Hydrogen is widely regarded as a key element of prospective energy solutions for alleviating environmental emission problems. However, hydrogen is classified as a high-risk gas because of its wide explosive range, high overpressure, low ignition energy, and fast flame propagation speed compared with those of hydrocarbon-based gases. In addition, deflagration can develop into detonation in ventilation or explosion guide tunnels if explosion overpressure occurs, leading to the explosion of all combustible gases. However, quantitative evidence of an increase in the explosion overpressure of ventilation tunnels is unavailable because the explosive characteristics of hydrogen gas are insufficiently understood. Therefore, this study investigated an explosion chamber with the shape of a ventilation pipe in a ship compartment. The effect of tunnel length on explosion overpressure was examined experimentally. For quantitative verification, the size of the hydrogen gas explosion overpressure was analyzed and compared with experimental values of hydrocarbon-based combustible gases (butane and LPG (propane 98%)). The experimental database can be used for explosion risk analyses of ships when designing ventilation holes and piping systems and developing new safety guidelines for hydrogen carriers and hydrogen-fueled ships.

As the world’s hydrocarbon supplies are gradually being depleted, the search for alternative energy sources with acceptably low emissions of environmentally harmful pollutants is a growing concern. Hydrogen has been proposed by numerous researchers as a fuel source for ships. Liquid hydrogen (LH₂) has been shown to be particularly attractive as a ship fuel with respect to its ability to reduce pollution, density, high performance in engines, and high caloric value per unit mass. However, working with hydrogen in the liquid phase requires very low (i.e., cryogenic) temperatures. The design of a cryogenic LH₂ pipeline is very different from the design of a normal fluid pipe due to the change between the liquid and gas states involved and the effect of thermal and structural characteristics on the cryogenic temperature during LH₂ transportation through the transfer pipeline. This study investigated the material and thermal-structural characteristics of a multi-layer vacuum-insulated pipeline system through experiments and finite element analysis. The experimental and numerical results can be used as a database of material parameters for thermal-structural analysis when designing applications such as LH₂ pipeline systems for hydrogen carriers and hydrogen-fuelled ships.

Blast walls are installed on the topside of offshore structures to reduce the damage from fire and explosion accidents. The blast walls on production platforms such as floating production storage, offloading, and floating production units undergo fire and explosion risk analysis, but information about blast walls on the well-test area of drillship topsides is insufficient even though well tests are performed 30 to 45 times per year. Moreover, current industrial practices of design method are used as simplified elastically design approaches. Therefore, this study investigates the strength characteristic of blast wall on drillship based on the blast load profile from fire and explosion risk analysis results, as well as the ability of the current design scantling of the blast wall to endure the blast pressure during the well test. The maximum plastic strain of the FE results occurs at the bottom connection between the vertical girder and the blast wall plate. Based on the results, several alternative design applications are suggested to reduce the fabrication cost of a blast wall such as differences of stiffened plated structure and corrugated panels, possibility of changing material (mild steel), and reduced plate thickness for application in current industrial practices.

X₁ - Fire duration (min): the time exposed to fire

The flight deck of aircraft carriers in operation is exposed to fire risks which must be mitigated by fire safety measures such as firefighting and suppression systems. To develop advanced fire safety measures, the quantitative risk assessment and management is essential, where fire hazards must be identified in a probabilistic manner considering operational conditions (e.g. sortie generation rates) and site-specific ocean environmental conditions (e.g. humidity, wave and wind profiles). In this paper, a set of realistic fire scenarios on the flight deck of a hypothetical short take-off/vertical landing (STOVL) type aircraft carrier are selected, which shall be used for the quantitative fire risk assessment and management. Potential fire hazards are formulated as a function of random parameters associated with operational and ocean environmental conditions, and probabilistic sampling technique is used to select hundred fire scenarios. Fire exceedance diagrams are established in association with fire-impacted (leak) area through the selected fire scenarios.