Problems in Storage and Transportation of High-Pressure
Gaseous Hydrogen/Hydrogen-blended Natural Gas
Seminar Report MM396
Submitted in partial fulfillment of the requirements for the award of the degree of
Bachelor of Technology
in
Metallurgical Engineering and Materials Science
by
Harshita Rathod (Roll No.:210110090)
Under the Supervision of
Prof. V. S. Raja, MEMS
Department of Metallurgical Engineering and Materials Science
INDIAN INSTITUTE OF TECHNOLOGY BOMBAY
CERTIFICATE
This seminar report titled “Problems in Storage and Transportation of High-Pressure Gaseous
Hydrogen/Hydrogen-blended Natural Gas” by Harshita Rathod (210110090) is approved for the
course MM 396.
Examiners
Supervisor
Date: 10/04/2024
DECLARATION
I declare that this written report submission titled “ Problems in Storage and Transportation of HighPressure Gaseous Hydrogen/Hydrogen-blended Natural Gas " contains my own words, and that I
have adequately credited and referenced the original sources when others' ideas or words have been
incorporated. I further declare that I have followed all academic honesty and integrity rules in my
submission and have not misrepresented or faked any idea, data, fact, or source. I understand that
any violation of the foregoing will result in disciplinary action by the institute, as well as legal action
from the sources who were not correctly referenced or from whose sufficient permission was not
obtained when required.
Harshita Rathod
210110090
Date: 10/04/2024
ACKNOWLEDGEMENT
I would like to express my gratitude to Prof. V.S. Raja, my seminar guide, for his guidance with
inputs and recommendations, as well as for presenting me with a fascinating topic to work on.
I would also like to thank Prof. Aswani Yella and Prof. Prasanna Kumar for keeping us informed on
the seminar procedure.
Harshita Rathod
210110090
Date: 10/04/2024
ABSTRACT
The integration of hydrogen into natural gas to create hydrogen-blended natural gas is a promising
solution for large-scale hydrogen transportation, yet it raises concerns regarding mechanical
integrity due to hydrogen embrittlement. This review comprehensively addresses various aspects
of hydrogen embrittlement in existing systems, covering compression, delivery, welding, and
storage devices. It explores factors influencing hydrogen embrittlement in pipelines and methods
to mitigate it, focusing on enhancing safety and performance. Moreover, as the transition to
hydrogen as a fossil fuel alternative aims to reduce carbon emissions and alleviate energy crises,
thorough examination of safety concerns in storage and transportation is imperative. Carbon and
low-alloy steels play a crucial role in high-pressure hydrogen gas vessels and pipelines, but
challenges arise due to hydrogen embrittlement. This chapter discusses their application and
considerations for material selection and operation in hydrogen energy infrastructure.
CONTENTS
List of Figures
iii
List of Tables
iv
1.INTRODUCTION
1
2.Hydrogen-blended natural gas system composition
1
3. Phenomenon and mechanism of hydrogen embrittlement
2
4. Hydrogen embrittlement in Hydrogen-blended natural gas
3
transportation systems
4.1 Compression devices
3
4.2 Delivery devices
4
4.3 Storage devices
6
i) Storage devices made of Cr-Mo steel
6
ii) Storage devices constructed from austenitic steel
7
5.THE IMPACT OF HYDROGEN GAS ON STEEL CONTAINMENT
VESSELS AND PIPELINES
8
5.1 Conditions affecting Vessel Steel in Hydrogen
8
i)Material Conditions
9
ii)Environmental Conditions
9
iii)Mechanical Conditions
9
5.2 Conditions affecting pipelines in Hydrogen
10
6. Vessels and Pipelines in Hydrogen Energy
11
CONCLUSION
12
REFERENCES
13
i
ii
LIST OF FIGURES
i) 2. Hydrogen blended natural gas transport system
2
ii) 3.History of HE Mechanism
2
iii) 4.B Factors affecting embrittlement of pipelines
4
iv) Tensile test data
5
v)GB maps
7
iii
LIST OF TABLES
1. Composition of (wt%) 34CrMo4 steel
9
2. Composition of (wt%) A106 Grade B steel
11
3. Composition of (wt%) API 5L steel
11
iv
1
1. INTRODUCTION
Hydrogen storage stands as a linchpin within the intricate framework of the hydrogen value chain,
serving as a pivotal component in reconciling the oscillating dynamics between production and
demand. Despite the profound potential of hydrogen as a clean and efficient energy carrier, its
widespread utilization faces numerous challenges, chief among them being the issue of storage. The
disparity between its high energy density on a mass basis and its comparatively low volumetric
energy density presents a formidable bottleneck, particularly when considering applications such as
vehicular usage where space and weight constraints are paramount. Furthermore, the practicality
and economic viability of hydrogen storage systems hinge upon a multitude of factors including
material costs, tank durability, operational efficiency, and safety considerations. The advent of
hydrogen energy has been met with significant enthusiasm on a global scale, underscored by
strategic initiatives and policy frameworks aimed at fostering its development and adoption. For
instance, major economies including the European Union, the United States, and China have
implemented ambitious plans and programs such as the "Fuel Cells and Hydrogen Joint
Undertaking" and the "Hydrogen Program Plan 2020", hinting a collective commitment to
transitioning towards cleaner and more sustainable energy alternatives. However, the realization of
hydrogen's potential as a mainstream energy source is contingent upon overcoming various technical
and logistical hurdles, one of the most pressing being hydrogen embrittlement in infrastructure
materials.
Carbon and low-alloy steels, commonly employed in the construction of high-pressure hydrogen gas
vessels and pipelines, are susceptible to hydrogen-induced degradation of mechanical properties,
leading to increased fracture susceptibility and compromised structural integrity. This phenomenon
poses significant safety risks and necessitates rigorous mitigation measures to ensure the reliability
and longevity of hydrogen infrastructure. As the global momentum towards hydrogen energy
continues to build, there is an urgent need for comprehensive research and development efforts
aimed at understanding and mitigating the effects of hydrogen embrittlement. By delving into the
intricacies of composition, mechanisms, and research status related to hydrogen embrittlement in
infrastructure components, this review endeavours to provide valuable insights and
recommendations for advancing the deployment of hydrogen-blended natural gas systems. In doing
so, it seeks to contribute to the realization of sustainable and resilient energy ecosystems aligned
with the imperatives of global climate action and environmental stewardship.
2. Hydrogen-blended natural gas system composition
The processes involved in producing, storing, transporting, and disposing of hydrogen are all
included in hydrogen-blended natural gas transportation systems (Fig. 1)[3]. Hydrogen is first
created by electrolyzing water with renewable energy. Part of the compressed hydrogen is then kept
in a high-pressure hydrogen storage device, and another part is combined with stabilized natural gas
in the subsequent injection blending device after the pressure-relief device depressurizes it. The
2
natural hydrogen blending material was then transferred via pipes. Lastly, the terminal device
assigns it to the user. Hydrogen can be separated and utilized or stored downstream, or it can be
combined with natural gas to be used directly as fuel for end consumers, depending on their
demands. [1]
3. Phenomenon and mechanism of hydrogen embrittlement
Metals' toughness, strength, and plasticity are all negatively impacted by hydrogen, which can result
in phenomena like hydrogen environmental embrittlement (HEE) and internal hydrogen
embrittlement (IHE). Advanced high-strength steels' ability to support loads is impacted by HE,
making them more susceptible to it. To reduce its negative effects and maintain mechanical
characteristics, it is essential to comprehend the mechanics behind HE. Studies of HE processes, as
seen in Fig. 2, include
reversible mechanisms such
as
hydrogen-enhanced
localized plasticity (HELP)
and
hydrogen-enhanced
decohesion (HEDE), as well
as irreversible hypotheses
such as hydrogen pressure
and hydrogen-induced phase
transition (HIPT).[4] To fully
address HE issues, the
synergistic combination of
these systems is being
researched more and more.
Numerous HE processes have
been
clarified
via
experimental and theoretical
research, including their
3
interaction and effect on fracture behaviour. However, further investigation is required to completely
understand HE occurrences and provide practical mitigating measures, particularly with regard to
hydrogen-blended natural gas transportation networks.[5][6]
4. Hydrogen embrittlement in Hydrogen-blended natural gas transportation systems
A. Compression devicesAn essential link in the hydrogen supply system is the compressor. They tackle the issue of
hydrogen's lower energy density than that of conventional fuels and guarantee the seamless
functioning of natural gas transportation networks after hydrogen mixing. As such, it is critical to
evaluate the compression units' operating state after integrating hydrogen with natural gas. There are
two main categories of hydrogen compressors: mechanical and non-mechanical. The most common
type of hydrogen compressors are mechanical ones since their technology is well-established.
Nevertheless, these compressors are vulnerable to hydrogen embrittlement (HE) and consequent
mechanical property degradation due to moving seal leakage and hydrogen absorption by metals.
This work investigates the HE phenomena in mechanical hydrogen compressors in detail, taking
into account the paucity of research on HE in non-mechanical compressors.
Centrifugal compressors are used for large volume flow, whereas reciprocating compressors are
usually used for low gas volume flow. Because of their dynamic seal structure, reciprocating piston
compressors are susceptible to helium evaporation (HE), as indicated by a number of studies;
nevertheless, specialized study in this field is still lacking. Material failure in centrifugal
compressors is frequently caused by direct contact with power mechanisms and hydrogen as well as
high pressure requirements. Furthermore, because hydrogen is lightweight, higher blade tip speeds
are required, which affects compressor performance and increases the danger of HE, especially for
the impeller.
Reciprocating piston compressors are recommended by several studies for the purpose of injecting
hydrogen into a pipeline network. Moreover, transmission equipment problems caused by trace
sulfur compounds in natural gas may worsen and present as sulphide stress cracking (SSC), a distinct
kind of hydrogen erosion. Remarkably, impeller fracture research has shown that environmental
variables including humidity and H2S exposure can hasten embrittlement.
The mechanical hydrogen compressors' extended lifespan, high wear, and high temperatures
aggravate hydrogen etching (HE) in components that come into contact with hydrogen. Therefore,
it becomes essential to use materials with good HE resistance. To reduce HE, polymers such as
nitrile rubber and ethylene propylene diene monomer (EPDM) are advised in substitution of
thermoplastics in compressor valve and seal assemblies. Similar to this, HE resistance may be
increased by using materials like AISI316L stainless steel in hydrogen ionic liquid compressors and
certain steel alloys in reciprocating compressors.
Compression device selection for hydrogen-mixed natural gas transportation takes into account
factors other than gas pressure and flow efficiency, such as component failure from hydrogen
explosion (HE). Selecting materials with a lower susceptibility to HE is one way to mitigate this
danger. Nevertheless, there hasn't been much study done on HE in compressors used in the
4
transportation of hydrogen-blended natural gas, especially reciprocating piston compressors. This
calls for more thorough investigation of these components that are exposed to hydrogen.
B. Delivery devices
Pipelines- Pipeline steel may be divided into four categories according to its microstructure:
tempered sorbite, acicular ferrite pipeline steel (X60eX100), bainite martensite (X100 and X120),
and ferrite pearlite pipeline steel (X70 and below). Hydrogen seeps through the steel wall of the pipe
in a hydrogen environment, resulting in HE, which subsequently presents a serious risk to the
hydrogen infrastructure as a whole. This affects carbon steel pipes, low- and high-alloy steel pipes,
and polymer pipes. Wasim and his partners After a year, soft steel in a 2.5 pH solution saw a
reduction in ultimate strength of 70 MPa and a percentage loss in yield strength of 17.8% due to the
coupling effect of hydrogen embrittlement and corrosion. The soft steel's basic elements—Fe, Si,
Cr, Mn, and so on—decline over time. During the transmission of natural gas/hydrogen mixtures,
hydrogen atoms enter the pipeline and interact with the metal components and additives. As a result,
the pipeline develops fatigue cracks, HE, and its
mechanical properties deteriorate. Because of
consequence, studies on the HE of pipelines transporting
natural gas mixed with hydrogen are essential to the
advancement and security of these systems. This section
aims to elucidate the effects of hydrogen on the
mechanical properties and failure behavior of pipeline
steels from both macro and micro perspectives.
These factors include temperature, material strength,
hydrogen pressure, hydrogen concentration, hydrogen
diffusion velocity, hydrogen blending ratio, and stress
intensity factor. The way these elements interact is
important because they frequently affect mechanical
behavior collectively as opposed to singly. Comprehending these factors is crucial in order to
precisely evaluate the hazards linked to the introduction of hydrogen into natural gas pipelines.
1. Transmission Medium: Natural gas composition varies, affecting pipeline materials differently.
While low hydrogen concentrations minimally impact pipeline mechanical properties, the presence
of gases like oxygen, sulphur dioxide, and carbon monoxide can mitigate hydrogen-induced
deterioration, except for hydrogen sulphide, which exacerbates it. Interactions between multiple
gases like CO2 and H2 further increase susceptibility to HE.
2. Hydrogen Blending Ratio: Varying proportions of hydrogen in natural gas significantly affect
pipeline performance. Higher hydrogen blending ratios reduce the Joule-Thomson coefficient of
natural gas, impacting its transport properties. Studies show that increased hydrogen blending leads
to decreased mechanical properties and increased HE susceptibility.
3. Hydrogen Diffusion Velocity: The rate of hydrogen diffusion influences HE. Factors such as alloy
elements, lattice defects, and crystal structure affect hydrogen permeation rates. Experimental
studies have shown correlations between hydrogen movement, crack growth, and diffusion rates,
highlighting the importance of understanding these dynamics in assessing HE.
5
4.Hydrogen Concentration: The concentration of hydrogen in gas mixtures can positively or
negatively affect pipeline steel properties. Studies demonstrate varying HE mechanisms under
different hydrogen concentrations, emphasizing the need for careful evaluation when introducing
hydrogen into natural gas pipelines.
5. Temperature: Temperature variations affect HE susceptibility, with lower temperatures generally
reducing susceptibility. Understanding temperature thresholds for HE in different steel grades is
crucial for maintaining pipeline integrity during operation.
6.
Material
Strength:
Higher material
strength
correlates with
increased HE
susceptibility.
Various
steel
grades exhibit
different
responses
to
hydrogen
exposure,
emphasizing the
complexity of
the relationship
between
material
strength and HE
susceptibility.
7. Hydrogen Pressure: Increasing hydrogen pressure accelerates HE due to higher hydrogen
solubility. Studies show a direct correlation between hydrogen pressure and mechanical property
degradation, highlighting the importance of pressure management in pipeline design and operation.
8.Stress and Stress Intensity Factor: Stress concentration plays a significant role in HE susceptibility,
with higher stress concentrations leading to increased susceptibility. Understanding the complex
relationship between stress intensity factors and HE susceptibility is essential for evaluating pipeline
integrity under varying operating conditions.
6
In conclusion, comprehensively understanding these factors is crucial for accurately assessing the
risks associated with hydrogen introduction into natural gas pipelines and ensuring their long-term
safety and reliability.
C. Storage Devices
Storage devices for compressed hydrogen-blended natural gas and separated hydrogen downstream
are typically stored in hydrogen vessels, primarily utilizing high-pressure hydrogen storage methods.
However, the susceptibility of pipelines and storage vessels to hydrogen embrittlement (HE) poses
a significant challenge. Commonly, Cr-Mo and austenitic stainless steels are employed for hydrogen
storage and transport, yet prolonged exposure to high-pressure hydrogen can lead to mechanical
property deterioration due to HE. Understanding the impact of HE on these materials, particularly
in hydrogen storage applications, is essential.
i)Storage devices made of Cr-Mo steel:
Cr-Mo steel high-pressure vessels represent a cost-effective solution for hydrogen storage and
transport. The HE of Cr-Mo steel in high-pressure hydrogen environments manifests in three main
aspects: cracking, fatigue properties, and tensile properties.
1. Effect on cracking:
Under high-pressure hydrogen environments, the threshold stress intensity factor for hydrogenassisted cracking (KIH) decreases with increasing hydrogen pressure, while it increases with
temperature. Intergranular fracture characteristics become more pronounced in high-pressure
hydrogen environments, potentially attributed to hydrogen enhanced debonding (HEDE)
mechanisms. Additionally, the critical heat-affected zone (CGHAZ) of certain steel compositions
experiences increased susceptibility to HE, showcasing the interplay of micromechanisms like
hydrogen enhanced localised plasticity (HELP) and HEDE.[1]
2. Effect on fatigue properties:
Fatigue-crack growth rates (FCGR) in Cr-Mo steel significantly accelerate in hydrogen
environments compared to air. The fatigue life of hydrogen storage vessels decreases as the initial
crack size increases, indicating an increased susceptibility to hydrogen-induced fatigue damage.
3.Effect on tensile properties:
While high-pressure hydrogen has a negligible effect on the tensile strength of Cr-Mo steel, it
significantly reduces ductility, as evidenced by decreased elongation fracture (EL) and reduction
area (RA). Severe deformation and dislocations occur at ultimate tensile strength, leading to
nonuniform deformation and necking. Stress-strain reversal tests reveal that regardless of the
environment (air or hydrogen), ductility decreases while strength increases with rising stress
triaxiality.
7
In conclusion, the understanding of HE effects on Cr-Mo steel is crucial for ensuring the integrity
and safety of hydrogen storage devices in various applications, particularly under high-pressure
hydrogen environments.
ii)Storage devices constructed from austenitic steel are prevalent in hydrogen gas storage
applications. However, their susceptibility to hydrogen embrittlement (HE) in high-pressure
hydrogen environments raises significant safety concerns. Consequently, understanding the
underlying causes of HE in austenitic steels is imperative. The following discusses the primary
factors influencing HE in austenitic steel:
1. Grain size: Grain-size refinement, as per the well-known Hall-Page theory, serves to enhance
material strength and HE resistance, particularly in austenitic stainless steels. Refining the grain size
alleviates hydrogen-enhanced strain localization, leading to a more uniform strain distribution and
higher HE resistance. Studies have shown that decreasing grain size correlates with decreased
embrittlement sensitivity in austenitic stainless steels.
2. Grain boundaries: Grain boundaries play a crucial role in hydrogen diffusion, with random grain
boundaries (RGBs) facilitating hydrogen diffusion but also inhibiting permeation. Grain boundary
engineering (GBE) has been explored to mitigate HE susceptibility by increasing the proportion of
special interfaces (SBs) while disrupting RGB networks. However, the role of RGBs in hydrogen
trapping and diffusion remains complex and requires further investigation.
3. Chemical composition modification: Alterations in the chemical composition of austenitic
stainless steel can reduce HE susceptibility. By adding alloying elements such as nickel (Ni), carbon
(C), and nitrogen (N), the material's twinning formation, grain boundary cohesion, and overall HE
resistance can be improved. Studies have demonstrated that increasing Ni content enhances material
ductility and reduces embrittlement in hydrogen environments.
4. Presence of martensitic materials: The presence of strain-induced martensite influences the HE of
austenitic stainless steel, as hydrogen tends to accumulate at the boundary between austenite and
8
martensite, leading to crack initiation. Martensitic structures are more sensitive to HE, thereby
increasing the likelihood of embrittlement in hydrogen storage materials.
5. Hydrogen-charging method: The method of hydrogen charging significantly impacts hydrogen
concentration, fracture processes, and HE susceptibility in austenitic stainless steel. Various
hydrogen-charging methods, such as electrochemical and high-pressure thermal methods, exhibit
differing effects on HE resistance due to their influence on hydrogen permeability and diffusivity.
In addition to these factors, manufacturing methods and micro interface characteristics also influence
the HE performance of materials. Additive manufacturing processes, for instance, have been shown
to affect material ductility and resistance to HE in hydrogen environments.
In conclusion, while numerous factors influence HE in austenitic stainless steel, the synergistic
interactions among these factors complicate the analysis. Further experimental investigations and
engineering efforts are necessary to comprehensively understand and address the challenges posed
by HE in austenitic hydrogen storage materials.
5.THE IMPACT OF HYDROGEN GAS ON STEEL CONTAINMENT VESSELS AND
PIPELINES
Common structural materials for high-pressure hydrogen gas pipelines and vessels are carbon and
low-alloy steels. These steels are inexpensive and can be processed, heat-treated, and alloyed to
produce a wide range of characteristics. Because steels can be shaped, welded, and heat treated in
big sections, it is easy to fabricate complex structures like pipelines and gas containment vessels.
One major problem in the containment and transportation of high-pressure hydrogen gas in steel
structures is- atomic hydrogen can be created on the steel surface through the adsorption and
dissociation of hydrogen gas. Referred to as hydrogen embrittlement, the subsequent dissolution and
diffusion of atomic hydrogen into steels can deteriorate mechanical characteristics. Hydrogen
embrittlement manifests as increased fracture susceptibility. Hydrogen increases the propagation of
fatigue cracks and creates new modes of material failure. It also affects standard metrics of fracture
resistance like tensile strength, ductility, and fracture toughness. In particular, time-dependent crack
propagation in hydrogen gas may become a concern for steel structures that do not collapse under
static loads in safe settings at room temperature.
1. Conditions Affecting Vessel Steel in Hydrogen
This research focuses on cylindrical and tube-shaped steel tanks that primarily convey hydrogen gas.
Several hundred thousand vessels are currently in use by European hydrogen gas distributors,
providing up to 300x10^6 m3 of 5 hydrogen gas to clients each year. These hydrogen gas containers
have operated dependably and safely for the previous 20 years. Additionally, it is anticipated that
India will be able to produce 5 million metric tons of green hydrogen annually. In Europe, hydrogen
gas vessel failures have been reported, especially in the late 1970s. The conclusion drawn from
further research on hydrogen gas containers was that surface imperfections facilitated the spread of
hydrogen-enhanced fatigue cracks, which in turn led to failures.
9
A) Materials conditions affecting Steel Vessel for Hydrogen
Based on empirical evidence, the primary factors influencing the failure of hydrogen gas containers
have been found to be the steel's microstructure and strength. These factors have an impact on how
vulnerable the steel is to hydrogen embrittlement. The documented experience with reliable
hydrogen gas vessels is limited to specific steel properties. In Europe, vessels carrying hydrogen are
made of 34CrMo4 steel. [2] The proportion of carbon and the alloying metals molybdenum and
chromium set apart the steel composition (Table 1). Through processing, the 34CrMo4 steels are
given a "quenched and tempered" microstructure. This microstructure is the result of a heat treatment
sequence that includes heating in the austenite phase field, quickly cooling (quenching) to generate
martensite, and tempering at a moderate temperature. The heat treatment settings for hydrogen gas
vessels are chosen to limit the tensile strength (σuts) below 950 MPa and to achieve a homogenous
tempered martensite microstructure. Hydrogen gas distribution vessels are seamless, which means
the vessel body is constructed without welds. Since welding adds residual stress and modifies the
optimum steel microstructure created by quenching and tempering, hydrogen gas tanks are best
served by seamless construction. Hydrogen-assisted cracking has occurred in high-pressure
hydrogen gas vessels made of low-alloy steel welds.
B) Environmental Factors Influencing Steel Vessel in Hydrogen
Gas pressure influences the degree of hydrogen embrittlement in steel because it controls the
quantity of atomic hydrogen that dissolves in the material. In hydrogen distribution applications, the
usual working pressure range for steel vessels is between 20 and 30 MPa.
Impurities in both hydrogen gas and steel can cause localized corrosion on the inner surface of
hydrogen gas vessels. Although the relationship between localized corrosion and hydrogen
embrittlement is unknown, hydrogen embrittlement is known to be impacted by impurities in steel
and gas.[2]
C) Mechanical Factors Impacting Hydrogen Vessel Steel
Hydrostatic tensile stress raises the hydrogen concentration in metals in addition to gas pressure. As
a result, hydrogen embrittlement is encouraged at stress risers like flaws where there are high,
localized concentrations of atomic hydrogen. Hydrogen gas vessels may develop flaws on their
interior surfaces during production or service. Localized corrosion pits are one type of fault that can
appear during service. Cyclic stress is one of the worst mechanical loading conditions for steel
hydrogen gas tanks because it promotes the spread of fatigue cracks. During servicing, filling and
10
emptying vessels causes pressure cycling. Surface flaws have an impact on the
mechanical parameters in the wall of the steel vessel. Surface imperfections increase local strains,
which concentrate atomic hydrogen in the steel and act as a mechanical catalyst for the spread of
fatigue cracks. Hydrogen embrittlement works in tandem with cyclic stress to spread cracks. Fatigue
cracks attain a threshold length after a specific number of cycles of the vessel being filled and
emptied. Hydrogen embrittlement mechanisms, which function in a filled hydrogen vessel under
static pressure, can then cause the cracks to widen.
5.2. Pipelines for Hydrogen Gas
This summary pertains to hydrogen gas-carrying steel transmission and distribution pipe systems.
The industrial gas companies are currently running over 1000 miles of pipeline in the US and
Europe, and they have decades of experience with hydrogen gas transmission pipelines. These
pipelines have proven to be dependable and safe in a variety of material, mechanical, and
environmental circumstances.
A) Hydrogen-Related Pipeline Steel Material Conditions
Steel pipes have been safely used with hydrogen gas, but there are restrictions on the steel's
characteristics. Pipelines carrying hydrogen gas are specifically designed to use carbon steels with
relatively low strengths. Steels such as API 5L Grade X42 and API 5L Grade X52, as well as ASTM
A106 Grade B, have been demonstrated to be suitable for hydrogen gas service.
Tables 2 and 3 give the compositions of these steels. "Microalloyed" steels are API 5L steels that
have trace levels of titanium, vanadium, and niobium. Pipelines for hydrogen gas have made
considerable use of microalloyed X52 steel.[2]
Uniform, fine-grained microstructures are produced through processing of steel used in hydrogen
gas pipes. In typical steels, a normalizing heat treatment can produce the required microstructure.
Normalizing heat treatment for steel usually involves heating it in an austenite 8-phase field and
then cooling it with air. To create fine-grained microalloyed steels, a more advanced method of hot
rolling in the austenite-ferrite phase field is employed. One significant factor influencing the
hydrogen embrittlement of pipeline steels is material strength. Limiting strength is one of the guiding
concepts in the choice of steel grades and production techniques. For hydrogen gas pipeline steel,
the maximum tensile strength (σuts) that is advised is 800 MPa. Weld characteristics are
meticulously regulated to prevent hydrogen embrittlement. Stringent control of weld properties is
vital to prevent hydrogen embrittlement. The carbon equivalent (CE) is pivotal in determining weld
characteristics, influenced by carbon and manganese levels. Higher CE values heighten the risk of
martensite formation during welding, which is highly susceptible to hydrogen embrittlement.
Despite efforts to minimize CE values, welds often retain higher hardness than the surrounding
pipeline base metal, increasing susceptibility to hydrogen embrittlement. It's advisable to limit the
maximum tensile strength for welds to 800 MPa.
11
B) Environmental Impact on Pipeline Steel in Hydrogen
Pipeline steel's susceptibility to hydrogen embrittlement varies with gas pressure. Hydrogen
pipelines have operated at pressures up to 13 MPa. External corrosion can cause occasional leaks,
but concerns about its interaction with hydrogen embrittlement are minimal.
C) Mechanical Impact on Pipeline Steel in Hydrogen
Pipeline steel is subjected to static mechanical forces due to constant pressure in transmission lines.
While cyclic loading hasn't been problematic, hydrogen-assisted fatigue can occur in distribution
piping.[8] Defects from welds, corrosion, or third-party damage are monitored, as they intensify
mechanical stress and hydrogen concentration in the steel, especially at weld sites.
6. Vessels and Pipelines in Hydrogen Energy:
An unresolved question pertains to the suitability of current steel usage in hydrogen gas vessels and
pipelines for applications in the hydrogen energy infrastructure. This hinges on structural design
constraints and steel properties. The information provided indicates that while steels are viable
structural materials within certain operational limits, the envisaged hydrogen energy infrastructure
might subject vessels and pipelines to novel service conditions. For instance, hydrogen gas storage
and transportation may involve pressures exceeding current industrial standards. This aims to
delineate potential constraints on steel properties by illustrating hydrogen embrittlement
susceptibility trends concerning crucial material, environmental, and mechanical variables.
The hydrogen embrittlement data herein pertain to structural steels akin to those employed in
existing hydrogen gas vessels and pipelines. Particularly, the data selected correspond to steels with
relevant compositions, microstructures, and tensile strengths. Some instances feature data for steels
deviating notably from those utilized in gas vessels and pipelines, though still offering valuable
insights. Fracture mechanics data are chosen to elucidate hydrogen embrittlement trends, given their
relevance to structures containing defects and furnishing conservative indicators of fracture
susceptibility in hydrogen gas.[7]
12
While much of the data urges caution against extending current steels to unfamiliar operational
conditions, certain findings hint at possibilities for enhancing steel's hydrogen embrittlement
resistance.
CONCLUSIONOne possible approach to the large-scale, economical, and effective transportation of hydrogen is to
integrate hydrogen into the current natural gas pipeline network infrastructure. It's also a way to
boost renewable energy systems' production. But adding hydrogen to pipeline steels causes HE,
which poses a major risk to the pipes' ability to operate safely. Numerous studies on the transmission
conditions of natural gas blended with hydrogen have been carried out recently, however the findings
and conclusions of these studies are not always the same. Thus, more study is required prior to the
widespread commercial use of natural gas combined with hydrogen. This study presents the
mechanism and phenomena of hydrogen evolution (HE), with particular emphasis on the state of
HE research in the current generation of hydrogen-blended natural gas transportation systems.
Different impacts of blending hydrogen are shown in the mechanical characteristics of distribution,
storage, and compression systems.
The following recommendations are made to encourage the development of hydrogen-blended
natural gas transportation given the state of research at this time1) Currently, a lot of nations are marketing natural gas technology that is combined with hydrogen
in a preliminary way. Nonetheless, there are variations in the composition of natural gas, pipeline
operating conditions, and storage materials between nations. To create a theoretical foundation for
safe transportation, it is advised to research the HE of such systems in conjunction with the
advancement of hydrogen-blended natural gas technology in various nations.
(2) The natural gas pipeline network system may differ significantly depending on the hydrogen
content. In addition, the acceptable levels of hydrogen concentration vary throughout network
system infrastructures. As a result, a precise evaluation that takes into account the particular
circumstances must be made. It is advised that while introducing various hydrogen mixing ratios,
demonstration projects be constructed. To give guidelines for large-scale transmission, the effects
of various hydrogen blending ratios on the HE resistance of infrastructures should be studied.
(3) As the need for hydrogen energy rises, every network system unit must survive more harsh
service circumstances. As a result, the main issue that has to be resolved is how to increase the HE
resistance of materials. Currently, it is unclear how the HE process works and how different devices'
rules change under different service circumstances. Furthermore, there aren't many platforms
available for evaluating a material's resistance to HE. To enhance pertinent technical indicators, it is
recommended to consider each infrastructure's compatibility with hydrogen-blended natural gas,
user demand, the economy, and other aspects.
13
REFERENCES
[1] Hydrogen embrittlement in hydrogen-blended natural gas transportation systems: A review
Guanwei Jia a , Mingyu Lei a , Mengya Li a , Weiqing Xu b,e,* , Rui Li c , Yanghui Lu d , Maolin
Cai b,e
[2] EFFECTS OF HYDROGEN GAS ON STEEL VESSELS AND PIPELINES
Brian P. Somerday and Chris San Marchi Sandia National Laboratories Livermore, CA
[3] Xu W, Lu Y Research progress on hydrogen embrittlement in hydrogen exposure on the
mechanical properties 2022
[4]Sun B, Wang D Current challenges and opportunities towards understanding hydrogen
embrittlement
[5]Lynch S Hydrogen embrittlement phenomenon and mechanisms 2012 105-23
[6]Li X, Ma X , Zhang J. Review of hydrogen embrittlement in metals; hydrogen diffusion
[7]Quarton, C.J., Samsatli, S., 2021. How to incentivise hydrogen energy technologies for net
zero: Whole-system value chain optimisation of policy scenarios. Sustain. Prod. Consump. 27,
1215–1238
[8]Review article Safety of hydrogen storage and transportation: An overview on mechanisms,
techniques, and challenges Hao Li a , Xuewen Cao a,∗ , Yang Liu a , Yanbo Shao a,b , Zilong Nan
b , Lin Teng c , Wenshan Peng d,∗ , Jiang Bian a,∗