Manganese Ore: IMSBC Code Schedule and Carriage

Manganese ore is a high-density Group C cargo under the IMSBC Code when shipped as lump material, with a bulk density up to 3,200 kg/m3 that places structural tanktop loading at the centre of every cargo plan. Manganese ore fines are classified separately as Group A, liable to liquefy when moisture content exceeds the Transportable Moisture Limit. The ore moves from South Africa, Gabon, and Australia to Chinese steel mills and ferroalloy plants in a seaborne trade of roughly 40 to 45 million tonnes per year.

The IMSBC Code, adopted under SOLAS Chapter VI by IMO Resolution MSC.268(85) and first entering force in January 2011, regulates every solid bulk cargo carried by sea through individual schedule entries in Appendix 1. Manganese ore appears under two separate entries: MANGANESE ORE, which covers the lump and coarse forms classified as Group C, and MANGANESE ORE FINES, which covers the fine-particle form classified as Group A. The distinction between these two entries is not academic: Group C imposes standard bulk handling procedures, while Group A requires pre-loading Transportable Moisture Limit (TML) certification and triggers the same pre-loading moisture management regime that applies to iron ore fines.

Manganese ore is the primary raw material for ferromanganese, silicomanganese, and refined ferroalloys that feed the global steel industry. Every tonne of steel produced contains 6 to 9 kg of manganese used as a deoxidizer, desulfurizer, and alloying element. The seaborne ore trade therefore tracks crude steel production, and China’s position as the world’s largest steel producer makes it the dominant importer by a wide margin.

The IMSBC Code schedule entries for manganese ore

MANGANESE ORE (Group C): schedule particulars

The IMSBC Code schedule for MANGANESE ORE covers lump, crushed, and agglomerated (pellet or sinter) forms of manganese ore that do not meet the fines definition. The schedule classifies the cargo as Group C with no significant chemical hazard designation.

The stowage factor range of 0.31 to 0.50 m3/t reflects the range from high-grade dense lump ore (lower stowage factor, higher bulk density) down to lower-grade porous or friable ore. For comparison, thermal coal typically sits at 1.10 to 1.50 m3/t and iron ore at 0.34 to 0.38 m3/t. Manganese ore at its denser end is among the heaviest cargoes shipped in bulk, making structural loading the dominant operational concern.

MANGANESE ORE FINES (Group A): schedule particulars

The IMSBC Code treats MANGANESE ORE FINES as a distinct schedule entry classified as Group A. The fines classification applies to cargoes where the particle size distribution places a sufficient proportion below 1 mm to generate liquefaction risk when the bulk moisture content exceeds the TML.

The pre-loading requirements for Group A cargoes are set out in IMSBC Code Section 4. The shipper must provide, before loading begins: a declaration that the moisture content of the cargo at time of loading is less than 90 per cent of the TML, and a certificate stating the TML value determined by a method approved under IMSBC Code Appendix 2. The TML certificate must not be older than six months; the moisture content certificate must not be older than seven days at the time of loading. The master may not accept cargo for which either certificate is missing or expired.

Mineralogy and commercial grades

Mineralogy

Manganese occurs in more than 300 minerals, but commercially recoverable deposits concentrate in a much smaller set. The primary manganese ore minerals are:

• Pyrolusite (MnO2, manganese dioxide): the most common and the highest-oxidation-state manganese mineral; typically 63.2 per cent Mn by mass; the principal mineral in the Kalahari Manganese Field in South Africa.
• Psilomelane / romanechite (Ba(Mn4+,Mn2+)8O16(OH)4): a mixed barium-manganese oxide that forms hard, dense botryoidal masses and is common in supergene enrichment zones.
• Braunite (3Mn2O3·MnSiO3): a manganese silicate oxide found in metamorphic manganese deposits.
• Cryptomelane (K(Mn4+7Mn3+)O16): a potassium manganese oxide tunnel-structure mineral.
• Hausmannite (Mn3O4): a mixed Mn2+/Mn3+ oxide found in higher-grade ore zones.
• Rhodochrosite (MnCO3): a manganese carbonate mineral that is the primary ore in some South American deposits; lower Mn grade but economically important in some contexts.
• Manganite (MnO(OH)): a manganese oxide hydroxide, typically associated with weathering profiles.

The Kalahari Manganese Field, which stretches across the Northern Cape Province of South Africa and contains roughly 75 per cent of known global manganese ore reserves, hosts ore in the Hotazel Formation, a Paleoproterozoic sequence of alternating braunite-rich and iron-oxide layers within the Transvaal Supergroup. The ore is largely pyrolusite and cryptomelane in the supergene upper zone, grading to braunite and hausmannite at depth.

Commercial grade specifications

Manganese ore is traded globally in several specification bands. Steel producers and ferroalloy smelters set minimum Mn content, maximum iron content, and maximum silica, alumina, and phosphorus contents, because each affects alloy output chemistry and smelting energy consumption.

Typical commercial grade specifications for seaborne trade include:

Iron content and silica content in the ore directly affect the energy balance of the blast furnace or electric arc furnace smelting process. Phosphorus is particularly critical: ferromanganese produced from high-phosphorus ore requires secondary treatment to reach acceptable steel grades, adding cost. Shippers and receivers negotiate phosphorus caps, often at 0.10 to 0.20 per cent maximum, in the sale contracts. Each of these parameters must be declared in the cargo documentation under the IMSBC Code, because they affect how the cargo behaves in closed holds and under heat.

The lump-versus-fines distinction and Group A risk

The boundary between Group C lump ore and Group A fines is determined by particle size distribution, not by Mn grade, origin, or mineralogy. A high-grade Kalahari lump ore consignment classified Group C at the time of shipping can effectively become Group A if it is crushed or degraded during stockpile handling so that the proportion of sub-1 mm fines rises above the threshold.

The IMSBC Code defines MANGANESE ORE FINES separately from MANGANESE ORE precisely because manganese ore is prone to generating fines during mining, crushing, screening, stockpiling, and shiploader reclaim. The Kalahari Manganese Field is mined with both underground and open-cast methods, and ore is processed through crushing and screening circuits that generate a range of product sizes. Material screened below approximately 6 mm is typically classified as fines or chips, and material below 1 mm is the fraction that drives TML determination.

Producers and shippers must screen product at the point of loading to confirm whether the consignment meets the lump definition or falls into the fines schedule. When particle size distribution puts the cargo in an intermediate zone, the conservative approach under the IMSBC Code is to declare and treat it as Group A. Intermediate-grade material with a borderline moisture content and a high fines fraction can shift into the liquefaction regime during a long voyage if hold moisture migrates.

The liquefaction mechanism for manganese ore fines is the same as for iron ore fines and mineral concentrates: ship motion compacts fine particles and builds positive pore-water pressure in the interstitial spaces. When pore pressure exceeds the effective stress holding particles apart, the cargo loses shear strength abruptly and behaves as a dense slurry. A partially liquefied hold generates a free-surface effect that reduces the vessel’s righting lever and, in the worst case, allows the cargo mass to slide to one side of the hold irreversibly.

The IMSBC Code does not list specific manganese ore fines liquefaction casualties in the same detail as it does for nickel ore or iron ore fines, but the generic Group A cargo liquefaction risk record includes casualties that involved manganese ore fines. P&I clubs have recorded claims involving manganese ore fines shipments with excess moisture. The TML certification requirement is therefore not a formality: it represents the Code’s minimum acceptable standard of evidence that the cargo is safe to load.

Seaborne trade geography

South Africa and the Kalahari Manganese Field

South Africa’s Kalahari Manganese Field in the Northern Cape Province around Hotazel and Kuruman is the largest concentration of manganese ore in the world. The field hosts deposits from multiple producers, including Assmang (a joint venture of African Rainbow Minerals and Assore), South32, Tronox, and several smaller operations.

Exports move by rail on the Sishen-Saldanha heavy-haul railway (the Orex line, 861 km) to Saldanha Bay, and by the Northern Cape rail network to Port Elizabeth and Ngqura (Coega). Saldanha Bay is the preferred export terminal for high-tonnage Capesize loading; Port Elizabeth and Ngqura handle a mix of Panamax and Handymax-scale parcels as well as containerized manganese products.

South Africa exported approximately 15 to 17 million tonnes of manganese ore per year in the 2020 to 2024 period, representing about 36 per cent of global seaborne trade. The Northern Cape mines supply both the export market and domestic ferroalloy smelters at Meyerton, Newcastle, Witbank, and Polokwane.

Gabon and the Comilog operation

Gabon is the world’s second-largest manganese ore exporter, with virtually all production coming from the Comilog mine at Moanda in the interior of the country, operated by Eramet subsidiary Comilog. The mine produced approximately 7 to 8 million tonnes per year through the 2018 to 2024 period. Ore is transported by the Trans-Gabonese Railway (the Transgabonais, 648 km) to Owendo terminal near Libreville on the Atlantic coast.

Gabonese ore is characterized by high Mn content (typically 46 to 48 per cent Mn) and relatively low phosphorus and iron, making it a premium feedstock for ferromanganese production. The export terminal at Owendo handles Panamax and smaller bulk carriers; very large bulk carriers must load at anchorage by transshipment from barges.

Australia: Groote Eylandt and Bootu Creek

Australia’s manganese ore exports come from two principal sources. The Groote Eylandt Mining Company (GEMCO), a South32 subsidiary operating on Groote Eylandt in the Gulf of Carpentaria in the Northern Territory, produces a medium-to-high grade lump and fines product. The operation exported roughly 3.5 to 4.5 million tonnes per year through the 2019 to 2023 period. Ore is loaded at the Groote Eylandt terminal directly onto bulk carriers in sheltered waters.

The Bootu Creek mine in the Northern Territory, operated by OM Holdings, exports smaller volumes of medium-grade ore through Darwin. Production reached a peak of approximately 1.5 million tonnes per year before operational interruptions in the late 2010s. Both operations ship predominantly to Chinese customers.

Brazil, Ghana, and other sources

Brazil exports manganese ore from operations in Para state (Vale’s Serra do Sossego and Buritirama deposits) and Minas Gerais through ports including Tubarão, Itaguai, and Santarém. Brazilian grades range from medium (35 to 40 per cent Mn) to high grade, and Brazil is an active supplier to European ferroalloy plants as well as China.

Ghana exports from the Nsuta mine operated by Ghana Manganese Company through Takoradi port. Burkina Faso has emerged as a smaller-scale exporter, routing product by truck and rail through Ghanaian and Ivorian port corridors. Côte d’Ivoire, Ukraine (before 2022), China’s own Guangxi province, and India are additional sources of smaller volumes.

Import patterns: China as the dominant buyer

China imported approximately 28 to 32 million tonnes of manganese ore in recent years, representing roughly 70 per cent of global seaborne trade. The ore feeds electric arc furnace ferroalloy smelters producing ferromanganese, silicomanganese, and electrolytic manganese metal (EMM), which in turn feed Chinese steel mills. Major smelting clusters are located in Guangxi, Inner Mongolia, Hunan, Guizhou, and Ningxia provinces. India is the second-largest importer, followed by Europe (principally Norway, France, and Czech Republic for their significant ferroalloy industries) and South Korea.

Structural tanktop loading: the dominant operational concern

Manganese ore at 2,800 to 3,200 kg/m3 bulk density exerts more load per unit area on a bulk carrier’s tanktop than almost any other regularly shipped dry bulk commodity. A single cargo hold filled to 12 metres depth contains approximately 33,600 to 38,400 tonnes of cargo per hold bay, and the load per square metre of inner bottom plating must be checked against the vessel’s rated tanktop strength before any loading plan is accepted.

Standard bulk carriers are rated for a range of tanktop strengths, typically expressed in tonnes per square metre (t/m2) for general cargo or, for Capesize and VLOC vessels, by the maximum total cargo mass per hold and per hold bay. Panamax bulk carriers are commonly rated for 10 to 12 t/m2 tanktop loading. Manganese ore at 3,000 kg/m3 and a fill depth of 10 metres gives a theoretical load of 30 t/m2, three times the rated limit, before any dynamic amplification from sloshing or ship motion is considered.

In practice, manganese ore can be safely loaded in standard bulk carriers because the cargo is distributed over the entire hold area, not concentrated at a point, and because structural assessment accounts for the actual hold geometry. The critical constraint is the maximum fill depth per hold, not total cargo mass. The loading manual (stability booklet) defines the maximum fill height for each hold as a function of cargo density. For high-density ores, this maximum fill height is often set at 5 to 8 metres in a Panamax hold rather than the 11 to 14 metres that would give full volumetric fill.

This means that loading manganese ore to the vessel’s deadweight capacity requires filling all holds simultaneously to the permitted fill depth, typically across all five to nine holds depending on vessel type. An uneven distribution, where some holds are filled deep and others are empty, creates a hogging or sagging bending moment in the hull girder that compounds the tanktop stress. Cargo plans for manganese ore must be approved by a licensed officer against the vessel’s loading manual before operations begin, and must be rechecked at each stage as tonnage accumulates.

The cargo draught survey sequence is particularly useful for manganese ore loading because it provides a running check on loaded tonnage at each stage, allowing the cargo plan to be confirmed against actual loaded weights before the structural limits of any single hold are approached.

Load distribution in alternate hold loading

Some Capesize and post-Panamax bulk carriers are designed for alternate hold loading, where cargo fills holds 2, 4, and 6 (or 1, 3, and 5 depending on vessel design) with holds 1, 3, and 5 empty. This mode is sometimes used for lower-density cargoes like grain. For manganese ore, alternate hold loading concentrates the entire cargo mass in fewer holds, dramatically increasing the load per square metre of tanktop in the loaded holds. Standard bulk carriers are generally not designed for alternate hold loading of high-density cargoes, and the ship’s loading manual will typically prohibit alternate loading for any cargo above a specified density threshold, often 1,800 to 2,200 kg/m3. Manganese ore, at 2,000 to 3,200 kg/m3, falls above this threshold on every vessel where such a limit exists.

Double-bottom flooding as a trim correction tool

Loading manganese ore to a full deadweight cargo with holds filled only partially creates a ship that is trim-positive (stern down) from the aft engine room mass and potentially light in the forward holds. Double-bottom ballast tanks are used to fine-tune trim, but they must be carefully managed: adding ballast water into a double-bottom tank beneath a hold already carrying a heavy ore cargo increases the total load on the tanktop structure. The combined pressure of the ore cargo above and the ballast water pressure from below is additive in terms of plating stress. This is specifically addressed in the loading manual and must be checked by the officer completing the stability calculation.

Dust generation and occupational health

Manganese ore generates dust during every stage of the cargo handling chain: at the mine crushers and conveyors, during stockpile reclaim by bucket-wheel reclaimers, at the shiploader drop point into the hold, and during hold entry for trimming operations.

The cargo is not classified as an MHB (Material Hazardous in Bulk) under the IMSBC Code, but the Code’s schedule notes that dust can be a nuisance and health concern. The relevant occupational exposure limit for inhalable manganese dust in the United States is 5 mg/m3 as a ceiling value for manganese fumes (OSHA General Industry Standard 29 CFR 1910.1000). The American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value for inhalable manganese as an 8-hour time-weighted average is 0.02 mg/m3 for inhalable fraction. Chronic manganese inhalation at elevated concentrations can cause manganism, a neurological condition with symptoms resembling Parkinson’s disease. At the concentrations encountered in the hold during active loading from a shiploader, respiratory exposure can be substantial.

Crew members entering the hold or working on deck during loading should wear appropriate respiratory protection: at minimum, a half-mask respirator with P100 particulate filter. Full-face respirators with P100 filters are appropriate for hold entry during active loading or trimming. Shore workers at the shiploader typically wear dust suppression equipment on site, but shipboard crew operating the hold inspection hatches during loading are in the direct path of dust rising from the cargo impact zone.

Dust suppression at the loading terminal, whether by water misting at the shiploader drop point or by enclosed transfer chutes, reduces dust generation at source. Several South African and Australian manganese ore export terminals have installed enclosed loading systems that substantially reduce airborne dust. Where such systems are not in place, crew on deck during loading should maintain upwind positions and limit time in the dust plume.

Post-discharge hold cleaning

Manganese ore leaves a dark, fine residue on the hold structure that is more adhesive than iron ore residue. Post-discharge hold cleaning for manganese ore requires pressure washing with fresh water followed by a scrubbing pass and another freshwater rinse. Bilge wells must be cleared of all ore fines because manganese ore fines in the bilges, combined with seawater ingress, form a compact slurry that can block bilge suctions.

If the vessel is changing cargo after manganese ore discharge, the degree of cleaning required depends on the incoming cargo. A change from manganese ore to grain requires a certified grain-ready hold cleaning: removal of all traces of ore, scale, rust, and contamination, typically requiring two to three wash cycles and hold cleaning inspection by a certificated hold-cleaner or surveyor.

Hold preparation before loading

The IMSBC Code schedule for both MANGANESE ORE (Group C) and MANGANESE ORE FINES (Group A) specifies that holds must be clean and dry. In practice, this means:

For Group C lump ore loading: bilge suctions must be operable and clear; any bilge water must be pumped out before loading begins; the hold structure must be free of any cargo residue from a previous incompatible cargo; hatch covers must be in good weathertight condition. The hold need not be swept to bare metal for lump ore, but loose rust scale and contamination from previous cargo should be removed.

For Group A fines loading: all Group C requirements apply, plus the bilge system must be confirmed fully operational before loading, because a blocked bilge suction under a fines cargo could trap water migrating to the bilge and contribute to moisture build-up. The bilge water must not only be pumped out but confirmed dry. Any standing water indicates a possible ingress problem that must be investigated and resolved.

A pre-loading survey by an independent cargo surveyor or a port-state control officer may be conducted to verify hold condition. In the South Africa manganese ore export terminals, terminal operators routinely inspect holds before shiploading commences; a hold rejection at this stage halts loading until corrective cleaning is completed.

Trimming requirements

Group C lump ore trimming

MANGANESE ORE in lump form is generally free-flowing. It forms a conical heap under the shiploader drop point with an angle of repose of approximately 37 to 42 degrees. For a standard bulk carrier hold, lump ore loaded from a single shiploader spout will produce a cone-shaped heap that does not reach the hold corners and hatch coaming at full fill height. The IMSBC Code requires the cargo to be trimmed to distribute it reasonably evenly through the hold and to fill the spaces between the heap and the hatch coaming corners.

Trimming for lump ore is done by the terminal’s shiploader operator repositioning the loading spout to direct successive pours into the corner spaces, or by a trim run where the shiploader traverses along the hatch. In some terminals, bulldozers or conveyor-mounted spreaders distribute the cargo within the hold. A level or near-level surface is required so that the cargo does not shift to create a permanent list.

Dense lump ore that has settled tightly may exhibit very limited spontaneous flow in the hold; however, it is not subject to the liquefaction risk of the fines, and a modestly heaped surface with the material occupying the full hold cross-section is acceptable.

Group A fines trimming

MANGANESE ORE FINES requires a level surface after loading, specified in the IMSBC Code schedule. This is not merely cosmetic: a level surface is required to minimize free-surface effect if any localized partial liquefaction occurs during the voyage, and to allow accurate visual assessment of cargo condition during hold entry or camera inspection.

Trimming of fines is more important because the material is prone to angular heaps with steep sides when dumped from a conveyor; without active spreading, large voids can remain in the corners and against the bulkheads. The shiploader operator or terminal bulldozer must spread the cargo evenly before the hatch is closed.

After trimming, a cargo surveyor typically conducts a final post-loading survey to measure the loaded depth from the hatch coaming to the cargo surface and to inspect for any obvious signs of excess moisture (standing pools, slumping, or unusually low angle of repose). These observations, recorded in the survey report, form part of the master’s cargo documentation.

Pre-loading moisture certification for Group A fines

The TML regime for MANGANESE ORE FINES follows the same framework as for all Group A cargoes under IMSBC Code Section 4. The shipper must:

1. Arrange laboratory testing of representative samples of the cargo within six months before loading to determine the TML. The test must use one of the three methods prescribed in IMSBC Code Appendix 2: the flow table test, the penetration test, or the Proctor-Fagerberg test. For manganese ore fines, the flow table and Proctor-Fagerberg tests are both used in practice depending on particle size and fines content.

2. Arrange a moisture content determination on representative samples taken within seven days before loading begins.

3. Certify in writing to the master, before loading commences, that the moisture content of the cargo is less than the TML.

If the cargo has been stockpiled in the open and rain has fallen in the week before loading, the shipper must demonstrate that moisture content was measured after the rain event, not before. Terminal-side and vessel-side surveyors routinely verify this by checking timestamps on laboratory reports against weather records at the loading port.

The can test as a screening tool

The can test, described in IMSBC Code Appendix 3, is a rapid shipside screening procedure that the master or cargo officer can perform without laboratory equipment. The procedure: fill a 0.5 to 1 litre cylindrical container (such as a tin can) with a representative sample of the cargo from the stockpile or from the conveyor stream; bring the base of the can down sharply onto a hard surface from a height of 200 mm and repeat 25 times at one- to two-second intervals; inspect the surface for free moisture or a glossy sheen.

A positive can test, where free water or a wet, reflective surface appears, indicates that the cargo moisture is close to or above the TML. It should trigger immediate suspension of loading and notification to the operator and P&I correspondent. A negative can test does not confirm that the cargo is below the TML: it is a screening tool only, and a certified laboratory result remains the required basis for accepting Group A cargo.

Some manganese ore fines cargoes from certain sources have been found to test negative on the can test at moisture contents still close to the TML, because the particle size distribution, clay content, or mineral surface properties affect the visible drainage response. The can test is a supplement to certification, not a substitute.

Loading rates and terminal equipment

South Africa export terminals

The Saldanha Bay ore terminal (Transnet Port Terminals) handles iron ore primarily but also loads manganese ore on rotations. The terminal is equipped with a two-berth facility with conveyor and shiploader infrastructure rated for approximately 5,000 to 8,000 tonnes per hour (t/h) shiploader output. Loading a Capesize vessel of 175,000 DWT with manganese ore at 5,000 t/h takes approximately 35 hours of continuous loading time, plus loading pauses for hold trimming and cargo plan checks.

Port Elizabeth Multipurpose Terminal and Ngqura Container Terminal (Coega) also handle manganese ore, with shiploaders rated at approximately 1,500 to 2,500 t/h. These terminals are used for Panamax and Handymax-size vessels. Typical loading rates for manganese ore at Port Elizabeth are 1,200 to 2,000 t/h actual over the entire cargo operation, accounting for breaks, repositioning, and trimming pauses.

Gabon (Owendo)

The Owendo Minerals Terminal near Libreville handles Comilog ore with a single-berth facility rated for Panamax-size vessels (approximately 80,000 DWT maximum). The shiploader output is approximately 1,200 to 2,000 t/h. For larger parcels that require Capesize tonnage, lightering at anchorage from barges reduces the effective loading rate further.

Australia (Groote Eylandt)

The GEMCO terminal at Groote Eylandt operates a sheltered water jetty with a shiploader rated for approximately 1,500 to 2,000 t/h. Vessel size is limited by the approach channel and berth depth; post-Panamax vessels are not accommodated at full draft. The terminal loads a mix of lump ore (Group C) and fines (Group A), with separate stockpile areas and conveyor routing to allow clean product separation.

Draft survey for manganese ore

A cargo draught survey is the standard method for determining loaded and discharged quantities of manganese ore. The high bulk density of manganese ore means that small differences in measured draft translate to large differences in calculated cargo mass, because the high cargo-to-water density ratio amplifies the draft reading into tonnage.

The draft survey sequence for manganese ore follows the standard IMSBC Code and IMO/BIMCO recommendations. Pre-loading, the surveyor measures the vessel’s draft at fore, aft, and amidships stations on both port and starboard sides; takes density readings of the dock water at multiple depths; and calculates the lightship displacement and initial deductibles (ballast, fuel, fresh water, stores). Post-loading, the surveyor repeats all measurements and calculates the net loaded cargo mass as the change in displacement.

For a Capesize vessel loading 150,000 tonnes of manganese ore with a bulk density of 2,900 kg/m3, a 1 cm draft reading error translates to approximately 200 to 250 tonnes of cargo error depending on vessel block coefficient and waterplane area at that draft. Terminal scales are typically used in parallel with draft survey as a cross-check; where significant discrepancy exists between scale weight and draft survey result, a joint surveyor investigation and re-reading is standard.

The draft survey is the basis for the bill of lading cargo quantity. For manganese ore, the shipping contract typically specifies a tolerance of 3 to 5 per cent plus or minus for deadweight cargo; the final bill of lading figure is agreed between the shipper’s surveyor and the vessel’s surveyor. Where disagreement persists, a mutually agreed surveyor or the terminal’s official weighbridge provides the reference figure.

Discharge operations

Terminal grab cranes

Manganese ore is discharged at receiving terminals, steel mills, and ferroalloy plants using shore-mounted grab cranes, portal cranes, or self-unloading gantry crane systems. Grab cranes sized for manganese ore use 10 to 25 cubic metre grabs, chosen to match the cargo density and the crane’s rated safe working load (SWL). A 15 m3 grab filled with manganese ore at 2,900 kg/m3 lifts approximately 43.5 tonnes per lift; the crane’s SWL must be rated above this figure with an adequate safety margin.

Manganese ore can compact in the lower levels of the hold during the voyage, particularly if some moisture migration has occurred. Compaction at the hold corners and against bulkheads reduces grab access efficiency; the terminal grab operator may need to use a digging motion to break through the compact mass before the grab closes on the cargo.

Residue handling and hold cleaning at discharge

After grab discharge reduces the cargo to the final layers, a bulldozer or pay-loader on the hold floor sweeps remaining ore to the grab pickup area. Hold residues of 100 to 300 tonnes are normal on a large Capesize vessel; the sweep quality depends on whether the terminal operates with a bulldozer-on-board or relies on grab trimming alone. Manganese ore residues left in hold corners after discharge can generate moisture retention and ore dust issues for the next cargo.

Discharge port choice and vessel constraints

Chinese receiving terminals for manganese ore include Tianjin, Qingdao, Rizhao, Lianyungang, Shanghai, and Zhangjiagang, as well as cluster ports in Guangxi Province. Ferroalloy smelters in Guangxi and Inner Mongolia receive the majority of Gabon-origin ore. The berth depth at Chinese manganese ore terminals typically accommodates Panamax vessels fully laden, with Capesize vessels subject to tide-dependent draft restrictions at some Yangtze River berths.

Voyage considerations

Hatch cover integrity

Hatch covers are the primary barrier against rainwater ingress during the voyage. For Group C manganese ore, rainwater intrusion increases cargo moisture content and, in theory, could push a borderline cargo into the Group A fines range if enough water migrates to the fine-particle fraction of the cargo. For Group A manganese ore fines, hatch cover leaks can directly push the cargo moisture above the TML, triggering liquefaction risk at sea.

Hatch cover inspection before departure should confirm that all hatch cover seals, cleat mechanisms, and drain channels are in good working order. The hatch cover compression test (ultrasonic or hose test) should be performed before loading at the shipper’s discretion or at the master’s request. If the vessel’s hatch covers have a known history of leaking, the master should notify the owner and the charterer before accepting a Group A manganese ore fines consignment.

Monitoring during the voyage

The IMSBC Code does not require continuous monitoring instrumentation for Group C manganese ore fines, but good practice includes visual bilge well checks at each watch, confirmed by pumping tests to confirm bilge suctions remain clear. Any increase in bilge accumulation rate may indicate rainwater ingress through the hatch covers or condensation drainage.

For Group A manganese ore fines, if the master or chief officer has any concern about cargo condition during the voyage, the vessel’s P&I correspondent and owner should be notified immediately. The absence of a reliable method to remeasure cargo moisture content at sea means that any initial excess moisture present at loading is effectively locked in for the voyage. Prevention at the loading port is the only available remedy.

Condensation and ventilation

The IMSBC Code schedule for both MANGANESE ORE and MANGANESE ORE FINES permits surface ventilation (hold ventilation by natural ventilation without forcing air into the cargo mass). In most manganese ore voyages, hold ventilation is conducted on the three-temperatures rule: ventilate when the dew point of the outside air is lower than the cargo temperature. Manganese ore does not generate gas or absorb oxygen in the way that coal or grain can, so ventilation management is simpler. The primary risk from ventilation is the introduction of moist ocean air that could condense on the cool cargo surface and increase surface moisture content.

Limitations

This article draws on the publicly available text of the IMSBC Code as amended through Amendment 07-23 (IMO Resolution MSC.539(107), adopted 8 June 2023, mandatory from 1 January 2025) and the general technical literature on manganese ore mineralogy and seaborne trade. Several limitations apply to this reference:

Schedule text supersedes this article. The exact figures for bulk density, stowage factor, TML test applicability, and all other schedule particulars are determined by the Appendix 1 schedule text in the current IMSBC Code edition and any subsequent MSC circular or resolution amendment. If the schedule text and this article differ, the schedule text governs in all circumstances.

Particle size definition varies. The boundary between MANGANESE ORE (Group C) and MANGANESE ORE FINES (Group A) depends on particle size distribution testing. The IMSBC Code definition is based on the proportion of material below specified sieve sizes. The practical boundary at the loading port is established by physical sampling and sieving. This article describes the general framework; every consignment must be assessed by competent laboratory analysis.

TML values are shipment-specific. This article does not state a TML value for manganese ore fines, because no single value applies across all manganese ore types and sources. TML is specific to a given ore’s particle size distribution, mineral composition, and moisture-retention characteristics. The six-month certificate required by the IMSBC Code is the authoritative figure for any given consignment.

Trade statistics are approximate. The production, export, and import figures cited in this article are drawn from public industry sources and reflect the 2020 to 2024 period. Manganese ore trade volumes are subject to mine output variability, steel market fluctuations, and political and logistical disruptions. Country-level trade statistics for manganese ore are compiled by multiple bodies with varying reporting lag; the figures here are indicative order-of-magnitude references.

This article does not constitute professional maritime advice. Masters, officers, shippers, and receivers must refer to the current IMSBC Code, the vessel’s stability booklet and loading manual, flag state requirements, and the advice of qualified marine surveyors and P&I correspondents for any specific cargo operation.

See also

• IMSBC Code
• IMSBC Group A Cargoes
• IMSBC Group C Cargoes
• Iron Ore: IMSBC Code Schedule and Carriage
• Chrome Ore: IMSBC Code Schedule and Carriage
• Mineral Concentrates: IMSBC Code Schedule
• Cargo Draught Survey for Bulk Carriers

Related calculators:

• IMSBC - Manganese Ore
• IMSBC - Manganese Concentrate
• IMSBC - Iron Ore
• IMSBC - Iron Ore Fines (IOF)
• IMSBC - Silicon Manganese
• IMSBC Group A/B/C Classification
• IMSBC Liquefaction Risk - Group A