Section 8.1: Iron Ore (Fines, Lump, Pellets – Liquefaction, High Density)

Iron ore is one of the most significant commodities transported by sea in bulk, forming the primary raw material for the global steel industry. It is shipped in vast quantities, primarily on Panamax, Capesize, and Very Large Ore Carriers (VLOCs/Valemax). While often considered a relatively straightforward cargo, certain forms of iron ore, particularly fines, can present serious safety hazards, most notably liquefaction. Its high density also poses significant challenges for vessel structure and stability if not managed correctly.

1. Main Types of Iron Ore Carried in Bulk:

Iron ore is typically shipped in several forms, each with slightly different handling characteristics and potential hazards:

Iron Ore Fines: Consist of small particles, often resulting from the crushing and screening processes during mining. This is the form most susceptible to liquefaction if the moisture content is too high.

Iron Ore Lump (or Lumpy Ore): Comprises larger pieces of ore. Generally considered a Group C cargo (not prone to liquefaction) and less dusty than fines, but still very dense.

Iron Ore Pellets: Fines that have been agglomerated into small, hard spheres (pellets) through a process involving heating. Pellets are generally free-flowing, less dusty than fines, and typically Group C cargoes. They are a premium product for steelmaking.

Iron Concentrate: This is a processed form where the ore has been ground to a very fine particle size and the iron mineral has been concentrated. Iron concentrates are almost invariably Group A cargoes and have a high risk of liquefaction if their moisture content exceeds the TML. While a distinct product, it’s often discussed alongside iron ore fines due to similar liquefaction risks.

2. IMSBC Code Classification and Key Considerations:

IRON ORE (Typical Lump/Pellets):

Group: Usually classified as Group C.

Hazards: Primarily relates to its high density and potential for shifting if not properly trimmed. Generally not prone to liquefaction or chemical hazards.

BCSN: IRON ORE

IRON ORE FINES:

Group: Can be Group A (if liable to liquefy) or Group C (if the conditions for safe carriage as such are met, e.g., moisture content is safely below TML, or the specific fines are known not to liquefy under any moisture condition – requiring strong evidence). Shippers must declare if it is Group A and provide TML/MC certificates. If declared as Group C, the Master must be satisfied that it will not behave as a Group A cargo.

Hazards:

Liquefaction (Primary Concern if Group A): As discussed extensively, this is a critical risk.

Shifting: Even if not Group A, fines can shift if not well-trimmed due to their relatively low angle of repose.

High Density: Shared hazard with all iron ore types.

Dust: Can be very dusty during loading/discharge.

BCSN: IRON ORE FINES

IRON CONCENTRATE (or specific mineral concentrates like Magnetite Concentrate):

Group: Almost always Group A.

Hazards:

Liquefaction (Very High Risk): This is the defining hazard.

High Density.

May also have other minor hazards depending on the specific mineralogy (e.g., some sulphide concentrates may have Group B properties too, though this is less common for typical iron concentrates).

BCSN: Various, e.g., IRON CONCENTRATE, MAGNETITE, etc. (refer to specific schedule).

3. Key Hazards and Precautions Associated with Iron Ore:

A. Liquefaction (Primarily Iron Ore Fines and Concentrates):

Mechanism and Consequences: As detailed in Chapter 4, Section 3.1, the potential for rapid loss of stability and capsize is severe.

Critical Reliance on TML/MC Certification:

The Master must receive valid TML and MC certificates from the shipper before loading any parcel declared as, or suspected of being, Group A.

Scrutinize these certificates for date of testing (should be recent, ideally within 7 days of loading), issuing authority, and test method used.

Crucially, the certified Moisture Content (MC) must be less than the certified Transportable Moisture Limit (TML). If MC ≥ TML, the cargo must not be loaded unless the vessel is specially constructed or fitted for such cargoes (IMSBC Code Section 7) and all conditions are met. This is a rare capability for standard bulk carriers.

Shipper’s Declaration: The shipper must declare if the cargo is Group A. If Iron Ore Fines are offered without this declaration, or if declared as Group C but there is any doubt about its potential to liquefy (e.g., visual appearance, local weather conditions like heavy rain on stockpiles), the Master must seek immediate clarification, request testing, and, if necessary, refuse the cargo.

Visual Checks and Can Test:

During loading, continuously observe the cargo for signs of excessive moisture (splattering, free water, fluid appearance).

The “Can Test” (IMSBC Code Section 8.4) can be used as a supplementary shipboard check if there are concerns. A “fail” (free moisture appearing on the surface after banging the can) is a strong indication of potential liquefaction risk, and loading should be stopped immediately pending further investigation and laboratory testing. However, a “pass” on the Can Test does not guarantee safety if certified MC is already near or above TML.

P&I Club Guidance: P&I Clubs provide extensive guidance and loss prevention material on the carriage of iron ore fines and other Group A cargoes. Masters should be familiar with their club’s recommendations. Many clubs advise extreme caution and advocate for independent testing if there is any doubt.

B. High Density / Low Stowage Factor (All Types of Iron Ore): Iron ore is a very dense cargo (Stowage Factor typically 0.28 – 0.80 m³/tonne, meaning it takes up little space for its weight). This has significant implications:

Tank Top Strength: The weight of iron ore in a hold can easily exceed the maximum permissible load on the tank top (tonnes/m²) if the hold is filled to a substantial height. The stowage plan must respect these limits for each hold. Concentrating too much weight in the center of a hold can overstress the tank top plating and supporting structures.

Longitudinal Stress (Shear Forces and Bending Moments):

Due to its density, iron ore occupies a relatively small volume, meaning a large proportion of the ship’s length (especially in end holds) might be empty or lightly loaded if carrying a full deadweight cargo. This can lead to high shear forces at the ends of the loaded sections and significant bending moments.

Alternate Hold Loading: To manage these stresses, especially on larger vessels, iron ore is often loaded in alternate holds (e.g., Nos. 1, 3, 5, 7 loaded; Nos. 2, 4, 6 empty or only partially filled/ballasted). The ship’s Loading Manual will specify approved alternate loading conditions, and the loading computer must be used to verify that stresses remain within limits for any such plan.

Block Loading / Part Cargoes: If loading only a partial cargo, or loading in specific “blocks” of holds, stress distribution is even more critical and must be carefully calculated.

High Center of Gravity of Cargo (if not trimmed): If untrimmed, the peak of the dense iron ore cone can be relatively high, raising the overall VCG of the cargo in that hold, which can adversely affect stability if not managed.

Structural Damage Risk: Improper loading sequences (e.g., filling one hold completely before others) or exceeding tank top/stress limits can cause immediate or cumulative structural damage, including buckling of plating, cracking of frames, or even catastrophic hull girder failure.

C. Shifting (All Types, but especially if not properly trimmed):

Even Group C iron ore (lump, pellets) can shift if not adequately trimmed, particularly if the angle of repose is relatively low or if the vessel encounters severe weather.

Trimming: Iron ore should be trimmed reasonably level in accordance with IMSBC Code Section 5 to minimize void spaces and reduce the likelihood of a surface slide or shift. This is especially important if the hold is not substantially full.

The high density means that even a relatively small volumetric shift can result in a significant transverse shift of weight, leading to a list and potential stability problems.

D. Dust (Especially for Iron Ore Fines):

Iron ore fines can generate significant reddish-brown dust during loading and discharge.

Health Hazard: Inhalation of fine iron ore dust can be detrimental to health. Crew and stevedores should wear appropriate respiratory protection (dust masks/respirators) and eye protection.

Environmental Concerns: Dust can cause local air pollution and contaminate surrounding areas or water if blown overboard. Many ports have strict dust control regulations.

Equipment Contamination: Dust can ingress into deck machinery, ventilation systems, and accommodation if not properly managed. Hatches of non-working holds should be kept closed and sealed. Accommodation doors and vents should be kept closed on the leeward side if possible.

Dust Control Measures: Terminals may use water sprays on stockpiles or at transfer points. The ship may need to wash down decks after loading.

E. Corrosion (Generally Low for Pure Iron Ore, but can be a factor):

Most typical iron ores are not highly corrosive. However, if the ore has a high moisture content and contains impurities like chlorides or sulphides (less common for standard iron ores but possible for some specific types or concentrates sometimes loosely termed “iron ore”), it can be corrosive to steel hold structures over time, especially if coatings are damaged.

Regular inspection and maintenance of hold coatings are always important.

4. Pre-Loading Preparations:

Hold Cleanliness: Typically, a “normal clean” or “sweep clean” standard is acceptable after a previous similar cargo. However, if the previous cargo was entirely different (e.g., grain, fertilizer, coal), or if the next cargo is a particularly high-grade iron ore sensitive to contamination, a higher standard may be required by the shipper/charterer. Always confirm specific requirements. Ensure holds are dry.

Bilge Wells: Clean, strum boxes in place and clear, suctions tested.

Stowage Plan and Loading Sequence: A detailed plan must be prepared using the loading computer, paying meticulous attention to:

Tank top strength limitations in each hold.

Permissible shear forces and bending moments at all intermediate stages and for the final loaded condition.

Alternate hold loading conditions as per the ship’s approved manual.

Final drafts and trim.

Coordination with de-ballasting sequence.

Stress Limits: Ensure all officers involved are aware of the vessel’s maximum permissible SF and BM values.

5. Loading Operations:

Strict Adherence to Sequence: The loading sequence approved by the Master must be followed by the terminal. The ship’s officer on watch must monitor this closely.

Continuous Stress and Stability Monitoring: The loading computer must be updated regularly (e.g., hourly or after significant tonnage is loaded into a set of holds) with actual cargo loaded and ballast discharged. SF, BM, GM, drafts, and trim must be checked against permissible limits.

Trimming: Ensure trimming is carried out as per the agreed plan and IMSBC Code requirements. Supervise any in-hold mechanical trimming (e.g., by bulldozers) to prevent damage to the ship’s structure.

Dust Control: Implement measures to minimize dust spread (e.g., keeping non-working hatches closed, strategic use of ship’s ventilation if it helps, regular deck washing if dust accumulates heavily).

Monitoring for Liquefaction (if loading Fines/Concentrates):

Constant visual watch on the cargo coming aboard and its appearance in the hold.

Perform Can Tests periodically if there are any concerns, even if certificates were initially satisfactory (e.g., if it starts raining heavily on stockpiles during a prolonged loading).

Be prepared to STOP LOADING IMMEDIATELY if any signs of potential liquefaction (cargo flowing, excessive splatter, free water on surface) are observed.

Draft Readings: Monitor drafts regularly and compare with loading computer predictions to cross-check loaded quantities.

6. Precautions During Voyage:

Cargo Shift: Particularly in heavy weather, be vigilant for any signs of cargo shifting (unexplained list, unusual vessel motion). If a shift is suspected, take appropriate action (e.g., alter course to reduce rolling, consider seeking shelter if severe).

Liquefaction Monitoring (for Group A Fines/Concentrates):

While liquefaction is most likely to initiate due to ship motion at sea, the conditions for it are set at the load port.

If there was any doubt about the cargo’s condition at loading (even if eventually loaded), the voyage requires heightened vigilance. Changes in vessel motion, unexplained list, or “slopping” sounds from holds could be late indicators. However, once liquefaction occurs on a significant scale, options are very limited. Prevention at the load port is paramount.

Ventilation: Generally, iron ore (Group C) does not require ventilation. For Group A fines, ventilation is usually not recommended as it doesn’t prevent liquefaction and can potentially alter moisture distribution near the surface. For some specific iron ore products that might have minor Group B characteristics (e.g., some DRI types are iron-based), the specific schedule must be consulted.

7. Discharge Operations:

Grab Damage: Iron ore is a very dense and abrasive cargo. Careless grab operation by stevedores during discharge can cause significant damage to tank tops, hopper plates, side frames (in single-hull ships), and other hold structures. Close supervision is necessary.

Dust Control: Similar to loading, dust can be a major issue during discharge.

Complete Discharge: Ensure holds are discharged as completely as possible to minimize residues, which can be heavy and affect future cargo operations or lightship displacement.

Monitor Stresses: Even during discharge, stresses must be monitored if discharging in a specific sequence or from alternate holds.

8. Master’s Key Responsibilities Specific to Iron Ore:

Absolute Vigilance on TML/MC for Fines/Concentrates: This cannot be overemphasized. The Master is the last line of defense against loading potentially liquefiable cargo.

Unyielding Adherence to Stress Limits: Given the high density, ensuring the vessel is not overstressed during any stage of loading is critical. Do not be pressured by terminals to deviate from safe loading sequences.

Effective Use of Loading Manual and Instrument: Ensure the Chief Officer and other deck officers are proficient in using the loading manual and instrument specifically for high-density cargo scenarios, including approved alternate loading conditions.

Clear Communication with Terminal: Ensure the terminal understands and follows the ship’s required loading sequence and trimming requirements.

Proactive Stoppage: Be prepared to stop loading immediately if unsafe conditions related to cargo properties (liquefaction risk) or vessel stress/stability arise.

Carriage of iron ore, while routine for many bulk carriers, demands constant vigilance and strict adherence to safety protocols, particularly when dealing with fines or concentrates due to the liquefaction risk, and always with respect to managing the stresses imposed by its high density. The Master’s unwavering commitment to these principles is paramount.