ITOPF’s report underscores that hydrogen spills pose different challenges and lead to distinct types of claims compared to conventional oil spills. This difference stems from hydrogen’s unique properties, particularly its toxicity and reactivity, which result in different environmental impacts and necessitate different response strategies, reports Safety4sea.
Decarbonization Fuel
The report “Fate, Behaviour and Potential Damage & Liabilities Arising From a Spill of Hydrogen Into the Marine Environment” discusses hydrogen as a potential decarbonization fuel for shipping.
Hydrogen is considered “emission-free” when produced through water electrolysis using renewable energy, known as “green hydrogen.”
Hydrogen can be used in shipping in various forms, including liquefied or compressed hydrogen for internal combustion engines, or as LH2 in fuel cells.
However, hydrogen technology and infrastructure are still in early stages compared to other alternative marine fuels.
Economic and technical challenges exist, and the future development of hydrogen as a marine fuel will depend on overcoming these barriers and identifying the most viable technological applications.
Flammability
While liquid hydrogen (LH2) itself isn’t flammable, its vapor is, with a wide flammability range of 4 to 75 percent in air. This means it can only ignite within these concentration levels, and specialized equipment is needed to detect it. Comparatively, diesel’s flammability range is much narrower.
In open spaces, any LH2 release will quickly disperse, dropping below the 4 percent flammability threshold. Therefore, the risk of ignition is limited to a small area very close to the leak.
However, in enclosed areas where vapors can’t dissipate, even a small leak can create a concentrated, flammable layer of hydrogen, especially near ceilings. Conversely, inside a fuel storage tank, the hydrogen concentration is too high for it to fall within its flammable range.
Explosivity
Hydrogen presents a significant explosion risk due to its broad explosivity range of 15 to 59 percent in air. This means even minor leaks can lead to combustion or explosions. In enclosed spaces, the risk is particularly high, as hydrogen concentrates and can be ignited by even small sparks or static electricity.
Ignition of a hydrogen-air mixture can potentially lead to a deflagration to detonation transition (DDT), resulting in a powerful explosion. This is due to the rapid burning speed of hydrogen flames and the short distance required for a DDT event. While these events have been documented, they remain unpredictable and not fully understood.
Liquid Hydrogen
Under specific circumstances, liquid hydrogen (LH2) could experience a Boiling Liquid Expanding Vapor Explosion (BLEVE). This occurs when a pressurized liquid, stored above its boiling point (-253°C), ruptures its container. This scenario could arise if the tank’s temperature increases and safety gas release systems fail.
When LH2 is spilled into ambient conditions, it may undergo a Rapid Phase Transition (RPT). This is a non-flammable overpressure event caused by the extremely fast change from liquid to gas. The resulting vapor cloud expands so rapidly that it produces a sonic boom and localized overpressure. It’s important to note that no reported RPT incidents involving LH2 have occurred, and some research suggests that the likelihood of an LH2-induced RPT is significantly lower than that of Liquefied Natural Gas (LNG). Similar to Deflagration to Detonation Transition (DDT) events, RPT events involving LH2 are not fully understood at this time.
Preventive Methods
In the event of a hydrogen spill, potential financial claims would likely stem from various preventive and mitigation actions, rather than traditional clean-up operations. These actions could include:
- Source control: Measures to stop or contain the leak at its origin.
- Fire-fighting measures: Actions taken to prevent or extinguish fires or explosions.
- Monitoring: Using expert modeling or sensors on Unmanned Aerial Vehicles (UAVs) and Remotely Operated Vehicles (ROVs) to track the spread and behavior of the hydrogen.
- Possible bunker fuel removal: If the incident also involves traditional bunker fuel.
Because hydrogen disperses so quickly, traditional clean-up methods are not feasible. Therefore, claims related to prolonged spill clean-up efforts are not expected.
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Source: Safety4sea
