Valve design considerations in liquid hydrogen systems to prevent failure

Hydrogen has potential as an alternative source of energy (energy carrier) because it can be converted, stored, and used efficiently, with a wide range of applications. It can be created from renewable energy sources and can thus serve as storage of renewable energy like wind- and sun-power. It shall be noted that Hydrogen liquefies at -252.9 °C, so cryogenic systems and sophisticated insulation techniques are necessary. Control of the flow has always been carried out by valve assemblies in processing plants. The proper design of industrial valves in every industry, including hydrogen systems, can significantly improve the safety and reliability of the valves specifically, as well as the plant as a whole. An overview of various previous studies is presented in this paper, discussing important design concepts for cryogenic valves. The main research question is to determine what are the main design considerations for valves used in liquid hydrogen systems, to minimize the risk of leakage from the valves to ensure required safety. In this study, different aspects of valve design for liquid hydrogen are examined, such as selection of steel materials, steel wall thickness calculations, stem design, sealing material selection, fire-safe design, cavity over-pressure protection, and body and bonnet extension.


Introduction
The decarbonization of the energy sector plays an important role in reducing greenhouse gas emissions towards establishing a zero-carbon society. Hydrogen is considered a promising alternative source of energy (energy carrier) that can be converted, stored, and utilized efficiently, offering a wide range of potential applications in the future [1]. Hydrogen has been proposed as a synthetic fuel or energy carrier during the post-fossil fuel era [2]. In addition, hydrogen has the potential to generate electricity and power systems [3]. There are many advantages associated with hydrogen as an energy source. As well as being relatively inexpensive to produce, it is capable of being converted into a variety of energy forms at the consumer end with much greater efficiency than other fuels; it is renewable, simplest and the most abundant element in the universe; [4,5]. and cooling, the liquefaction processes employ a combination of compressors, heat exchangers, expansion engines, and throttle valves. The simplest liquefaction process is the Linde cycle or Joule-Thomson expansion cycle [9][10][11]. The use of liquid hydrogen presents several challenges, including its extremely low temperature, which is referred to as cryogenic. In order to support the development of liquid hydrogen technology, an infrastructure for the production and transportation of the liquid hydrogen is needed [12]. The term piping refers to a system of pipes used to transport fluids from one place to another. Piping and valves are an integral part of any process plant in every industry, including liquid hydrogen production and transportation; therefore, they should be designed with precision. In order for a plant to function efficiently, it must be able to transport fluid through pipes to various equipment that work together [13]. Fig. 1 illustrates the liquid hydrogen phase diagram. At standard conditions, hydrogen exists as a gas. However, at very low temperatures and/or high pressures, the gas becomes a liquid or solid. The hydrogen phase diagram illustrates the phase behaviour with changes in temperature and pressure. According to the curve between the critical point and the triple point, the hydrogen boiling point decreases as pressure increases. Additionally, it shows the saturation pressure as a function of temperature.
In different industries, such as in the hydrogen industry, valves are, therefore, essential components of the piping systems. They are used for stopping and starting of fluid flow, fluid flow control, flow regulation, and backflow prevention [14][15][16][17]. In the hydrogen industry, various valve types, as shown in Table 1, are used, including ball, gate, butterfly, globe, and check valves. Figure 2 shows a cryogenic wedge gate valve used for stopping and starting the flow. A list of the valve's main parts, as well as its materials, can be found in Table 2. Materials selected for the valve in Fig. 2 can withstand temperatures as low as -252.9 °C. Failure of industrial valves to function due to various factors such as corrosion and mechanical malfunction is a significant risk with adverse consequences, including environmental pollution, assets loss, production losses, and even human death in case of release of toxic gases, fires or explosions [17,18]. In fact, valves are used within pipes to produce or transport products and are vital because, if they fail, the entire process could be interrupted [19].

Research problem, contribution, novelty and motivation
The Health and Safety Executive has asked the Health and Safety Laboratory to identify and address issues related to bulk liquid hydrogen transportation and storage and to update/develop guidelines for such facilities [20]. The primary conclusion of this study is that liquid hydrogen applications present additional fire and explosion risks in comparison to the use of hydrogen in gaseous form, which must be taken into consideration. The safety level of handling liquid hydrogen is comparable to that of fuels such as petrol and liquefied petroleum gas. With air, hydrogen readily forms an explosive mixture and the amount of energy required to initiate a hydrogen/air explosion is very small. An ignition energy of only about 0.02 mJ is required for a 2:1 mixture of hydrogen and oxygen [21]. This is less than one tenth of the cost of other fuels, such as methane, liquified petroleum gas (LPG) or gasoline [21]. It is critical to note that hydrogen gas has a very low viscosity, so it is very difficult to prevent leaks from developing in hydrogen systems. It is not unusual for pipes and valves that are leak-tight when pressure-tested with nitrogen to leak profusely when used with hydrogen. Hydrogen leakage through welds, flanges, seals, gaskets and other components of piping and valve systems is an important consideration for hydrogen systems during design and operation [22]. The other risk with hydrogen leak is related to its high diffusivity. Hydrogen diffuses more quickly through air and solid materials than other fuel gases such as methane or propane, so if released, it is more likely to disperse quickly and become a greater threat [23]. A topic of great interest in many industrial applications is hydrogen embrittlement (HE) of steels [24]. In fact, hydrogen can cause embrittlement of high strength steels, titanium alloys, and aluminium alloys, resulting in cracking and catastrophic failure of the metals at stress levels below the yield stress [25]. The facilities used for the production, transportation, and storage of liquid hydrogen must be safe [26]. One past study has focused on the risk assessment for liquid hydrogen facilities through various risk techniques such as failure mode and effect analysis (FMEA) and a hazard and operability study (HAZOP) [26].
There have been studies conducted in the past on the design of essential valves for cryogenic use in general and for liquified natural gas (LNG) in particular, but none of them have addressed valves for liquid hydrogen [27][28][29][30][31]. The first study referred to, examines the thermal conductivity 1 3 a high-pressure cryogenic ball valve under conditions of -196°C against stresses, deformations, and vibrations during the early stages of engineering design? [29]. The concept behind the second study is to determine the structural integrity and operability of the cryogenic ball valve through numerical finite element analysis [29]. In contrast to the previous reviews that analyzed only the metallic parts of cryogenic valves, the third study proposes a laminated seal for triple offset butterfly valves in LNG plants [30]. The primary research question involves the design and validation of a seal for triple offset butterfly valves in an LNG marine plant operating at a temperature of -196°C [30]. The key idea of this paper is to design and validate an optimized seal by considering the effects of design parameters such as pressure and temperature in order to improve sealing performance [30]. The critical theory or model for design validation of the seal is FEA, as in the previous study [30]. This study concluded that the LNG butterfly valves should be sealed using a laminar seal, including a layer of austenitic stainless steel and a layer of graphite [30]. In general, both austenitic stainless steels and graphite are suitable for cryogenic applications. Testing of the tightness of the optimized designed seal by air for the butterfly valve was successful [30]. Another study focused on the design and development of austenitic stainless-steel check valves for cryogenic applications [31]. In piping systems, check valves serve as non-return valves in order to prevent backflow [33,34]. Different challenges are associated with design of check valves in cryogenic services, such as different thermal expansion rates between the valve parts that may lead to leakage from of a small-sized globe valve operating in LNG at a temperature of -169°C [27]. Globe valves are widely used in flow regulation in the oil and gas industry [32]. This study [27]. employs thermal analysis of the bonnet of a globe valve in 1/2" with ANSYS software to observe and calculate the thermal deformation and temperature distribution. This research relies heavily on finite element analyses (FEA).
The temperature values obtained at two different points on the valve's bonnet are compared with those obtained during actual experiments [27]. It is found that the analysis temperature is close to the actual measurement temperature [27]. Consequently, the FEA method, thermal values, and stresses are validated by actual experimentation. Figure 3 illustrates the results of FEA in the form of thermal analysis of a cryogenic valve installed at an LNG plant [28]. According to the figure, all valve components have been subjected to thermal analysis. It can be seen in the illustration that the top part of the valve where the handwheel is installed is red, which indicates that the temperature is above 0°C. The handwheel area that may come into contact with an operator's hand must remain above 0°C to prevent skin tissue damage to the operator. However, onsite personnel must wear personal protective equipment (PPE) such as gloves to prevent possible damage to their skin or other organs. Essentially, the objective of the first study was to evaluate the cryogenic thermal effect on different points of the valve bonnet [27].
More or less the same concept is addressed by the second reviewed paper regarding the analysis and design of cryogenic ball valves [29]. In the second study, the main question examined was how to prove the structural integrity of leakage. As a result of cryogenic fluid, loads and stresses, and corrosion, the design of cryogenic valves is very important to prevent valve failure [35]. Ensuring the safety and reliability of piping and valves connections, especially those carrying cryogenic and flammable fluids like liquid hydrogen, is essential for reducing the operational cost (OPEX) of piping and valves and increasing their lifetime during the project. Hence, the aim of this paper is to focus on essential design considerations for liquid (cryogenic) hydrogen valves to avoid valve failure and leakage.
In order to achieve this aim, the following objectives and steps should be taken. Note that the study objectives listed below are closing those gaps identified from previous studies.
Ø Cryogenic valve body and bonnet extensions are designed to keep the packing and the operator away from the cryogenic fluid when the temperature is above 0 °C; Ø Design of stem seals to prevent external leakage into the environment; Ø Calculation of body and bonnet wall thicknesses to ensure that pressure containing parts do not leak; Ø Robust connections between the body and the bonnet or body pieces to prevent leakage through the body and the bonnet or body pieces; Ø Fire-safe design to enhance the functionality of the valve during a fire; Ø Determination of stem length as part of stem design to prevent buckling of stems or failure due to torsion; Ø A cavity relief mechanism to protect the valve from over-pressurizing in the cavity; Ø A robust design prevents cavitation in globe valves that control the flow of liquids and gases. Fig. 4 summarizes the research question, aim, and objectives

Methods and materials
It is undeniable that international and national standards play a significant role in the design of industrial valves. Many of essential design requirements for cryogenic valves in liquid hydrogen are extracted from cryogenic valve standards listed below: International Organization of Standardization (ISO) 28921 [ [38].] : Industrial valves -Isolating valves for low temperature applications, Part 1: Design, manufacturing and production testing.
the valve, providing a satisfactory seal between the disk and seat that is exposed to metal-to-metal contact, and finally, functional requirements that may be subject to high number of cycles (opening and closing). To resolve the first issue, all of the main components of the valves, including the disk, seat, and body, are made from the same material. It is possible to perform very precise machining between the disk and seat to prevent internal leakage. In order to determine a valve's functionality in the operating condition, a cycle test can be performed to simulate valve opening and closing. Nevertheless, based on the experiences of the present authors, there should be a lot of similarities in the design of cryogenic valves, regardless of whether they are used for LNG or liquid hydrogen. There are, however, many parameters that must be considered when designing valves for liquid hydrogen to prevent hydrogen leakage and fire hazards that are not addressed in any study. The main research question is therefore, what are the most important design considerations for valves that must be taken into account for liquid hydrogen service to prevent leakage, fires, and explosions?
Based on the literature review, it appears that the following is already known about cryogenic valves including information regarding valves for liquid hydrogen.

Research aim and objective
There have been previous discussions regarding the safety and reliability of industrial valves [14][15][16][17][18]. It is important that cryogenic valves are designed, manufactured, selected, and used so that cryogenic gases, including hydrogen, can be transported and stored safely and efficiently. Due to the extreme coldness and flammability of liquid hydrogen, care must be taken in the design and selection of valves in order to prevent the leakage of cryogenic fluids. In addition to being hazardous, cryogenic fluid leakage can also be economically costly. In addition to the cost of the fluid, the conversion process is also considered in the cost of cryogenic fluid environment [28]. The effect of cryogenic fluid on the skin is similar to that of thermal burns. Particularly, it may result in frostbite, a condition in which the skin becomes very red, cold, and numb, followed by paleness, hardness, and numbness [41,42]. The operator of a manual valve, such as a lever or handwheel, must maintain a safe distance from the flow of cryogenic fluid inside the valve in order to avoid serious injury [36]. As shown in Fig. 5, a cryogenic wedge gate valve has heat, cryogenic, and atmospheric zones. There is normally a layer of ice on the surface of the cryogenic zone at the bottom of the valve, formed by the flow of cryogenic material. In addition to the bottom and middle of the extended bonnet, there is a cryogenic zone that surrounds the valve body. Between the cryogenic and atmospheric zones lies the second zone, the heat zone. This section is directly exposed to the atmosphere on the upper bonnet extension. Since this area is separated from the cryogenic material flowing inside the valve, it is less affected by ice and has a lower cryogenic temperature than the lowest area. The third and final section is the atmospheric zone. The • International Organization of Standardization (ISO) 21,011 [40].: Cryogenic vessels -Valves for cryogenic service. • British Standard (BS) 6364 [36].: Specifications for valves for cryogenic service. • European Standard (EN) 12,567 [39].: Industrial valves -Isolating valves for LNG -Specification for suitability and appropriate verification tests.
As well as standards, this paper refers to existing literatures on valve design that have been published in industrial and scientific journals. Here are some considerations for cryogenic liquid hydrogen valve design that are emphasized as the objectives of this study:

Extended bonnet and stem
The first element of the cryogenic valve design for liquid hydrogen is the need for an extended bonnet and stem to protect the seals and the valve operator from the cryogenic Nevertheless, none of these seals can be used at cryogenic temperatures. For cryogenic valves, different methods of stem sealing are available. A lip seal is typically made of Teflon and a metallic spring and is suitable for cryogenic temperatures as low as -252.9 °C [45,46]. Graphite is another material suitable for cryogenic temperatures. For the stem sealing of liquid hydrogen cryogenic valves, valve engineers can choose graphite packing [35,43]. PTFE is a very common soft material for seats of industrial valves in the oil and gas industry. However, since the minimum temperature for Polytetrafluoroethylene (PTFE) is -46℃ according to some standards and specifications such as NORSOK (Norwegian petroleum standards), [35,44,[48][49][50]. Cryogenic hydrogen valves do not commonly use PTFE as a non-metallic material. If PTFE is reinforced with graphite or fiberglass, the minimum temperature can be reduced to -150 °C [35,44,48,49]. Therefore, reinforced PTFE, which is known as Reinforced Polytetrafluoroethylene (RPTFE), can be used in cryogenic (liquid) hydrogen service for the soft seats of ball and butterfly valves. PCTFE (polychlorotrifluoroethylene) is an alternative material for cryogenic applications, including liquid hydrogen [35,44]

Body and bonnet wall thickness
It is possible for leaks to occur when the bodies and bonnets of valves are not sufficiently thick, resulting in health, safety, and environmental risks. Cryogenic valves must packing area and the handwheel are included in this section. In this area, the atmospheric temperature is high due to its proximity to the cryogenic zone. As a result, no ice forms in the atmospheric zone, and the existing ice is converted to vapor. It is possible to determine the length of the extended bonnet and stem using a cryogenic valve standard. Using the finite element method (FEM), the valve manufacturer may conduct a heat transfer analysis on the valve using the finite element method (FEM) [27,35]. For evaluating the distribution of temperature values on different parts of the cryogenic valve, including the bonnet and stem extensions, the valve manufacturer may consider various parameters, such as thermal conductivity coefficient, cryogenic temperature, thermal conductivity area, and surface [27,35].

Seal material selection
In order to reduce fugitive emissions, or emissions coming from industrial valves, including cryogenic hydrogen valves, the stem seals must be able to seal effectively and have a long life [43][44][45][46]. A valve leak can be classified as an internal leak from the valve seat and an external leak from the stem seal area. It is more hazardous to have external leakage from the stem seal area since it may contact personnel working in the valve area or could leak into the environment. For non-cryogenic applications, elastomeric seals such as nitrile rubber, hydrogenated nitrile and silicon, and Viton are commonly used to seal valve stems [43][44][45][46][47].

Equation 1: Minimum valve wall thickness calculation
Where: P C : designation number for the valve pressure class (e.g., for class 150, P C = 150 and for class 300, P C = 300) D Valve inside diameter (mm/inch); S F : Constant value equal to 7,000; T Thickness of the valve (mm/inch); meet American Society of Mechanical Engineers (ASME) B16.34 requirements for thickness, including the extension of the bonnet, as set forth in MSS SP 134, ISO 28921-1, and ISO 21,011 [51,52]. An alternative method for determining the minimum wall thickness of valves is provided in ASME B16.34, mandatory appendix VI. In this method, the internal diameter and pressure class of the valve are taken into account. A summary of the fundamental equations for calculating minimum wall thickness is found in ASME B16.34, mandatory appendix VI, Table 3. Based on mandatory appendix VI, Table 3 provides values for the wall thickness. There is a great deal of conservatism in these values. In these circumstances, the wall thickness values provided for valves are relatively large, resulting in heavier and bulkier valves. Due to this, ASME B16.34 specifies another method of calculating valve wall thickness based on Eq. 1 [51,52].   [35,51] 55]. One of the fire-safe features relates to a valve that seals once its soft seat is melted during a fire [35,55]. Secondly, the valve's soft materials, particularly the seals, should be made from fire-resistant materials such as graphite [35,55]. Lastly, electrical continuity is a key element of fire-safe valve design. In order to accomplish this, anti-static devices or springs can be used [35,55].

Stem design
It was explained in previous sections that the stem of a cryogenic valve is extended in all services, including liquid hydrogen, thereby increasing its length as well. Stem buckling and misalignment are caused by increasing stem length, parameter L. In the industrial practices, for gate and globe valves with linear stem motion, the stem design is emphasized in order to prevent buckling. As illustrated in Fig. 6, buckling occurs when a component, such as a bar or pipe, deflects or deforms under compression [35].
The ratio of stem length to diameter, known as parameter L D ,has a direct effect on buckling: the more value of L D ratio, The greater the likelihood of buckling.
According to MSS SP134 [37]., gate and globe valves with a stem-disk connection by using the stem nut, must have a limited stem length to diameter ratio in a closed position according to Eq. 2 [56].

Equation 2: Stem-guided disk globe and gate valve length-to-diameter ratio in a closed position
Where:

Body and bonnet connection
It is possible to connect the valve body and bonnet using bolts, welding, or threading, with or without a seal weld and union. Most standards allow bolted and welded body and bonnet joints for cryogenic hydrogen valves. [36,37,38,39,340] Threaded joints may be acceptable provided they are sealed welded; however, the authors do not recommend threaded joints even if they are sealed welded [36,37]. This type of valve features a bolted body and bonnet design in which the body and bonnet are flanges that are attached by bolts and nuts; between the body and bonnet is a gasket that prevents leakage. The bolted connection between the body and bonnet allows valve maintenance to be carried out. However, the main disadvantage of a welding connection is that the valve body and bonnet cannot be disassembled for maintenance or any other reason. It is also necessary to apply a post-weld heat treatment to the welding, as stipulated in ASME boiler and pressure vessel code (BPVC), section VIII, division. 01, rules for pressure vessel assembly [35,52]. The Post weld heat treatment (PWHT) method of welding involves heating a welded material to a temperature below its critical transformation temperature and maintaining that temperature for a specified time following the welding procedure [35,53]. During welding activities, PWHT is primarily intended to reduce residual stress caused by residual heat. There is a term called residual stress that refers to stresses that remain in the material after welding and can cause cracking, brittle fractures, and ultimately failure of the weld [35,53]. PWHT also has the advantage of controlling hardness and even enhancing the strength of the material [35,53]. The other essential post-welding requirement, as per ASME B16.34 standard, [51]. is to perform a non-destructive testing (NDT) of the welds, as per ASME boiler and pressure vessel code (BPVC) section VIII div. 01, in order to enhance the welding joint efficiency [52].

Fire safe design
It is possible to ignite liquid hydrogen with only a small amount of energy when it is mixed with air [63]. This material has explosive properties as well as extreme low temperatures, making it extremely difficult to handle in a safe manner [54]. As a result of the use of liquid hydrogen, which is a flammable liquid, many cryogenic valves require a fire-safe design [54,55]. Oil and gas plants are highly susceptible to fires and explosions. Preventing fires is the best safety measure [55]. Fire prevention strategies may, however, not be effective in all cases, and fires may still occur. It is therefore important to design and test valves in order to ensure their fire resistance [35,55]. A fire-safe valve should incorporate three main design characteristics [35,

Cavity relief mechanism
Body cavity or body/bonnet cavity refers to the space between a valve's body and/or bonnet (see Fig. 7) [37].
There are some valves that don't have a body cavity; for example, butterfly valves don't have body cavities [37]. A body cavity is present in wedge-gates, slab-gates, expanding-gates, and ball valves. Fig. In Fig. 6, the fluid pressure inside the cavity exerts force on the valve body. A piping or pipeline valve shall not have a cavity pressure exceeding 133% of the valve's pressure rating at its maximum specified design temperature, in accordance with API 6D [57]. EN 12,567, the standard for LNG isolation valves, states that "The valve shall be designed in such a way that LNG cannot be trapped in any cavity." [39]. In the authors' opinion, liquid hydrogen should not be trapped in the cavities of valves in liquid hydrogen. According to the same standard, LNG shall not be released into the atmosphere under any circumstances [39]. There is an instruction in MSS SP 134 that states, "The manufacturer must provide a vent hole in the closure member to prevent over-pressurization of the body/bonnet extension cavity." [37]. If a ball valve is used, the hole could be drilled in the ball, whereas a gate valve would require drilling in the wedge or disk [37].

Cavitation
There are some valves designed to control flow, also known as regulating or throttling fluid flow [60,61]. A flow control valve adjusts the amount of flow passing through the valve and changes the flow rate within a valve; this has an impact L = Distance between the upper stem guide and the interface between the stem and the disk that is not supported (meters/inches). d = Diameter of the stem (meters/ inches). E = Modulus of elasticity of stem material that is typically expressed in pound per square inch (psi)/pascal. S P L = Material proportional limit, which is generally less than yield strength of the material (psi/pascal). N = 2. When a gate valve or globe valve has a body-guided disk/gate connection, the stem length to diameter ratio in the closed position should be determined by Eq. 3.

Equation 3: Body-guided disk/gate globe and gate valve stem length to diameter ratio in the closed position
Unlike ball, butterfly, and plug type valves, quarter turn valves do not apply axial (linear) loads to their stems, which prevent them from buckling. To prevent excessive stem torsional deflection, the stem length to diameter ratio is critical in quarter turn valves. It is important to note that the source of the axial force and torque on the stem is either the operator's hand or an automatic actuator. According to a MSS SP 134 standard requirement, the stem length and diameter combination of a quarter turn valve should limit the stem torsional deflection or angle of twist to π 90 or 0.0349 radian or 2 degrees. Equation 4 determines the angle of twist.  In addition to stem design to prevent buckling and torsion, the one-piece long stem construction and the antiblowout feature are essential considerations. In order to prevent stems and shafts from being ejected when the sealing or operating devices are removed from the valve, the valve must be designed in such a way that they cannot be ejected [35]. The requirement is a valve-stem safety feature designed to prevent the valve stem from being blown out by Fig. 7 The entry of fluid into the cavity of a gate valve [37] the authors provide recommendations on cryogenic valve design requirements and considerations. In order to prevent seals and valve operators from being exposed to cryogenic environments, cryogenic valves are designed with extended bonnet and stem conditions. Extreme cold temperatures limit the choice of materials for soft seals and seats to graphite, lip seals, Kel-F, and Reinforced Polytetrafluoroethylene (RPTFE). Calculating valve wall thickness in accordance with ASME B16.34 directly impacts structural integrity and load analysis results. Bolts or welding connect the body and the bonnet. Fire safety is another major consideration in cryogenic valve design, which improves their reliability, safety, and functionality. Additionally, the valve stem should be robust against buckling and torsional loads. To prevent overpressure situations in the valve cavity, a cavity release mechanism is required. When compared to cryogenic valves used in LNG, cryogenic hydrogen valves require more robust materials that can withstand lower cryogenic temperatures. Due to the possibility of lower temperatures, cryogenic valves used in cryogenic hydrogen may require longer stem and bonnet extensions than cryogenic valves used in LNG services [64]. As a result, accurate stem analysis is more critical for liquid hydrogen valves in order to prevent stem buckling and torsion [64]. A few modifications or alternations are suggested to prevent cavitation in globe valves in the study. Future studies are recommended in the next section.

Recommendations of additional work
A couple of studies are recommended by the present author for the future: • A review on the material selection of metallic parts of cryogenic valves in liquid hydrogen fluid. • A review of required tests for cryogenic hydrogen valves to validate their design and improve the safety and reliability. • Review of the thermal insulation of cryogenic valves in liquid hydrogen.
Acknowledgements Not applicable to this paper.
Author contribution Liquid hydrogen research and the first part of the manuscript were mainly conducted by professor Gudmestad, whereas Karan Sotoodeh focused on liquid hydrogen valves.
Funding The authors have no relevant financial or non-financial interests to disclose.
Code or data availability Not applicable to this paper.
on other parameters of the fluid process, such as temperature, pressure, and level [60,61]. Globe valves have been widely used in different sectors of the oil and gas industry for flow control. There are some globe valves with the T-pattern (or tee pattern) that may be used for liquid hydrogen services. In this type of valve, the pressure can drop below the vapor pressure of the liquid, causing bubbles to form [60,61]. The bubbles of gas that are separated from the liquid in the narrow area due to the highpressure drop can regain their pressure and collapse firmly in a manner that produces pressure waves. This phenomenon is referred to as cavitation and it can damage the globe valve's internals including seats and plugs [60,61]. Cavitation can be considered a type of corrosion; it may cause metal loss or create pits on the valve trims (internal) [60,61]. In 2013, the American Petroleum Institute (API) released the first edition of its new globe valve design standard (API 623) to control and avoid operating problems associated with globe valves, such as cavitation, vibration, and leakage [62]. API 623 specifies hard facing with stellite 6 or other hard alloys for the seat, the plug, and the guided disk, especially in high pressure classes. In API 623, the stem diameter of the valves is larger than that of standard valves and the connection between the plug and the stem is stronger to minimize the effect of cavitation [62]. Despite API 623 standard recommendations, some end users (like Equinor) may prefer to switch from t-type globe valves to y-type or axial valves, which are less susceptible to cavitation.

Conclusion
Since hydrogen can be converted, stored, and utilized efficiently, it is considered by many to be a promising alternative source of energy (energy carrier). A long storage period, long transport distances, and economic viability make liquid hydrogen attractive, providing sufficient safety can be assured. Hydrogen, liquefies at -252.9 °C, which is why cryogenic systems and sophisticated insulation are required. In processing plants, especially in liquified (cryogenic) hydrogen units, valve assemblies are used for a variety of purposes, including flow control and isolation. As its name suggests, cryogenic valves are used in freezing applications. In order to prevent freezing fluid leakage, liquid hydrogen should be designed and selected carefully. The essential design concepts for cryogenic valves are discussed in this paper, which reviews several past studies. The topics include thermal analysis and temperature distribution analysis in cryogenic globe valves, finite element analysis for ball valves, laminated seats for cryogenic butterfly valves with triple offset, and cryogenic check valve design challenges. Based on international standards and practical experience,