1_ basic definitions cargo work

8/3/2019 1_ Basic Definitions Cargo Work

1/5

Basic Definitions

Carriage of cargo is the main purpose of existence of a merchant ship. With the 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.

Technically, it can be defined as the cubic capacity of a cargo space when the breadth ismeasured from the inside of the cargo battens (spar ceiling) , depth is measured from the

wood sheathing on the tank top to the underside of the deck beams and the 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 toshell plating and from tank top to under deck.

An allowance is given for the volume occupied by frames and beams. This space is not only associated with the carriage of grain, as such, but with any form of

bulk cargo, which would stow similarly, that is to say completely filling the space.

Although both grain and bale capacities are normally used to show the volume or capacityof a ship to carry cargo, other units of measurement are more appropriate for specific

trades, e.g. TEUs for container ships.

Figure 1 Bale Cargo Figure 2 Cargo on pallet

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, which is taken into consideration.


2/5

Generally, bale capacity is less than the grain capacity but in some ships where hold sidesare 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 aftdirection inside the ships 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 ofhooks, so that they can be removed.

The cargo battens keep the cargo free from moisture orsweat, which may condense on the ships 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 laidsingularly 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 cargo and so prevent cargo sweat and to spread theload .

It should be noted that cargo battens are placed on the ship side while Dunngae is placed on thetank top.

Stowage Factor (SF)

It is defined as the volume of cargo space in cubic meter occupied by a unit tonne ofcargo .For example, if SF of a cargo is 1. 2 m3/T , it means that one tone of that cargo

will occupy 1.2 m3 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 willhave a low stowage factor and vice versa.

SF of cargo may vary since it depends upon the packing and nature of cargo and howthe 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.


3/5

Formula to Use:

OR

Thus, In order to find the weight of cargo which will fit in a particular cargo hold dividethe volume of cargo space by SF

It should be noted that it is the volume of the cargo space not the volume of cargo intoconsideration.

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 notof 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 ofcargo 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 m3

If the SF of granite slabs is 0.48 m3/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)

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


4/5

(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.

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 calledpermissible load density (PLD) and can be found as

Required height of cargo to load=

(SF X Weight of cargo)/L X B SF=Volume/ Weight or Volume=SF X Weight SF X ( Weight of cargo )/L XB SF X PLDMore specifically, we can write

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.

Required height to load cargo= SF ( after allowing BS) X PLD (Permissible Load Density)


5/5

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 1.22m3/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 m3/T

Weight=300/1.76=170.45 T

Load density=170.45/(60)=2.8 T/m2

If PLD is 2.0 T/m2 What will be height of cargo?

=SF X PLD

=1.76 X 2.0=3.52 m

1_ basic definitions cargo work

Documents