Transport Malta reports an explosion leading to equipment and structural damages onboard an oil tanker.
What happened?
On March 18, 2021, an oil tanker was in transit to Al Duqm, Oman for drydocking. In preparation for the drydock, technicians assisting the crew dismantled the walkway ramps on the main deck to check their condition and the condition of the underlying piping.
Two of the bolts on the last ramp were particularly hard to undo, and a technician opted to use an angle grinder to facilitate the work. Sparks emitted from the grinding disk and flew toward the vent head of the vessel’s Nr.2 fuel oil tank, resulting in an explosion.
The explosion caused damage to the vessel’s steel structure and port-side lifeboat and liferafts. Because the SEASCOUT interests swiftly adopted certain safety actions, the responding port state did not issue any recommendations.
Immediate cause
The safety investigation considered that spark(s) and high temperature particles either passed through the mesh of the flame arrestor, or landed inside the save-all of the tank head, leading to the explosion. Oily/waxy residues on the flame arrestor, found after the accident may have contributed to the flame propagation at the tank’s vent head and into the tank.
What followed gave clear indications to the safety investigation that an explosive atmosphere was present inside and potentially around the vent head. The subsequent flash and the ejection of flames from the vent head were signs that the gases generated by the fuel within the tank were within the flammable range. However, since a fire or subsequent explosions did not occur, it was hypothesized that not enough oxygen was present within the tank to sustain combustibility.
Safety actions taken
The Company had carried out the following preventative actions, following this occurrence:
- Refresher webinars were organised to emphasise the ‘stop work authority’ and the handling of riding teams for vessels and crew.
- A safety officer will be on board the vessel(s) whenever riding teams are employed for pre-dry-docking preparations.
- When a riding team is employed on board, the planning of jobs will be done daily, authorized by the master, and submitted to the Company for review and approval.
- Riding teams will be accompanied by the vessel’s assigned safety officer who will constantly monitor the jobs.
- Safety related training material is presented to riding teams prior to their embarkation.
- A webinar on bunkering operations was delivered to relevant office and seagoing personnel.
- All superintendent engineers and relevant sea going personnel completed a refresher training on fuel handling and storage safety with particular focus on the new VLSFO properties and characteristics.
- The Fuel Management Plan was updated to include precautions on the storage and handling of VLSFO.
- The risk assessment for bunker heating was updated.
- New buildings will be equipped with closed-type vapour locks over the bunker tanks to facilitate the measurement of tank atmosphere.
- The frequency of bunker tanks’ atmosphere checks was set to be carried out daily.
- The planned maintenance schedule was updated to include bimonthly inspections of the vent heads, for the removal of any accumulated oily and waxy residues.
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Source: Transport Malta
