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Cargo Work
Bulk Cargo (Not Grain)
Bulk
cargoes (other than grain)
The officer of the watch should know the pre-planned loading procedure regarding quantities to be loaded in each space, the order of deballasting tanks and shifting the vessel under loading chutes. The procedure will have been worked out to keep stresses within acceptable limits and to finish with a satisfactory weight distribution and trim. The officer of the watch should see that the plan is followed, particularly at berths with only one loading chute, to avoid over-stressing the ship.
Code of Safe Practice for Solid Bulk Cargoes BC Code
is intended to set a standard for the safe stowage and carriage of solid bulk
cargoes.
This Code is a recommended guide for ship owners,
shippers and masters and shall apply to all shipments of bulk cargoes.
The list of products appearing in the Appendices of
the BC Code, however, is by no means exhaustive. Consequently, before any bulk
cargo is loaded, it is essential to ascertain (normally from the shipper) the
current physical and chemical properties of the cargo, as required under SOLAS
Chapter VI.
General requirements
Before and during loading, transport and unloading of
bulk cargoes, all necessary safety precautions including any regulations or requirements
should be observed, including the following:
1. Dangerous Bulk Material Regulations
2. Safe Working Practices Regulations
3. International Maritime Dangerous Goods Code (IMDG
Code)
4. Emergency Procedures For Ships Carrying Dangerous
Goods
5. Medical First Aid Guide for Use in Accidents
Involving Goods (MFAG)
6. IMO BC Code - Code of Safe Practice for Solid Bulk
Cargoes
Poisoning and asphyxiation hazards
Certain bulk cargoes are liable to oxidation, which in
t urn may result in oxygen depletion, emission of toxic fumes and self-heating.
Other bulk cargoes may not oxidize but may emit toxic fumes.
It is important therefore that the shipper inform the
master before loading of the existence of any chemical hazards. The master
should refer to Appendix B of the BC Code and take the necessary precautions,
especially those pertaining to ventilation.
Certain cargoes may emit toxic gases when wetted. In
these cases the ship should be provided with the appropriate gas detection
equipment.
A flammable gas detector is only suitable for testing
the explosive nature of gas mixtures.
Emergency entry into a cargo space should be
undertaken only by trained personnel wearing self-contained breathing
apparatus, and protective clothing if considered necessary, always under the
supervision of a responsible officer.
In the event of emergency entry into a cargo space, in
addition to the above requirement, spare self-contained breathing apparatus,
safety belts and safety lines should be readily available.
Health hazard from dust
To minimize the chronic risks from exposure to the
dust of certain materials carried in bulk, a high standard of personal hygiene
for those exposed to the dust cannot be too strongly emphasized. The
precautions should include not only the use of appropriate protective clothing
and barrier creams when needed but also adequate personal washing especially
before meals, and laundering of outer clothing.
Flammable atmosphere
Dust created by certain cargoes may constitute an
explosion hazard, especially, during loading, unloading and cleaning. This risk
can be minimized at such times by ensuring that ventilation is sufficient to
prevent the formation of a dustladen atmosphere and by hosing down rather than
sweeping.
CARGOES
THAT MAY LIQUEFY (section 7 of the BC Code)
Properties, characteristics and hazards
Cargoes that may liquefy include concentrates, certain
coals and other materials having similar physical properties. Appendix A of the
BC Code contains a list of such cargoes, which generally consist of a mixture
of small particles in contrast with natural ores that include a considerable
percentage of large particles or lumps.
Section 5 of the BC Code - Trimming Procedures
At moisture content above that of the transportable
moisture limit, shift of cargo may occur as a result of liquefaction.
The major purpose of the sections of this Code dealing
with these cargoes is to draw the attention of masters and others to the latent
risk of cargo shift, and to describe the precautions deemed necessary to
minimize this risk.
Such cargoes may appear to be relatively dry and
granular when loaded, but may contain sufficient moisture as to become fluid
under the stimulus of compaction and the vibration that occurs during a voyage.
In the resulting viscous fluid state, cargo may flow
to one side of the ship when it rolls one way, but not completely return when
it rolls the other. Thus, the ship sways progressively until it reaches a
dangerous heel and capsizes.
To prevent subsequent shifting, and also to decrease
the effects of oxidation of material with a predisposition to oxidize, these
cargoes should be trimmed reasonably level on completion of loading,
irrespective of the angle of repose.
Amended
Extract from SOLAS Chapter VI
Part B
Special
provisions for bulk cargoes other than grain
Regulation
6
Acceptability
for shipment
Concentrates or other cargoes which may liquefy shall
only be accepted for loading when the actual moisture content of the cargo is
less than its transportable moisture limit. However, such concentrates and
other cargoes may be accepted for loading even when their moisture content
exceeds the above limit, provided that safety arrangements to the satisfaction
of the Administration are made to ensure adequate stability in the case of
cargo shifting and further provided that the ship has adequate structural
integrity.
Prior to loading a bulk cargo which is not a cargo
classified but which has chemical properties that may create a potential
hazard, special precautions for its safe carriage shall be taken.
Regulation
7
Loading,
unloading and stowage of bulk cargoes
To enable the master to prevent excessive stresses in
the ship’s structure, the ship shall be provided with a booklet, which shall be
written in a language with which the ship’s officers responsible for cargo
operations are familiar. The booklet shall, as a minimum, include:
.1 stability data,
.2 ballasting and de-ballasting rates and capacities;
.3 maximum allowable load per unit surface area of the
tank top plating;
.4 maximum allowable load per hold;
.5 general loading and unloading instructions with
regard to the strength of the ship’s structure including any limitations on the
most adverse operating conditions during loading, unloading, ballasting
operations and the voyage;
.6 any special restrictions such as limitations on the
most adverse operating conditions imposed by the Administration or organization
recognized by it, if applicable; and
.7 where strength calculations are required, maximum
permissible forces and moments on the ship’s hull during loading, unloading and
the voyage.
Before a solid bulk cargo is loaded or unloaded, the
master and the terminal representative shall agree on a plan* which shall
ensure that the permissible forces and moments on the ship are not exceeded
during loading or unloading, and shall include the sequence, quantity and rate
of loading or unloading, taking into consideration the speed of loading or
unloading, the number of pours and the de-ballasting or ballasting capability
of the ship. The plan and any subsequent amendments thereto shall be lodged
with the appropriate authority of the port State.
Bulk cargoes shall be loaded and trimmed reasonably
level, as necessary, to the boundaries of the cargo space so as to minimize the
risk of shifting and to ensure that adequate stability will be maintained
throughout the voyage.
When bulk cargoes are carried in ‘tween-decks, the
hatchways of such ‘tween-decks shall be closed in those cases where the loading
information indicates an unacceptable level of stress of the bottom structure
if the hatchways are left open. The cargo shall be trimmed reasonably level and
shall either extend from side to side or be secured by additional longitudinal
divisions of sufficient strength. The safe load-carrying capacity of the ‘tween-decks
shall be observed to ensure that the deck-structure is not overloaded.
The master and terminal representative shall ensure
that loading and unloading operations are conducted in accordance with the
agreed plan.
If during loading or unloading any of the limits of
the ship are exceeded or are likely to become so if the loading or unloading
continues, the master has the right to suspend operation and the obligation to
notify accordingly the appropriate authority of the port State with which the
plan has been lodged. The master and the terminal representative shall ensure
that corrective action is taken. When unloading cargo, the master and terminal
representative shall ensure that the unloading method does not damage the
ship’s structure.
The master shall ensure that ship’s personnel
continuously monitor cargo operations. Where possible, the ship’s draught shall
be checked regularly during loading or unloading to confirm the tonnage figures
supplied. Each draught and tonnage observation shall be recorded in a cargo
logbook. If significant deviations from the agreed plan are detected, cargo or
ballast operations or both shall be adjusted to ensure that the deviations are
corrected.
At a moisture content above that of the transportable
moisture limit, shift of cargo may occur as a result of liquefaction.
Many cargoes may appear to be relatively dry and
granular when loaded, but may contain sufficient moisture as to become fluid
under the stimulus of compaction and the vibration that occurs during a voyage.
In the resulting viscous fluid state, cargo may flow
to one side of the ship when it rolls one way, but not completely return when
it rolls the other. Thus, the ship way progressively reaches a dangerous heel
and capsize.
Ships other than specialist suited ones shall carry
only those cargoes having a moisture content that is not in excess of the
transportable moisture limit as defined in this Code.
Specially suited ships
Specially suited ships may carry concentrates having a
moisture content in excess of the transportable moisture limit if the ship
possesses a valid document of approval from her administration, accompanied by
such stability information as her administration may require. The document of
approval must clearly state “For carriage of concentrates having a moisture
content in excess of the transportable moisture limit”.
When concentrates are loaded that have a moisture
content in excess of the transportable moisture limit, the whole surface area
of each cargo space shall be trimmed level.
Cargoes having a moisture content in excess of the
flow moisture point shall not be carried in bulk.
Before loading, the shipper or his appointed agents
shall provide to the master and the port warden, if requested, details, as
appropriate, of the characteristics and properties of any material constituting
bulk cargo, such as flow moisture point, stowage factor, moisture content,
angle of repose, chemical hazards, etc. so that any necessary safety
precautions can be put into effect.
To do this the shipper shall arrange, possibly in
consultation with the producers, for the cargo to be properly sampled and
tested. Furthermore, the shipper should provide the ship’s master and the port
warden, if requested, with the appropriate certificates of test, as applicable
for a given cargo.
Before and during loading, auxiliary check tests of
the moisture content may be carried out using instruments designed specifically
for that purpose, such as the “SPEEDY MOISTURE TESTER”. Tests conducted with
this instrument indicate a precision of ±1% compared with the laboratory
method, i.e., with a laboratory reading of 10%, the “SPEEDY” reading could
range from, 9% to 11%. If the readings obtained by this method are consistently
higher than those shown on the certificate, loading of the cargo should cease
and a further laboratory test be conducted.
If the master has doubts as regards the appearance of
condition of the cargo for safe shipment, the following auxiliary method may be
used on board ship or at the dockside to perform a check test for approximately
determining the possibility of flow:
Half fill a cylindrical can or similar container
(0.5-1 litre capacity) with a sample of cargo. Take the can in one hand and
bring it down sharply from a height of about 0.2m to strike a hard surface such
as a solid table. Repeat the procedure twenty-five times at one or two second
intervals. Examine the surface for free moisture or fluid conditions. If free
moisture or a fluid condition appears, make arrangements to have additional
laboratory tests on the cargo conducted before it is accepted for loading.
COAL is very
liable to spontaneous heating. If there
is sufficient oxygen available, combustion is liable to take place. The amount
of heating that takes place depends on the type of type coal and how much heat
can be dispersed by ventilating the coal.
Ventilation can be a double-edged weapon as although it takes heat from
the coal it also allows unwanted oxygen into the coal. To keep the coal as cool as possible it
should be stowed away from hot bulkheads.
To keep oxygen away from the coal only surface ventilation should be
allowed.
All spar ceiling or cargo battening should be removed
as besides the liability of it to damage, it can give unwanted air pockets in
the coal. Unwanted air may also get into
a cargo through a temporary wooden bulkhead. If such a bulkhead has been
constructed all cracks should be sealed, preferably by pasting paper over both
sides of the bulkhead.
Freshly mined coal absorbs oxygen, which, with
extrinsic moisture, forms peroxides.
These in turn breakdown to form carbon monoxide and carbon dioxide.
Heat is produced by this exothermic reaction causing
further oxidation and further heat. If
this heat is not dissipated ignition will occur. This is called Spontaneous combustion.
As this is essentially a surface reaction the smaller
the surface available for the absorption of oxygen the better. Every attempt
should be made to prevent undue breakage of the coal whilst it is being loaded.
It may be noted that 1 MT of coal in an unbroken cube has a surface area of
about 3.72m2, whereas if it is broken up to pass through a 1.5mm mesh screen
its surface area is nearly 4000m2. If a large amount of breakage occurs the
small coal with the large surface area is found in the centre of the hold,
whilst the large coal will roll down the sides. This aggravates the situation,
as the large coal gives a good path for air to flow to the smaller coal where
the spontaneous heating is most liable to occur.
Most coal fires in cargo occur at about ‘tween deck
level and this is the area where the greatest attention should be paid to
temperature and the restriction of through ventilation.
The following are recommendations for the carriage of
coal.
The ventilators to the lower holds should be so arranged
that they might be opened or closed at will during the voyage.
As the critical temperature at which the process of
spontaneous heating in coal becomes greatly accelerated is in some varieties of
coal as low as 36˚C, and generally is not much higher, the need of keeping
the exteriors surface of the hull, and thereby the interior of the ‘tween decks
and holds, as cool as possible is manifest.
The iron decks of ships carrying coal in the tropics can be covered with dunnage to lessen heating.
Suitable means should be provided for ascertaining
from time to time the temperature of the lower mass of coal, particularly below
the hatchways, and this might be done by means of two pipes leading down to the
bottom of the coal at each hatchway.
The temperature tubes should have closed ends to
prevent admission of air into the cargo. The temperature of the coal at three
heights should be taken daily.
Gas from the holds or ‘tween decks space may find its
way into shaft, peaks, chain lockers or similar space unless the bulkheads and
casings are maintained in gas tight conditions.
Naked lights should not be used in holds or other
spaces in which gas may accumulate until the spaces have been well ventilated.
Full use should, when necessary, be made of the
breathing apparatus or smoke helmet and the safety lamp, which form part of the
ship’s statutory fire appliances.
The employment of the crew in chipping and painting
below decks during the voyage should be avoided. The danger from smoking should be realized
and no oily waste, wood, old rope, sacking etc. should be left below where it
can become ignited by spontaneous heating
On arrival at the port of discharge the hold
ventilators should be unplugged and the lower hold well ventilated before
commencing to work cargo.
Coal is frequently loaded from a single tip and
earlier it was necessary to drift the vessel
fore and aft so that all holds may be filled. To keep these shifts to a minimum No.2 was
first put under the tip.
After about one third the capacity of the hold was
loaded the vessel was shifted so that No. 3 was loaded to about one third of
its capacity. Likewise the remaining
after holds were loaded and then the tip was shifted astern to reach No. 1,
half the capacity was put in, before shifting to No. 2, which was then
filled.
The other after holds were now filled in order
excepting the aftermost. The aftermost hold and the No.1 were now worked so
that the vessel would complete loading in a good trim.
Coal is sometimes graded, when this in so, care should
be taken to prevent undue breakage.
Lowering the first few truckloads into the hold helps
as do control of the rate of tipping down and chute.
Some ports have conveyor belts and an endless bucket
system for loading; this is excellent for graded coal and also keeps the dust
down with the ordinary coal.
Fortunately it is mainly the better coals, which are
graded, and in generally these are not so friable.
Coal will need to be trimmed and its angle of repose
is quite high, especially if large coal is loaded.
There is no danger for coal shifting unless it is the
very small stuff known as mud coal, slurry or duff.
This is very fine coal, almost dust, and if the
moisture content is high it behaves almost like a liquid.