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Inline Inspection & Integrity Management - [Ask the Experts] Questions Answered

Originally published by Pipeline Technology Journal, April 2023.*

How does repurposing existing pipelines for hydrogen use impact their integrity?

One of the main challenges when repurposing existing pipelines for hydrogen use is the lower BTU energy content of hydrogen, which means that a larger volume of hydrogen needs to be transported to maintain the same downstream energy delivery. This can result in higher pressures exceeding the pipeline's maximum allowable operating pressure (MAOP). Furthermore, hydrogen atoms can permeate the pipeline material and cause embrittlement, leading to increased fatigue crack growth rates that can be several orders of magnitude higher.

As a result, pipeline operators must carefully assess their existing pipeline networks, line, and station components for their compatibility with hydrogen. Ensuring the safe transport of hydrogen through existing pipeline networks also requires a proactive and comprehensive approach to pipeline integrity management that considers the unique characteristics of hydrogen and the risks associated with transporting it.

How can we better assess the risks associated with ageing pipelines and develop effective mitigation strategies?

A comprehensive approach is required to better assess the risks associated with ageing pipelines and develop effective mitigation strategies. This involves data collection and analysis to identify potential hazards and assess the likelihood and consequences of failure. Based on the risk assessment results, appropriate mitigation strategies should be developed and implemented, such as regular inspection and maintenance, repair or replacement of damaged pipeline sections, and the use of advanced technologies to monitor the pipeline's health. Ongoing monitoring and review of the pipeline and its associated risks are also crucial to ensure the effectiveness of mitigation strategies.

Can LNG pipelines (Unloading/loading jetty to LNG Tanks) be Inspected by ILI tools? Has it been done previously?

In theory, there are no fundamental constraints that would prevent the inspection of LNG pipelines using in-line inspection (ILI) tools. Depending on factors such as pipeline size and flow rates, magnetic flux leakage (MFL) technology may be used to inspect the pipeline. Alternatively, a robotic crawler could be employed, although this option can be more costly. One key challenge would be pressurizing and depressurizing the pipeline traps during the inspection process, as this could result in a phase change and temperature change. To mitigate any potential issues, operators could implement appropriate processes and procedures around the traps to ensure safe and effective inspection.

Which Inline Inspection can detect girth weld anomalies with actual sizing in gas pipelines?

Magnetic flux leakage (MFL) and ultrasonic testing (UT) are two potential methods that could be employed for detecting and sizing pipeline defects. One of the advantages of MFL is that it does not require a liquid coupling medium, as opposed to UT. However, MFL tools are generally limited to detecting and sizing metal loss defects, and their accuracy may be impacted by factors such as pipeline diameter, wall thickness, and the presence of coatings or liners. UT, on the other hand, will require the introduction of a liquid such as gel to run effectively. UT can provide a higher probability of detection (POD) of anomalies and does not require a physical sensor to run on the pipeline.  However, there is a risk of liftoff and mechanical removal of sensors due to pipe issues, which can impact results. The type of defect that can be detected and the accuracy of sizing and detection will vary depending on the specific tool used.

It is also important to note that the accuracy and reliability of the inspection results will depend on the specific tool used, the experience of the operator, and the interpretation of the results. To ensure the safe and reliable operation of pipelines, it is crucial to conduct regular inspections using appropriate NDT techniques and follow up with appropriate maintenance and repair activities.

What are the latest developments for ILI of hydrogen pipelines?

The development of intelligent pigging or in-line inspection (ILI) technology for hydrogen pipelines is ongoing. Currently, ILI tools designed for natural gas pipelines are being tested for use with hydrogen pipelines, with modifications made to address the unique characteristics of hydrogen.

Regarding the ILI of hydrogen pipelines, there are some concerns due to the harsh environment in which they operate. However, some ILI tool vendors are working on updated MFL tools with magnets that can endure the hydrogen environment. Additionally, NDT experts are developing sensors that can operate in harsh chemical environments, which could potentially be used for hydrogen pipelines. Additionally, research is being conducted to determine the optimal operating pressures and temperatures for hydrogen pipelines to minimize the risk of pipeline failures.

How can ILI be performed in pipelines used for the storage of CO2?

Performing inline inspection (ILI) in pipelines used for the storage of CO2 is possible, but it is important to consider the physical and chemical properties of CO2. The high-pressure operation of CO2 pipelines limits the options for ILI, and the pipelines may have heavier than normal wall thickness.

However, magnetic flux leakage (MFL) technology can be used, and ART Scan, an acoustic resonance technology initially developed for offshore applications, can also work well in high-pressure and heavy-wall pipelines.

It is crucial to ensure that the ILI tool does not introduce any additional risks or hazards into the pipeline system, such as temporary pressure or temperature increases that could lead to pipeline failure. Pipeline operators must carefully evaluate and select the appropriate ILI technology and procedures to ensure the safe and effective inspection of CO2 pipelines.


The Experts

Alex Woll, Pipeline Risk Team Lead, DNVAlex Woll

Alex Woll worked as a risk and integrity engineer with major gas and liquid operators before joining as part of the Pipeline Risk Team. He has substantial experience implementing different risk model types and forming different IMP approaches around risk and PMMs as they fit into the larger integrity program. Alex’s day-to-day is focused on driving risk modelling innovation to better support integrity decision making.

Ben Allen, Principal Consultant Digital Solutions, DNVBen Allen

Ben works in DNV Digital Solutions and is responsible for assisting operators with our risk and integrity software, and risk modeling.  Ben has 20+ years in software, with the last 12 predominantly in the oil and gas industry.  Ben has consulted and led large implementations integrating risk and asset management with GIS throughout North America, as well as providing ILI solutions and associated engineering services.

Troy Weyant, Product Manager - Pipeline Product Line, DNVtroy weyant

Troy joined DNV in 1994 and is currently responsible for the risk & integrity management software strategy and roadmap to meet the needs of the global integrity management market. Before this role, Troy held the position of Principal Integrity Solutions Consultant responsible for the implementation of projects based upon DNV's Asset Integrity Management suite of products. He has also been responsible for the development of DNV's MAOP management solution and has served as a Synergi Pipeline technical lead for large integrity and GIS implementation projects in the US and abroad.


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*To view the original article, visit Pipeline Technology Journal