Segregation of Cargoes

Stowage and segregation requirements

Materials that are required to be separated during stowage must not be handled at the same time. Any residue from previous material must be removed if it is not compatible with the cargo to be loaded.

Dangerous Goods

Segregation of Dangerous Goods

According to IMDG code:

Segregation is the process of separating two or more substances or articles which are considered mutually incompatible when their packing or stowage together may result in undue hazards in case of leakage or spillage, or any other accident.

The IMDG Code requires that the dangerous goods have to be stored and segregated according to their hazard, class and compatibility.

The code also provides detailed information of where dangerous goods should be stowed and how they should be separated or segregated from other cargoes.

The dangerous goods identified as non compatible should not be carried in the same Cargo Transport Unit (CTU).

The IMDG Code gives four segregation terms:

“Away from”

“Separated from”

“Separated by a complete compartment or hold from”

“Separated longitudinally by an intervening complete compartment or hold from”

IMDG Code segregation, stowage and Dangerous Goods is applied to all cargo spaces on deck or under deck of all types of ships and cargo in transport units and incompatible goods shall be segregated from one another. For the purpose of segregation, the IMDG Code has grouped together similar chemical properties in the dangerous goods list. In the dangerous goods list, the group substances are referred as follows:

1. Acids
2. Ammonium Compound
3. Bromates
4. Chlorates
5. Chlorites
6. Cyanides
7. Heavy metals and their salts
8. Hypochlorite
9. Lead and its compounds
10. Liquid halogenated hydrocarbons
11. Mercury and mercury compounds
12. Nitrites and their mixtures
13. Perchlorates
14. Permanganates
15. Powdered metals
16. Peroxides
17. Azides
18. Alkalis

 

 Following diagrams show the Segregation methods for:

• Packaged Dangerous Goods
• Container Ships
• Ro-Ro Ships
• Bulk Carriers  

The following media explains about the Dangerous Cargo Disaster:

        

Dry Cargoes

Segregation requirement for dry cargoes

It is the responsibility of the ship to discharge the cargo as it was at the loading port. Failure to comply may lead to unwanted delay, claims and litigations. When loading more than one parcel of cargo, one should be more careful to protect each cargo as they may belong to different receivers and would expect their cargo as it was at the loading port.

 

In stowing many types of cargo in same compartment, one needs to take account of the type, nature and compatibility of the cargoes. Precautions to be taken to ensure that, the holds are free from rust, insect and previous cargo. Electrical fittings if any in the hold must be isolated.

Dry cargoes need to be segregated for the following reason:

• Cargo contamination - edible cargo mixed with cargo not suitable for human consumption may be rejected by the consignee.
• Cargo which can taint other cargoes - cargo which gives off strong odour should not be loaded with other cargoes' especially edible cargo 
• Cargo need ventilation - cargos give off heat or dangerous gases should be ventilated, hence should not be stored in the same compartment as cargoes which should not be ventilated. 
• Bulk and packaged cargoes - bulk cargoes are generally dusty in nature. Dust deposited packages may not be accepted by the consignee.
• Cargo with reactive nature - should never be loaded along with general cargo
• Edible cargo - generally should not be loaded with other cargoes in the same compartment. A clean hold is very important.
• Cargoes liable to spontaneous combustion should not be loaded with other cargoes.
• Some cargoes may oxidize and emit toxic gases, some are self heating - should not be loaded with other cargoes in the same compartment.

Wet Cargoes

Segregation of wet cargoes

Wet cargoes are generally not loaded together in a compartment with other cargo because many have peculiar behavior and may not be compatible with other cargoes.

• Some cargoes when they are wet emit toxic fumes. 
• Some may oxidize and cause oxygen depletion in the compartment.
• Some cargoes when they are wet become corrosive cause damage to the ship and affect skin and eyes.
• Some cargoes emit flammable gas.
• Some ore cargoes when loaded in wet condition liquefy and may lead to a loss of stability.

Wet cargoes are generally loaded in separate holds.

Delicate Cargoes

Delicate cargoes are susceptible to damage if precautions not taken to protect them from other non compatible cargoes in the same compartment. The following are some delicate cargoes carried by ships:

• Temperature sensitive - to be kept under refrigeration.
• Perishable - to be kept under refrigeration.
• Fragile - to be packed accordingly and stowed and secured where less affected by ships movements.
• Foodstuffs - perishable and non-perishable - proper ventilation and temperature control to be provided.
• Electronics - away from heat and vibration.
• Chemicals - as per segregation methods prescribed in the Chemical Code.
• Pharmaceuticals - to be kept under refrigeration.
• Susceptible for taint - away from cargoes emitting strong odour.
• Cargo that may give off strong fumes - away from cargoes susceptible to taint.
• Reactive - as per segregation methods prescribed in the IMDG Code.
• Polymerizing - as per segregation methods prescribed in the Chemical Code.
• Toxic - as per segregation methods prescribed in IMDG Code.

Separating Adjacent Parcels of Cargo

Need for separation

When similar looking cargo or same cargo for different ports is to be loaded in the same hold, they need to be separated effectively so that they don't get mixed. This will prevent cargo contamination and short-landing/over-carriage claims.

Separation of Dry Bulk Cargo

Minerals

• Polythene Envelope – This is best suited for separating small to medium sized parcels of mineral cargo, though it is rather cost effective
• Vertical Bulkhead/Container Bulkhead – This temporary athwarship bulkhead can be quickly constructed and is best suited for larger parcels of cargo
• Horizontal Steel Plate – This is best suited for large parcels which are lighter than most other types of minerals

Grain

• Burlap Tarpaulin – Burlap are polythene tarpaulins can be used along with timber chocking.
• Burlap and plywood – The cargo is trimmed before fitting a burlap tarpaulin overlaid with plywood

For bagged cargo and cartons, coloured nylon net is sufficient. 

But for bulk cargo, net cannot be used as a separation material. For bulk cargo, materials used for separation include tarpaulin, polythene sheets or burlap.

Before laying the separation for bulk cargo, lower parcel cargo should be trimmed leveled. Otherwise due to ship's vibration and movements, cargo will settle down and the separation material can be stretched and damaged, causing cargo contamination.

If the angles of repose of the parcels are different, the cargo with a low angle of repose is loaded first and the cargo with high angle of repose is loaded on top to minimize the depression of the lower parcel of the cargo while loading with loaders from higher levels.

If the separation of the cargo happens to be at lower hopper area, since the larger separation material is used for separation, settling of the cargo will not cause any cargo contamination. If the separation takes place at the upper hopper area where relatively smaller separation material is used will not be sufficient to cover the larger area at lower level when the cargo settles down during transit, hence cargo contamination can take place. 

It is a good practice to measure the distance of the separation from the hatch coaming, to locate it in the discharge port.