Safety Shells: Extra Protection for Hydrogen Storage

High-pressure hydrogen storage is safe when engineered properly—but Flexyshell takes safety a step further. Our external safety shells are designed to contain and control hydrogen in the unlikely event of a vessel leak or rupture, providing redundant protection, controlled venting, and debris containment.

How It Works

A safety shell is a larger, pressure-rated enclosure that surrounds the primary hydrogen vessel. The space between the inner vessel and the outer shell is filled with inert nitrogen gas, maintained at moderate pressure.

This configuration creates a double containment system with distinct functions:

  • Inner Vessel:
    Stores high-pressure hydrogen, either in a Flexyshell tank , or in an existing COPV or metallic cylinder installed without modification.

  • Outer Safety Shell:
    Acts as a protective enclosure, filled with nitrogen and designed to withstand much higher pressures than the nitrogen fill itself.
    The nitrogen layer serves three critical purposes:

    1. Prevention of Ignition: In the event of an inner-vessel rupture, hydrogen cannot ignite inside the nitrogen-filled space, as no oxygen is present.

    2. Containment of Released Hydrogen: The outer shell is engineered to safely contain the full pressure and gas volume released from a failed internal tank.

    3. Controlled Venting: Any hydrogen escaping into the safety shell is vented through dedicated systems, allowing safe dispersion or recovery.

Safety shells can be implemented in two configurations:

  • Individual Protection Units: Each high-pressure vessel is enclosed in its own nitrogen-pressurized safety shell — ideal for high-risk environments such as aerospace systems or refueling stations in populated areas.

  • Array Containment Systems: A single, larger safety shell houses multiple high-pressure tanks, providing collective containment and venting for storage yards, transport modules, or stationary installations.

This architecture eliminates the most dangerous failure mode of conventional high-pressure systems — uncontrolled hydrogen release and ignition — by ensuring that even a catastrophic rupture remains a non-explosive, fully contained event.

Key Features

Modular, Pressure-Capable Design

Safety shells are built as modular, dismantlable pressure enclosures, allowing complete access to the internal storage vessels when needed.
Unlike permanently sealed containment systems, each shell can be opened for inspection, maintenance, or replacement of the hydrogen tanks it protects — without cutting, welding, or destroying the structure.

Routine inspection remains fully feasible:

  • Modular Access: Shell sections can be separated to remove or replace individual tanks.

  • Monitoring Integration: Sensors for temperature, pressure, and leak detection can be installed directly inside the nitrogen-filled space, providing real-time status of both the stored hydrogen and the containment atmosphere.

  • Serviceability: Regular visual or non-destructive inspections of internal tanks are possible, ensuring continued safety and compliance without dismantling the entire installation.

This modular, pressure-capable configuration turns the safety shell into a maintainable containment system, not a one-time-sealed box — combining the integrity of pressure containment with the practicality of long-term service access.

Inerting

The annular space of the safety shell is  pressurized with an inert gas such as nitrogen.

Because this internal space contains inert nitrogen instead of air, the hydrogen vessels inside are completely isolated from oxygen, preventing any risk of explosion or ignition in the event of a leak or even total failure.

Vertical Installation for Minimal Footprint

Thanks to the Flexyshell’s pressure-stiffened design, the safety shell can withstand external loads when pressurized with nitrogen, allowing vertical installation without additional supporting structures — even when it houses an array of internal high-pressure vessels.

Failure Containment & Controlled Release

Safety shells are engineered to manage extreme scenarios:

  • Catastrophic Failure Containment:
    Safety shells are engineered to withstand the sudden pressure surge caused by a complete rupture of an internal vessel. The resulting shock and gas release are absorbed and stabilized through optimally tuned flow restrictors, expansion chambers, and energy-dissipating elements, preventing structural overload and uncontrolled venting.

  • Blast & Fragment Mitigation: Shells and internal racks absorb energy and limit high-velocity debris

  • Predictable Venting: A carefully configured system of pressure relief valves, rupture discs, and fast-acting bypass valves ensures predictable, controlled venting under all possible failure scenarios. Even in the event of a sudden inner-vessel rupture, the safety shell prevents any uncontrolled hydrogen release, ignition, or fragment ejection — the kind of catastrophic outcome that single COPV failures can produce.

 

Safety and Operational Advantages

Deploying a safety shell designed according to Flexyshell concept:

  • Eliminates catastrophic release risks associated with conventional high-pressure vessels

  • Contains debris and shock energy, protecting infrastructure and personnel

  • Enables vertical, compact layouts for limited-space installations

  • Supports inspection and modular maintenance, extending asset life

With this design, hydrogen storage becomes safer, more manageable, and resilient, whether you’re installing a new Flexyshell array or upgrading existing COPVs.