When a fire breaks out on board a vessel there is no fire
service ready to assist in extinguishing it – it is up to the crew themselves.
The Swedish P&I Club issued a new guide for quick reference to the causes
and prevention of cargo fires and explosion onboard.
The consequences
of a fire onboard can be catastrophic, and all those who have worked on board a
vessel are aware of the difficulties involved with managing a fire and the
crucial importance of fire prevention. The guide focuses on self-heating,
explaining the principles of self-heating, and investigating several types of
cargo fires and explosions including those in bulk cargoes, containers and
tankers.
This graph identifies
those vessel types which have suffered most cargo fires. The relatively low
tanker figures are a testament to the tight regulation and safety culture that
exists in this industry. The ro-ro figure is however surprisingly high, and can
be explained by the non-homogeneous nature of the cargo these vessels carry.
The operator has to rely on a number of shippers correctly declaring the nature
and risk of the cargo in the manifest, and is unable to easily check the
condition of the goods. Old batteries, unstable equipment, leaks – none of
these will necessarily be made obvious.
Causes
of self-heating
·
Availability of oxygen: For example, with many bulk coal
cargoes the holds need to be kept closed and sealed. This restricts the access
of air (oxygen) to the cargo which restricts the oxidation reactions, so that
temperatures do not rise to problematic levels.
·
Availability of water: For example, DRI needs to be kept
dry so that it cannot react with water. If water does enter holds containing
DRI it can start a self-heating reaction which can then worsen, leading to
oxidation reactions with air and then severe heating.
·
Reactivity of cargo: Some cargoes need to be ‘aged’ by
exposure to air/oxygen so that the most easily oxidised parts have reacted
before loading. This means that the rate of oxidation of the cargo is reduced
and so self-heating is less likely.
·
Ability of air/oxygen to diffuse into the cargo:
Self-heating due to oxidation can only progress to a problematic level if
enough oxygen can pass into the cargo to produce heat that cannot be
dissipated. For example, some cargoes, such as activated carbon, may need to be
carried in hermetically sealed bags to stop air/oxygen contacting the cargo.
·
Temperature of cargo : Reactions are faster
at higher temperatures, so the loading temperature of some cargoes needs to be
restricted so that oxidation rates are not too fast. For example, bulk coal
needs to be at a maximum temperature of 55°C when loading.
·
Size of the body of cargo : Heat
is dissipated less effectively from a larger body, for example, some cargoes
have package size restrictions or maximum container load restrictions.
Other
causes of cargo fires and explosions
1. Cargo
lights : Cargo lights in holds need to be properly isolated before
cargo is loaded. This is best done by removing fuses or other physical links in
the electrical circuits so that the lights cannot be switched on by mistake.
2. Smoking
and hot work : Smoking and hot work need to be properly controlled. Control
of smoking can be difficult where stevedores are working on board. Hot work
permits need to be properly considered, not just a ‘tick box’ exercise.
3. Cars
and other vehicles : Cars and other vehicles carried on board ships present some
risk of fire. Risks include cargo shifting in heavy weather and used vehicles
in poor condition giving rise to electrical faults.
4. Fumigants :
Fumigants can cause fire or explosion, particularly if there is an excessive
amount of fumigant in one place; or if the fumigant is in contact with liquid
water e.g. from sweating or condensation. In these situations the fumigant can
react too quickly, evolving excessive heat or explosive gas/vapour. Fumigants
must be correctly applied by qualified personnel.
Further details may be
found by reading the full report at the links,
Or
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