Lifecycle Management of Hydrogen Pipelines: Design, Maintenance, and Rehabilitation Strategies for Canada’s Clean Energy Transition

Abstract

This paper examines the crucial elements of pipeline-based hydrogen transportation, highlighting the particular difficulties and technical developments required to guarantee the sustainable, effective, and safe supply of hydrogen. This study lists the essential phases of hydrogen pipeline management, from design to repair, as the relevance of hydrogen infrastructure in the worldwide energy transition continues to rise. It discusses the upkeep, monitoring, operation, and rehabilitation procedures for aged pipelines with an emphasis on the cutting-edge techniques and technology used to mitigate the dangers related to hydrogen’s unique features, such as leakage and embrittlement. Together with highlighting the legislative and regulatory frameworks that enable the infrastructure, this paper also discusses the material, economic, and environmental difficulties related to hydrogen pipelines. Lastly, it emphasizes how crucial it is to fund research, create cutting-edge materials, and implement sophisticated monitoring systems to guarantee the long-term dependability and safety of hydrogen pipelines. These initiatives will be crucial in allowing hydrogen’s contribution to the future of renewable energy, together with international collaboration on regulatory standards.

1. Introduction

Hydrogen has become a cornerstone in the current drive for clean energy worldwide. In Canada, the demand for hydrogen is essentially driven by its application as a feedstock for industrial purposes, especially in the manufacture of ammonia, a major feedstock or input to the fertilizer industry. Other highly emitting industries where hydrogen is greatly applied include oil refining, methanol production, and steel manufacturing. These sectors depend on hydrogen due to its chemical characteristics, which enable efficient production processes [1]

Hydrogen has become a multi-faceted energy carrier with great potential for decarbonizing certain key industrial processes. With its abundant natural resources and well-developed industrial base, Canada is in an ideal position to be a serious player in the global hydrogen economy. Yet this will require significant investment, innovation, cleaner production, transport, and infrastructure development pipelines to sustain the transition [2]. Hydrogen pipelines provide the ability to generate, transport, and utilize hydrogen on a large scale in major sectors of the economy where decarbonization is particularly essential. There are several impediments to infrastructure that will facilitate this shift, not least among them being old pipelines [3]. Such pipes are vulnerable to degradation resulting from environmental causes, corrosion, and material fatigue, which in turn may become an issue related to the safety and efficiency of hydrogen transportation. This paper addresses these concerns, with a focus on how adequate maintenance and rehabilitation approaches will surely enable these pipelines to ensure safe and efficient operation over extended periods. In addition, important information is given to policymakers, engineers, and industry players in making appropriate decisions on the investments, innovations, and tactics that will be implemented for the hydrogen sector [4].

This paper aims to provide a detailed overview of the life cycle of the hydrogen pipeline system, from the design stages to the rehabilitation processes at the end of operational life. This study delves more into the intricacies found in the life cycle of hydrogen pipelines, bringing forth key factors to consider and the challenges to face at each stage. These issues will be discussed in detail in the present study, starting from the Design Phase to the Installation Techniques, Utilization and Operation, Maintenance Strategies, and finally the Rehabilitation Phase. Each of these stages is critical to ensure safe and efficient, yet reliable hydrogen transportation that will become essential to tap into this source of energy fully [5]. A particular interest in this study is focused on a detailed discussion of the problems and solutions associated with the rehabilitation processes of aging hydrogen pipelines. As the infrastructure of the pipeline ages, addressing issues related to wear, corrosion, and other structural challenges becomes imperative to maintain safety, efficiency, and continuity of operation. Rehabilitation, therefore, becomes not only an essential phase to extend the life span but also one that would certainly attest to their capability to stand strong against various and sometimes hostile geological environments of Canada.

2. Literature Review

Hydrogen pipeline transportation is a fast-evolving knowledge area since hydrogen occupies the central place in any vision of a clean energy system. This section reviews key recent research contributions on those aspects of hydrogen pipeline transport: materials selection, safety issues, technical challenges, and regulatory issues.

2.1. Hydrogen Pipeline Materials

Material selection for hydrogen pipelines is critical due to hydrogen’s unique properties. Hydrogen embrittlement is known to affect the mechanical properties of metals, which results in pipeline failure under stress. Presently, high-strength carbon steels such as X52 and X70 are usually applied; however, these steels are susceptible to hydrogen embrittlement. It has been shown that hydrogen embrittlement can cause a reduction in ductility, loss of fracture toughness, and an increase in crack propagation on pipeline materials during cyclic loading [6]. On the other hand, austenitic stainless steels and composite materials have been investigated for their enhanced resistance to hydrogen-induced damage [7]. Material selection is essential not only for preventing embrittlement but also for ensuring the structural integrity of pipelines over long-term operation.

Hydrogen embrittlement is most commonly encountered in high-strength steels, with studies indicating that the higher the yield strength of the material, for example, X65 and X100, the better the tensile properties but the more embrittling the material is [2]. This led to further research into improving pipeline materials by coatings or other materials such as HDPE, which have been considered to exhibit less hydrogen permeation susceptibility [8]. Non-metallic and composite material development seems very promising in mitigating hydrogen embrittlement risks; a few promising materials are already being tested for hydrogen transport pipeline applications as well [9].

2.2. Safety and Leakage Concerns

Hydrogen has a very small molecular size and hence is highly prone to leakage and its high flammability creates significant safety issues. Being a colorless, odorless, and highly flammable gas, hydrogen can escape through even the most minute cracks in the material of pipelines; hence, sophisticated leak detection systems are called for. Hydrogen-specific leak detectors and remote monitoring systems are necessary to maintain the integrity and safety of hydrogen pipelines [10]. Using sensors like fiber-optic monitoring systems allows for real-time leak detection, offering a more proactive approach to safety [8].

Furthermore, pipeline safety is also dependent on rigorous safety protocols and the proper training of personnel. As hydrogen is more explosive than natural gas, the potential for catastrophic accidents is greater, making safety a paramount concern. Regulations like [11] ASME B31.12 requires extensive testing of pipeline materials and the presence of contaminants to mitigate these risks. These standards and safety measures must be regularly updated as new technological advancements emerge [12].

2.3. Environmental and Operational Challenges

Hydrogen pipelines have to undergo many environmental challenges, including fluctuating temperatures, corrosive soils, and seismic activity. For example, the appropriate design for cathodic protection and coatings must be considered to prevent corrosion and crack initiation during operational service, particularly under extremely harsh environmental conditions [6]. In addition, the thermal expansion of materials that occurs in certain kinds of pipelines may be another contributing risk factor for fissures in pipes or leakage in unfriendly weather conditions.

2.4. Cost Analysis

Hydrogen pipelines have been known to be extremely expensive in construction and maintenance since labor, material, and technological advancements add up to the overall cost. Exactly how new hydrogen pipelines are quite expensive to construct, but existing natural gas pipelines can easily be repurposed into hydrogen pipelines at much cheaper costs [13]. This conversion would entail heavy testing and changes to resolve certain issues related to hydrogen: embrittlement and leakage. However, this option can still significantly reduce costs compared to constructing new infrastructure. Innovations in materials, such as with the use of advanced coatings or lighter and stronger alloys, could help reduce long-term costs associated with maintenance and operational efficiency.

2.5. Regulatory and Policy Framework

Putting in place effective policies and regulatory frameworks is vital to the successful implementation of hydrogen pipeline networks. Government regulations should be directed toward the unique risks created by hydrogen, including its flammability, permeability, and embrittlement effects [5]. Such rules would ensure that pipelines are constructed with safety factored in and frequently inspected and maintained to avert disasters. Policymakers are called upon to encourage investment in hydrogen technologies through subsidies, tax breaks, or other grants. Further, international coordination on safety and technical standards is imperative, since hydrogen pipelines might cross over borders and need to be guided by harmonized rules for maintaining consistent safety and operational standards.

3. Methodology

3.1. Design Phase of Hydrogen Pipelines

Several important factors should be considered during the construction of hydrogen pipes with the intent of ensuring efficiency and safety in the system. Material selection would, perhaps, be the most salient point because hydrogen induces embrittlement in certain metals, which eventually causes these metals to weaken, become brittle, and crack. It is common practice to select high-strength steels, sophisticated alloys, and specific polymers to stop gas leaks and preserve pipeline integrity. To maximize flow and lower the chance of leaks, hydrogen is normally delivered under high pressure [10]; pressure management is another important factor. As a result, the pipeline design needs to be strong enough to endure these pressures without sacrificing security. When designing hydrogen pipelines, the pressure due to hydrogen flow on the pipeline surface is a crucial parameter that requires careful consideration. As shown in Figure 1, the pressure on the pipe surface can be measured with Piezometer Tube, U-Tube Manometer (between two points), Aneroid barometer (based on spring deformation), and Pressure transducer (Barometer, Toricelli 1644).

The size and thickness of the pipeline are other important factors to be considered. These characteristics are derived from calculations that account for design pressure, material performance factors, and safety factors to guard against hydrogen embrittlement [13]. Also, there is a need to higher fracture toughness requirements for pipeline steels in hydrogen environments, including specific impact energy values and to ensure adequate resistance to brittle fracture. Furthermore, the geology of the area has a significant impact on the stability and support of the pipeline. To prevent deformation or failure, the density, moisture content, and porosity of the soil and rock must be evaluated to ensure that they offer adequate foundational support [13]. Rock mechanics is very crucial in rocky terrain areas to comprehend the way the pipeline would interact with surrounding stresses and strains, which might result in damage if not effectively handled. External stressors such as moving rocks or sinking soil might exacerbate the issue. It is important to take into account stress and strain variables, particularly in areas that see notable temperature variations, since these lead to the thermal expansion and contraction of the pipeline material [14]. Because of the stiffness of the rock, the pipeline may experience higher stress concentrations in rocky places; in softer soils, however, settlement may result in changes that induce bending or buckling. Last but not least, topographical and environmental factors are crucial in places like Canada, where pipelines cross a variety of terrains, including permafrost areas and rugged, rocky areas. To guarantee long-term dependability and prevent structural damage, the design needs to account for these changing circumstances. A reliable and secure hydrogen pipeline system may be created to satisfy the rising demand for clean energy transportation by taking all of these factors into consideration [5].

Designing hydrogen pipelines must comply with standards.

Z662: Oil and gas pipeline systems.

Figure 2 illustrates the hydrogen pipeline system consists of an interconnected series of transmission and distribution pipelines, which connect production sites with major ammonia plants, combined heat/power sites, residential customers, and hydrogen fueling stations [1].

3.2. Installation Techniques for Hydrogen Pipelines

Hydrogen pipeline installation calls for careful consideration of the pipeline’s surroundings as well as the technique employed. The pipeline installation technique most frequently employed is open-trench pipe lying [1]. The depth of the trench is determined by the diameter of the pipeline and operating conditions, usually between one and three meters deep. In vulnerable areas, hydrogen pipelines should be buried deeper than normal gas pipelines to prevent damage from external loads. If the current soil is not a sufficient bed for the pipe, this entails digging a trench along the intended path and deepening it. It is possible to add bedding materials to provide a solid and safe base.

However, more specialized methods like trenching and horizontal directional drilling (HDD), illustrated in Figure 3, are required in more complicated contexts like metropolitan areas, agricultural regions, or underwater bodies. These techniques make it possible to install the pipeline with the least amount of disturbance to the surface, and they are especially helpful when passing through developed or sensitive regions [10]. After the pipeline is installed, it is crucial to make sure the joints are intact. Strong welds that are resistant to hydrogen embrittlement, seamlessly connected, and leak-proof, are essential, making effective welding methods vital. When compared to human welding, advanced procedures like automated welding equipment offer more uniformity and precision. Furthermore, X-ray welding inspections are required to find any flaws or weaknesses in the welds, assisting in maintaining the pipeline’s overall structural integrity. Since hydrogen is particularly prone to leaks, these inspection methods can spot even the tiniest flaws that may cause eventual malfunctions when being transported. To avoid corrosion, protective coatings on the outside of the pipeline should be applied to avoid corrosion. Corrosion protection systems reduce this risk, especially in the presence of wet or highly corrosive soils. After welding, applying coating, and testing, side boom or specialized cranes are used to safely place the completed pipeline into the trench [2].

During the procedure, care is taken to prevent damage to the coating or pipes. Before the pipeline is put into service, it must undergo extensive testing after installation [10]. Testing a pipeline requires several activities that include pressure testing, which ensures that the pipeline can support the high pressures necessary for transferring hydrogen. Hydrogen purity testing is required as well to ensure that hydrogen in transit does not contain any impurities, which can reduce performance in fuel cells or any industrial operation. Lastly, integrity validation verifies that the pipeline can operate as intended under all operational scenarios and is leak-free. Through careful attention to these installation and testing details, the pipeline can deliver hydrogen securely and effectively throughout its operation, reducing the possibility of leaks or failures. To prevent the pipeline from pebbles and other abrasive objects, it is lined with sand or soft dirt before the trench is backfilled [10]. Finally, restore the surface to its original condition, when necessary, especially in areas intended for agriculture or sensitive ecological grounds, as illustrated in Figure 4.

3.3. Operation and Monitoring of Hydrogen Pipelines

Some essential procedures need to be followed for hydrogen pipes to operate successfully and sustainably over time. These methods include efficient pipeline control room operations, sophisticated monitoring systems, flow management approaches, pulsation control, and energy-saving tactics. Over time, each of these components is essential to maintaining the integrity, safety, and operating effectiveness of the pipeline [13].

3.3.1. Flow Management

Ensuring the safe and efficient delivery of hydrogen requires effective flow management. Since hydrogen is usually delivered at high pressures, compressor stations are essential to sustaining the required pressure and flow rates throughout the pipeline system [10]. To avoid problems like cavitation, which can harm the pipeline, pressure regulators and valves make sure that flow rates stay within the parameters specified in the design. To limit energy consumption during compression and lower the possibility of failure due to over-pressurization, careful management is also necessary. Operators can further ensure operational efficiency by optimizing flow rates depending on changing demand and environmental circumstances through the use of real-time data from monitoring systems in dynamic flow control techniques [12].

3.3.2. Energy Efficiency

Reducing energy loss during compression and transit is essential for effective hydrogen transportation. Due to its small weight and high pressure needed during transportation, hydrogen gas might require a substantial amount of energy in the form of compression power. Reducing energy usage requires maximizing pressure levels, pipeline diameters, and flow rates. Another important consideration is compressor efficiency, where using contemporary, energy-efficient compressor systems may significantly lower energy use [10]. Compressor stations can also benefit from the installation of heat recovery systems, which recover energy wasted as heat and increase total energy efficiency. Energy loss may be avoided by minimizing needless compression and preserving the thermodynamic balance of hydrogen flow, which will guarantee that the energy delivered to the end user’s location stays as near to its created value as possible.

3.3.3. Pipeline Control Rooms

The hubs of real-time pipeline management are known as pipeline control rooms. Operators keep an eye on important parameters including pressure, temperature, and flow rates using both automatic equipment and human supervision. Emergency shutdown systems, which immediately stop flow when abnormal circumstances are recognized, are essential for averting catastrophic failures like pipeline breaks or spills. Modern control systems with remote troubleshooting capabilities enable operators to fix problems without physically touching the system, reducing downtime and preserving operational effectiveness [1]. These control rooms are essential for initiating safety procedures, organizing reactions, and making sure that equipment shuts down on time to reduce hazards. To minimize undue stress on the pipeline material, operators must also keep an eye on variations in pipeline pressure, particularly in areas with diverse environmental conditions.

Safety measures during operation include the following [1]:

• Emergency Response Plans: Developing and regularly updating emergency response plans to address potential incidents.
• Routine Training: Impact of regular training on personnel in the procedures for emergencies and safety.

3.4. Maintenance Strategies for Hydrogen Pipelines

The preservation of hydrogen pipeline infrastructure by regular inspections, corrosion control, leak detection technology, and a strong pipeline integrity management system are all essential components of a proactive strategy. To reduce possible dangers, improve operational dependability, and increase the pipeline’s lifespan, certain actions must be put into place.

3.4.1. Routine Inspections

Finding early indications of corrosion, fractures, or material deterioration requires routine examinations. Advanced inspection methods in conjunction with regular maintenance plans enable operators to proactively handle possible issues before they become more serious. The technique that could be utilized in finding the interior defects is ultrasonic testing; this method uses the way of sound waves to scan the pipeline material for imperfections or splits [10]. The alternative technique of non-destructive inspection, which is appropriate against other techniques in the finding of surface fractures in ferromagnetic materials, is magnetic particle inspection. Second, fiber-optic sensors installed down the length of the pipeline monitor further strain, temperature, and pressure continually. This real-time data may be used to anticipate sections that are likely to break. In addition, material sampling and testing also give ground for mechanical properties analysis, such as hardness and fracture toughness in the laboratory, which plays an important role in material performances and the effects of hydrogen exposure to pipeline [15]. In addition, the monitoring of hydrogen embrittlement should be conducted to spot possible weak points that could affect structural integrity. Detailed records of all maintenance activities, test results, and inspection findings are vital for regulatory requirements. Operators can lower the risk of unplanned failures by better detecting problems and scheduling timely maintenance by combining physical inspections with automated monitoring technology [8,15].

3.4.2. Corrosion Prevention

One of the most important threats to the lifetime of pipelines, especially in hydrogen pipes due to the material’s susceptibility to hydrogen embrittlement, is corrosion. Coatings applied as protection include fusion-bonded epoxy or polyethylene layers and generally work as a physical barrier separating the pipeline from the surrounding corrosive elements present in the soil or atmosphere. Besides coating, cathodic protection is a very important technique for the protection of submerged or underground pipes. To prevent the electrochemical processes that naturally lead to corrosion, CP operates by supplying a regulated electrical current, so “shielding” the pipeline from rust or deterioration [10]. These corrosion prevention strategies must be integrated into regular maintenance plans to ensure they remain effective over time, particularly as hydrogen is a challenging medium to transport.

3.4.3. Leak Detection

Prompt leak identification is essential for averting dangerous situations and reducing the negative effects on the environment. Since hydrogen is a colorless and odorless gas, leaks might be hard to find, but there are good solutions thanks to contemporary technologies. While sensors designed specifically to detect hydrogen gas can directly feel its existence, acoustic sensors can identify the sound waves produced by pipeline breaches [1]. Furthermore, particularly in difficult-to-reach places, drones fitted with thermal imaging cameras provide an extremely portable and effective method of surveying pipelines. These drones give controllers useful real-time information by rapidly identifying temperature changes or gas discharges that point to leaks. By putting these early-warning systems into place, the amount of time that passes between a leak’s beginning and the reaction is minimized, protecting pipeline safety and minimizing damage [10].

3.4.4. Pipeline Integrity Management

Hydrogen pipeline integrity refers to the capability of pipelines to safely transport hydrogen without failure, ensuring both operational efficiency and public safety. Hydrogen pipelines cannot be operated sustainably without a detailed plan to oversee pipeline integrity. To ensure that the pipeline stays in optimal condition for the duration of its operating life, this plan consists of both preventative measures and remedial operations [13]. The goal of preventive measures is to handle minor problems before they become significant failures by conducting routine inspections, real-time monitoring, and continuing maintenance. Key aspects of maintaining hydrogen pipeline integrity include the following:

Material Selection: Choosing suitable materials that can withstand hydrogen properties, such as carbon steel grades (e.g., X52, X70) that are less susceptible to hydrogen embrittlement. The selection process should consider factors like microstructure, grain size, and the existence of subsurface anomalies [5].

Monitoring and Inspection: Periodically conduct inspections by monitoring and NDT techniques, such as visual inspection, to detect any wear and/or corrosion or structural failure early. This will call for periodic monitoring against hydrogen embrittlement and crack growth to avoid sudden failure [5].

Pressure Management: The right pressure levels inside the pipe must be maintained constantly to minimize the probability of hydrogen permeation and to maintain the integrity of the material. To ensure safety under given conditions, the hydrogen partial-pressure–material performance relation will have to be known.

Regulatory Compliance: Conformity with the relevant standards and regulations, such as [16] CSA Z662 and [11] ASME B31.12, which have given specifications on the design, construction, and operation of hydrogen pipelines. Conformity gives rise to safety measures that protect infrastructures and the public [1,17].

Safety Analysis and Mitigation: Detailed risk analyses are to be carried out to identify possible dangers of hydrogen transportation, taking into account the consequences of impurities as well as environmental conditions. These may include additional treatments such as the use of inhibitors or protective coatings to enhance pipeline integrity [10,15].

Emergency Response Planning: Established procedures are to be there in case of an emergency. Leak detection, and immediate response measures to be involved in the process of minimizing risks about hydrogen release. Training of personnel concerning emergency response is essentially important to keep the safety aspect intact [8,15].

Overall, hydrogen pipeline integrity is important in terms of safety and efficiency for hydrogen transport. This requires an integrated process that takes into consideration material science, and best practices in engineering, followed by regulatory requirements, and goes right up to active monitoring. Such integration allows various aspects to combine in a way that operators are better able to predict and avoid any form of threat while guaranteeing the structural integrity of the pipe for long-term safety in hydrogen transportation [9,13].

3.5. Rehabilitation Phase for Aging Hydrogen Pipelines

3.5.1. Assessment of Aging Pipelines

Evaluating the state of aged hydrogen pipelines is crucial to guarantee their continued safety and integrity, especially because hydrogen poses special difficulties because of its small molecular size, which can lead to embrittlement and increased leak risks. The process of condition monitoring plays a vital role in evaluating pipeline health, using advanced techniques like ultrasonic sensors, fiber-optic systems, and acoustic emission monitoring to detect early signs of wear, corrosion, or cracks. These proactive measures help operators identify vulnerabilities before they lead to failures. Coupled with risk assessments, which evaluate the potential dangers of continuing to operate aging infrastructure, this process allows operators to prioritize maintenance, rehabilitation, or replacement of specific sections of the pipeline [12,18].

3.5.2. Rehabilitation Methods

Assessment and Inspection: Performing a detailed assessment of the pipeline’s current condition by ocular inspection, NDT, and material sampling. This type of assessment points out regions of concern for corrosion, cracks, or hydrogen embrittlement that need rehabilitation.

Replacement or repair of material: Depending on the results of testing, degraded sections could be replaced or repaired. The work could be carried out with the latest materials developed for hydrogen service-advanced high-strength steels or composite materials offering improved resistance against hydrogen-related issues [2].

Coating and Corrosion Protection: Application of protective coatings to the surface of the pipeline to prevent corrosion and mitigate hydrogen exposure effects. It may include special coatings for hydrogen compatibility and resistance to operating conditions of the pipeline.

Pressure Testing and Validation: Following the execution of rehabilitation works, pressure testing of the pipeline shall be carried out to validate its integrity with respect to safety and specification requirements. This step is important in confirming the capability of operating the pipeline safely at the intended pressure conditions [12].

Monitoring and Maintenance: An effective monitoring program after rehabilitation, caring for the pipeline performance and allowing early detection of future problems. Maintenance activities like inspections and repairs are scheduled to continue its integrity.

Regulatory Compliance: Ensuring that all rehabilitation activities comply with related regulations and standards, such as [16] CSA Z662 and [11] ASME B31.12, to keep safety and operational integrity. The rehabilitation of hydrogen pipelines is required to extend their service life, enhance safety, and ensure compliance with driving standards, ultimately supporting the transition to hydrogen as a clean energy source [15].

Testing and recommissioning an older pipeline requires extended testing to be safe to go back into service. First is hydrostatic testing, a process where the pipeline is filled with water and then pressurized beyond normal operating pressures as a check for leaks or other weak spots. Following that, leak testing using inert gasses such as nitrogen can confirm that no hydrogen is escaping. The pipeline is not progressively pressurized with hydrogen again and put back into operation until all testing has been completed successfully [19].

3.5.3. Safety Considerations

Hydrogen is explosive and easy to inflame; hence, there is a danger involving safety while working with this gas. Upon restoration, some actions have to be performed, such as filling the pipeline with inert gases and good ventilation, to avoid fire.

Around the repair site, hydrogen-specific leak detectors are required since the gas is odorless and colorless, making it challenging to find without specialist equipment. In addition, trained workers are needed to manage the particulars of hydrogen pipeline repairs, which are different from those of typical natural gas pipelines [10]. These particulars include embrittlement and leak detection issues. Pipeline operators may guarantee the long-term safety and functioning of hydrogen infrastructure by adhering to these preventive maintenance and rehabilitation methods, reducing the hazards to the environment and workers while continuing to support the expanding hydrogen economy.

4. Challenges and Innovations in Hydrogen Pipeline Transportation

Hydrogen pipelines introduce specific challenges that must be met if they are to reach sustainability as an integral part of the hydrogen economy. These difficulties include those related to the environment, problems with material integrity such as hydrogen embrittlement, financial concerns, and the requirement for strict laws and regulations to maintain the infrastructure [8].

4.1. Environmental Challenges

Pipelines carrying hydrogen frequently pass through a variety of difficult terrains, which can expedite pipeline damage and worsen soil corrosion. It is necessary to carefully design the cathodic protection systems and protective coatings of pipelines in places with unfavorable soil conditions, such as high salt or moisture content, to prevent corrosion. Furthermore, the integrity of the pipeline is in danger from temperature variations [6]. For instance, pipelines undergo thermal expansion and contraction in areas of severe cold or heat, which puts stress on the materials and weld joints. This may result in leaks or ruptures that cause long-term harm. Risks of groundwater pollution and other environmental issues including ecosystem disturbance must also be properly controlled. Pipelines have to be planned with the least amount of environmental impact possible, using sustainable building methods and making sure that any possible leakages are swiftly detected and contained. Existing defects in pipelines can grow to critical sizes under hydrogen presence, exacerbated by internal pressure fluctuations and geological movements [8].

4.2. Hydrogen Affects the Life Fatigue of Pipelines

Hydrogen provides different degradation mechanisms, namely, hydrogen-induced cracking (HIC) and hydrogen embrittlement (HE). Even low concentrations of hydrogen can cause significant reductions in the fatigue life of pipelines by accelerating the propagation of existing cracks. This necessitates more frequent inspections and monitoring during operations to detect potential failures early. Considering that existing pipelines have inherent defects in both the base metal and welds due to their fabrication and service, the fatigue crack growth rate (FCGR) shortens the time for cracks to reach critical sizes. The introduction of atomic hydrogen into pipeline materials can lead to a loss of ductility and reduced fracture toughness, making the material more susceptible to cracking under cyclic loading conditions [6]. The interaction among hydrogen, stress, and susceptible material leads to hydrogen embrittlement as shown in Figure 5. This results in an increased fatigue crack growth rate (FCGR), which is required for damage tolerance analysis and residual life calculations. Among the most important issues related to hydrogen pipeline technology, hydrogen embrittlement is one wherein hydrogen molecules diffuse into the material of the pipeline and degrade its structural strength, increasing the likelihood that it will break.

4.2.1. Mechanism of Hydrogen Embrittlement

Hydrogen Diffusion: The hydrogen atom diffuses into the pipeline and interacts with various types of defects such as dislocation, grain boundary, and inclusion to cause material property changes. This leads to changes in the material’s mechanical properties. High hydrogen diffusion rates in metals lead to embrittlement, which makes the material brittle and thus more prone to crack development. This process, sometimes referred to as hydrogen embrittlement, is a serious concern in industries dealing with hydrogen gas in pipeline systems. Knowledge and control of hydrogen diffusion are needed to achieve better performance and increased safety and component life [7].

Trap Sites: Hydrogen can be trapped in irreversible sites, (hydrogen traps permanently or over a very long duration). Hydrogen accumulation at these sites enhances the possibility of hydrogen embrittlement, which eventually makes hydrogen pipelines more brittle and prone to cracking over time. This becomes a huge problem inside the hydrogen pipelines.

Hydrogen also can be trapped in reversible sites (temporary trapping or they easily may escape and continue to diffuse through the pipeline). The understanding of reversible trapping can help in developing the rate of hydrogen diffusion by the choice of structures or treatments that control the reversible site behavior in an effective way [3].

Crack Propagation: Hydrogen presence promotes the growth of cracks under applied or residual stress to premature failure, as illustrated in Figure 6. This growth can lead to structural failure if not managed or detected early. Crack propagation occurs through a combination of material properties, stress concentrations, and environmental factors. Understanding crack propagation is essential for predicting the lifespan of hydrogen pipelines [2].

4.2.2. Factors Influencing Hydrogen Embrittlement

Material Compositions: HE is more prone in certain alloys, particularly high-strength steels, which depend upon their microstructure and chemical composition. Certain elements, microstructures, and impurities can either increase or decrease a material’s susceptibility to hydrogen embrittlement. Understanding these effects is crucial for materials used in hydrogen-rich environments, like pipelines, pressure vessels, and hydrogen fuel systems [7].

Hydrogen Concentration: Hydrogen concentration within a material is one of the most critical parameters responsible for HE. The amount of hydrogen that can be taken up by a material and its distribution as such plays a major role in the susceptibility of a material toward embrittlement. Much effort, therefore, is put into minimizing the concentration of hydrogen in materials so that the risks of hydrogen embrittlement can be minimized [14].

Environmental Conditions: In general, characteristics such as temperature, humidity, and the presence of other gasses may affect the extent of hydrogen absorption and embrittlement. (Challenges are discussed in detail in Section 4.1).

4.2.3. Effects on Mechanical Properties

Reduced Ductility: In general, HE will result in a serious loss of ductility. Materials become more brittle and lose their capacity for plastic deformation. Thus, it becomes prone to sudden fracture instead of gradual deformation [7].

Fracture Toughness Decrease: Fracture toughness is a symptom of material property, which decides the behavior of the material under stress in case of defects or cracks in it. Lowering fracture toughness means the materials become more susceptible to fail suddenly without significant prior deformation or warning [18].

Increased Rate of Fatigue Crack Growth: The growth of cracks under cyclic loading conditions is accelerated by hydrogen presence leading to a faster progression of crack growth and reducing the material’s fatigue life. This means that cracks reach a critical size more quickly, increasing the risk of sudden failure [4].

Coatings and Inhibitors: The protective coatings or inhibitors of hydrogen can reduce the entry into the material. Since hydrogen embrittlement primarily results from hydrogen absorption, which weakens and embrittles metals, these protective layers serve as barriers or chemical shields that inhibit hydrogen from penetrating the surface. Properly designed coatings and inhibitors are especially important in industries where materials are exposed to hydrogen-rich environments [7].

Control of Operating Conditions: Effectively managing operating conditions can mitigate HE risks, prolong material lifespan, and reduce maintenance costs. Through the careful regulation of temperature, pressure, stress, and exposure to hydrogen, operators can minimize the chances of embrittlement in hydrogen pipelines.

Testing and Evaluation: Tests are performed by using various tests, either slow strain rate testing (SSRT) or notched tensile tests for understanding and quantifying a material’s resistance to environmentally induced failures, providing essential data for designing and selecting materials for the appliances [8].

Monitoring Techniques: Pipe integrity is maintained by periodic nondestructive inspection for embrittlement as manifested by the appearance of cracks, or the loss of mechanical properties.

4.3. Material Selection for Hydrogen Pipeline

High-strength carbon steel (such as X70 or X80), austenitic stainless steel (where embrittlement is a major issue), and composite-lined pipes are suggested for hydrogen transit in Canada. The pipeline system has to be upgraded with particular coatings and monitoring systems to stop corrosion and embrittlement. Hydrogen pipelines in Canada’s diverse and harsh environment will be able to operate securely thanks to these materials and technologies. For hydrogen pipelines, it is crucial to assess the strength, resilience, cost, and other crucial features of different materials, such as resistance to corrosion, resistance to hydrogen embrittlement, and environmental adaptation [1].

Choosing materials is a risk-reduction method that involves selecting materials with less susceptibility to HE. Hydrogen embrittlement can be summarized as a critical problem of materials used in hydrogen service, which deserves consideration regarding material properties coupled with environmental conditions in terms of prevention [5]. To mitigate the risks of hydrogen embrittlement and other potential damages associated with transporting hydrogen through steel pipelines, an alternative solution is to utilize non-metallic pipes, specifically polyethylene (PE) pipelines.

High-Density Polyethylene (HDPE)

The innovative structure composites are where the enhancement of base polyethylene material properties with a layer of HDPE lining has been performed. The overall strength, durability, and resistance to gas permeation increase by this combination, making the material fit for such applications as the transportation of hydrogen. This lining of HDPE will reduce problems concerning gas leakage and increase the safety of the pipeline system. Normally, HDPE pipes bear different pressure values starting from 0.4 MPa to 1.0 MPa, that is, from approximately 58 to 145 psi, for the different grades and thicknesses of HDPE material used. The specific pressure rating, however, would depend upon the design of the pipe, the dimensions, and the specific application requirements of the pipe [9]. The common diameter of PE pipes used for hydrogen transportation lies in the range between 25 mm and 200 mm. Nonetheless, diameters larger than these, as illustrates in Figure 7, can be used, which completely depends upon the specific requirement of a hydrogen distribution system and the volume of the gas that has to be transported. In selecting the diameter, flow rate, pressure, and installation conditions are guiding parameters. A 200 mm HDPE pipe for hydrogen transportation, depending upon grade and wall thickness, can generally support up to 1.0 MPa or 145 psi. The actual pressure rating would depend on the manufacturer’s specification and intended application, hence the need to revert to the appropriate standards and product data sheet for exact information.

4.4. Cost Considerations

Building new hydrogen pipes and upgrading already-existing natural gas pipelines might come at a significant financial cost. The total cost is increased by the price of labor, materials, and cutting-edge technology for upkeep and monitoring. Innovations in building methods and material design, however, can help offset some of these costs. For instance, using stronger, lighter materials might result in decreased maintenance expenditures and installation expenses. Moreover, robotics for interior inspections and automated welding technologies can guarantee greater precision and fewer mistakes while saving a substantial amount of labor.

The developments and increased production volume will determine how cost-effective hydrogen pipelines will be in the long run. Research and development expenditures for inexpensive hydrogen-resistant materials will be essential in lowering the overall cost over time [13].

Once produced, hydrogen must be transported from the point of production to the point of use. For near-term and long-term hydrogen introduction as an energy carrier for transportation and stationary power applications, a hydrogen delivery infrastructure that is cost-competitive and energy-efficient must be developed. Among several hydrogen delivery options, an extensive pipeline infrastructure would provide the most cost-effective and energy-efficient means to transport very large amounts of hydrogen to much of the market, as is done with natural gas [9,23]. Additionally, blending hydrogen with natural gas can enhance energy efficiency and reduce carbon emissions, contributing to a more sustainable energy system [23].

4.4.1. The Re-Purposing of Natural Gas Pipelines

The re-purposing of natural gas pipelines for pure hydrogen transport is relatively more feasible, as it offers a suitable solution with partial use of existing infrastructure, minimizing material failures for secure transport of hydrogen [4] and can be more economical than the construction cost for new natural gas pipelines, as it avoids the high costs associated with new construction, although it requires extensive testing. It involves applying standards like [11] ASME B31.12, which requires extensive testing of the pipeline materials and the presence of contaminants in the gas mixture must be evaluated, as they can influence the behavior of hydrogen in the pipeline. This can be quite a labor-intensive process and may have to guarantee safety, as hydrogen can introduce new modes of damage and alter existing ones [12]. Overall, while repurposing may incur additional costs for safety compliance and testing, it is generally less expensive than building new dedicated hydrogen pipelines. It is inferred from the analysis that reassignment can reduce transmission costs by up to 30% in some scenarios, compared to the construction of new pipelines [4].

The cost analysis for pipeline reassignment to deliver hydrogen includes capital and operational expenditures. CAPEX is dominated by the installation of new compressors and gas pressure regulation stations, while operational and maintenance costs are the main cost drivers of OPEX. Comparatively speaking, adapting hydrogen delivery through existing pipelines is significantly less costly than building brand-new hydrogen pipeline systems. It allows for a pathway leading to overall lower system cost and better utilization in the long run, coupled with huge savings from capital and operational expenditures. With a rise in demand for hydrogen, the reassignment methods have been and will continue to enhance those economic benefits, thereby setting full financial viability of hydrogen infrastructures at underpinning the transition to a low-carbon transport sector [4].

4.4.2. Hydrogen Blending to Natural Gas Pipelines

Hydrogen blending into natural gas pipelines depicts the former as a more cost-effective financial model. Blending hydrogen into utility infrastructure means that utilities would save vast sums of money not being put into the full conversion of a pipeline to carry hydrogen. Other major benefits of blending for those trying to make the switch inexpensively are that it is an achievable means by which gradual changes can occur based on existing assets, providing much lower financial impacts [24]. A cost-effective approach involves leveraging existing infrastructure and collaborating with peer utilities to share best practices, thereby reducing individual utility costs associated with modernization efforts. Utilities can enhance their operational capabilities for higher hydrogen blends by establishing cost-share agreements and seeking government support while minimizing budget impacts. While the current practices are adequate for blending up to 5% hydrogen, increasing the hydrogen percentage beyond that will lead to more cost-effectiveness over time [24].

However, with the increase in hydrogen blending ratio, the increased danger of explosions arises due to the fast diffusion and lower minimum ignition energy of hydrogen compared to methane. Increased HBR thus results in an earlier ignition time, stronger shock wave intensity, and higher peak explosion pressures, further increasing safety risks in confined spaces. There is a growing need for utilities to implement advanced safety measures and monitoring technologies as these challenges are addressed. Updating operational protocols, improving material standards, and developing predictive models to determine risks from explosions are key next steps [25]. In addition, hydrogen blending in natural gas affects the performance of compressors by increasing the outlet temperature, pressure drops and reduces the efficiency of fuel-driven and electrically driven compressors. Total energy consumption increases with the increased hydrogen blending ratio, while carbon emissions decrease. These implications thus show the necessity for operational adjustment in view of compressor efficiency and effective management of energy use in hydrogen-blended systems [23]. These challenges make hydrogen blending nonetheless feasible and economical, considering a sensible strategy to use already available natural gas infrastructure as the world transitions into a sustainable future for energy.

4.5. Stress Consideration

The X52 alloy is typically the most economical option among the three pipeline steels X52, X65, and X100, primarily due to its simpler composition and lower strength characteristics. It provides adequate performance for applications where cost is a significant factor, but it does not offer the same level of strength as the other alloys [2].

In contrast, the X65 alloy strikes a balance between cost and strength, making it a moderate choice for applications that require improved performance without a substantial increase in expenses. It offers better tensile properties compared to X52, making it suitable for more demanding environments.

The X100 alloy, while the strongest of the three, comes with a higher price tag due to its complex microalloying and processing requirements. This alloy is ideal for high-strength applications where performance is critical, but the increased cost may limit its use in less demanding situations. Overall, the choice between these alloys depends on the specific requirements of the application, including budget constraints and strength needs [2].

Here is the comparison of allowable bending stress and bending stress due to dead load on it for X52 which is equivalent to [26] CSA Z245.1 as mentioned at Table 1.

Allowable bending stress of CSA Z245.1 G359, σ b = ø σ y

= 0.66 × 360 = 237.6 MPa = 237,600 kN/m2

Dead load on one unit weight of the pipe = Soil density × Area

= 18 kN/m3 × 0.4 × (6/3.281)

= 13.167 kN/m

Pipe own weight = 78.60 kg/m (OD 400 mm, thickness 8 mm) (Regarding the supply range and applicable steel tube and pipe from Mannesmann Line Pipe GmbH, the unit weight of the 400 mm outer diameter with 8 mm thickness of the pipe is 78.6 kg/m)

= 0.771 kN/m

w = 13.167 + 0.771 = 13.938 kN/m

Consider for 10 m length of pipeline.

M = (wl2)/12

= 116.15 kNm

do = 400 mm

di = 384 mm

I = [π (do4 − di4)]/64 = 0.0002 m4

Bending stress σ bc = σ bt = (Mc)/I, (c = r0)

σ bc or σ bt = 116,150 kN/m2 < σ b

In this case, the allowable bending stress of the pipe is greater than the actual bending stress caused by the external load (soil) and its own weight. The compression stress will be on the top of the pipe and the tension stress will be at the bottom of the pipe.

A specified minimum yield strength (SMYS) of 359 MPa, which is equivalent to X52, or lower is the recommended pipe grade for hydrogen service by ASME B31.12. Higher grades with SMYS up to 550 MPa (80 ksi) are allowed but require additional consideration.

Table 1. Steel pipe standard grades and their equivalent base on SMYS [17].

CSA Z245.1 Standards Grades	API 5L Equivalent Grades	SYMS (MPa)
241	B	241
290	X42	290
359	X52	359
386	X56	386
414	X60	414
448	X65	448
483	X70	483
550	X80	550
620	X90	620
690	X100	690
825	X120	825

Table 1. Steel pipe standard grades and their equivalent base on SMYS [17].

CSA Z245.1 Standards Grades	API 5L Equivalent Grades	SYMS (MPa)
241	B	241
290	X42	290
359	X52	359
386	X56	386
414	X60	414
448	X65	448
483	X70	483
550	X80	550
620	X90	620
690	X100	690
825	X120	825

4.6. Policy and Regulatory

The creation of favorable laws and regulations is just as important to the success of hydrogen infrastructure as technological developments. Policies from the government should promote investment in hydrogen technology by offering tax exemptions, subsidies, or other benefits to businesses that construct or renovate pipelines. Additionally, explicit safety laws need to be implemented to guarantee that hydrogen pipes are built, maintained, and operated to the greatest safety standards [8]. Comprehensive risk analyses that take into account the special characteristics of hydrogen, such as its high flammability and tiny molecular size, should form the foundation of these laws.

Working together, government agencies and business organizations may create policies that are both useful and efficient. Given the likelihood of hydrogen pipes crossing national borders, this cooperation needs to be global as well. Ensuring that safety regulations are uniform across nations will enable pipelines to be built and run in a manner that promotes the global hydrogen economy. Conclusively, the issues presented by hydrogen pipeline technology necessitate an integrated strategy involving cost-effective tactics, smart technologies, material advancements, and robust regulatory frameworks [13]. These initiatives have the potential to make hydrogen pipelines an essential component of the world’s shift to sustainable energy, guaranteeing the efficient, safe, and effective transportation of hydrogen.

5. Safety Measures

Hydrogen pipelines raise major safety issues mainly because of the very small molecular size of hydrogen, which makes it prone to leakage. In addition, hydrogen has low ignition energy, making it more prone to explosion compared to other flammable gasses. Another major concern is the embrittlement of hydrogen whereby steel materials, and their weld joints lose ductility, threatening the integrity of the pipeline.

5.1. Preventative Measures

Preventive measures for hydrogen pipeline safety will include the use of materials specially designed to resist hydrogen embrittlement, such as high-strength alloys or composite materials [9]. Protocols on regular inspection and maintenance will also be employed for early leak detection using advanced technologies like fiber optic sensors for real-time monitoring. Besides these, strict operational procedures and safety training for personnel will also contribute to mitigating risks related to hydrogen transportation.

Materials chosen for hydrogen pipelines in Canada must adhere to or beyond CSA Z662 specifications, taking into account high-pressure operations, environmental issues, and safety and this standard must be adjusted or modified to handle issues like permeability and embrittlement that are unique to hydrogen [17].

5.2. Operational Measures

5.2.1. Method of Statement (MOS)

A Method of Statement, or simply MOS, is a detailed procedure that outlines how every activity should be conducted for the safe and efficient execution of works at sites. The procedure has to be reviewed and approved by the safety team prior to the commencement of any activity, as well as relevant authorities for approval. This would ensure that the procedures will be in compliance with regulations and standards on safety concerns. All steps and procedures in the MOS are documented and filed for reference and accountability.

5.2.2. Risk Assessment (RA)

The RA is developed based on the approved MOS to identify and address any potential risks at every step involved in the process, including material transportation and handling, construction, and operation. This involves the ability to foresee possible hazards and plan strategies for the reduction or mitigation of such risks effectively. The RA will detail all the foreseeable problems and outline control measures with respect to personnel and the work environment. Long-distance transportation of hydrogen by pipeline involves moving from a generally remote production site to a consumption area, urban or industrial, through high-pressure pipelines allowing efficient flow. Effective risk management in this regard would mean continuous monitoring and maintenance, as well as deploying appropriate safety protocols to reduce risks during the pipeline system’s operational life [27].

5.2.3. Safe Work Procedure (SWP)

SWP refers to the work procedure for safety, which the operation team shall follow. In other words, it is the practical guideline from RA and MOS that shall ensure the execution of all operational activities safely and by following the laid down protocol. Before commencing routine tasks every day, the members engaged should be educated and informed regarding SWP through routine safety meetings or toolbox talks. Additionally, the safety team should provide follow-up and verify the operation team’s adherence to the instructions and protocols reviewed in the briefings.

6. Discussion

6.1. Key Results and Interpretation

Hydrogen pipelines remain one of the most economical and efficient ways of transportation for huge amounts of hydrogen, especially in comparison with all other methods. Pipelines, mainly converted natural gas pipelines, can be considerably cheaper; this, however, involves very extensive testing due to the unique properties that hydrogen exhibits, and strict adherence to safety. Building new hydrogen pipelines or retrofitting existing ones incurs significant costs due to labor, materials, and advanced maintenance and monitoring technology requirements. However, innovations in materials, construction techniques, and robotics are expected to reduce these costs over time [3]. The growing demand for hydrogen infrastructure will likely drive economies of scale, further lowering costs.

Materials used in hydrogen pipelines must resist hydrogen embrittlement and other degradation types. Carbon Steel choices like X52, X65, and X100 were examined, with X65 providing a balance between cost and strength, and X100 being ideal for high-strength applications despite its higher cost [7]. The paper emphasizes that materials should meet or exceed standards like CSA Z662 to ensure reliable performance under high-pressure operations [17].

The success of hydrogen infrastructure also heavily depends on sound policies and regulations. Governments must implement safety standards, provide financial incentives, and collaborate internationally to establish consistent regulations that support cross-border hydrogen transport [8]. Regulatory frameworks must consider hydrogen’s unique traits, such as high flammability and embrittlement potential.

The stress analysis in the study shows that, for pipelines made from X52 (aligned with CSAZ245.1) [17], the allowable bending stress surpasses the stresses from external load and the pipeline’s own weight. This indicates that the pipeline can maintain structural integrity under standard operating conditions.

This paper, therefore, provides a comprehensive analysis in regard to factors of viability and design influencing hydrogen pipelines for large-scale transportation of hydrogen. It provides cost, material, safety, and regulatory considerations needed for the development of a hydrogen infrastructure to support global change towards clean energy [17]. Key interpretations drawn from the paper support hydrogen pipelines as a viable, cost-effective, and efficient means for hydrogen transport compared to alternatives like trucks or rail. Repurposing natural gas pipelines offers a clear cost advantage but requires thorough testing to ensure material compatibility with hydrogen [12].

Building new pipelines and upgrading existing ones entails high initial costs, but the paper highlights that construction, materials, and automation advancements will likely reduce costs over time. A comparison of materials reveals that X65 steel offers an optimal balance of price and strength, while X100 is suitable for high-strength applications [17]. Emphasizing compliance with standards like CSA Z662 ensures that materials can withstand the operational demands of hydrogen transport.

The development of hydrogen pipelines requires more than technological solutions; policy and regulatory measures will be essential. Governments should implement enabling policies, including tax policies and safety standards that will facilitate investment in hydrogen infrastructure. International regulations will also be paramount to a global hydrogen economy, with frameworks designed to consider hydrogen’s unique characteristics [8].

Safety is paramount due to hydrogen’s small molecular size, flammability, and potential for embrittlement. Comprehensive safety protocols, including the use of specially designed materials, regular inspections, and advanced monitoring systems, are recommended to mitigate risks and maintain hydrogen pipeline reliability [1]. Stress analysis confirms that X52 pipelines meet safety standards for typical operational conditions, suggesting they can uphold structural integrity under normal stress loads. However, this will involve continuous monitoring and adjustments to the pipeline design to avoid degradation over long periods.

In summary, this paper presents hydrogen pipelines as an efficient solution for large-scale hydrogen transportation. Challenges regarding cost, safety, material selection, and regulatory frameworks are there, but they can be overcome by technological innovation, supportive policies, and global collaboration. The findings and insights presented in this paper contribute to understanding the necessary measures for achieving safe, efficient, and economically viable hydrogen pipeline infrastructure.

6.2. Implications and Future Results of the Paper

The paper highlights the essential role of robust safety measures, including regular inspections and real-time monitoring systems, like fiber optic sensors, in hydrogen pipeline operations. Pipeline operators must integrate advanced monitoring technologies to detect and address risks such as leakage, embrittlement, and structural failure. Implementing rigorous safety protocols alongside thorough employee training will be critical to managing the unique risks associated with hydrogen transport [10].

Despite high initial costs for building hydrogen pipelines, the paper suggests that innovations in materials, construction techniques, and economies of scale will help reduce expenses over time. This offers insights for financial planners and investors, who should anticipate these cost declines, making hydrogen infrastructure more competitive compared to traditional energy transport systems. Additionally, repurposing existing natural gas pipelines can optimize investment by leveraging current assets and minimizing the need for new builds [10].

The advancement of pipeline technologies, such as robotics and automated welding, presents increasing opportunities for investment in these innovations. Early adopters are likely to gain a competitive edge, especially as hydrogen demand grows and efficient pipeline systems become crucial [9].

Standardized regulations are necessary for safe hydrogen pipeline operations, given hydrogen’s unique properties. The paper emphasizes that governments and regulatory bodies must enforce policies that ensure hydrogen’s safe and efficient transport, which may involve updating standards like CSA Z662. Collaboration with industry stakeholders is essential to create practical and enforceable frameworks that encourage the swift development of hydrogen infrastructure [1].

Hydrogen pipeline infrastructure will require an integrated policy development process in overcoming technical, economic, and environmental hurdles and promoting innovation and international cooperation. The governments should thus put in place specific regulations that minimize the peculiar risks of hydrogen: its flammability, permeability, and embrittlement. These policies would include the installation of state-of-the-art safety features, periodic monitoring, and using materials in the transport pipelines that would resist hydrogen for structural stability and durability in the long term [1]. Additionally, there are economic motives or incentives necessary to attract private investment into the area of hydrogen-based energy systems: subsidies, tax breaks, and grants.

PPPs are encouraged to pool resources and expertise to enable large-scale development of hydrogen pipeline networks. International cooperation is important in terms of harmonization of safety and operational standards, especially for cross-border pipelines, to avoid fragmentation of regulations and ensure efficiency in global trade [8]. Policymakers should underline that hydrogen pipeline projects must be in line with sustainability goals by encouraging low-carbon methods of hydrogen production, reutilization of existing natural gas pipelines, and integration of renewable energy sources into pipeline operations.

In addition, future policy directions should nurture innovation through incentives for research and development in materials science and smart technologies for pipeline monitoring and maintenance. The policies should have comprehensive risk assessment frameworks that can easily adapt to the evolving technical and environmental challenges. Long-term policies should encourage the use of the circular economy, including recycling of pipeline materials, so as to limit environmental impacts [9].

By addressing these policy implications and aligning future directions with sustainability and innovation goals, stakeholders can make sure that hydrogen pipeline infrastructure effectively contributes to the global energy transition and supports the establishment of a sustainable hydrogen economy.

Pipeline operators must prioritize safety, cost-effectiveness, and reliability by using advanced monitoring technologies and materials that resist embrittlement to maintain operational efficiency over time [1].

While the study concentrates on materials like X52, X65, and X100, other new material groups being developed do acknowledge composites and non-metallics, and although in their infancy in practical application, these do offer some potential for new options for hydrogen transportation in the future [7].

Looking forward, the study anticipates that advancements in pipeline technology, regulatory developments, economic trends, and industry collaboration will shape the hydrogen infrastructure’s future. New materials with improved resistance to hydrogen embrittlement and advanced robotics for inspections will likely enhance pipeline durability, safety, and cost-efficiency. Improved real-time monitoring systems allow earlier detection of leaks with fewer failures, more efficient maintenance, and thereby enhancing the safety and reliability of hydrogen infrastructure [17].

With the growth in the hydrogen markets and economies of scale, costs for building and maintaining hydrogen pipelines should be less expensive with more competitive hydrogen across energy markets. Infrastructure costs will also be saved by repurposing existing natural gas pipelines. As costs decline, more industries will adopt hydrogen, supporting a broader shift toward clean energy [2]. Global standardized regulations on hydrogen pipelines will further facilitate cross-border infrastructure deployment [9,13]. Governments are likely to continue expanding their support to hydrogen projects via financial incentives, promoting public–private partnerships for hydrogen infrastructure development.

Once hydrogen pipeline networks develop, they will contribute significantly to the decarbonization of the most difficult-to-electrify industries, reducing overall emissions worldwide. Integrating renewable energy into hydrogen production and transportation systems will contribute to further reducing hydrogen’s carbon footprint for the long-term sustainability of hydrogen pipelines. Widespread adoption of hydrogen pipelines will facilitate the establishment of hydrogen hubs that constitute a global hydrogen economy [1]. Higher demand for it will stimulate pipeline construction in new parts of the world, connecting producers, consumers, and storage facilities throughout continents.

Hydrogen pipelines will likely integrate with existing energy infrastructure, enhancing energy security and diversification. Future hydrogen transport may involve a hybrid approach, combining pipelines, storage facilities, and transport vessels for optimal distribution, enabling reliable hydrogen delivery across diverse markets. In conclusion, the future of hydrogen pipeline technology involves advancements that enhance economic feasibility and create a supportive regulatory environment, all of which will accelerate hydrogen adoption as a vital energy source [10]. These developments will strengthen the hydrogen infrastructure sector and support the global shift toward sustainable, clean energy systems.

6.3. Contribution and Summary of Paper

The paper comprehensively analyzes the underlying economic rationale, the standards of safety concern, and technological development for the efficient transportation of hydrogen. By showing both technical and economic challenges, it represents a balanced view of hydrogen pipeline feasibility for large-scale hydrogen delivery.

Several recommendations in the paper are offered that might help bring down these initially high costs for hydrogen pipeline infrastructure: repurposing existing natural gas pipelines and innovative construction techniques [4]. Meanwhile, the paper points out that economies of scale and technological development will be crucial in the long term. The paper also emphasizes the need for sound policy frameworks accompanying the development of hydrogen infrastructures. It demonstrates how government regulations can allow the deployment of hydrogen pipelines to be safe and successful, along with international collaboration and standards for safety. This insight will be of particular use to policymakers, regulatory bodies, and industry stakeholders who deal with issues regarding hydrogen infrastructures [1].

The paper addressed the unique safety challenges of hydrogen pipelines: hydrogen leakage, material embrittlement, and explosion hazards. It then called for choosing the appropriate materials, installing modern monitoring technologies, and developing strict operation guidelines to minimize these risks to ensure pipeline operations are safe and reliable. Anticipated advances in pipeline technology, enhanced materials, and cost reductions all portend a brighter future [5]. The paper serves as a forward-looking guide for researchers, engineers, and policymakers charged with ongoing development in hydrogen transport systems. Valuable insight and recommendations are brought to the fast-growing body of knowledge on hydrogen’s contribution to the ambition of sustainable energy to ensure safety, efficiency, and cost-effectiveness during the development of hydrogen pipeline systems [13]. The present and future perspectives of hydrogen pipelines for the transportation of hydrogen-a clean source of energy are highlighted in this report.

Hydrogen demand in the transportation and power sectors necessitates infrastructure development in a cost-effective and energy-efficient manner. Pipelines are noted in all delivery options as the most feasible delivery option for the large-scale transport of hydrogen, similar to the existing natural gas infrastructure. The paper assesses the costs of constructing and maintaining hydrogen pipelines, noting high initial costs but identifying potential savings through material innovations, technology, and economies of scale. The repurposing of natural gas pipelines is suggested as the cheaper alternative but would require extensive testing and considerations on safety [4].

The need for policy and regulatory frameworks is underlined as being critical to hydrogen infrastructure success. Government incentives, safety standards, and international coordination, the paper emphasizes, are needed to spur investments and ensure pipeline safety and efficiency, all while in line with efforts to harmonize regulations across borders as part of efforts to enable global hydrogen infrastructure. Safety issues related to hydrogen transport, such as leakage, explosion risk, and material embrittlement, are considered in this paper [19]. Preventative measures, including specialized materials, advanced monitoring technologies, and strict protocols, are recommended to manage these risks effectively. Material selection for hydrogen pipelines is also evaluated, with a comparison of different steels like X52, X65, and X100. The paper concludes that material choice should balance performance and cost, with X52 being the most economical option for less demanding applications [2]. Key findings emphasize the importance of technological innovation for long-term cost reduction in hydrogen pipelines, as well as rigorous safety standards to address hydrogen’s unique risks. The paper suggests that global cooperation and well-developed regulatory frameworks will be instrumental in promoting hydrogen’s adoption as an energy carrier.

Looking ahead, the paper anticipates that advancements in pipeline materials, cost reductions, and enhanced safety features will shape the future of hydrogen infrastructure. As the hydrogen market expands, evolving global standards for pipeline safety and operation will further facilitate hydrogen adoption across industries. Ultimately, the paper underscores hydrogen pipelines’ vital role in achieving global sustainability targets by enabling efficient, safe, and economical hydrogen transportation [13].

6.4. The Limitations of the Paper

This study recognizes several limitations that could impact the comprehensiveness and applicability of its findings. First, while the research evaluates commonly used pipeline materials such as X52, X65, and X100, it does not fully investigate other promising options, such as composite materials or non-metallic alternatives. These materials are emerging in research and may hold potential for hydrogen transportation but have yet to see widespread application or detailed analysis. Second, the regulatory and policy frameworks discussed in this study may not adequately reflect the significant variability in standards across different countries or regions. Safety priorities, regulatory requirements, and industrial practices can vary substantially, and these differences could affect the adoption and implementation of hydrogen pipeline standards in diverse contexts.

Furthermore, this study provides an overview of recent technological advancements, such as robotics and leak detection systems, but acknowledges that the rapid pace of innovation could lead to significant changes in cost structures and safety profiles in the near future. As a result, some technological forecasts presented in this study may quickly become outdated. Economic factors analyzed in this paper are based on current material prices and construction methodologies. However, these considerations are subject to fluctuations in global markets, changes in energy prices, and variations in the cost of raw materials, making it challenging to predict the long-term economic feasibility of hydrogen pipeline projects [12].

The environmental impact of hydrogen transportation is another area requiring further exploration. While this study touches on this topic, it does not provide a comprehensive lifecycle analysis of pipeline materials or account for the environmental consequences of pipeline failures. Such analyses would offer a deeper understanding of the ecological costs associated with building and maintaining hydrogen pipelines [6]. Similarly, this study discusses some safety concerns, such as hydrogen embrittlement and leakage, but does not thoroughly examine how extreme weather conditions, natural disasters, or prolonged use over decades might impact pipeline integrity and long-term safety [10].

Additionally, while this paper advocates for a global strategy for hydrogen pipeline infrastructure, it does not address key geopolitical and market dynamics that could influence widespread adoption. Factors such as competition in energy markets, trade regimes, and the requirement for international cooperation, which are crucial to such efforts, have not been fully analyzed. Finally, the reliability of the results of this study is inherently limited by the availability and quality of data that were available. Comprehensive, practical data on the long-term performance of hydrogen pipelines under diverse environmental conditions are scarce, and such a gap in data could restrict the accuracy of some of the findings of this study.

7. Conclusions

This study has been able to give a broad overview of the challenges and considerations involved in the development of hydrogen pipeline infrastructure. It has looked at the technical, economic, safety, and environmental aspects, each indicating that for hydrogen pipelines to be successfully deployed, advances in materials, construction methodologies, and safety protocols are required. This research highlights that hydrogen-resistant materials, like high-strength carbon steel and composite alternatives, have to be developed to deal with the problem of hydrogen embrittlement for the long-term durability of pipelines

Repurposing existing natural gas pipelines, where feasible, will be cost-effective, considering proper testing and purifying mechanisms. It is also important that safety standards, such as ASME B31.12, are globally harmonized with strong regulatory frameworks to support the safety, operation, and maintenance of hydrogen pipelines. In this regard, the integration of smart technologies and continuous research will be pivotal for enhancing safety, reducing maintenance costs, and ensuring the reliability of hydrogen transport networks

In addition, this paper underlines the importance of public–private collaboration and the role of government incentives in driving investment into hydrogen infrastructure. Soil stabilization and the use of appropriate materials for different operational pressures are also critical to maintaining the integrity of the pipelines. The recommendations offered aim at the creation of a more efficient, cost-effective, and reliable hydrogen pipeline system that will contribute to the establishment of a sustainable global hydrogen economy.

While this study provides a great view of the current state of hydrogen pipeline infrastructure and future potential, further research and innovation are needed to address continuing challenges, especially in the areas of material science, economic feasibility, and international cooperation. In the end, this will be instrumental in helping to realize these recommendations and ultimately enable the widespread adoption of hydrogen as a clean and sustainable energy source, which is essential for the transition to a low-carbon future.

Based on the findings and analysis presented in this paper, some recommendations are made to help in the development, safety, and cost-effectiveness of hydrogen pipeline infrastructure. Among the key priorities is research and development into hydrogen resistant materials to handle issues such as hydrogen embrittlement for long-term durability of the pipelines [1]. Advanced materials, including high-strength carbon steel and composite alternatives, should be explored to reduce maintenance costs and improve the overall performance of pipelines. Future research on hydrogen scavengers should prioritize the development of advanced materials with improved surface reactivity and resistance to oxidation. These materials should also be designed to function effectively in environments containing impure hydrogen, ensuring better mitigation of hydrogen embrittlement in structural applications [28]. Furthermore, their key properties should be evaluated for hydrogen trapping applications, with an emphasis on comparing long-term durability, capital cost, and minimum attractive rate of return.

Another significant recommendation is the repurposing of existing natural gas pipelines, which offers a cost-effective solution compared to constructing new pipelines [4]. This approach, however, involves intensive testing to confirm the material type is compatible with hydrogen and purifying mechanisms that eliminate impurities while, at the same time, there are strict safety protocols put into place by policymakers and regulators for secure operations.

High-capacity safety standards and regulations will be paramount to establish and improve this form of hydrogen pipeline infrastructure. Adapting frameworks like the ASME B31.12 and supporting international collaboration will not only harmonize global best safety practices but also ensure that pipelines are designed, operated, and maintained to the highest standards possible [17]. Integrating smart technologies such as fiber optic sensors, robotics, and automated welding into the pipeline infrastructure can enable real-time monitoring, facilitate early leak detection, and significantly reduce maintenance costs while enhancing safety and reliability in the hydrogen pipeline network [5]. Governments should support policies with tax incentives, subsidies, or grants for investment in hydrogen pipeline construction, renovation, and repurposing projects. Such incentives should also foster international cooperation and harmonized regulations that will help establish a continuous hydrogen infrastructure across the globe [1].

Another key area of focus is reducing the initial investment cost of hydrogen pipelines. It would be prudent to look for new construction methods and technologies. These might include lighter yet stronger materials, modular ways of construction, and automation in the laying and maintenance of the pipelines. Effective development of hydrogen pipelines requires cooperation between the public and private sectors. The governments also need to collaborate with all the key players in industry, research institutions, and technology developers to come out with an integrated, cost-effective, and efficient hydrogen infrastructure. It could drive forward improvements in material sciences, methods of construction, and safety technologies [1].

Soil assessment and stabilization as a routine maintenance program will be necessary for the long-term safety and performance of hydrogen pipelines. Properties of the soil, such as density and composition, can greatly affect pipeline stability in subsidence or shifting areas. Stabilization by compaction of soil and use of geosynthetic reinforcements will enhance structural integrity and reduce the risk of leakage or deformation of the pipelines. Material recommendations should consider the pipelines’ operational pressure and the materials’ susceptibility to hydrogen embrittlement. Though copper steel has better strength among the high-strength steels, such high-strength steels are often preferred for transmission pipelines with high pressure and this is a matter of great concern for embrittlement; hence, advanced coatings, protection, and real-time monitoring systems have to be adopted to avoid any risks [1]. It gives the measures that are important for minimizing the risk of leakage and structural failure with long-term durability and safety of the pipeline infrastructure. On the other hand, high-density polyethylene should be used for low-pressure distribution pipelines because of its flexibility, cost-effectiveness, and ease of installation in urban and suburban settings. HDPE is resistant to leakage and can adapt to most varied terrains, making it quite practical for end-use distribution.

The above recommendations are put forward with the common objective of ensuring that hydrogen pipeline systems are designed and maintained with the best principles of safety, reliability, and economic efficiency to support the overall goal of a sustainable hydrogen infrastructure.

These recommendations will assist all stakeholders in developing a more efficient, safer, and more cost-effective hydrogen pipeline infrastructure that would serve critical importance in the successful transition toward a sustainable energy future. However, it is important to note that these recommendations do not fully encompass all strategies for hydrogen pipelines. Some limitations and challenges are separately detailed in Section 6.4, “The Limitations of the Paper”, to provide a balanced perspective on the scope of this study.