Maritime investigators in the UK have released an interim report into the large explosion on board the chemical tanker Stolt Groenland in Ulsan, South Korea back in September, pointing to the chemical reaction involving the ship’s styrene monomer cargo as a main focus of the investigation going forward.

The explosion took place September 28, 2019 as the moored Stolt Groenland was awaiting to commence a ship-to-ship cargo transfer with the product tanker Bow Dalian.

The UK Marine Accident Investigation Branch (MAIB) was asked to participate in the investigation by Maritime Authority of the Cayman Islands, with which the Stolt Groenland is registered.

According to the MAIB’s interim report, released today, the explosion occurred due to the sudden build-up of pressure in the Stolt Groenland’s number 9 cargo tank containing styrene monomer, a highly flammable chemical used in the making of plastics, paints and synthetic rubber. The resulting explosions and fireball could be seen and heard for miles, and passed very close to a road bridge above where the Stolt Groenland was moored.

Amazingly, only relatively-minor injuries were sustained by crew members of the vessels and emergency responders. Damage to the Stolt Groenland’s cargo manifold and accomodation block, however, were extensive.

In releasing its initial report, the MAIB has requested information regarding any accident or ‘near-misses’ involving the carriage of styrene monomer on board ships, including any actions subsequently taken, so that investigators can pinpoint what may have initiated the polymerization of the styrene monomer.

So far, the MAIB has identified a similar incident taking place November 20, 2019 in which the Cayman Islands-registered chemical tanker Stolt Focus witnessed the temperature of the ship’s styrene monomer cargo was steadily rising. Only after the crew distributed the cargo between four cargo tanks and mixed it with sea water did the styrene monomer stabilize.

Along with styrene monomer, the MAIB said it will also look at cargo monitoring and the emergency response as part of the on-going investigation in the Stolt Groenland incident.

No word yet on when a final report is expected. 

The MAIB interim report can be found here.