SEPARATION OF CARGOES:
The purpose of separation of cargoes is to prevent either:
- Different cargoes OR
- Different parcels of the same cargo…from being over-carried (inadvertently left in the ship’s hold).
Separation refers to the material used to separate blocks of cargoes by port rotation or by consignee (receivers). The idea is that if the cargo is properly separated and marked it would avoid confusion during discharge of the cargo and thereby prevent over carriage.
There may be numerous ways of separating cargoes bound for different ports or for same port and different consignees. Though there is no hard and fast rule, the principle is to ensure that cargoes destined for a particular port or consignee is delivered accordingly.
Failure to do this at the time of loading would create chaos at the discharging port, with short landings – residual cargo, since the excess cargo that would remain would not be permitted to be discharged in a subsequent port without creating more paperwork and expenditure.
In fact cases have arisen where ships have been arrested for landing cargo not destined for that port – customs take a very strict view of this in many parts of the world.
Thus it is of paramount importance to ensure that cargoes are efficiently separated and marked so that to an un-initiated the cargo discharge may proceed smoothly.
Markings may be made by different means for different cargoes; the following are some of the few:
- Hessian separation strips,Burlap in various colours – used to encircle the parcel.
- Markings by shoring, blocking and securing the cargo parcel.
- Paper sheets – Separation of small cartons or cases bound for different ports but stowed adjacent to each other is separated by using heavy paper with appropriate marks on the exterior.
- Lashing ropes with coloured strips of cloth: – Lumber needs careful separation and consignee marks. This may be marked by laying lashing rope with coloured strips of cloth. Lumber can also be separated by paint marking.
- Different cargo used as a separation between two similar cargoes.
- Water based colours: used as port marking or consignee marking – this method though is used more often for consignee marking.
- Tarpaulin: Can be used to separate bulk cargoes.To prevent over carriage and to allow freight forwarders to correctly identify cargoes, most break bulk cargoes are labelled or stencilled with identifying marks.
- Where bare steel cargo is loaded oil based paint is also sometimes used, since the others may not be suitable due to partial rusting of the plates as well that hessian strips are in-efficient for these cargoes.
SEGREGATION OF DIFFERENT CARGOES:
One of the fundamental requirements in the protection of cargo is the proper segregation of the various types of cargo such as wet cargo, dry cargo, dirty cargo etc.
Segregation refers to the stowage of cargoes in separate parts of the ship so that one cannot damage the other due to its inherent properties.
For e.gWet cargoes (Liquids in containers) must be kept away from Dry cargoes (Paper products, flour, rice etc).
Segregation of heavy and light cargoes is necessary with respect to their vertical position.
Odorous cargoes (Cargoes that give off fumes such as kerosene, turpentine, ammonia etc. that are likely to taint certain cargoes) must be stowed away from delicate cargoes such as rice, flour, tea and cereals.
The IMDG Code (International Maritime Dangerous Goods) Code is an international code for the shipment of dangerous goods by sea. It covers amongst other matters, segregation of incompatible substances. Once the initial stowage plan is made the segregation requirements must be dealt with in accordance to chapter 7.2 of Volume 1 of the IMDG Code. The segregation requirements between dangerous goodscarried on the same ship are laid out in a tabular format.
Is any material that is used to protect goods and their packing from moisture, contamination or mechanical damage.
Dunnage can be wood, plastic, tarpaulin or a range of other materials.
How Dunnage is used.
There are a few reasons why dunnage is so necessary on general cargo ships while loading general cargo.
Of prime importance is to keep the cargo away from the steel bottom of the hold.
The moisture in the air condenses on the steel bottom and these droplets of moisture over a period of time can damage cargo.
This is known as ship sweat. And only by dunnage can the cargo be safeguarded against this. Good ventilation certainly helps but some amount of sweat is ever present.
The second reason why dunnage is spread about on the holds is to bring about some amount of frictional resistance between the cargo and the steel bottom. Thus lashing becomes easier.
Another factor is the dunnage helps in spreading the cargo weight evenly.
In the event of small ingress of water the dunnage helps in channelling the water into the bilgewells.If this were not prevented then any accidental ingress of water would be absorbed or retained in pools by the cargo.
If the hold bottom is dirty due to stain and hard coating of earlier cargo and hosing down is not possible then a double layer of dunnage would prevent the cargo in coming into contact with the stain.
In general, lower holds are laid with double dunnage while tween decks are layered with single dunnage. The double dunnage works by providing a channel due to the bottom layer and cargo support due to the second tier.
The size of the dunnage may vary but usually they are about 6” X 1” X 6 feet. These are laid about 6” to 10” apart, though the gaps may again vary depending upon the nature of the cargo. The bottom tier of the hold dunnaging may be laid in the fore and aft direction and the top tier in the athwart ship direction. At the aft of the hold a clearing of two feet is laid with the bottom tier in the athwart ship direction. This helps in the water/ condensation from trickling to aft and then subsequently finding the bilge well.
Tween deck dunnaging is of one tier – exceptionally may be two tiers and it really doesn’t make much difference if the dunnage is laid out in the fore and aft direction or in the athwart ship direction.
For heavy cargo where spreading the weight takes precedence over other hazards, the dunnage or timber used is generally 4” X 4” X 6 feet (they may be also of stouter variety).
These heavy timbers are laid out in the fore and aft direction in order that the load is spread on as many frame spaces as possible.
Dunnaging also forms a very important factor when ventilation is of primary concern especially when loading a consignment of Rice.
Extra channels are created within the bagged cargo to allow good ventilation, together with double dunnaging being provided between stacks of 4-6 bags.
If this is not done then the cargo sweat that may be generated is not removed and condenses on the cargo itself allowing the cargo to rot.
Dunnage is used primarily for the protection of the cargo from sweat related damage and consequently it is used so that the cargo does not get too closely packed thereby obstructing to the flow of air.
Special cargoes use more dunnage where air channels have to be kept so that the airflow is not hampered. Rice is one such cargo.
Advantage of dunnaging is also from the fact that it spreads the weight of the cargo evenly all across the tank top or tween deck top, but this advantage is a side benefit, the main reason is protection from sweat. And to some extent from heat from the boiler spaces in the engine room.
Dunnage is thus primarily for the prevention of sweat damage to cargo.
The structure of the ship is made of steel; this steel being a good conductor of heat cools down faster than wood as such the temperature of the steel may fall below the dew point of the air within the compartment leading to sweat. However if this steel can be prevented from coming into contact with the cargo by a layer of wood, which being a poor conductor of heat does not cool down so drastically, then the effect of the sweat coming into contact with the cargo and thus damaging the same may be limited.
If despite precautions being taken, sweating does occur, the damage caused may be minimized by adequate dunnaging of the boundaries of the compartment.
The permanent dunnage of the ships side is known as SPAR Ceiling or CARGO BATTENS. It consists of timber about 150mm x 50mm fitted over the side frames. It is usually fitted horizontally into cleats on the frames. There is a vertical distance of not more than 230mm between the battens. On some ships the spars are fitted vertically and this gives better protection to the cargo as well as it suffers less damage and is thus more long lasting. Spar ceiling may also be fitted on the bulkheads at the ends of the compartment; this is especially the case where the bulkhead is the engine room bulkhead.