Cargo Work
Deck Cargo
Cargo which are normally carried on
deck include the following but are not limited to these and many exceptional
cargoes may be carried and also have been carried in the past.
Dangerous cargo – IMDG cargo not permitted on deck
Large packages which due to any size restriction may
have to be loaded on to the deck
The above includes engineering or construction
equipment
Odd size package
Where the bulk volume far exceeds the weight of the
cargo – knocked down bridges, port equipment – not easily liable to weather
damage.
Occasionally livestock in limited numbers
Onions or other perishables – short voyages with the
weather holding
Yachts – luxury boats.
Cast iron goods – man hole covers – pipes.
The list is endless and it all depends on the routes,
the trading pattern and the weather.
The cargo whether on deck or under deck stow has to be
stowed well and the cargo should be prevented from moving and gaining enough
momentum to part lashings and damage the ship structure.
Deck cargo is liable to damage itself – fall overboard
and thus be lost. However the misery does not stop here in the act of parting
lashing and going overboard the deck cargo unleashes considerable damage to the
ship structure as well as the crewmembers.
Small apparently insignificant items such as sounding
pipes and air pipes are often torn out and this may endanger the ship from the
resulting chances of flooding lower down compartments.
Crewmembers ordered to lash cargo where the lashings
have parted have been seriously injured and some have lost lives combating the
shifting cargo.
The point is to have a good solid stow – prevent the
cargo from shifting and gaining momentum with the shift. Since this would part
any strong lashing. The lashing undertaken should be for the worst sea
condition that may be experienced.
Deck cargo loading on top of hatch covers should be
carefully planned. All loading of under deck spaces should have been completed
– lashing may continue with portable lights.
The hatch covers should be closed and battened down –
all side wedges as well as cross wedges (centre wedges) should have been
fitted. With the hatch cover sealed for sea, the space should then be given out
for loading of deck cargo.
The permissible load density of the hatch covers
should be checked and timbers laid to spread the weight of the cargo. The load
density of the hatch covers are given for a new vessel and as the ship ages the
load density would reduce due to fatigue of the metal as well as wear and tear.
Thus the utmost need to spread the weight using timber.
Shoring and toming of the hatch cover from below deck
is practically useless since the hatch cover moves/ slides somewhat with the
motion of the ship.
The height of the cargo on the hatch covers as well as
that on deck should not be so high that the view is obstructed from the Navigating Bridge.
Ice accumulation on hatch cover and on deck
The above photographs show the extent
of the weight that Ice accumulation can pose for a ship. The weight on deck may
eventually lead a ship to progress to a condition of ‘angle of loll’.
The weight of the ice may be in excess of a hundred
tonnes, and thus the danger of a ship regarding stability.
As with the above any deck cargo for that matter would
have a very high KG as such the GM (F) would be quite small. Especially in the
case of GC vessels, which do not have a very large GM (F) the loading of deck
cargo, is bound to lead to further loss of GM (F). If the ship loads the deck
cargo with her own gear then the ship would during the loading operation have
still further low GM (F) due to the KG of the load being at the top of the
derrick/ crane for part of the loading sequence.
Containers on deck
Containers when they are loaded on deck are subject to
the following consideration – barring stability, which would have been planned
for.
The load density of the deck
Spreading the load of the container evenly
Chocking the container base to prevent shifting due to
rolling or pitching
Lashing the container for the above as well to prevent
the container from being bodily lifted.
Placing the containers in as close a group as possible
Safeguarding the sounding pipes and the air pipes
within the periphery of the container space.
Keeping the fire hose boxes clear as well as the
passage leading to them, the fire hydrants should similarly be kept clear.
No lashing should be taken which would damage or cause
to be damaged the fire lines.
Checking that the leads for the lashing wires are
adequate as well as that the chocking points are well supported
Keeping a passage for crew members to check the
lashings during g voyage.
In general the close stow is difficult on GC vessels
where the container is usually loaded between the hatch coaming and the
bulwark. So the container should be loaded as close as possible to the hatch
coaming, as well as close to the Mast House structure. If few containers are
being loaded then the shelter offered by the Mast House structure should be
kept in mind.
The load is spread by having the container loaded onto
timbers at least 4” x 4”. The timbers should be extended to well beyond the
shoe of the container in all directions to spread the load. Once this is done
the chocking of the container is started. Again heavy timbers are used and the
container is first secured to prevent any lateral and transverse shifting.
While selecting chocking points all heavy framework should be selected. Bulwark
stays are not strengthened enough to be used as chocking points. Hatch coamings
may be used and as a last resort bulwark stays. After the chocking is completed
the container is lashed. The lashing is further to prevent the longitudinal as
well as the transverse shifting. For this the base shoes offer the best lashing
points. To prevent the container being bodily shifted out the lashings are continued
to the top shoes.
All lashing should be separate in the sense that a
single lashing wire should not be passed over a few shoes and then lashed at
the final point. Each lashing should have a turnbuckle or bottle screw
incorporated and there should be at least 60% free thread in them after
completion of lashing.
The bottom lashing and the top lashing should not be
counted together fore the purpose of assessing the total number of lashings
taken for the container.
The top lashings are for bodily rise and as such
should be counted separately.
As a thumb rule, if the SWL of the lashing wire is 2T
then to lash the top of a 20T container the number of lashings should be a
minimum of 10 (all well positioned), similarly the bottom should have 10. The
bottom lashings may be reduced depending upon the chocking of the container and
the availability of the lashing point.
Note that a single strong point for lashing should not
have more than 2 lashing wires – the preferred would be 1, however it is often
impossible to find so many lashing points.
This shows a container ship lashing; note that the
container is loaded onto the ship shoe slots which are strengthened, the rod
lashings are only for the top of the containers.
Here the bottom shoes are not lashed since the ships
sunken shoes and twist locks effectively chock and lash the bottom of the
container.
Stowage and
Lashing of Timber deck cargoes as laid down by IMO code of Safe Practice for
Ships Carrying Timber Deck Cargoes
Purpose
The purpose of the Code is to make recommendations on
stowage, securing and other operational safety measures designed to ensure the
safe transport of mainly timber deck cargoes.
Application
This Code applies to all ships of 24 m or more in
length engaged in the carriage of timber deck cargoes. Ships that are provided
with and making use of their timber load line should also comply with the
requirements of the applicable regulations of the Load Line Convention.
Timber means sawn wood or lumber, cants, logs, poles,
pulpwood and all other type of timber in loose or packaged forms. The term does
not include wood pulp or similar cargo.
Timber deck cargo means a cargo of timber carried on
an uncovered part of a freeboard or superstructure deck. The term does not
include wood pulp or similar cargo.
Timber load
line means a special load line assigned to ships complying with
certain conditions related to their construction set out in the International
Convention on Load Lines and used when the cargo complies with the stowage and
securing conditions of this Code.
Weather deck means the uppermost complete deck exposed
to weather and sea.
The
stability of the ship at all times, including during the process of loading
and unloading timber deck cargo, should be positive and to a standard
acceptable to the Administration. It should be calculated having regard to:
The increased weight of the timber deck cargo due to:
Absorption of water in dried or seasoned timber, and
Ice accretion, if applicable;
Variations in consumables;
The free surface effect of liquid in tanks; and
Weight of water trapped in broken spaces within the
timber deck cargo and especially logs.
Safety precautions to be taken as far as stability of
the ship is concerned
The master should:
Cease all loading operations if a list develops for which
there is no satisfactory explanation and it would be imprudent to continue
loading;
Before proceeding to sea, ensure that:
The ship is upright;
The ship has an adequate metacentric height; and
The ship meets the required stability criteria.
Ships carrying timber deck cargoes should operate, as
far as possible, with a safe margin of stability and with a metacentric height
which is consistent with safety requirements but such metacentric height should
not be allowed to fall below the recommended minimum.
However, excessive initial stability should be avoided
as it will result in rapid and violent motion in heavy seas which will impose
large sliding and racking forces on the cargo causing high stresses on the
lashings. Operational experience indicates that metacentric height should
preferably not exceed 3% of the breadth in order to prevent excessive
accelerations in rolling provided that the relevant stability criteria are
satisfied.
This recommendation may not apply to all ships and the
master should take into consideration the stability information obtained from
the ship’s stability manual.
STOWAGE
General
Before timber deck cargo is loaded on any area of the
weather deck:
Hatch covers and other openings to spaces below that
area should be securely closed and battened down;
Air pipes and ventilators should be efficiently
protected and check valves or similar devices should be examined to ascertain
their effectiveness against the entry of water;
Accumulations of ice and snow on such area should be
removed; and
It is normally preferable to have all deck lashings,
uprights, etc., in position before loading on that specific area. This will be
necessary should a preloading examination of securing equipment be required in
the loading port.
The timber deck cargo should be so stowed that:
Safe and satisfactory access to the crew’s quarters,
pilot boarding access, machinery spaces and all other areas regularly used in
the necessary working of the ship is provided at all times;
Where relevant, openings that give access to the areas
can be properly closed and secured against the entry of water;
Safety equipment, devices for remote operation of
valves and sounding pipes are left accessible; and
It is compact and will not interfere in any way with
the navigation and necessary working of the ship.
During loading, the timber deck cargo should be kept
free of any accumulations of ice and snow.
Upon completion of loading, and before sailing, a
thorough inspection of the ship should be carried out. Soundings should also be
taken to verify that no structural damage has occurred causing an ingress of
water.
On ships provided with, and making use of, their
timber load line, the timber deck cargo should be stowed so as to extend:
.1 over the entire available length of the well or
wells between superstructures and as close as practicable to end bulkheads;
.2 at least to the after end of the aftermost hatchway
in the case where there is no limiting superstructure at the aft end;
.3 athwartships as close as possible to the ship sides,
after making due allowance for obstructions such as guard rails, bulwark stays,
uprights, pilot boarding access, etc., provided any area of broken stowage thus
created at the side of the ship does not exceed a mean of 4% of the breadth;
and
.4 to at least the standard height of a superstructure
other than a raised quarterdeck.
The basic principle for the safe carriage of any
timber deck cargo is a solid stowage during all stages of the deck loading.
This can only be achieved by constant supervision by shipboard personnel during
the loading process.
SECURING
General
Every lashing should pass over the timber deck cargo
and be shackled to eye plates and adequate for the intended purpose and
efficiently attached to the deck stringer plate or other strengthened points.
They should be installed in such a manner as to be, as far as practicable, in
contact with the timber deck cargo throughout its full height.
All lashings and components used for securing should:
.1 possess a breaking strength of not less than 133
kN;
.2 after initial stressing, show an elongation of not
more than 5% at 80% of their breaking strength; and
.3 show no permanent deformation after having been
subjected to a proof load of not less than 40% of their original breaking
strength.
Every lashing should be provided with a tightening
device or system so placed that it can safely and efficiently operate when
required. The load to be produced by the tightening device or system should not
be less than:
.1 27 kN in the horizontal part; and
.2 16 kN in the vertical part.
NOTE: 1 Newton equals
0.225 lbs. force or 0.1 kgf.
Upon completion and after the initial securing, the
tightening device or system should be left with not less than half the threaded
length of screw or of tightening capacity available for future use.
Every lashing should be provided with a device or an
installation to permit the length of the lashing to be adjusted.
The spacing of the lashings should be such that the
two lashings at each end of each length of continuous deck stow are positioned
as close as practicable to the extreme end of the timber deck cargo.
If wire rope clips are used to make a joint in a wire
lashing, the following conditions should be observed to avoid a significant
reduction in strength:
.1 the number and size of rope clips utilized should
be in proportion to the diameter of the wire rope and should not be less than
four, each spaced at intervals of not less than 15 cm;
.2 the saddle portion of the clip should be applied to
the live load segment and the U-bolt to the dead or shortened end segment;
.3 rope clips should be initially tightened so that
they visibly penetrate into the wire rope and subsequently be retightened after
the lashing has been stressed.
Greasing the threads of grips, clips, shackles and
turnbuckles increases their holding capacity and prevents corrosion.
Uprights
Uprights should be fitted when required by the nature,
height or character of the timber deck cargo.
When uprights are fitted, they should:
.1 be made of steel or other suitable material of
adequate strength, taking into account the breadth of the deck cargo;
.2 be spaced at intervals not exceeding 3 m;
.3 be fixed to the deck by angles, metal sockets or
equally sufficient means; and
.4 if deemed necessary, be further secured by a metal
bracket to a strengthened point, i.e., bulwark, hatch coaming.
Loose or packaged sawn timber
The timber deck cargo should be secured throughout its
length by independent lashings.
The maximum spacing of the lashings should be
determined by the maximum height of the timber deck cargo in the vicinity of
the lashings:
.1 for a height of 4 m and below, the spacing should
be 3 m;
.2 for heights of above 4 m, the spacing should be 1.5
m.
The packages stowed at the upper outboard edge of the
stow should be secured by at least two lashings each.
When the outboard stow of the timber deck cargo is in
lengths of less than 3.6 m, the spacing of the lashings should be reduced as
necessary or other suitable provisions made to suit the length of timber.
Rounded angle pieces of suitable material and design
should be used along the upper outboard edge of the stow to bear the stress and
permit free reeving of the lashings.
Logs, poles, cants or similar cargo
The timber deck cargo should be secured throughout its
length by independent lashings spaced not more than 3 m apart.
If the timber deck cargo is stowed over the hatches
and higher, it should, in addition be further secured by:
.1 a system of athwarthship lashings (hog lashings)
joining each port and starboard pair of uprights near the top of the stow and
at other appropriate levels as appropriate for the height of the stow; and
.2 a lashing system to tighten the stow whereby a dual
continuous wire rope (wiggle wire) is passed from side to side over the cargo
and held continuously through a series of snatch blocks or other suitable
device, held in place by foot wires.
The dual continuous wire rope should be led to a winch
or other tensioning device to facilitate further tightening.
Testing, examination and certification
All lashings and components used for the securing of
the timber deck cargo should be tested, marked and certified according to
national regulations or an appropriate standard of an internationally
recognized standards institute. Copies of the appropriate certificate should be
kept on board.
No treatments, which could hide defects or reduce
mechanical properties or strength, should be applied after testing.
A visual examination of lashings and components should
be made at intervals not exceeding 12 months.
A visual examination of all securing points on the
ship, including those on the uprights, if fitted, should be performed before
loading the timber deck cargo. Any damage should be satisfactorily repaired.
Lashing plans
One or more lashing plans complying with the
recommendations of this Code should be provided and maintained on board a ship
carrying timber deck cargo.
Personnel
Protection And Safety Devices
During the course of the voyage, if there is no
convenient passage for the crew on or below the deck of the ship giving safe
means of access from the accommodation to all parts used in the necessary
working of the ship, guard lines or rails, not more than 330 mm apart
vertically, should be provided on each side of the deck cargo to a height of at
least 1 m above the cargo. In addition, a lifeline, preferably wire rope, set
up taut with a tightening device should be provided as near as practicable to
the centreline of the ship. The stanchion supports to all guard rails or
lifelines should be spaced so as to prevent undue sagging. Where the cargo is
uneven, a safe walking surface of not less than 600 mm in width should be
fitted over the cargo and effectively secured beneath, or adjacent to, the
lifeline.
Where uprights are not fitted, a walkway of
substantial construction should be provided having an even walking surface and
consisting of two fore and aft sets of guard lines or rails about 1 m apart,
each having a minimum of three courses of guard lines or rails to a height of
not less than 1 m above the walking surface. Such guard lines or rails should
be supported by rigid stanchions spaced not more than 3 m apart and lines
should be set up taut by tightening device.
As an alternative a lifeline, preferably wire rope may
be erected above the timber deck cargo such that a crewmember equipped with a
fall protection system can hook onto and work about the timber deck cargo. The
lifeline should be:
.1 erected about 2 m above the timber deck cargo as
near as practicable to the centreline of the ship;
.2 stretched sufficiently taut with a tightening
device to support a fallen crewmember without collapse or failure.
Properly constructed ladders, steps or ramps fitted
with guard lines or handrails should be provided from the top of the cargo to
the deck, and in other cases where the cargo is stepped, in order to provide
reasonable access.
Action To
Be Taken During The Voyage
Tightening of lashings
It is of paramount importance that all lashings be
carefully examined and tightened at the beginning of the voyage as the vibration
and working of the ship will cause the cargo to settle and compact. They should
be further examined at regular intervals during the voyage and tightened as
necessary.
Entries of all examinations and adjustments to
lashings should be made in the ship’s logbook.
