SAFETY
THE RISKS AND COSTS OF HYDROGEN LEAKAGE Hydrogen leakage isn’t just a technical nuisance—it’s a serious safety and economic concern.
Safety hazards: Hydrogen is extremely fl ammable, and even a small leak can result in explosive mixtures with air. Adding to the danger, hydrogen fl ames are nearly invisible to the naked eye. Undetected leaks can lead to catastrophic events if not managed properly.
Economic and environmental impact: Every leak represents a direct fi nancial loss. Beyond the cost of lost hydrogen, maintaining systems to prevent or detect leaks adds signifi cant operational expenses. Environmentally, while hydrogen itself is clean, its production, especially when fossil- fuel-based, has a carbon footprint. Minimising losses is vital to making hydrogen a truly sustainable energy solution.
COMMON LEAKAGE POINTS: PRESSURE RELIEF VALVES One of the most common, yet often overlooked, sources of hydrogen leakage is through pressure relief valves (PRVs). PRVs are essential safety devices, designed to open when system pressure exceeds safe limits, then reclose to maintain system operation. However, PRVs are particularly vulnerable to hydrogen leakage owing to their design. Most PRVs use metal-to-metal seals
to achieve leak tightness. Because hydrogen molecules are so small and mobile, they can ‘weep’ through these seals. Over time, valve components wear down, increasing the rate of leakage. Even valves designed with soft seats (such as O-rings) to improve sealing can degrade under long-term hydrogen exposure, losing their eff ectiveness owing to permeability and chemical interaction with the gas.
A Fike rupture disc
The benefi ts of rupture discs
THE SOLUTION: PAIRING PRVS WITH RUPTURE DISCS To address the challenge of leakage through PRVs, many hydrogen systems now incorporate rupture discs as an added layer of containment. Rupture discs are non-reclosing
safety devices that burst at a predetermined pressure, providing a one-time release point. While a PRV can be completely replaced by a rupture disc, the reclosing nature of a PRV is often a desired feature in the overpressure protection system design. When installed upstream of a PRV (between the PRV and the process), the rupture disc acts as a barrier under normal operating conditions. This setup signifi cantly reduces leakage, as rupture discs are typically much more leak-tight than PRVs.
Enhanced leak prevention: A well-chosen rupture disc, especially one made from hydrogen-compatible materials like austenitic stainless steels or Inconel 625, can virtually eliminate leakage under normal conditions Material cost savings: With the rupture disc shielding the PRV from constant hydrogen exposure, more cost-effective PRV materials such as carbon steel or standard stainless steel can be used, reducing system cost. Operational effi ciency: This setup allows for in-situ PRV testing. By pressurising the volume between the PRV and the rupture disc to the opening pressure of the PRV it can be tested without removing it from the system. As a rupture disc can withstand a back pressure it will not open, or be damaged, during this process.
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