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Iron ore loading & causes of iron ore liquefaction during sea passage & countermeasures
Most dry cargo ship losses mainly involved while carrying ores and, frequently, the practice of loading alternate holds. While this method has advantages such as making the ship less stiff and reducing loading, trimming, discharging and cleaning costs, it has the major disadvantage of imposing severe stresses on the hull in periods of heavy weather thus making her susceptible to structural damage.
While SOLAS Chapter XII recognises this problem in bulk carriers of over 150 metres in length and over ten years of age by prohibiting them from loading alternate holds, many owners and operators have also recognised the dangers and ships unaffected by SOLAS XII have also stopped alternate hold loading. Thus, it is important to plan stowage carefully to ensure that individual holds are not overloaded and that excessive sheer forces and bending moments are avoided.
Hold preparation is relatively simple in that there are no special requirements for iron ore apart from the necessity for holds and bilges to be clean and free of previous cargo residues. Bilges should be covered with burlap to prevent cargo entering the bilge system. Other ores, such as chrome and manganese, may require a stricter cleaning regime to ensure that they are not contaminated. If chrome and manganese ores are being carried in the same ship great care must be taken to avoid cross contamination.
Loading of iron ore has usually been carried out by pouring the cargo into the middle of the hold where it forms a pile with a gradually increasing broad base. To a certain extent this method of loading is in conflict with the requirement of the IMSBC Code "... to ensure that the tanktop is not overstressed during voyage and during loading by a pile of the cargo." While many terminals still have fixed shiploaders, more modern loaders can move along the quay and reach both the inner and outer parts of the hold thus ensuring a far more even distribution of the cargo over the tanktop.
The use of spout extensions can help achieve the same result while the ability to lift a bulldozer or front loader onto the cargo may be necessary if neither other option is available. However, if loading is by a fixed loader it will be necessary to warp the ship along the quay to ensure that the cargo is well distributed in a particular hold. A fast loading rate may also contribute to excessive stresses.
Iron ore liquefaction cases
In 2009 two ships - the Asian Forest and the Black Rose - capsized and sank following liquefaction of iron ore fines which they had loaded at the Indian ports of Mangalore and Paradip. There have been other incidents of liquefaction, particularly when iron ore fines have been loaded during or after the Indian monsoon season, resulting in ships becoming unstable and being forced to seek refuge.
Iron ore fines in good condition after
loading in a hold
Iron ore fines liquefied after transportation
in the same hold
In other cases cargoes loaded have been found to have a moisture content in excess of the Transportable Moisture Limit (TML) prior to the ships departure and the ships in question have been prevented from sailing by the local authorities until the situation has been rectified, leading to substantial delays.
The Master or his representative should monitor the loading operation from start to finish. Loading should not be commenced until the Master or the ships representative is in possession of all requisite cargo information in writing as described above.
The Master has an overriding authority under SOLAS not to load the cargo and/or to stop the loading of the cargo if he has any concerns that the condition of the cargo might affect the safety of the ship.
The shipper must provide the Master or his representative in writing with all information and documentation required under the IMSBC Code in sufficient time before loading to ensure that the cargo can be safely loaded onto, carried and discharged from the ship .
The documentation must include: (a) A certificate/declaration certifying the moisture content of the cargo loaded in each of the ships holds together with a statement that to the best of the shippers knowledge the moisture content is the average moisture content of the cargo.
(b) A certificate certifying the TML of the cargo together with the FMP test result prepared by a competent laboratory
(Source : Britannia circular 2010)
Iron ore characteristics
Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3). Hematite is also known as "natural ore", a name which refers to the early years of mining, when certain hematite ores containing up to 66% iron could be fed directly into iron-making blast furnaces.
Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel. 98% of the mined iron ore is used to make steel. Indeed, it has been argued that iron ore is "more integral to the global economy than any other commodity, except perhaps oil".
Iron ore Bulk density ( Kg/m3) 1250 to 3448
Stowage Factor (m3/t) = 0.29 to 0.80
Iron ore Loading Port: Haldia, Paradip, INDIA
Discharging port: Xingang, China
Consideration prior loading
- Weather precautions : Loading in good weather and shall stop if rain
- Hazard : No specific hazard.This cargo is non-combustible or has a low fire risk
- Ventilation : No special requirement
- Stowage & segregation : No special requirement
- Hold cleanliness : Clean and Dry as relevant to the hazards of the cargo.
- Carriage : No special requirement
- Discharge : No special requirement
- Clean up : Prior to washing out the residues of the cargo, the bilge wells of the cargo spaces shall be cleaned.
Trim in accordance with the relevant provisions required under section 4 and 5 of the IMSBC code. As the density of the cargo is extremely high, the tank top may be overstressed unless the cargo is evenly spread across the tank top to equalize the weight distribution. Due to consideration shall be paid to ensure that the tank top is not overstressed during voyage and during loading by a pile of the cargo.
Precautions during loading
Loading rates of this cargo are normally very high. Due consideration shall be paid on the ballasting operation to develop the loading plan require by regulation vi/9.3 in the solas convention To stop loading if further moisture and/or can tests are conducted, as necessary, on any parts of the cargo presented for shipment (sections 4.5.2 and 8.4 of the IMSBC Code). To monitor the stockpiles and/or barges to ensure that the cargo presented for shipment is from the designated and tested stockpiles and/or barges. This will involve keeping a careful tally and identification of barges offered for loading. To ensure loading is suspended during periods of rainfall.
Problems in Brazilian ports
There are reports of iron ore sinter feed (or sinter feed) shipments from Brazilian ports, including Ponta da Madeira, Tubarao and Itaguai, liquefying en route. Some Brazilian shippers declare sinter feed as a Group C cargo, under the IMSBC Code. This categorises the cargo as not being prone to liquefaction, so shippers do not have to provide test results for moisture content, Transportable Moisture Limit (TML) and Flow Moisture Point (FMP). Sinter feed is clearly listed in the IMSBC Code as Iron Concentrate, under the schedule for Mineral Concentrates. All cargoes covered by this schedule are Group A cargoes and are prone to liquefaction.
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- Care of cargo during loading- Trimming pours
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- Cargo loading agreement between ship and terminal
- Bulk carrier loading manual
- Handling of deballasting (ship duties) during high loading rate
- Cargo and ballast handling guide
- Responsibility of ship during cargo operation
- Shipboard hazards & bulk carriers safety guideline
- Asymmetric cargo and ballast distribution for bulk carriers
- Limitations on exceeding load lines
- Risk of deviation from the loading limitations
- Cargo handling guidance for deck officers
Ventilation requirement for bulk cargo loaded
- Preparation for ships carrying bulk cargo & standard loading condition
- Monitoring cargo operation safety checks in a bulk terminal
- How to avoid cargo damage by applying proper ventilation methods
- Measures against liquefaction of bulk cargo
- How to plan cargo discharge in a safe manner ?
Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
It is vital to reduce the likelihood of over-stressing the ship's structure and also complying with all essential safety measures for a safe passage at sea. Our detail pages contain various bulk carrier related topics that might be useful for people working on board and those who working ashore in the terminal. For any remarks please Contact us
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