Fig: Bulk Coal Discharging
An instrument required for measuring methane, oxygen and carbon monoxide concentrations should be fitted with an aspirator, flexible connection and a length of tubing, thus enabling a representative sample to be obtained from within the square of the hatch.
Stainless steel tubing approximately 0.5m in length and 6mm nominal internal diameter with an integral stainless steel threaded collar is often preferred. The collar is necessary to provide an adequate seal at the sampling point.
A suitable filter should be used to protect the instrument against the ingress of moisture as recommended by the manufacturer. The presence of even a small amount of moisture would compromise the accuracy of the measurement
Australia is the world's largest coal exporter with an
estimated 240 million tonnes exported every year.
Other significant coal exporters include the USA,
Canada and South Africa.
Major coal importing countries include Japan, Korea,
the UK, Germany, India and Italy to generate electricity.
There are four categories of coal:
This is a mixture of solid coal containing water and is
obtained as a by-product during mining. The coal particle
size is usually less than 1 mm. It is regarded as a cargo
that may liquefy due to its high moisture content.
This is a mixture of coal and water with the largest coal
particles around 7 mm. Less liable to liquefaction than
coal slurry, but does require its moisture content to be
Solid residues obtained by distillation of petroleum
products, or half burnt coal with less gas content but
with a tendency to absorb moisture at up to 20% by
Contains particles of coal less than 7 mm in size; small
coal is likely to develop a flow state due to its high
According to IMO classification, coal is considered
MHB. Three characteristics of coal need to be
Most coals emit methane, which is highly explosive if a
gas concentration of 516% is present in atmosphere.
A naked flame or spark is sufficient to ignite it.
Methane is lighter than air and so it flows towards
the top empty part of the cargo compartment and
may even travel to adjacent compartments, including
a hatch top. Coals that emit methane should be
monitored carefully and, if the methane level becomes
unacceptable, surface ventilation should be carried
out as recommended by the IMSBC Code.
Some coals are liable to spontaneous combustion due
to the presence of moisture that causes exothermic
oxidation (a reaction that results in production of heat)
of coal at ambient temperature. If this heat is not
dissipated, the temperature rises and the coal may ignite.
Some types of coal react with water to produce acids
that can cause excessive corrosion of the ship's
structure, known as `cargo corrosion'. As a result of the
chemical reaction during the process of forming acid
and then corrosion, colourless and odourless gases
such as hydrogen are produced.
Precautions for Carriage of Coal
General precautions for the carriage of coal include:
- The Master should be informed about the cargo
in the `Cargo Information Form'
( ie. Shipper's Declaration/Cargo Information )
and the material safety data sheet (MSDS) prior
- The precautions that need to be taken depend
upon the information provided, eg if the cargo is
liable to emit methane, then the Master should
refer to the IMDG Code to obtain the loading,
stowage and carriage information.
- It is, therefore, imperative that the cargo
information be supplied to the Master prior to
commencing loading, or they may not allow the
- Before loading cargo:
Extra monitoring should be implemented when
coal is loaded in holds adjacent to hot areas,
such as heated fuel DB tanks and engine room
The ideal place to monitor the temperature
of the load is the centre of the stow. If the
temperature is measured from the side, top or
corners of the hold it must be remembered that
the temperature at the centre of the cargo will be
several degrees higher.
A no smoking policy should be fully implemented
on the ship and hot work should not be allowed,
particularly in the vicinity of cargo compartments.
Except where the shipper provides specific
instructions to ventilate the cargo, compartments
containing coal should only be ventilated for
the first 24 hours after departure from the
loading port. There should be regular monitoring
of atmosphere to check the concentration of
pH of bilge water. Ventilation
should only be continued if the amount of
methane rises above the acceptable level. Coal
should also be ventilated prior to discharge owing
to the danger of the build-up of gases that could
be ignited by a spark from the opening of the
The gases may escape the cargo compartment
to adjacent stores, mast houses, etc. These
spaces should also be monitored on a regular
A higher pH value reading indicates the likelihood
of increased corrosion. In such cases the
bilges should be kept dry by pumping out any
accumulated water. However, records should be
kept in the deck logbook for the quantity of bilge
water discharged to justify any claims of cargo
If any suspected problem is observed during the
passage the shipper should be contacted, not
only to update their information but also to seek
Special Precautions for Coals Emitting Methane
- i) Bilge wells should be cleaned, residual
cargoes removed, suction tested and covered
with taped down double wrapped burlap.
- ii) Hatch top wheels and associated equipment
should be greased to ensure that no sparks
are caused during opening and closing.
- iii) Electrical cables, cargo hold lights and any
other electrical instruments within cargo
holds should be checked for insulation
damage to ensure that they are safe for use
in an atmosphere containing explosive gases.
On bulk carriers, as no lighting is needed, the
fuses should be pulled to isolate electricity.
- iv) Ships that carry coal are required to carry
instruments to measure:
a) Methane, oxygen and carbon monoxide
levels in cargo holds
b) cargo hold temperature (between 0-100°C)
c) the pH of bilge water.
The installation of these instruments or
the taking of measurements, should be
possible without entering the cargo space.
Arrangements should also be made to
calibrate and test the instruments.
If the shipper has declared that the cargo is liable
to emit methane or the methane concentration
in the cargo compartment is above 20% of the
Lower Explosive Limit (LEL), the following additional
precautions should be taken:
Special Precautions for Self-Heating Coals
- Surface ventilation should be maintained
- hatch covers should not be opened until the
accumulated gases have been removed. Hatch
covers should then be opened carefully ensuring
no sparks are initiated
- all enclosed spaces such as store rooms, tunnels
and passageways, etc, should be thoroughly
monitored for methane
- enclosed hatch covers should be ventilated.
If the shipper has declared that the cargo is liable to
self-heat, then the following additional precautions
should be taken:
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- If required, the Master should seek additional
guidance from the shipper on the adequacy of the
- if analysis of the atmosphere of the cargo
compartment indicates an increased carbon
monoxide concentration, then
i) the hatch covers should be closed after
loading and additional seals applied
ii) surface ventilation should be kept to minimum
iii) carbon monoxide concentration should be
regularly measured and recorded
iv) if the hold temperature exceeds 55°C or the
carbon monoxide concentration rises steadily,
expert advice should be sought.
- Special precaution & IMSBC code guideline for handling bulk coal
- Various grade coal -Anthracite coal & Bituminous coal Handling guides
- Coal loading and related safety considerations
Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
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It is vital to reduce the likelihood of over-stressing the ship's structure and also complying with all essential safety measures for a safe passage at sea. Our detail pages contain various bulk carrier related topics that might be useful for people working on board and those who working ashore in the terminal. For any remarks please
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