Hydrogen is the smallest molecule on earth – and one of the most difficult to contain safely. As industries accelerate the adoption of hydrogen for clean energy, mobility, and industrial processes, the integrity of high-pressure connections becomes critical.

Yet too often, traditional cone & thread (C&T) fitting specifications are carried over from legacy hydraulic designs, without recognising the unique challenges hydrogen presents.

At Northern Valve & Fitting Company Ltd (NVFCL), as the authorised UK and Northern Ireland distributor for FITOK, we believe that relying on outdated connection technology puts projects at risk. Here’s why cone & thread can be a poor fit for hydrogen – and how FITOK’s 20D high-pressure two ferrule fittings provide a safer, certified alternative.

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The Downfalls of Cone & Thread Connections with Hydrogen

1. Originally Designed for Hydraulic Service
Cone & thread connections were developed decades ago primarily for high-pressure hydraulic fluid applications. In those systems, the fluid itself exerts a stabilising force on the coned sealing face. Any microscopic movement of the joint is resisted by the incompressible hydraulic medium, meaning minor imperfections rarely translate into leaks.
With hydrogen gas, the story is very different. Hydrogen is highly compressible, extremely light, and unforgiving. Its tiny molecules will exploit even the smallest pathway. What is tolerable in hydraulics becomes a critical safety risk in hydrogen service.

2. Increased Potential for Leakage
Cone & thread fittings rely on a metal-to-metal seal at the coned surface. Any imperfection in preparation, assembly, or surface finish increases the risk of leakage. Due to it’s molecular size, this risk is magnified with hydrogen. Even tiny leaks not only compromise safety but can cause embrittlement or contaminate surrounding processes.

3. Time-Consuming Assembly
Each cone & thread connection requires precision machining of tubing ends, threading, and careful torquing. This process is approximately 5 times more time-consuming than the equivalent two-ferrule system. It is operator-dependent, which increases labour costs and introduces variability. Rushed or imperfect preparation can lead to premature failure under high-pressure cycling.

4. Prone to Galling and Damage
Threads are inherently vulnerable to galling, cross-threading, and surface wear during repeated assembly and disassembly. Once damaged, fittings often cannot be reused, leading to higher replacement costs and unplanned downtime.

5. Maintenance Burden
In hydrogen refuelling stations, test bays, or industrial systems, maintenance windows must be short and efficient. Cone & thread fittings require disassembly, inspection, and often re-machining or replacement. This slows down servicing and adds cost compared to modern two-ferrule designs.

6. Hydrogen Embrittlement Risks
The stresses introduced at the coned sealing surface and threaded regions can exacerbate hydrogen embrittlement in susceptible alloys. This raises long-term reliability concerns, particularly in cyclic service at pressures ranging from 350 to 700 bar.

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Why FITOK’s 20D Twin Ferrule is the Better Choice

FITOK’s 20D high-pressure twin ferrule fittings are engineered specifically to overcome these challenges.

✅ Gas-tight Integrity
The two-ferrule design provides a robust, double-seal mechanism that minimises leak paths, even under hydrogen’s demanding conditions.

✅ No Tube Preparation Required
Unlike cone & thread, there’s no coning, threading, or machining of the tube ends. This reduces assembly time, eliminates variability, and lowers installation cost.

✅ Repeatable Performance
Ferrule-based make-up is simple, quick, and highly repeatable. Even less-experienced technicians can achieve consistent, safe connections.

✅ Reduced Downtime
Connections can be remade multiple times without damaging tube ends or compromising sealing performance – cutting maintenance costs dramatically.

✅ Extreme Pressure Capability
The 20D series is rated for service pressures up to 20,000 psi (1,379 bar), making it a direct replacement for cone & thread fittings in demanding high-pressure applications – with all the added safety benefits of twin ferrule design.

✅ Hydrogen Type Approval (EC-79)
FITOK’s 20D range is fully EC-79 type-approved for hydrogen vehicle and infrastructure applications, ensuring compliance with European regulations.

✅ Proven FITOK Quality
FITOK products are manufactured to the highest standards, tested for hydrogen service, and supported by NVFCL’s local stock, technical expertise, and customer support across the UK & Northern Ireland.

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The Safer, Certified Path Forward

Hydrogen projects demand more than legacy solutions that were merely “good enough.” Cone & thread fittings, while once the default choice for high-pressure service, don’t match hydrogen’s unique challenges.

With FITOK’s 20D twin ferrule fittings, you get a connection system that is:

• Safer
• Quicker/Easier to assemble and maintain
• Fully rated to 20,000 psi
• Certified under EC-79 for hydrogen service

At NVFCL, we stock and support the full FITOK high-pressure product range, which includes tubing, valves, fittings, and accessories specifically designed for hydrogen applications.

CLICK TO OPEN – 👉 Medium Pressure Tube Fittings, 20D Series

📞 Contact NVFCL today to discuss how FITOK’s EC-79-approved 20D twin ferrule can improve the safety, reliability, and efficiency of your hydrogen systems on 01942 601209.