Hydrogen fuel cell technology joint should have four qualities
Time：2023-04-19
The physical and chemical properties of hydrogen itself are one of the most serious challenges in developing safe, reliable and hermetically-sealed hydrogen fuel cell vehicles and infrastructure.
Hydrogen is a small molecular gas. Hydrogen can easily escape through tiny cracks and diffuse into the material designed to hold it. In the transportation market, hydrogen also has to be stored at pressures in excess of 700 bar in order to achieve the necessary energy density in vehicles. At the fueling station, rapid temperature and pressure changes as hydrogen leaves the tank and depressurizes can also affect the integrity of the system.
These conditions highlight the importance of maintaining excellent performance in joints that connect key components of high-pressure hydrogen fuel systems. Joints used in hydrogen fuel cell technology must demonstrate a number of key characteristics to ensure long-term reliability. While traditional cone-threaded joints were used in these applications, higher performance joints are available today. In this article, we will delve into the design features of some specific joints that achieve the desired performance in hydrogen technology:
leakproofness
Considering that hydrogen can escape through very small openings, air tightness and leakage resistance are important performance indicators of the joint.
Reliable gas seal
Two contact zones, one along the casing and the other along the joint body, provide excellent sealing.
Many conventional bushing joints form a contact line seal on a narrow surface. While this seal is sufficient for many liquids and some gases, the tricky physicochemical properties of hydrogen pose a hazard once in use. Vibration can also be challenging for wire-sealed joints.
The better hydrogen containment seal design consists of two contact lines spanning the longer sealing surface, one along the casing and the other along the joint. These contact surfaces should be slightly inclined to provide better stress levels and maintain adequate sealing. This sealing integrity is achieved with a specific style of double sleeve joint.
grip
The joint's grip on the bushing is another key performance indicator, which ensures that the joint can withstand the high pressures required for hydrogenation and the violent vibrations that occur in a moving vehicle.
Grip performance up to 1050 Bar
The low temperature carburized and hardened sleeve enables high pressure levels, making it ideal for on-board and hydrogenation infrastructure hydrogen storage.
intransigence
Vibration resistance Swagelok FK Series bushing couplings maintain grip even under high vibration and load with dual bushing hinge clamping action.
The combined mechanical grip with two sleeves is the ideal design for the hydrogen joint to achieve a firm grip. The hardened front casing allows the joint to bite into the casing effectively, resulting in very high bearing capacity. At the same time, the unique rear sleeve design allows the joint to move a little in the joint (called "rebound") while maintaining the grip. This type of design achieves excellent vibration resistance and is ideal for on-board operations and in hydrogenation infrastructure, where compressors and dynamic conditions produce significant vibration.
The mechanical double sleeve design allows for springback and also helps the joint withstand drastic temperature changes that cause the material to expand or contract. During hydrogenation, the hydrogen temperature can vary from temperatures as low as -50ºC to ambient temperatures, resulting in problems with the performance of conventional conical threaded joints.
Easy to install
Correct joint design is essential for reliable performance. It could also lead to significant installation and assembly efficiency gains for hydrogen fuel cell vehicle manufacturers and hydrogenation infrastructure developers.
5 times faster installation
The innovative design enables faster installation speeds compared to conventional conical threaded joints. Pre-installed inserts enable the installer to use common tools and require only simple training.
Some available mechanical grip joints are designed with pre-installed inserts. This enables installers to use common tools and achieve fast, error-free installation with simple training. Innovative designs such as the Swagelok ® FK series connectors offer significant installation and assembly advantages over the traditional cone-threaded connectors used in conventional hydrogen refueling stations.
Reliable cone-threaded connections require specialized equipment, high installation skills, and typically up to five times longer installation and inspection times than Swagelok FK series products. Vehicle manufacturing is all about speed, and ease of installation is critical as hydrogen infrastructure scales up. The right joint technology speeds up installation and inspection.
Material integrity
Corrosion resistance is important in any application where the reliable performance of the casing joint is required. Corrosion occurs when metal atoms are oxidized by the fluid, resulting in material loss on the metal surface. This loss reduces the wall thickness of the component and makes it more prone to mechanical failure. In hydrogen transport applications, both vehicles and hydrogen pumps are often exposed to harsh weather conditions, making it particularly important that structural materials resist problematic corrosion throughout the life of the system.
In addition, hydrogen molecules can be adsorbed on the surface of stainless steel, and individual atoms can split apart. Its diameter is very small, so it diffuses into the austenite lattice formed from much larger atoms of iron, nickel, chromium, and molybdenum. Diffusion to 316/316L stainless steel is very slow, but after a long time under high pressure, a large number of hydrogen atoms will accumulate in the lattice. This phenomenon is called hydrogen embrittlement. Even in high concentrations, hydrogen atoms do not have any adverse effect on the strength of 316/316L. However, if there are fatigue cracks in the component, hydrogen atoms will make it easier for these cracks to spread and propagate through the component. In the long run, low-performance alloys may be more susceptible to this problem.
Higher levels of chromium and nickel in fluid system components can help resist common corrosion and hydrogen embrittlement by maintaining greater ductility of key components. The American Society for Materials and Testing (ASTM) requires that the nickel content in 316 stainless steel be at least 10%. However, it turns out that high-quality 316 stainless steel with a minimum nickel content of 12% is better suited to the unique challenges of hydrogen.
Meet the needs of hydrogen systems
Although there are a variety of compression bushing joints and other styles that may be suitable for hydrogen fuel systems, few products are designed to meet the many unique performance requirements required for hydrogen applications.
Swagelok's FK series connectors are an exception. With its patented design, EC-79 and EIHP certifications and pressure ratings up to 1551 bar, the FK series is designed for hydrogen applications. Made from 316 stainless steel with a minimum nickel content of 12%, the series has been used in a wide variety of industries and applications since its launch and remains the best choice for today's '- and tomorrow's - vehicles and infrastructure.
The long-term viability of hydrogen transportation will depend on safe, reliable and durable hydrogen fuel cell vehicles and infrastructure. Selecting and specifying appropriate components for critical systems can help achieve these goals. Interested in learning more? Contact Swagelok today to discuss how we can help meet your shipping needs.
Hydrogen is a small molecular gas. Hydrogen can easily escape through tiny cracks and diffuse into the material designed to hold it. In the transportation market, hydrogen also has to be stored at pressures in excess of 700 bar in order to achieve the necessary energy density in vehicles. At the fueling station, rapid temperature and pressure changes as hydrogen leaves the tank and depressurizes can also affect the integrity of the system.
These conditions highlight the importance of maintaining excellent performance in joints that connect key components of high-pressure hydrogen fuel systems. Joints used in hydrogen fuel cell technology must demonstrate a number of key characteristics to ensure long-term reliability. While traditional cone-threaded joints were used in these applications, higher performance joints are available today. In this article, we will delve into the design features of some specific joints that achieve the desired performance in hydrogen technology:
leakproofness
Considering that hydrogen can escape through very small openings, air tightness and leakage resistance are important performance indicators of the joint.
Reliable gas seal
Two contact zones, one along the casing and the other along the joint body, provide excellent sealing.
Many conventional bushing joints form a contact line seal on a narrow surface. While this seal is sufficient for many liquids and some gases, the tricky physicochemical properties of hydrogen pose a hazard once in use. Vibration can also be challenging for wire-sealed joints.
The better hydrogen containment seal design consists of two contact lines spanning the longer sealing surface, one along the casing and the other along the joint. These contact surfaces should be slightly inclined to provide better stress levels and maintain adequate sealing. This sealing integrity is achieved with a specific style of double sleeve joint.
grip
The joint's grip on the bushing is another key performance indicator, which ensures that the joint can withstand the high pressures required for hydrogenation and the violent vibrations that occur in a moving vehicle.
Grip performance up to 1050 Bar
The low temperature carburized and hardened sleeve enables high pressure levels, making it ideal for on-board and hydrogenation infrastructure hydrogen storage.
intransigence
Vibration resistance Swagelok FK Series bushing couplings maintain grip even under high vibration and load with dual bushing hinge clamping action.
The combined mechanical grip with two sleeves is the ideal design for the hydrogen joint to achieve a firm grip. The hardened front casing allows the joint to bite into the casing effectively, resulting in very high bearing capacity. At the same time, the unique rear sleeve design allows the joint to move a little in the joint (called "rebound") while maintaining the grip. This type of design achieves excellent vibration resistance and is ideal for on-board operations and in hydrogenation infrastructure, where compressors and dynamic conditions produce significant vibration.
The mechanical double sleeve design allows for springback and also helps the joint withstand drastic temperature changes that cause the material to expand or contract. During hydrogenation, the hydrogen temperature can vary from temperatures as low as -50ºC to ambient temperatures, resulting in problems with the performance of conventional conical threaded joints.
Easy to install
Correct joint design is essential for reliable performance. It could also lead to significant installation and assembly efficiency gains for hydrogen fuel cell vehicle manufacturers and hydrogenation infrastructure developers.
5 times faster installation
The innovative design enables faster installation speeds compared to conventional conical threaded joints. Pre-installed inserts enable the installer to use common tools and require only simple training.
Some available mechanical grip joints are designed with pre-installed inserts. This enables installers to use common tools and achieve fast, error-free installation with simple training. Innovative designs such as the Swagelok ® FK series connectors offer significant installation and assembly advantages over the traditional cone-threaded connectors used in conventional hydrogen refueling stations.
Reliable cone-threaded connections require specialized equipment, high installation skills, and typically up to five times longer installation and inspection times than Swagelok FK series products. Vehicle manufacturing is all about speed, and ease of installation is critical as hydrogen infrastructure scales up. The right joint technology speeds up installation and inspection.
Material integrity
Corrosion resistance is important in any application where the reliable performance of the casing joint is required. Corrosion occurs when metal atoms are oxidized by the fluid, resulting in material loss on the metal surface. This loss reduces the wall thickness of the component and makes it more prone to mechanical failure. In hydrogen transport applications, both vehicles and hydrogen pumps are often exposed to harsh weather conditions, making it particularly important that structural materials resist problematic corrosion throughout the life of the system.
In addition, hydrogen molecules can be adsorbed on the surface of stainless steel, and individual atoms can split apart. Its diameter is very small, so it diffuses into the austenite lattice formed from much larger atoms of iron, nickel, chromium, and molybdenum. Diffusion to 316/316L stainless steel is very slow, but after a long time under high pressure, a large number of hydrogen atoms will accumulate in the lattice. This phenomenon is called hydrogen embrittlement. Even in high concentrations, hydrogen atoms do not have any adverse effect on the strength of 316/316L. However, if there are fatigue cracks in the component, hydrogen atoms will make it easier for these cracks to spread and propagate through the component. In the long run, low-performance alloys may be more susceptible to this problem.
Higher levels of chromium and nickel in fluid system components can help resist common corrosion and hydrogen embrittlement by maintaining greater ductility of key components. The American Society for Materials and Testing (ASTM) requires that the nickel content in 316 stainless steel be at least 10%. However, it turns out that high-quality 316 stainless steel with a minimum nickel content of 12% is better suited to the unique challenges of hydrogen.
Meet the needs of hydrogen systems
Although there are a variety of compression bushing joints and other styles that may be suitable for hydrogen fuel systems, few products are designed to meet the many unique performance requirements required for hydrogen applications.
Swagelok's FK series connectors are an exception. With its patented design, EC-79 and EIHP certifications and pressure ratings up to 1551 bar, the FK series is designed for hydrogen applications. Made from 316 stainless steel with a minimum nickel content of 12%, the series has been used in a wide variety of industries and applications since its launch and remains the best choice for today's '- and tomorrow's - vehicles and infrastructure.
The long-term viability of hydrogen transportation will depend on safe, reliable and durable hydrogen fuel cell vehicles and infrastructure. Selecting and specifying appropriate components for critical systems can help achieve these goals. Interested in learning more? Contact Swagelok today to discuss how we can help meet your shipping needs.