MAIB Issues Investigation Report on ‘Catastrophic’ Stolt Groenland Explosion in Korea

The UK Marine Accident Investigation Branch has issued its investigation report on the 2019 explosion and and fire on board the chemical tanker Stolt Groenland in Ulsan, South Korea.

Footage of the explosion was captured on video that went viral online.

On 28 September 2019, a cargo tank containing styrene monomer on board the Cayman Islands registered chemical tanker Stolt Groenland ruptured due to runaway polymerisation, a type a chemical reaction.

At the time of the accident, the tanker was moored alongside a general cargo berth in Ulsan, and the Singapore registered chemical tanker Bow Dalian was moored outboard. The catastrophic rupture released a large quantity of vapor to the atmosphere, which subsequently ignited in a large fireball that reached the road bridge above.

Both vessels were damaged, and two crew suffered minor injuries. Fire-fighting efforts by the emergency services took over six hours and involved more than 700 personnel and 117 units of fire trucks, pumps and fire tugs. Fifteen emergency responders were injured during the fire-fighting.

Video of the explosion:

The MAIB previously issued an interim report pointing to the chemical reaction involving the ship’s styrene monomer cargo as a main focus of the investigation. The interim report also alerted the chemical tanker industry to the circumstances of the accident and requested information about previous similar accidents or incidents.

In the Stolt Groenland report, the MAIB revealed a similar dangerous styrene monomer polymerisation incident occurred a couple of weeks prior on board another Stolt Tankers ship, Stolt Focus. In that case, the heat generated by the polymerisation process was noticed before the critical runaway temperature was reached.

The MAIB investigation found that the styrene monomer cargoes on board both tankers was loaded at a similar time from the same tank in Houston and were exposed to similar environmental conditions.

Although the Stolt Focus incident was not reported to the ship’s Flag State, Korea’s Ministry of Oceans and Fisheries learned of the incident and prohibited ship-to-ship transfer operations for dangerous cargo on general cargo berths in Ulsan. The MAIB said Stolt Tankers took immediate action to ensure that the temperatures of all cargoes carried on board its ships were monitored and reported to its shore management, and it also took steps to enhance crew awareness on the hazards of inhibited and heat sensitive cargoes.

Safety issues identified in the MAIB’s Stolt Groenland investigation included that the styrene monomer was affected by other heated cargo tanks; heat transfer from other cargoes was not fully appreciated; and the styrene monomer temperature was not monitored.

The MAIB has made six recommendations as a result of the investigation:

• A recommendation (2021/122) has been made to Stolt Tankers B.V. aimed at ensuring the wider marine chemical sector benefits from the lessons learned from the Stolt Focus incident and research initiatives that were carried out as a result of this accident.
• The Internantional Chamber of Shipping and INTERTANKO have been recommended (2021/118 and 2021/119) to promulgate our report to their members.
• Recommendations (2021/117, 2021/120 and 2021/121) have also been made to the Cayman Island Shipping Registry, the Chemical Distribution Institute and Plastics Europe (Styrene Producers Association). These are intended to assist in ensuring that the guidance provided in certificates of inhibitor and styrene monomer handling guides is consistent and achievable given the limitations of equipment and testing facilities on board ships.

The MAIB notes that the investigation was carried out on behalf of the Cayman Islands and is the first investigation report the agency has published as part of its Memorandum of Understanding with the Red Ensign Group Catergory 1 registries of Bermuda, Cayman Islands, Gibraltar and the Isle of Man, under which MAIB agreed to carry out investigation for Very Serious Marine Casualties involving ships in those registries.

The full MAIB investigation report can be found here.

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