Basic Definition Definitionss Carriage of cargo cargo is the main purpose of existence of a merchant ship. With the wide wide variety of cargoes carried by sea ,the safe carriage of cargo is essentially an important task.
Bale Capacity
It is the capacity used for the cargo in bales or pallets ( i.e. packaged form)
Cargo does not conform to the shape of cargo space. Some space is left unused.
Figure 1 Bale Cargo
Figure 2 Cargo on pallet
Technically, it can be defined as the cubic cubic capacity of a cargo space when the breadth is measured from the inside of the cargo battens battens (spar ceiling) , depth is measured measured from the wood sheathing on the tank top to the underside of the deck beams beams and the length length is measured from the inside of the fore and aft bulkhead stiffeners or spar ceiling where fitted.
Grain Capacity
This is the total internal volume of a cargo compartment measured from shell plating to shell plating and from tank top to under deck. An allowance is given for the volume volume occupied by frames and beams. This space is not only associated associated with the the carriage of grain, as such, but but with any form of bulk cargo, which would stow similarly, that that is to say completely filling the space. It is obvious that a solid cargo can be stowed only up to the limits of the frames and beams whereas bulk cargo will flow around such members. Therefore when measuring for general cargo, it is the bale capacity, capacity, which is taken into consideration. consideration.
bale capacities are normally used to show the volume or capacity Although both grain and bale of a ship to carry cargo, cargo, other units of measurement are more appropriate for specific trades, e.g. TEUs for container ships.
Generally, bale capacity is less than the grain capacity but in some ships where hold sides are smooth both can be same. However, bale capacity will never be more than the grain capacity.
Cargo battens or sparring
Cargo battens are fitted horizontally in the fore and aft direction inside the ship’s frames in the holds and tweendecks at a regular distance to prevent contact between the cargo and the frames or shell plating.
These are wooden planks fitted to the frames by means of hooks, so that they can be removed.
The cargo battens keep the cargo free from moisture or sweat, which may condense on the ship’s sides.
Used in general cargo ships.
Dunnage
In the context of cargo operation, this is the term used to describe timber boards which can be laid singularly or in double pattern under cargo parcels to keep the surface of the cargo off the tank top (steel plate). Its purpose is to provide air space around the car go and so prevent ‘cargo sweat’ and to spread the load .
It should be noted that cargo battens are placed on the ship side while Dunngae is placed on the tank top.
Stowage Factor (SF)
It is defined as the volume of cargo space in cubic meter occupied by a unit tonne of cargo .For example, if SF of a cargo is 1. 2 m 3/T , it means that one tone of that cargo will occupy 1.2 m 3 of cargo space. Other units such as cubic feet/ tones are also in use.
It should be noted that it is the reciprocal of density, i.e. cargoes with high density will have a low stowage factor and vice versa. SF of cargo may vary since it depends upon the packing and nature of cargo and how the goods have been processed. For a same kind of cargo, there can be more than one SF depending upon these factors. For example, SF of coal is 1.25-1.35 and depends upon the country of origin.
Formula to Use:
OR
Thus, In order to find the weight of cargo which will fit in a particular cargo hold divide the volume of cargo space by SF It should be noted that it is the volume of the cargo space not the volume of cargo into consideration.
Broken Stowage ( BS)
This is defined as unfilled space in a loaded cargo hold which is not filled with cargo. It is the space occupied by dunnage, the space between packages and the space that is left over the last tier placed in stowage. Broken stowage is expressed as a percentage of the total volume of the cargo and not of the space in which the cargo is stored. The percentage that has to be allowed varies with the type of cargo and with the shape of cargo hold.
It is greatest when packages are of large size and irregular shape.
BS must always be added to SF to get the realistic space that a cargo will occupy.
In order to clarify the concept of SF and BS, let us consider the following example. Say, there is a cargo hold of length 12.5m, breadth 9 m and depth 6.3 m. The volume of the cargo hold= 12.5 x9 x 6.3=708.75 m 3 If the SF of granite slabs is 0.48 m 3/T, weight of granite slabs which will fit in the cargo hold will be Volume of cargo hold divided by SF i.e. 708.75/0.48= 1476.56 T (A)
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However due to the shape of granite slabs and the available cargo space, BS of 11.2% is taken into consideration, now space occupied by the slabs ( effective SF)= SF+ %BS
0.48 +11.2% of 0.48=0.48 +0.0538 0.5338 m3/T
(11.2 X0.48)/100 Weight of granite slabs that can fit in the hold=708.75/0.5338=1327.74 T (B)
Note the difference in (A) and ( B) .Due to BS less cargo is loaded.
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Load density It is the maximum weight that can loaded safely on unit area.
The height to which a cargo can be stowed on a deck will depend upon load density called permissible load density (PLD) and can be found as
Required height of cargo to load=
(SF X Weight of cargo)/L X B SF X ( Weight of cargo )/L XB SF X PLD
SF=Volume/ Weight or Volume=SF X Weight
More specifically, we can write Required height to load cargo= SF ( afte r allowing BS) X PLD (Permissible Load Density)
Now again let us consider the above example. Load density in use or, weight of granite loaded per sq meter in the cargo hold = 1327.74/ (12.5 x9)=11.802 T. If the permissible load density of the deck is 8.5 T/m 3, it means we can not load the granite slabs to full height of 6.3 m (Too heavy for that height). The height required= SF ( after allowing BS) X PLD =0.5338 X 8.5=4.537m It means though cargo hold is up to 6.3 m, we cannot load granite slabs more than 4.537 m.
Deadweight Cargo This is the cargo on which freight is usually charged on its weight. Cargoes which have SF 1.22m3/T or less stowage factor are classed as deadweight cargo.
Measurement Cargo This is the cargo on which freight is usually charged on the volume occupied by the cargo and this cargo is usually light cargo having a stowage factor of more than 1.22m 3/T .
Ad Valorem Cargo Freight for certain expensive cargoes, e.g. precious stones, gold bars, etc. is not levied based on weight or measurement but on the value of the cargo.
Ex- A cargo hold of 10m X 6 m X 5m is loaded with Chemical drums ( SF 1.6). Find the weight occupied by the drums if broken stowage is 10 % V=10x6X5=300 M3 SF=1.6 +10 % of 1.6 =1.6+0.16=1.76 m 3/T
Weight=300/1.76=170.45 T
Load density=170.45/(60)=2.8 T/m 2 If PLD is 2.0 T/m2 What will be height of cargo?
=SF X PLD =1.76 X 2.0=3.52 m
