While unloading a ship, an explosion occurred around the end of the day at a methane tanker terminal that contained 3 tanks connected to a flare network. The terminal was shut down for scheduled maintenance, with the outstanding LNG (liquefied natural gas) shipments authorised for unloading given the upcoming resumption of activity. The explosion happened inside the terminal’s flare casing, blasting the base door into the control room causing physical damage there: broken window panes, dust and debris inside the room. The terminal operator reported no injuries and only limited damage. The control room continued to function normally and no evacuations were ordered. The internal emergency plan was activated: fire-fighters remained on-site for 90 min. The gas unloading operation was halted (boat moored at the dock, the liquid connecting arm unsynchronised, and the gas-vapour piping system kept in place). All flare use was stopped. Gaseous releases from the terminal, evaluated at 4,000 N-m³/hour, were discharged into the atmosphere while awaiting repairs to the flare or the re-injection of evaporated gases into the network (requiring some 20 hours). All 3 tanks had been fitted with a vent operated from the control room. Moreover, the tanks featured a permanent pressure meter and relief valves. According to the operator, the cold cloud stayed confined near the vents (5-m diameter, 35-m height above the tanks). The visible cloud encompassed the ignition zone. The south-to-north wind was blowing at 1-2 km/hour.

Among the conservation measures implemented, gas detection devices were installed along the access road and around the site boundary: recordings were carried out every 30 min at 6 points without indicating the presence of gas. The inspection authorities for classified facilities proposed that the Prefect subject flare operations as well as ship unloading to performing a diagnostic assessment of the situation, accompanied by a risk analysis. As the cause of this accident, the absence of a liquid seal on the drain siphon of the gas quality seal at the top of the flare allowed gases to migrate and an explosive atmosphere to be created inside the flare casing itself, followed by an accumulation of cold gas (density: 1.05) at the low point. For purposes of experience feedback, the flare was modified and the safety report appropriately revised.