Components Designed for Hydrogen Reliability

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Whether hydrogen achieves its full potential as a clean energy solution depends on many factors, but the one that is especially critical is reliable containment from production to transport to dispensation. That reliability hinges on overcoming two big challenges:

• Size. Hydrogen is one of the smallest molecules found in nature, posing a unique challenge for infrastructure designers. Hydrogen gas can escape from even the smallest connection gaps, leading to leaks and safety concerns. Further, hydrogen atoms can diffuse into metals, leading to a phenomenon known as hydrogen embrittlement and hydrogen-induced cracking.
• High-pressure storage requirements. High-containment pressures (875 bar) require high-performance components where traditional options simply are not suitable. Pressure changes during fluid transfer can also lead to extreme thermal changes, requiring further integrity from containment materials.

Hydrogen Fitting Solutions for Clean Energy Systems

Optimized tube fittings specifically for hydrogen applications offer a reliable path forward. Designed for seal tightness, grip strength, vibration resistance, and material integrity, these fittings address hydrogen’s unique containment demands. With efficient installation and long-term durability, they empower professionals to scale operations safely, confidently, and sustainably. Swagelok FK series fittings are designed specifically to achieve reliable performance, minimal maintenance, and outstanding safety in clean energy applications. Distinct from the standard Swagelok^® tube fitting, FK series fittings meet the needs of the hydrogen landscape.

Today’s Clean Transportation and Hydrogen Mobility Landscape

While electric vehicles (EVs) tend to dominate the clean energy transportation discourse, they face significant limitations that hydrogen can overcome. Onboard hydrogen storage enables vehicles—both passenger and commercial—to achieve extended range. Meanwhile, refueling is comparable to typical gasoline or diesel engine applications, requiring just a few minutes. And as the hydrogen infrastructure ramps up, economies of scale will likely lead to competitive pricing.

That means hydrogen is poised for significant growth, and professionals in this space require the right technologies to seize the opportunity.

Unique Considerations for Hydrogen Storage and Containment

The very nature of hydrogen itself as a small-molecule gas presents the most formidable challenge in the development of safe, reliable, and leak-tight hydrogen fuel cell vehicles. Due to its structure, it can easily escape through the tiniest of crevices and diffuse into the materials designed to contain it. Given this circumstance, hydrogen fluid systems must maintain two important conditions:

• Leak tightness. Traditional oil and gas system designs are not equipped to handle the leak-tight requirements of hydrogen containment. Unlike larger molecules, hydrogen can easily escape through microscopic gaps. Standard seals, materials, and connection methods commonly used in oil and gas applications are not sufficient to ensure the integrity needed for hydrogen systems.

  This is especially critical at the point of dispensation, where common consumers interact with hydrogen fluid systems. To mitigate safety concerns, hydrogen infrastructure must be designed with specific use challenges in mind.

• Material integrity. Corrosion control is important in any application where tube fittings are concerned, but hydrogen containment poses a specific, unique challenge. Hydrogen embrittlement can impact 316 stainless steel, a widespread alloy type used for fittings, valves, and tubing, including those commonly used in hydrogen vehicle architecture.

  Over time, hydrogen can degrade durable materials like 316/316L stainless steel. At elevated pressures and with sustained exposure, hydrogen atoms can diffuse into the metal’s crystal structure, leading to embrittlement. While the material typically retains its mechanical strength, the presence of hydrogen can exacerbate existing microcracks, making components more vulnerable to fatigue failure. This risk increases in lower-grade alloys, where material integrity may already be compromised. For hydrogen infrastructure systems, especially those under constant stress, selecting materials engineered to resist embrittlement is essential to long-term reliability.

The Necessity of Components Designed for Hydrogen

One of the most important components of a hydrogen fluid system—whether in production infrastructure, on-vehicle applications, dispensation units, or any other application—is the tube fitting. Tube fittings form critical connections throughout hydrogen systems

The Swagelok FK series tube fitting meets each of these needs, demonstrating these critical performance characteristics in every application:

• Highly effective sealing. Because leak prevention is so critical, hydrogen fittings should maintain the utmost levels of gas seal tightness to enable optimal safety, reliability, and efficiency.

  FK series fittings incorporate two contact zones across longer sealing surfaces—one along the tube and another along the fitting. These contact surfaces are angled slightly, providing optimized stress levels to maintain an uncompromising seal. The fitting achieves such a seal with two ferrules—one to create a long plane of contact while another effectively grips into the tubing itself and creates its own surface seal. Long, precisely machined surfaces on the front ferrule further contribute to a highly reliable gas-tight seal.

• Uncompromising grip strength. The fitting’s grip strength on the tube is another key performance attribute that ensures the fitting can withstand the high pressures required for hydrogen refueling as well as the significant vibration that can occur in a moving vehicle.

  FK series fittings incorporate a hinging-colleting mechanical grip using two ferrules—an ideal design to create a robust grip. A hardened front ferrule enables the fitting to physically bite into the tubing, creating a very high-pressure rating. Meanwhile, a unique back ferrule design allows for a slight amount of movement in the fitting (called “spring back”) while maintaining grip and force. This type of design creates robust vibration resistance, ideal for both on-vehicle operation and for use on refueling infrastructure, where compressors and dynamic conditions can create significant vibration.

  The mechanical, two-ferrule design that allows for spring back also helps fittings withstand dramatic thermal changes that can cause materials to grow or shrink. During refueling, hydrogen gas temperatures may vary from as low as -50°C to ambient temperatures, causing issues in conventional cone and thread fitting performance.

• High-performance materials. While hydrogen embrittlement is one of the primary concerns when it comes to the material integrity of hydrogen fluid system components, other factors can lead to detrimental corrosion as well. For example, on-vehicle componentry may contend with adverse weather conditions, including salted roadways, which can compromise material integrity.

  As such, hydrogen fittings should be made from high-performance materials. It’s why Swagelok FK series fittings (and a variety of other available components) contain a higher concentration of chromium and nickel to defend against hydrogen embrittlement and other forms of corrosion by promoting greater ductility and corrosion resistance. The American Society for Testing and Materials (ASTM) standard requires a minimum of 10% nickel in 316 stainless steel formulations, but Swagelok 316 stainless with 12% minimum nickel is better suited for the unique challenges of hydrogen.

• Ease of installation. For effective scalability, an optimal hydrogen fitting should also deliver simplified installation, enabling professionals to more efficiently build critical hydrogen systems.

  Cone and thread fitting assembly can be labor-intensive and time-consuming. It also requires specialized tools and materials, such as coning and threading equipment and cutting lubricants, to complete installation and reduce friction during the cutting process.

In contrast, FK series fittings are designed with preassembled cartridges. This enables installers to use common tools and requires minimal training for efficient, error-proof assembly. When compared to traditional cone and thread fittings, the FK series fitting can deliver significant installation and assembly benefits, including fewer opportunities for errors, increased consistency, and overall improved service life for the application.

The Swagelok FK Series Fitting Advantage

The Swagelok FK fitting delivers the characteristics hydrogen applications demand, including:

• Robust seal tightness
• Outstanding grip strength
• Uncompromising vibration resistance
• Superior material integrity
• Easy and efficient installation

The FK fitting’s patented two-ferrule design and hinging-colleting action are compatible with a variety of tubing types and materials, delivering required performance for the most demanding hydrogen applications. From hydrogen production to transfer infrastructure to on-vehicle and dispensation applications, designers can rely on the FK fitting to meet their needs.

The FK fitting additionally meets relevant hydrogen industry standards, and is certified by the European Integrated Hydrogen Project (EIHP). Further, FK fittings are made from high-performance 316/316L stainless steel, with 12% minimum nickel and 17% minimum chromium to resist common corrosion and hydrogen embrittlement.

As part of a complete suite of hydrogen fluid system solutions, the FK fitting is offered along with other critical components including:

• Ball valves
• Needle valves
• Check valves
• Relief valves
• Double block and bleed valves

These solutions are also backed by a full suite of engineering services from Swagelok, including specialized training, on-site evaluations, prefabricated design and assembly services, and more.

Get in touch with one of our fluid system specialists to start a conversation about how you can achieve greater application reliability, more efficient installations, and enhanced safety in your hydrogen systems with superior fitting technology.

Contact a Swagelok Hydrogen Specialist