Led by the University of Strathclyde, SAFeCRAFT Task 7.4 is conducting probabilistic and deterministic risk assessments to support the risk-based design of the project’s AIP1 Capesize bulk carrier.
The ongoing Quantitative Risk Assessment examines eight accident scenarios involving hydrogen leakage, dispersion, fire and explosion. The results obtained so far provide important insights into the positioning of safety equipment, ventilation outlets, pipelines, gas detectors, as well as potential bunkering safety distances.
Simulations show that, under wind speeds of 10–15 m/s, hydrogen released from the vent mast may be directed towards the navigation bridge and accommodation block, creating a potential risk of flammable gas entering HVAC intakes. The findings indicate that relocating the vent stack or increasing its height could reduce this risk.
Figure 1. Simulated hydrogen dispersion from the vent mast under different wind-speed conditions.
A release through the Fuel Preparation Room ventilation system was found to produce a flammable cloud extending approximately 4 metres from the outlet. This finding indicates the need for a suitable separation distance around the ventilation outlet where potential ignition sources are excluded.
Figure 2. Modelled flammable extent of approximately 4 metres from the Fuel Preparation Room ventilation outlet.
The assessment also showed that, even after Emergency Shutdown activation, a significant quantity of hydrogen may remain trapped within the 70-metre pipeline between the storage system and the Fuel Preparation Room. This trapped inventory can continue to feed a release and potentially form a flammable cloud near critical structures, including the accommodation block.
Figure 3. Hydrogen mole-fraction distribution at 1.0 second following ESD activation: (a) Scenario S3-C1-1 and (b) Scenario S3-C1-2.
Further studies examined pipeline damage during cargo handling. Although the assessed 10 kg spherical objects did not rupture the pipe, the simulations showed that thin-walled pipelines may remain vulnerable to heavier or sharp-ended objects. Impact shields or sacrificial barriers may therefore be required in areas where cranes operate above exposed pipelines.
Figure 4. Pipeline impact assessment: (a) global deformation of the pipe segment at different stages and (b) stress distribution at the pipe joint.
The assessment also examined jet-fire behaviour at the vent mast. The simulations showed that the vent-mast position can significantly influence flame direction and potential thermal exposure to nearby structures.
Figure 5. Flame-temperature distribution for the assessed vent-mast position: (a) 3D distribution of the flame plume, (b) temperature contours in the XZ plane and (c) temperature contours in the YZ plane.
The assessment of potential explosions around the fuel-storage system showed that hydrogen could accumulate to hazardous levels inside the storage container within just 0.3 seconds. During the early stages of a release, dispersion is driven primarily by jet momentum rather than buoyancy. A downward-directed leak may therefore cause hydrogen to accumulate initially near the bottom of the container, underlining the need to position gas detectors according to expected flow paths rather than only at ceiling level.
Figure 6. Flame propagation for different hydrogen-leak configurations at 0.06 and 0.10 seconds: (a) cylinder forward, −Z direction; (b) cylinder forward, +Z direction; and (c) cylinder centre, −Z direction.
The assessment also examined a jet fire at the bunkering station, showing how wind can tilt the flame and extend the thermal-hazard region along the vessel.
Figure 7. Flame-temperature distribution at the bunkering station: (a) 3D distribution of the flame plume and (b) temperature contours in the XZ plane.
For the assessed bunkering scenarios, probabilistic risk footprints were calculated for the Port of Rotterdam. The modelled hazard did not reach personnel height for a 5 mm crack, while the hazardous extent reached 187.9 metres for a 50 mm crack and 401.5 metres for a full rupture. These findings will support the further assessment of suitable exclusion zones and emergency procedures during bunkering.
Through this work, SAFeCRAFT is translating complex accident scenarios into practical recommendations that can strengthen the safe integration of hydrogen fuel systems onboard large vessels.
