The fertiliser in the holds began to decompose. The crew could not stop it and left the ship.
In August 2017 the bulk carrier Cheshire, carrying ammonium nitrate based fertiliser, suffered a self-sustaining decomposition of the cargo off the Canary Islands. The holds filled with toxic gas and heat, the crew was evacuated by helicopter and the ship drifted for days before being towed to port. Nobody died.
Words in this case
- self-sustaining decomposition
- A reaction in the cargo that keeps going on its own once started.
- ammonium nitrate based fertiliser
- A common bulk fertiliser that can decompose when heated.
- toxic gas
- Gas that poisons; here nitrogen oxides and ammonia.
- heat source
- Anything hot enough to start a reaction: a lamp, hot work, machinery.
- evacuation by helicopter
- Taking the crew off by winch when boats cannot be used.
More words like these in the glossary and in listening practice.
What happened
Cheshire loaded fertiliser in Norway for Thailand. Ammonium nitrate based fertiliser is carried as a bulk cargo under the IMSBC Code; it does not burn, but once part of it is heated enough it can start to decompose on its own, giving off toxic gases and spreading through the cargo without any flame.
Some days into the voyage the crew noticed heat and gas from one hold. They tried to cool the cargo with water, but the decomposition spread to other holds. Gas concentrations on deck and in the accommodation rose to dangerous levels. The master anchored off the Canary Islands, the crew was taken off by helicopter, and the ship was left to drift until salvors could board. The cargo decomposed almost completely. The hull survived.
The Marine Accident Investigation Branch found that the decomposition had most likely been started by a source of heat in a hold, that once it was self-sustaining the ship's crew had no realistic way to stop it, and that the guidance on this cargo needed to be clearer for crews.
Why it happened
- A source of heat in a hold started the decomposition of the fertiliser cargo.
- Self-sustaining decomposition spreads through the cargo without flame; water cooling from above cannot reach it.
- Toxic gases made the deck and accommodation unsafe and forced the evacuation.
What to remember on board
- Read the IMSBC schedule for every cargo: the hazards, the precautions, and what to do if it heats or gases.
- Hold lighting, hot work and machinery near a reactive cargo are heat sources; isolate them and check them.
- Gas detection and temperature monitoring of holds are daily routine with cargoes that can self-heat or decompose.
- Evacuation of a crew by helicopter in open sea takes hours; call early, not when the accommodation is already full of gas.
What changed afterwards
The report led to clearer guidance for ships carrying ammonium nitrate based fertilisers and to proposals to amend the IMSBC Code schedule for the cargo.
Three questions
The kind of questions a knowledge test asks about this case. Keys 1 to 4 answer, Enter goes on.
Read more
Source: Cargo decomposition and evacuation of the bulk carrier Cheshire off the Canary Islands, Marine Accident Investigation Branch (UK), report 2018. Find the report.
On this site: Bulk carriers.
Plain-English summary of an official investigation report. Facts and findings are the investigators'; the wording is ours. Nothing here is legal advice or a substitute for the report itself.