proper investment decisions. Table 1 shows ultrasound, electromagnetic acoustic transducer and eddy current as possible technologies to detect cracking in pipelines. Cracking (internal SCC) is also a potential threat for both CO2 and ammonia pipelines, meaning crack detection technologies are likely to be required for most future fuel pipelines.

There are different implementations of ultrasound technology available; one of special interest for non-liquid (hydrogen or CO2) pipelines is electro-magnetic acoustic transducer (EMAT) technology. Mainly utilised in natural gas pipelines to assist in the management of stress-corrosion cracking and long seam integrity, EMAT has a significant advantage over conventional ultrasound: it does not require a liquid couplant, meaning it can be run in a gas line without the need for liquid batching. There are several generations of inspection tools available, with the latest implementations showing signification improvements in circumferential resolution and sensitivity. The technology allows for the detection, identification, and sizing of axial planar flaws, which can be helpful when in-service inspections in hydrogen or CO2 pipelines are required, or repurposing activities are executed in natural gas pipelines without the need to include a liquid batch.

Figure 3 illustrates the EMAT principle. EMAT induces an acoustic wave by generating an eddy current and magnetic flux field in the pipe. An additional benefit of EMAT is that it can give information about the external coating condition, which can be valuable when assessing external integrity threats. More information about the technology can be found in [7] and [8]. Figure 4 shows the latest implementation of the technology in a larger diameter. These inspection tools are equipped with speed control units to ensure a proper velocity profile and thus adequate data quality.

Figure 4: RoCD EMAT-C inspection tool.


There are three  main challenges to overcome when it comes to inspection solutions for future fuel pipelines. Safe on-site operation depends on updated processes for the people and machinery involved. Furthermore, existing concepts for explosion protection (ATEX) may be upgraded to include the lighter hydrogen. Materials and components used on in-line inspection tools can be tested in a laboratory environment to characterise their durability and adapt them if necessary. High-quality datasets depend on proper tool run behaviour and sensor-to-wall contact. Simulations can support these assessments to understand fluid dynamics in future fuel pipelines before executing the inspections.


[1]  Siemens Energy, “Power-to-X: The crucial business on the way to a carbon-free world,” 2021.

[2]  R. van Rossum, J. Jaro, G. La Guardia, A. Wang, L. Kuehnen and M. Overgaag, “European Hydrogen Backbone,” Guidehouse, Utrecht, 2022.

[3]  D. Bothe, M. Janssen, S. van der Poel, T. Eich, T. Bongers, J. Kellermann, L. Lueck, H. Chan, M. Ahltert, C. A. Quinteros Borras, M. Corneille and M. Kuhn, “Der Wert der Gasinfrastruktur in Deutschland,” Frontier Economics, 2017.

[4]  Frontier Economics, “Potentials of sector coupling for decarbonisation,” European Union, Luxemburg, 2019.

[5]  N. Gallon, M. Humbert and M. Tewes, “Energy Transition And The Impact On Pipeline Integrity,” Pipeline Technology Journal, 2022.

[6]  J. Becker, C. Richards, G. Sundag and R. Wittig, “Improving Data Collection With In-Line Inspection in Low-Pressure Gas Distribution Networks,” in International Pipeline Conference, Calgary, 2020.

[7]  R. Kania, K. Myden, R. Weber and S. Klein, “Validation of EMAT ILI Technology for Gas Pipeline Crack Inspection: A Case Study for 20″,” in 9th Pipeline Technology Conference, 2014.

[8]  M. Tomar, T. Fore, M. Baumeister, C. Yoxall and T. Beuker, “Graded EMAT Performance Specification Validated in Blind Test,” in International Pipeline Conference, Calgary, 2016

This article featured in the May edition of The Australian Pipeliner. Access the digital copy of the magazine here.

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