Copper Concentrate: IMSBC Code Schedule

Copper concentrate is a Group A cargo under the IMSBC Code, liable to liquefy if the moisture content at loading equals or exceeds the Transportable Moisture Limit. The concentrate is primarily chalcopyrite (CuFeS2) with pyrite as a major gangue mineral; sulphide oxidation can deplete hold oxygen and generate toxic gases in addition to the liquefaction risk. Global seaborne trade runs at approximately 25 to 30 million dry-tonne equivalents per year, dominated by Chilean and Peruvian exports to Chinese smelters, placing the cargo on Handysize, Supramax, and Panamax vessels across the Pacific on nearly every sailing day.

The IMSBC Code, mandatory under SOLAS Chapter VI since January 2011 (Resolution MSC.268(85)), assigns all solid bulk cargoes to one of three groups. Group A cargoes are those that may liquefy when shipped above their Transportable Moisture Limit (TML). Copper concentrate is one of the archetypal Group A cargoes; its fine particle size, high bulk density, and residual filtration moisture place it squarely in the class of cargoes that have caused bulk carriers to capsize with minimal warning. The cargo liquefaction mechanism and the TML regulatory framework are common to all Group A cargoes; the specific properties of copper concentrate, particularly its sulphide chemistry, high density, and concentrated trade flow through a handful of South American ports, give it a distinct handling profile within that class.

The companion IMSBC TML Moisture Check calculator lets masters and cargo officers verify compliance against a declared TML and moisture content before loading. The IMSBC Group A Liquefaction Risk calculator provides a liquefaction risk assessment based on cargo-specific inputs.

Schedule particulars

The IMSBC Code Appendix 1 entry for COPPER CONCENTRATE records the following physical and hazard properties. The values in the table below are drawn from the published schedule; actual values for a specific shipment must come from the shipper’s cargo declaration and laboratory certificates.

The schedule does not assign a fixed TML value because TML is cargo-specific. Two copper concentrates from two different porphyry deposits can differ by 2 to 3 percentage points in TML because of differences in grind size, clay mineral content, and residual sulphide composition. The shipper must provide a TML certificate for each shipment, determined by an accredited laboratory on a representative sample from that specific cargo batch.

Angle of repose is listed as not applicable for copper concentrate in the IMSBC Code because a cohesive fine cargo does not form a stable free-flowing cone under dry conditions; instead, it holds a cut face angle when dry but transitions to a fluid state as pore-water pressure rises above the effective confining stress.

Stowage factor and structural loading implications

The stowage factor of 0.43 to 0.56 m3/t means that copper concentrate is one of the densest bulk cargoes in regular trade. A Supramax vessel with five holds loading a full cargo of copper concentrate may be tanktop-limited: the cargo weight per unit of hold floor area approaches or reaches the structural design limit of the vessel’s double-bottom structure before the holds are filled to full volumetric capacity. This is the structural loading constraint that distinguishes dense concentrates from lighter cargoes such as grain or fertiliser, where the vessel’s draft is the binding constraint rather than the hold floor strength.

Loading plans for copper concentrate must allocate the weight distribution across holds to stay within the tanktop loading limits specified in the vessel’s loading manual. Overloading a single hold can cause permanent deformation or fracture of the inner bottom plating. The requirement under Amendment 07-23 (mandatory from 1 January 2025 under Resolution MSC.539(107)) for the shipper to declare bulk density on every cargo declaration is directly relevant here: without a specific declared density, a master working from a generic estimate of 2.0 t/m3 could underestimate the actual tanktop load if the cargo runs denser at 2.3 t/m3.

The same density that drives structural loading concern also amplifies the stability hazard from liquefaction. A given volumetric shift of a 2.3 t/m3 slurry produces a larger destabilising moment than the same volumetric shift of a 1.6 t/m3 cargo. This is why copper and lead concentrates, which are denser than zinc concentrate or iron ore fines, produce more rapid capsizing once liquefaction begins.

Cargo composition and origin

Mineralogy and beneficiation

Copper concentrate is produced from porphyry copper deposits and, to a lesser extent, from volcanic-hosted massive sulphide deposits and sediment-hosted copper systems. Porphyry deposits account for about 75% of world copper mine output, with the giant Escondida, Collahuasi, Los Pelambres, and Antamina mines in Chile and Peru collectively producing a large share of globally traded concentrate.

The ore is mined by open-pit methods, crushed and ground in semi-autogenous and ball mills to a liberation size typically between 80 and 200 micrometres, and then subjected to froth flotation. Selective collectors (xanthates and dithiophosphates) and frothers separate the copper sulphide minerals from the silicate gangue. The resulting flotation concentrate contains principally:

• Chalcopyrite (CuFeS2): the primary ore mineral; copper content approximately 34.5% by mass of the pure mineral.
• Pyrite (FeS2): the dominant sulphide gangue mineral; the concentrate copper-to-sulphur ratio and pyrite content vary by deposit type and flotation circuit design, sometimes by a factor of two or more.
• Chalcocite (Cu2S) and covellite (CuS): secondary copper sulphides present in the upper oxidised zone of some deposits; associated with higher-grade concentrates.
• Bornite (Cu5FeS4): present in enriched supergene zones; contributes to the dark purplish-grey colour typical of some Chilean concentrates.
• Silicate gangue minerals: quartz, feldspar, biotite, and chlorite, retained to varying degrees depending on the cut grade of the flotation circuit.
• Trace heavy metals: arsenic (as arsenopyrite or enargite), bismuth, antimony, and lead are present at concentrations that vary by deposit; elevated arsenic is a significant impurity in concentrates from deposits such as those in northern Chile’s Atacama region.

After flotation the concentrate slurry is thickened and pressure-filtered to a moisture content suitable for shipping, typically in the range of 7 to 12% by wet mass. The target moisture is set to balance three competing requirements: the shipper wants the moisture as close to the TML as possible to minimise freight per tonne of dry copper, the buyer (smelter) has moisture specifications to avoid problems in the smelter feed system, and the IMSBC Code prohibits loading above the TML.

The resulting product is a dark grey to greenish-grey fine powder with a coppery metallic sheen and a sulphurous odour, with copper content typically between 24 and 32% by dry mass at the mine gate. Payable copper content and the treatment charge and refining charge (TC/RC) deducted by smelters are the key commercial parameters; the concentrate’s physical properties for shipping purposes are the moisture content, bulk density, and TML.

The Chile-Peru-to-Asia trade pattern

Chile is the world’s largest copper mine producer, with output around 5.5 to 5.7 million tonnes of copper-in-concentrate per year (approximately one-third of global mine production). The major export ports are Antofagasta (serving Escondida, Collahuasi, and Spence/Cerro Colorado), Mejillones, Iquique, and Coquimbo for northern mines, and San Antonio, Ventanas, and San Vicente for the central Andean producers. The state miner Codelco and private majors including BHP (Escondida), Glencore (Collahuasi), Antofagasta Minerals (Los Pelambres), and Anglo American (Los Bronces) are the principal shippers.

Peru is the world’s second-largest copper producer, with output of approximately 2.7 to 3.0 million tonnes of copper-in-concentrate per year. Major export ports include Callao, Ilo, and Matarani. The Antamina copper-zinc mine in Ancash is one of the world’s largest copper-zinc producers and ships polymetallic concentrate that may be declared under a copper concentrate or mineral concentrates shipping name depending on composition.

China is the destination for about 50 to 60% of global copper concentrate trade, receiving approximately 25 to 27 million wet metric tonnes per year (figures reflecting customs data for recent years). Chinese smelter locations span the country, with major smelting clusters in Shandong, Jiangxi, Yunnan, Guangdong, and Inner Mongolia. The primary vessel types for the Chile-to-China and Peru-to-China routes are Panamax (65,000 to 80,000 dwt) and Supramax/Ultramax (52,000 to 63,000 dwt) bulk carriers. Voyage distance from Antofagasta to Qingdao or Ningbo is approximately 10,500 nautical miles, with a typical laden passage of 24 to 28 days.

Japan and South Korea are also significant importers, receiving concentrate from Chile, Peru, Australia, and the Philippines. Japan’s major copper smelters at Kosaka, Saganoseki, Naoshima, Toyo, and Tamano have dedicated concentrate handling terminals. Australia exports from Port Hedland, Port Kembla, and Townsville; Indonesian concentrate from the Grasberg deposit (Freeport-McMoRan) moves through Amamapare to smelters in Japan, Korea, India, and China.

The trade’s scale means that any period of sustained non-compliance with IMSBC TML requirements at the loading ports would affect a large number of voyages simultaneously. Chile’s competent maritime authority (DIRECTEMAR) and Peru’s (DICAPI) are responsible for enforcing IMSBC provisions at their ports; both have worked with the IMO and industry bodies to strengthen TML and moisture-content verification requirements following liquefaction incidents.

Group A liquefaction hazard

Why copper concentrate liquefies

Cargo liquefaction occurs when pore-water pressure in the interstitial spaces of a fine-grained cargo rises faster than drainage can dissipate it. Under the cyclic rolling and pitching of a ship, each motion cycle applies a stress pulse to the cargo mass. In a dry or low-moisture cargo, the grains bear those stresses through direct grain-to-grain contact. As moisture content approaches and exceeds the TML, the pore spaces fill with water, and each stress pulse is transmitted as a pressure pulse through the pore fluid rather than dissipated through grain contacts. When the accumulated pore pressure equals the overburden stress, the grains lose contact and the cargo flows as a dense slurry.

Copper concentrate is particularly susceptible because flotation milling grinds the ore to a liberation size of 50 to 150 micrometres, with 80 to 90% of particles below 75 micrometres. This uniform fine gradation, with minimal coarse fraction to provide drainage channels, creates the textbook conditions for pore-pressure build-up. The fine fraction that makes the cargo difficult to drain is the same fraction that makes it commercially valuable; you cannot coarsen the grind without losing copper recovery in the flotation circuit.

Partial liquefaction is more dangerous than the name implies. The lower layers of a hold, under the greatest overburden pressure, liquefy first. The overlying dry or semi-dry cargo then sits on a fluid base and can slide as a block on each roll. Each sliding cycle moves the cargo slightly toward the low side. Over successive rolls the list increases. At some critical angle the shift becomes irreversible. This process can develop from a normal-looking cargo surface to a dangerous list in two to four hours under moderate sea conditions. An officer watching the cargo through the hatch sees a dry surface; the failure is invisible until the vessel takes a permanent lean.

TML: the regulatory control

The Transportable Moisture Limit is the regulatory threshold below which a Group A cargo may be loaded on an ordinary bulk carrier. It is defined by its relationship to the Flow Moisture Point:

where FMP is the moisture content at which the cargo first exhibits flow behaviour under defined laboratory agitation. The 10% safety factor below the FMP accounts for sampling variability, test subjectivity, and the fact that conditions in a ship hold are far more energetic than those in a laboratory.

For copper concentrate specifically, field data from P&I surveys of Chilean and Peruvian loadings suggest that shipper-declared moisture contents cluster in the range of 7.5 to 11.5%, with TML certificates typically showing values between 9 and 13%. The gap between declared moisture content and declared TML is frequently 1 to 2 percentage points, which is narrow when the measurement uncertainty of moisture content testing (typically ±0.3 to ±0.5 percentage points for a well-conducted test on a representative sample) is considered.

The Code requires that moisture content be tested no more than seven days before the commencement of loading. TML certification is valid for six months. If rain or other moisture input to the stockpile occurs after the moisture test, the shipper must retest before loading starts.

Laboratory test methods for TML determination

Proctor-Fagerberg test

The Proctor-Fagerberg test is the standard method for copper concentrate in most major exporting countries, including Chile and Peru. It was developed specifically for ore concentrates with a maximum particle size of 5 mm and is the method most familiar to accredited laboratories in South American mining regions.

The test compacts the cargo sample in a cylindrical mould using a standardised falling hammer, with multiple test runs at progressively increasing moisture content. Each compaction run produces a dry density value, and the resulting compaction curve is plotted against moisture content. A saturation line is constructed from the specific gravity of the solid mineral fraction and the void ratio. The TML is the moisture content on the compaction curve corresponding to 70% degree of saturation. No FMP is determined directly; the TML comes from the shape of the compaction-saturation relationship.

The Proctor-Fagerberg method requires precise sample preparation and careful data processing, but it avoids the subjective operator judgment required by the flow table test. Accredited laboratories in Chile and Peru that perform Proctor-Fagerberg tests on Escondida, Collahuasi, and similar concentrates are familiar with the specific gravity and grind characteristics of these materials. A well-conducted test by a competent laboratory typically reproduces TML values to within ±0.5 percentage points on repeat testing of the same sample.

Flow table test

The flow table test is the oldest of the three IMSBC Code Appendix 2 methods and is more widely used in Asian ports and in countries with coal-oriented TML testing infrastructure. A weighed sample is placed in a brass mould on the flow table, compacted by a spring-loaded tamper, then the mould is removed and the table is dropped through a 12.5 mm rise 25 times in 15 seconds (in some protocol variants, 50 drops are specified). The spread of the cargo cone is measured, and the test is repeated at increasing moisture levels until the cone spreads more than 3 mm beyond the reference diameter.

The moisture content at which flow first appears is the FMP, and TML = 0.9 x FMP. The limitation of the flow table test for copper concentrate is operator subjectivity: the onset of flow in a chalcopyrite concentrate, which has a dense, cohesive character different from lighter mineral concentrates, can be difficult to judge consistently. Different analysts can produce FMP values 1 to 2 percentage points apart on the same sample, which maps directly to a TML difference of 0.9 to 1.8 percentage points.

Penetration test

The penetration test places the sample in a vessel on a vertically oscillating platform. Brass weights are placed on the cargo surface, and the platform vibrates for six minutes while water is added incrementally between runs. The FMP is identified from the penetration depth of the brass weights, with the threshold at 50 mm penetration. Like the flow table test, TML = 0.9 x FMP. The penetration test replaces the subjective visual judgment of the flow table test with a measurable physical threshold and is suitable for particles up to 25 mm top size.

For copper concentrate, which is typically below 2 mm top size, all three methods are technically applicable. The choice of method in practice is driven by the laboratory’s accreditation and the competent authority’s accepted procedures at the loading port. The IMSBC Code allows any of the three Appendix 2 methods unless the specific schedule entry prescribes a particular one.

Test house selection and data quality

P&I clubs and cargo surveyors have documented cases where different laboratories in the same port produced TML values for the same copper concentrate shipment that differed by 2 to 3 percentage points. This spread is large enough that a cargo certified as compliant by one laboratory’s TML would fail the loading test if the other laboratory’s TML were applied. The problem stems from differences in sample preparation, operator training, and, in some cases, commercial relationships between test houses and shippers.

Masters dealing with unfamiliar loading ports should verify that the TML certificate has been issued by a laboratory accredited under an internationally recognised scheme (ISO/IEC 17025 or equivalent) and that the laboratory is approved by the competent authority of the flag state or loading port. A TML certificate from an unaccredited laboratory is not valid under the IMSBC Code, regardless of what the certificate says.

The shipboard can test

The can test, described in IMSBC Code Section 8, is a rapid screening procedure available to the master and officers during loading. The procedure is straightforward: a representative sample from the loading stream is placed in a cylindrical container of 0.5 to 1 litre capacity, and the container is brought down sharply onto a hard flat surface from about 0.2 metres height, repeated 25 times at one- to two-second intervals. The cargo surface is then examined for free moisture or fluid behaviour.

A positive result, meaning free moisture appears on the surface, is a significant warning sign. Loading should stop. The master should contact the operator and the P&I correspondent, and arrange for independent laboratory sampling and TML testing before deciding whether to resume. A positive can test on copper concentrate means the moisture content is likely close to or above the TML; it does not mean it is safe to continue loading slowly.

A dry result does not confirm the cargo is below TML. A copper concentrate at 95% of TML, with genuine liquefaction risk, will typically pass the can test because no free surface water appears at that moisture level. The can test is a screening tool, not a certification instrument. Officers should not use a dry can test result as documentary evidence of compliance; only the laboratory moisture certificate governs.

Can tests should be performed at the start of each loading shift and whenever there is a change in cargo appearance, consistency, or feed source. Chilean and Peruvian export terminals frequently feed from multiple stockpile positions; a stockpile section exposed to overnight dew or light rain can be wetter than the bulk of the cargo without any visible difference at the loading face. A change in the grain size or colour of concentrate being loaded can indicate a shift to a different stockpile section with different moisture characteristics.

Rising bilge levels during loading are a separate, more serious warning sign. If bilge levels rise at a rate that cannot be explained by minor condensation or hatch infiltration, the cargo may already be partially liquefied or releasing moisture in the lower hold. The master should halt loading immediately, sound all holds and bilges, and investigate before resuming.

Oxygen depletion and toxic gas hazards

Sulphide oxidation chemistry

Copper concentrate is not solely a liquefaction hazard. The chalcopyrite and pyrite content create a chemical hazard that is independent of moisture: sulphide oxidation in the presence of atmospheric oxygen and moisture.

Pyrite oxidises according to:

This reaction, combined with related iron sulphide oxidation pathways, generates sulphur dioxide (SO2), consumes oxygen, generates heat, and under reducing conditions can yield hydrogen sulphide (H2S). The rate of oxidation depends on the pyrite content of the concentrate, the surface area of exposed mineral (which is high in a finely ground product), the temperature, and the available oxygen in the hold atmosphere.

In practice, copper concentrates with high pyrite content, which is common in Chilean deposits where pyrite rejection in the flotation circuit is incomplete, can measurably deplete hold oxygen within days to weeks of loading. P&I club documentation includes cases where crew entered holds to inspect copper concentrate stow and were overcome by depleted oxygen atmospheres before reaching the cargo surface. Oxygen depletion to below 19.5% by volume by itself is immediately dangerous; the simultaneous presence of SO2 at tens of parts per million constitutes a toxic atmosphere that may be lethal at concentrations well below the olfactory threshold of some workers.

Entry precautions

No crew member may enter any hold or enclosed space associated with a copper concentrate cargo without first testing the atmosphere for:

• Oxygen content: minimum 19.5% by volume before entry is permitted.
• Hydrogen sulphide (H2S): threshold limit value as a short-term exposure limit is 5 ppm (some national standards set lower limits); H2S is highly toxic, causes olfactory fatigue, and is immediately dangerous to life above 100 ppm.
• Sulphur dioxide (SO2): immediately dangerous to life at concentrations above 100 ppm; noticeable irritation at 1 to 3 ppm; toxic at 5 ppm over extended exposure.
• Combustible gas: relevant if the concentrate contains minor organic fractions (not common in copper concentrate but possible in some polymetallic products).

The IMSBC Code provisions on enclosed-space entry apply to all cargo holds carrying Group A or B concentrates. The ship’s safety management system must include a formal enclosed-space entry procedure covering pre-entry atmospheric testing, standby personnel, rescue equipment, and communication protocols. These requirements are not specific to copper concentrate but are applied to it.

Ventilation of holds carrying copper concentrate is generally not permitted during the voyage under IMSBC Code requirements for Group A and B concentrates. This is because ventilation would introduce ambient humid air that could raise hold moisture and accelerate the oxidation reaction, rather than dilute accumulated gases safely. The Code’s position is that hold atmosphere management is better achieved through pre-loading controls and sealed hatches than through active ventilation.

Self-heating

Sulphide oxidation is exothermic. Pyrite oxidation releases approximately 1,180 kJ per mole of FeS2 fully oxidised. In a well-loaded hold where the pyrite content is modest and the hold atmosphere is largely isolated from fresh oxygen, the rate of oxidation is limited by oxygen availability, and heat generation remains low. In a partially loaded hold with free air exchange, or in a hold where the hatches have poor sealing, the reaction can proceed more rapidly.

Concentrated pyrite-rich copper concentrates, particularly those from deposits where flotation pyrite rejection is poor, have been reported to show elevated hold temperatures during multi-week Pacific voyages. Hold temperatures above ambient by more than 10 degrees Celsius warrant investigation and logging. The IMSBC Code requires that any cargo with a tendency to self-heat be handled in accordance with the schedule’s specific requirements; the copper concentrate schedule notes the potential for self-heating from sulphide content.

Loading operations: port procedures and master’s duties

Pre-loading documentation review

The master must review the shipper’s cargo declaration, TML certificate, and moisture content certificate before accepting any copper concentrate cargo. The documentation checklist under IMSBC Code Section 4 and Amendment 07-23 includes:

1. Bulk Cargo Shipping Name: “COPPER CONCENTRATE” (the declared BCSN must match the cargo’s actual composition; blended or polymetallic concentrates with significant zinc or lead content may require a different BCSN).
2. Hazard group: Group A, with any applicable MHB designation for chemical hazards.
3. Chemical composition: declared copper content, sulphide content, arsenic and other impurity levels where relevant to hazard assessment.
4. Moisture content: measured value (wet mass basis), test date (within seven days of loading commencement), and testing laboratory identity.
5. TML: declared value, test method (Proctor-Fagerberg, flow table, or penetration), test date (within six months), and laboratory accreditation details.
6. Bulk density: mandatory from 1 January 2025 under Amendment 07-23. Must be an actual measured value, not a generic estimate.
7. Shipper’s certification that the declared moisture is below TML.

If any of these elements is absent, the master is not permitted to begin loading. Commercial pressure does not change this requirement. The master’s P&I club should be notified in writing if the master is under pressure to load with incomplete or unsatisfactory documentation.

Pre-loading hold inspection

Before loading copper concentrate, the chief officer should conduct a formal hold inspection covering:

• Bilge suction system operability: test the bilge pump and confirm suction lines are clear and suction covers are fitted with appropriate screens to prevent fine concentrate from blocking the system.
• Hatch cover integrity: test all hatch cover sealing with a chalk test or hose test. Even small gaps allow rain to infiltrate a loaded hold and raise surface moisture above TML, which then becomes the vessel’s liability rather than the shipper’s.
• Hold cleanliness: remove all residues of previous cargo. Organic cargo residues can react with sulphide concentrate; hygroscopic residues (fertiliser, potash, salt) can alter moisture balance.
• Internal coaming drainage: confirm tank top drain holes and bilge well covers are clear.

Hold washing and drying after a previous cargo and before a copper concentrate loading is standard P&I practice. Some charter parties specify hold cleanliness standards; even where they do not, a contaminated hold at the start of a Group A cargo loading is a risk the master should document and refuse.

Loading sequence and trimming

Loading copper concentrate follows standard Group A cargo procedures. The shore shiploader delivers the cargo by conveyor belt through an open hatch, and the concentrate self-trims to a reasonable degree during normal loading. The final trim should ensure that the cargo surface height variation does not exceed 5% of the vessel’s beam, as required by the IMSBC Code for Group A cargoes.

For a Supramax with a 32-metre beam, the 5% rule means no peak-to-trough variation exceeding 1.6 metres in the finished cargo surface. In practice, concentrate loads through a single pour point often create a central cone 2 to 3 metres high. A mechanical trim pass, either via a bulldozer working in the hold or by moving the pour point, is required to level the surface. Any crew entry to the hold for trimming requires atmospheric testing first, as noted above.

Loading should stop during precipitation. Rain falling into an open hatch onto the cargo surface can raise surface moisture above TML within minutes. The decision about when to stop loading in light or intermittent rain is a judgment call, but both the IMSBC Code and P&I club guidance consistently err toward stopping loading early rather than waiting for heavy rain.

During loading, the cargo officer on watch should perform can tests at the start of each shift and whenever the concentrate feed changes in appearance. Concentrate from a different stockpile section, a different mine lot, or following a rain event at the terminal may have a different moisture character than what the certificate described.

Tanktop structural loading

Loading plans for copper concentrate on Handysize, Supramax, or Panamax vessels must respect the tanktop loading limits from the loading manual. At a bulk density of 2.0 to 2.3 t/m3, copper concentrate imposes a load on the inner bottom plating per unit area of approximately 14 to 19 kN/m2 per metre of cargo depth, depending on exact density. A hold loaded to 8 metres depth with 2.2 t/m3 concentrate imposes roughly 170 kN/m2 on the tanktop, which approaches or exceeds the structural limit of many older Handysize vessels.

The loading computer must be used in real time during loading, not just as a pre-voyage planning tool. Weight per hold is adjusted during loading as the cargo density may vary slightly between stockpile sections. Any hold where the loading computer shows tanktop stress approaching the limit should have its loading rate slowed or the pour point shifted to spread the load.

Structural damage to inner bottom plating from overloaded copper concentrate cargoes has been documented in class society casualty analyses. Such damage can occur without any liquefaction event; it is a function of cargo weight density alone.

Voyage precautions and monitoring

Bilge monitoring

Bilge monitoring is the primary shipboard indicator of cargo moisture migration during the voyage. Before departure, the chief officer should record baseline bilge well levels in all loaded holds. Any rise in bilge levels not attributable to condensation or minor hatch infiltration during the voyage warrants investigation.

The IMSBC Code advises continuous bilge monitoring for Group A cargoes. In practice, the logging frequency for bilge soundings should be every four hours in the first 48 hours after departure (the highest-risk period for newly loaded cargo settling under initial sea conditions), then every eight hours thereafter. Any hold showing more than 50 mm rise in bilge level per watch should be flagged and the rate of rise logged for trend analysis.

Fine copper concentrate particles will enter the bilge system during loading and over the voyage. These particles are acidic when wet (from sulphide oxidation), corrosive to steel, and can accelerate corrosion of bilge pipework if not flushed. The bilge water from a copper concentrate cargo is also a regulated discharge; it cannot be pumped overboard in port or coastal waters and must be managed in accordance with the vessel’s MARPOL Annex V requirements.

Hatch cover management

Hatch covers should remain closed during the voyage except for the mandatory safety inspections. Copper concentrate’s combination of sulphide chemistry and Group A status means that ventilating the holds is generally counterproductive: it introduces humid air that can promote condensation on cargo surfaces, raises the moisture content at the top of the cargo (which is already the most exposed surface), and does not address the deeper moisture distribution that governs liquefaction risk.

If a hatch seal fails during the voyage and water infiltrates, the captain should assess whether the affected hold cargo can be re-secured or whether the vessel should divert to a port for inspection.

Cargo shifting and list management

A vessel developing an unexplained list on a copper concentrate cargo must be treated as a potential liquefaction event, not a minor ballast irregularity. The standard ballast adjustment to correct list can mask a progressive liquefaction. If list correction by ballasting requires abnormal quantities of water, or if the list recurs after correction, the situation must be escalated.

The correct response to suspected liquefaction in a loaded copper concentrate hold is to alter course to reduce the vessel’s rolling motion, reduce speed, notify the owner and P&I club, and consider diverting to the nearest suitable port for investigation. No amount of ballast can substitute for mechanical measures to secure a hold in which the cargo has transitioned to fluid state.

Arsenic and impurity considerations

High-arsenic concentrates

A significant proportion of copper concentrates from northern Chilean deposits, including those from the Atacama highlands, contain elevated arsenic levels, with arsenic content in the concentrate sometimes exceeding 0.5% by dry mass. Arsenic occurs as arsenopyrite (FeAsS) or enargite (Cu3AsS4). High-arsenic concentrates attract penalty deductions from smelters under the TC/RC calculation, but their physical shipping properties are otherwise similar to low-arsenic concentrates.

From a hazard perspective, elevated arsenic in a sulphide concentrate means that the dust generated during loading, discharge, and any hold entry operations contains arsenic compounds. Arsenic trioxide (As2O3) is highly toxic (oral LD50 in rats approximately 15 mg/kg). Workers handling high-arsenic concentrate at loading and discharge terminals must use appropriate respiratory protection and follow the terminal’s COSHH (or equivalent national) risk assessment. This is primarily a terminal and port health and safety issue rather than a maritime IMSBC Code issue, but crews performing hold entry for inspection or trimming should be aware that fine concentrate dust can contain significant arsenic.

Concentrate blending and BCSN selection

Where a mine produces concentrate from a polymetallic deposit with significant co-product content, the BCSN on the cargo declaration must reflect the actual composition. A copper concentrate with more than a threshold proportion of zinc or lead content may be more accurately declared under the MINERAL CONCENTRATES entry or under a lead-copper or zinc-copper concentrate classification, depending on composition. Declaring a polymetallic concentrate simply as “COPPER CONCENTRATE” when its hazard profile is driven by the lead or zinc sulphide content is a misclassification. The shipper is responsible for correct BCSN selection; the master should verify that the declared name is consistent with the chemical composition stated on the cargo declaration.

Documented casualties involving copper and mineral concentrate

Historical record

Cargo liquefaction from mineral concentrates, including copper concentrate, has contributed to bulk carrier losses over many decades. The documented record is not limited to iron ore fines and nickel ore; concentrate cargoes appear in casualty analyses going back to the 1970s and 1980s, before the IMSBC Code existed in its current form.

The IMO’s 1991 BC Code (the predecessor to the IMSBC Code) already included Group A classification for concentrates and TML testing requirements, but enforcement was inconsistent and test methods were not yet standardised. The 1991 Code’s TML provisions were substantially revised and tightened in the 2004 Code and again in the 2008 IMSBC Code, with Amendment 04-15 (MSC.393(95)) and subsequent amendments progressively strengthening the cargo declaration requirements.

The Intercargo Bulk Carrier Casualty Report 2025, covering the decade 2015 to 2024, attributes 55 seafarers’ deaths to cargo liquefaction, representing 61.8% of all bulk carrier fatalities in that period. While the specific breakdown by cargo type is not published for every casualty, the report identifies cargo liquefaction as the leading cause of fatalities in the dry bulk sector, with Group A cargoes as the class implicated.

Chilean and Peruvian P&I club correspondents have documented near-miss incidents involving copper concentrate cargoes, including vessels that departed port with bilge levels already rising during the first 24 hours. In several documented cases the moisture certificate proved to have been issued by a laboratory that did not test the actual cargo batch but used historical data from previous shipments of nominally the same concentrate grade.

The role of certification fraud

Falsified or misleading TML and moisture certificates are a documented problem in the concentrate trade. P&I club reports from Chilean and Peruvian ports note instances of moisture certificates that were issued before the cargo was actually in the stockpile from which it would be loaded, or where the test sample was taken from a surface layer that was drier than the interior of the stockpile. The legal and insurance consequences for shippers and their agents if a vessel is lost or damaged due to falsified documentation are severe, but this has not eliminated the practice.

The master’s only defences against certificate fraud are independent pre-loading survey and the can test during loading. Where the economics of a cargo are significant, owners and P&I clubs advise appointing an independent cargo surveyor to witness sampling and confirm that the moisture certificate reflects the cargo actually being loaded. This is particularly important for large parcels from unfamiliar shippers or terminals.

Master’s right and duty to refuse

The master’s authority to refuse or suspend loading is established in SOLAS Chapter VI Regulation 2 and in IMSBC Code Section 4.3. It is not merely a commercial right that can be waived; in many circumstances it is a professional duty.

A master who loads copper concentrate knowing that the moisture certificate is older than seven days cannot use the certificate failure as a defence before a maritime inquiry if the cargo subsequently liquefies. A master who loads with no certificate at all is in breach of both SOLAS and the IMSBC Code. A master who loads after a positive can test, without arranging independent verification, has failed the minimum shipboard screening requirement.

Exercising the right to refuse is commercially difficult. Charter parties impose demurrage liability for loading delays, and shippers routinely dispute moisture-based refusals. The correct procedure is to document the refusal in writing, specifying the regulatory basis (IMSBC Code Section 4 and SOLAS Chapter VI), the documentary deficiency or the observable condition that prompted the refusal, and the action requested (re-testing, independent survey, or provision of valid documentation). The master’s P&I club should be notified by message before any confrontation escalates.

Where a master accepts a cargo under explicit reservation, the reservation must be stated in writing in the mate’s receipt, the cargo declaration endorsement, and any shipboard log entries. A reservation does not make the cargo safe to carry, but it preserves the documentary record for investigation and insurance purposes.

If the shipper’s response to a documented refusal is to present fresh documentation that the master suspects may also be fabricated, the master should arrange for an independent cargo survey by a surveyor appointed jointly by the P&I club and the shipper’s P&I correspondent. Joint survey results are more difficult for either party to dispute and provide the strongest evidential basis for the decision that follows.

Related wiki articles and calculators

• IMSBC Code
• IMSBC Group A cargoes: Cargoes that may liquefy
• Cargo Liquefaction: TML, FMP, and Group A Controls
• Mineral Concentrates: IMSBC Code Schedule
• Zinc Concentrate: IMSBC Code Schedule and Carriage
• Lead Concentrate: IMSBC Code Schedule and Carriage
• Iron Ore Concentrate: IMSBC Code Schedule and Carriage
• Nickel Ore: IMSBC Code Schedule and Carriage
• Bulk Carrier

Related calculators:

• IMSBC TML Moisture Check
• IMSBC Group A Liquefaction Risk
• IMSBC Copper Concentrate
• IMSBC Group A/B/C Classification

Limitations

This article reflects the IMSBC Code as amended by Resolution MSC.539(107) (Amendment 07-23, mandatory from 1 January 2025). The official text is the definitive source; this article does not reproduce schedule tables verbatim. Masters and operators must consult the current mandatory edition of the Code and confirm which amendment is in force in the jurisdiction of the loading port.

TML values stated here are indicative ranges derived from published data and industry survey reports. A TML for a specific copper concentrate shipment must be determined by an accredited laboratory on a representative sample of that specific batch within the validity window. No generic TML can be used in place of shipper-certified test data.

The chemical properties of copper concentrate, including sulphide content, arsenic levels, and potential for gas generation, vary by deposit and processing plant and can differ by a factor of three or more between concentrate types. The hazard characterisation in this article reflects the typical Chilean and Peruvian export concentrate; concentrates from other deposits may have materially different chemical profiles. Shippers and receivers with unusual concentrate compositions should seek competent authority guidance.

Casualty statistics are drawn from published Intercargo reports and from secondary sources including P&I club analyses. Where a cause of sinking is attributed to liquefaction, this reflects the official or most widely accepted finding of the responsible investigation authority; in some cases the attribution is probable rather than confirmed.

Regulatory requirements may differ between flag state and port state where the flag state has not yet adopted the current IMO amendments. Masters should verify that the version of the IMSBC Code applied by the competent authority of the loading port corresponds to the current mandatory edition.