A catastrophic container explosion aboard the vessel YM Mobility last year at Ningbo has been traced back to thermal runaway involving a shipment of organic peroxides, according to an investigation by the China Maritime Safety Administration (CMSA).
The incident is the latest in a series of maritime accidents linked to dangerous self-heating chemicals, which pose a persistent risk of fires and explosions in containerized cargo operations.
The Cause: Unrefrigerated Organic Peroxides
The explosion was linked to a refrigerated container (reefer) loaded with tert-butyl perbenzoate (TBPB) — a chemical commonly used in the production of plastics like polyethylene and polyester. TBPB is known for its instability at elevated temperatures, with a thermal tipping point near 140°F (60°C). Beyond this threshold, it can self-heat rapidly, leading to combustion or explosion.
While the cargo was packed in a refrigerated container, it was not plugged in during transit. When the container was loaded onto the YM Mobility in Shanghai on August 6, it was stowed on deck at the starboard bow — exposed to ambient summer temperatures of around 95°F (35°C) — and left unrefrigerated.
Rapid Escalation and Explosion
YM Mobility departed Shanghai on August 7 and reached Ningbo on August 9. That afternoon, a crewmember patrolling the bow noticed an irritating smell, along with hissing sounds, white smoke, and yellow liquid seeping from the container — all early indicators of TBPB decomposition.
The situation deteriorated quickly:
- Within minutes, heavy white smoke engulfed the foredeck.
- The crew evacuated the area and sounded the fire alarm.
- At approximately 1346 hours, the container violently exploded, ejecting six containers overboard and destroying three others.
Fortunately, no injuries were reported. Firefighting teams from shore controlled the blaze by the next morning, though it took another day to extinguish lingering hot spots. The blast caused significant structural damage, including warping of the hatch coaming and deformation of nearby container structures.
Investigation Findings: Mismanagement of Thermal Risk
CMSA’s post-incident analysis concluded that the transportation plan was fundamentally flawed. Reefer containers are airtight and thermally insulated; without active cooling, any heat generated inside — especially in hot ambient conditions — would be trapped, rapidly accelerating the chemical’s self-heating process.
The investigation cited failure to monitor container temperatures during transport and negligent planning by the cargo’s shippers. Specifically, CMSA noted that:
“Transporting TBPB in unplugged refrigerated containers during the hot season was inappropriate. Shippers failed to account for the thermal insulation and airtightness of unplugged reefers.”
The YM Mobility incident underscores ongoing challenges with handling dangerous goods at sea, particularly with cargoes that exhibit temperature-sensitive and self-reactive behavior.