Mineral Concentrates: IMSBC Code Schedule

Mineral concentrates shipped in bulk are Group A cargoes under the IMSBC Code, meaning they may liquefy if loaded above their Transportable Moisture Limit. The generic MINERAL CONCENTRATES schedule covers beneficiated base-metal concentrates without individual schedule entries, including polymetallic sulphide mixtures and lesser-traded single-metal concentrates. Liquefaction has contributed to the confirmed or suspected loss of over a dozen bulk carriers and several hundred seafarers since 1980.

The IMSBC Code, adopted under SOLAS Chapter VI and first entering force in January 2011 as Resolution MSC.268(85), classifies all solid bulk cargoes into three groups. Group A cargoes are those that may liquefy if shipped at a moisture content exceeding their Transportable Moisture Limit (TML). Mineral concentrates are the archetypal Group A cargo class. Their uniform fine particle size, moderate to high bulk density, and residual process moisture from filtration and dewatering create the conditions for pore-pressure build-up and eventual cargo flow under repeated ship motion.

The Code’s Appendix 1 contains individual schedules for the highest-volume concentrates, including copper concentrate, iron ore concentrate, lead concentrate, and zinc concentrate. The generic MINERAL CONCENTRATES entry captures the remainder: polymetallic sulphide concentrates from mixed zinc-lead-copper deposits, celestine (strontium sulphate) concentrate, manganese concentrate, fluorspar concentrate, silver concentrate, tin concentrate, and other base and precious metal concentrates that share the same physical character but do not appear under a dedicated schedule name. Under Amendment 07-23, adopted by Resolution MSC.539(107) on 8 June 2023 and mandatory from 1 January 2025, celestine concentrate was formally added as a named Bulk Cargo Shipping Name (BCSN) within the MINERAL CONCENTRATES entry, and shippers became required to declare bulk density on all cargo declarations.

Schedule structure and scope

What the MINERAL CONCENTRATES entry covers

The IMSBC Code defines concentrates as materials obtained from a natural ore by a process of enrichment or beneficiation, through physical or chemical separation and removal of unwanted gangue constituents. A mined ore that has merely been crushed and dried without beneficiation does not qualify as a concentrate; a product that has been floated, magnetically separated, or hydrometallurgically leached to raise the target metal content does.

The schedule groups concentrates into two hazard sub-categories depending on their chemistry:

• Group A only: concentrates that present a liquefaction hazard but no significant chemical toxicity or reactivity. Many copper concentrates declared under the generic entry, certain oxide-mineral concentrates, and some single-metal concentrates without sulphide content fall here. The notation in the Code reads “Group A” in the Hazard column.
• Group A and B (MHB): sulphide-bearing concentrates that present both a liquefaction hazard and a material hazard to the ship (MHB), typically through generation of hydrogen sulphide gas, toxic inhalation risk from heavy-metal dust, or self-heating from sulphide oxidation. Lead-zinc polymetallic concentrates and many sulphide-rich mixed concentrates fall into this sub-category, which requires additional handling provisions beyond the basic Group A rules.

Concentrates from polymetallic deposits, such as concentrates from the Antamina copper-zinc deposit in Peru or the McArthur River lead-zinc mine in Australia, are commonly declared under MINERAL CONCENTRATES rather than under a single-metal schedule when the composition does not match any named individual entry. The shipper’s cargo declaration must state the full chemical composition, including all significant metal and sulphide contents, so the vessel’s master and the carrying vessel’s P&I correspondent can assess both the liquefaction and chemical hazard profiles.

Named cargoes within the generic entry

The IMSBC Code’s Appendix 1 entry for MINERAL CONCENTRATES lists specific BCSNs that fall under it when no individual schedule exists. Following Amendment 07-23 (mandatory from 1 January 2025), these include celestine concentrate (strontium sulphate mineral from celestine ore beneficiation). Other concentrates covered by the generic entry historically include:

• Manganese concentrate (from manganese ore beneficiation; high bulk density, Group A)
• Silver concentrate (fine grey sulphide product; Group A and B owing to argentite sulphide content)
• Tin concentrate (cassiterite-rich flotation concentrate; Group A)
• Fluorspar concentrate (calcium fluoride mineral; Group A; Hui Long, a vessel lost in 2005, carried fluorspar mineral)
• Molybdenum concentrate (molybdenite MoS₂ flotation product; Group A and B)
• Bismuth concentrate and cobalt concentrate (from polymetallic deposit processing; Group A or A and B)

Individual high-volume concentrates, copper, zinc concentrate, lead concentrate, iron ore concentrate, and nickel ore (which is not strictly a concentrate but shares Group A treatment), each have dedicated schedules and are discussed in those respective articles.

Schedule particulars

The IMSBC Code schedule entry for MINERAL CONCENTRATES records the following typical physical properties. These are indicative ranges rather than fixed values; the shipper must declare the actual values for each specific shipment:

For common base-metal sulphide concentrates declared under this entry, the bulk density at loading typically lies between 1,800 and 3,500 kg/m³. A polymetallic zinc-lead concentrate might measure approximately 2,500 to 3,200 kg/m³, while a lighter manganese concentrate may be closer to 1,800 to 2,200 kg/m³. The high bulk densities mean that even a small volumetric shift of liquefied cargo generates a large heeling moment, which is why concentrate-carrying bulk carriers have capsized with minimal warning once liquefaction begins.

Angle of repose is listed as “not applicable” for cohesive fine cargoes in the IMSBC Code, because the cargo does not form a free-flowing cone under dry conditions. Instead, it holds a face angle while dry but transitions rapidly to a fluid state once the pore-water pressure exceeds the effective confining stress at the cargo’s depth.

The Group A liquefaction hazard

How liquefaction develops

Liquefaction of a mineral concentrate is not a simple wetting process. At low moisture content, the fine particles are held together by capillary tension and by direct grain-to-grain contact, and the cargo behaves as a coherent solid mass. As the moisture content rises toward and then past the TML, the pore spaces between particles begin to fill with water. Under repeated dynamic loading from ship rolling and pitching, the grain structure transmits each load cycle as a pulse of pore-water pressure. These pulses accumulate faster than the water can drain. When the accumulated pore pressure reaches the level of the overburden stress, the grains lose contact and float in the interstitial water, transforming the cargo from a stiff solid into a dense fluid slurry.

This transformation does not require that the entire cargo liquefy simultaneously. Partial liquefaction in the lower layers of a deep hold is sufficient to allow the overlying cargo to slide as a block. On each roll of the ship, the partially liquefied base allows the cargo mass to shift, and the ship’s righting moment is reduced. Over successive rolling cycles the static angle of the cargo surface increases. At some critical inclination, the shift becomes irreversible and the vessel takes on a permanent list that may precede capsize.

The mechanism is well understood but hard to detect from the bridge. The cargo surface above a liquefied lower layer appears dry. Bilge well levels may rise slowly rather than suddenly. The vessel’s roll period may lengthen, which is a measurable sign of reduced metacentric height, but officers may attribute the change to normal variations rather than to cargo failure.

Why concentrates are especially vulnerable

Mineral concentrates share three physical properties that make them more susceptible to liquefaction than many other bulk cargoes.

First, the particle size is uniformly fine. Flotation milling, which is the standard process for producing sulphide concentrates, grinds the ore to a liberation size typically between 50 and 150 micrometres. The resulting size distribution contains a high fraction of particles below 75 micrometres, the boundary the IMSBC Code uses to define fine material for the purpose of Group A classification. Fine particles pack tightly with small inter-particle pores that retain water by capillarity and transmit pore pressure efficiently under cyclic loading.

Second, the bulk density is relatively high. Lead concentrate at 3.0 to 3.8 t/m³ and zinc concentrate at 2.4 to 2.8 t/m³ are substantially denser than iron ore fines at approximately 1.9 to 2.2 t/m³. The higher density amplifies the heeling moment produced by a given volumetric shift.

Third, the moisture content at loading tends to lie close to the TML. Concentrate producers filter their product to reduce freight cost and to meet buyer specifications, but over-drying is expensive and can cause dust problems. The incentive is to ship at the maximum permitted moisture content, placing the cargo at or near the boundary of safe carriage. Field data from P&I club surveys consistently show that a proportion of concentrate cargoes are presented at or above certified moisture limits.

Transportable Moisture Limit and Flow Moisture Point

Definitions

Transportable Moisture Limit (TML) is defined in the IMSBC Code as the maximum moisture content that is considered safe for carriage in a ship. It is the regulatory threshold: no Group A cargo may be loaded when the actual moisture content equals or exceeds the TML, except on specially fitted vessels meeting IMSBC Code Section 7 requirements.

Flow Moisture Point (FMP) is the moisture content at which a representative sample of the material, tested by the prescribed method, first exhibits a flow state. FMP is not a regulatory limit in itself; it is the laboratory measurement from which TML is derived.

The TML equals 90% of the FMP when determined by the flow table test or the penetration test:

The 10% safety factor reflects both the inherent variability of sampling and testing and the fact that the FMP is determined on a static laboratory sample while the cargo in the ship hold is subjected to much more energetic cyclic loading. The Proctor-Fagerberg test does not use the FMP directly; it derives TML from the moisture content producing 70% degree of saturation in the compacted sample, a different but comparable physical threshold.

Safety margin in practice

A TML determined by flow table or penetration test at, say, 10% moisture content means the FMP for that cargo is approximately 11.1%. The loading limit of 90% of FMP (or, equivalently, of TML with no further reduction) means the maximum permitted moisture at loading is 10%. A shipper measuring moisture at 9.5% on a cargo with TML 10% is technically compliant but operating with a 0.5 percentage-point safety margin, which is narrow when measurement uncertainty and cargo heterogeneity are considered.

The Code requires that moisture content testing be conducted no more than seven days before the commencement of actual loading. If rain or snow falls between the sampling date and the start of loading, the shipper must conduct additional tests to confirm that the cargo moisture has not risen above the TML. TML testing itself must be conducted within six months before loading. The six-month window reflects the fact that the TML is a property of the cargo’s composition and physical character, which does not change materially over months, while moisture content changes with weather and storage conditions.

Laboratory test methods

Flow table test

The flow table test is the original method prescribed in IMSBC Code Appendix 2 and is the standard choice for finely ground mineral concentrates with a maximum grain size up to 1 mm, with some allowance up to 7 mm for coarser fractions.

A weighed sample of the cargo is placed in a brass mould on the flow table and compacted with a standard spring-loaded tamper. The mould is removed and the table is operated by lifting one edge through a prescribed rise of 12.5 mm and dropping it, repeating the cycle 25 times within two minutes in some variants, or 50 times in others, depending on the specific test protocol. The resulting spread of the cargo cone is measured, and the diameter increase is compared to the reference. The test is repeated at progressively increasing moisture levels until the sample spreads by more than 3 mm beyond the reference diameter, indicating the flow state.

The moisture content at which the flow state first appears is the FMP. TML is then 90% of that value. The test requires skilled operators to judge the onset of flow, and this subjectivity is one of its recognised limitations. A well-trained analyst in an accredited laboratory produces consistent results; a less experienced one may determine an FMP that is 1 to 2 percentage points too high or too low, which translates directly into a TML error of similar magnitude.

Penetration test

The penetration test was developed partly to address the subjectivity limitation of the flow table test. The sample is placed in a cylindrical vessel on a vertically oscillating platform. Brass weights are placed on the sample surface. The platform vibrates for six minutes while water is progressively added in increments between test runs. The FMP is identified as the average moisture content between the test run at which the brass weights penetrate the sample surface by more than 50 mm and the preceding run where they did not.

The objective, measurable penetration depth eliminates operator judgement of the flow state. The penetration test is suitable for material up to 25 mm top size, making it more versatile than the flow table test for coarser concentrates and for coal. Like the flow table test, TML = 0.9 × FMP from the penetration test result.

Proctor-Fagerberg test

The Proctor-Fagerberg test, developed specifically for ore concentrates and validated for IMSBC Code purposes, is the third and most technically demanding method. The cargo sample is compacted into a cylindrical mould in several layers using a standard hammer, and the dry density and moisture content are measured at each compaction level. Multiple test runs at different moisture levels generate a data set from which the operator constructs a compaction curve and a saturation line.

The TML is the moisture content on the compaction curve that corresponds to 70% degree of saturation in the interstitial void space. No FMP is determined directly; the result comes from the shape of the compaction-saturation curve. This approach produces a TML that is not the result of a subjective visual observation, but requires more careful sample preparation and data processing than the flow table method.

The standard Proctor-Fagerberg procedure is applicable to concentrates with a maximum top size of 5 mm. A modified version using different hammer energy and mould geometry has been developed for iron ore fines and other specific cargoes. The IMSBC Code specifies which version is appropriate for a given material type.

For most practical purposes, a well-conducted penetration test and a well-conducted Proctor-Fagerberg test on the same mineral concentrate will agree to within approximately 0.5 to 1 percentage point, but this is not guaranteed. P&I clubs have documented cases where different test houses produced TML values differing by 2 to 3 percentage points on the same cargo, which is enough to push a marginal moisture content from compliant to non-compliant depending on which result the shipper uses.

Which method to use

The IMSBC Code does not mandate a single test method for mineral concentrates in general. The schedule entry for each cargo type may specify a preferred or required method; otherwise, any of the three Appendix 2 methods may be used, provided the sample characteristics (maximum particle size, organic content, and cohesion) fall within the stated applicability range for that method.

In practice, concentrate producers and shippers in Australia, Chile, Peru, and other major mining countries predominantly use the Proctor-Fagerberg test for sulphide concentrates, because it was developed specifically for this cargo class and is most familiar to accredited laboratories in those countries. The flow table test is more common in Asia and in countries with a longer tradition of coal-oriented TML testing.

The can test: shipboard screening

The can test is described in Section 8 of the IMSBC Code as a rapid shipboard method that the master and officers can use during loading to screen for obvious moisture excess. It is not a substitute for the laboratory certificates required before loading; it is a check that may reveal a cargo in a deteriorating condition or a gross discrepancy between the declared moisture and the actual state of the cargo being loaded.

The procedure is straightforward. A representative sample is collected from the loading stream and placed in a cylindrical metal container of 0.5 to 1 litre capacity. The can is held in one hand and brought down sharply onto a solid table or flat surface from a height of approximately 0.2 metres. This is repeated 25 times at one- to two-second intervals. The surface of the cargo is then examined for free moisture, glistening surface water, or any tendency of the material to behave as a fluid.

If free moisture appears on the surface after the impacts, the cargo shows behaviour consistent with a moisture content near or above the TML. Loading should stop immediately. The master should contact the operator and arrange for independent laboratory sampling and TML determination before any decision is made about whether to resume.

A dry result does not confirm safety. A cargo at 95% of TML, with genuine risk but no free surface moisture under the can test, will pass the can test while still being dangerously close to the loading limit. The Code explicitly states this limitation. The can test catches failures at the upper end of the moisture scale; it tells you nothing reliable about the lower portion of the risk zone.

Officers should perform can tests at the beginning of each loading shift and whenever the cargo appearance or consistency changes during loading. Changes in the terminal’s feed, rehandling of cargo stockpiles after rain, or blending of different moisture-content batches can all raise the effective moisture content above what the certificate measured.

Cargo declaration and certification requirements

What the shipper must provide

Before any Group A cargo including mineral concentrates may be loaded, IMSBC Code Section 4 and SOLAS Regulation XII/10 require the shipper to provide the master, in writing, with:

1. A cargo declaration stating the Bulk Cargo Shipping Name (BCSN), the cargo group, the chemical composition, the declared moisture content (on a wet mass basis), and, following Amendment 07-23, the bulk density.
2. A TML certificate issued by an accredited laboratory, covering TML determined by an Appendix 2 method applicable to the cargo’s particle size, and valid within six months of the loading date.
3. A moisture content certificate, confirming that the moisture was measured within seven days before the commencement of loading, and that the measured moisture content is less than the TML.
4. For Group A and B concentrates: additional information on chemical hazards including MHB classification, toxicity, self-heating risk, gas generation potential, and any special handling requirements.

The shipper’s declaration must reach the master before loading commences. If any of the required documents is absent, the master is not permitted to begin loading, regardless of commercial pressure or charter-party terms.

Bulk density requirement under Amendment 07-23

The requirement to declare bulk density on the cargo declaration, which became mandatory from 1 January 2025 under MSC.539(107), addresses a gap that P&I clubs and cargo surveyors identified over many years. Bulk density affects hold structural loading and vessel stability calculations. Without a declared value, masters and loading computers were often working from generic estimates that could be substantially wrong for an unusual concentrate type. A manganese concentrate at 2,000 kg/m³ and a lead concentrate at 3,500 kg/m³ have radically different implications for tanktop loading and for the stability profile of a partially loaded vessel.

TML certificate validity and recertification

The six-month TML validity period is intentionally long. The TML reflects the physical character of the cargo as a product, and a concentrate from a given mine and processing plant will have a stable TML that does not change week to week. The short 7-day window for moisture content testing, by contrast, reflects the fact that moisture changes rapidly with weather conditions and cargo handling after sampling.

If the cargo has been exposed to rain or other moisture sources between sampling and loading, the shipper must test again and issue a new moisture certificate. This requirement is frequently cited in P&I casualty analyses as a point of failure: shippers have been found to present the original certificate without re-testing after rainfall events, resulting in loading a cargo that is already above the TML at the berth.

Loading precautions and trimming

Pre-loading hold inspection

Before a Group A mineral concentrate cargo is accepted, the master should ensure that bilge suction systems are tested and confirmed operational, that bilge well covers are correctly fitted (and in some implementations fitted with additional strainer protection to prevent fine particles from blocking the suction system), and that hatch covers seal correctly with no open gaps or damaged gaskets. Water-tight integrity is the primary defence against external moisture ingress. Cargo moisture that rises above TML after loading due to rain infiltration through a defective hatch cover is not a shipper failure; it becomes the vessel’s problem.

Hold cleanliness matters too. Residues of a previous cargo, particularly a reactive cargo such as fertiliser or a hygroscopic cargo such as potash, can change the effective moisture balance in the hold space or react with the incoming concentrate. A fresh-water wash-down and drying of the hold before loading is standard practice for any fine mineral cargo.

Trimming requirements

The IMSBC Code requires that Group A cargoes be trimmed so that the height difference between peaks and troughs in the cargo surface does not exceed 5% of the ship’s breadth. This rule exists because uneven loading creates unequal distribution of static pressure across the cargo mass, producing zones of higher effective stress where liquefaction is more likely to nucleate. It also affects the ship’s transverse stability; an uneven cargo surface whose high spots are all to one side produces an off-centre static moment.

Mineral concentrates generally self-trim to a reasonable degree during loading through a spout or shiploader, but the final trim pass may require mechanical assistance, either a bulldozer working in the hold or redistribution of cargo flow between different hold positions. Any trim correction involving crew entering the hold must be performed with the hold atmosphere checked for oxygen depletion; sulphide concentrates can deplete hold oxygen through oxidation.

Loading suspension during rain

The IMSBC Code requires that Group A cargo handling stop during precipitation. Rain falling directly into an open hatch onto a partially loaded concentrate cargo can raise the surface moisture content significantly, creating a surface layer that exceeds TML even if the bulk of the cargo is compliant. The critical issue is not how much rain falls in total but how quickly the rain raises surface moisture, because the fresh rainwater mixes with the upper cargo layers and the moisture may not redistribute evenly before the next sampling or visual inspection.

In practice, terminal operators and vessel masters must have a clear protocol for:

• Identifying the rain-start threshold at which loading halts
• Specifying the inspection and re-sampling interval after rain stops
• Deciding whether can testing of surface cargo is sufficient or whether laboratory re-testing is needed before resuming

The Code does not specify a numerical rainfall rate threshold, leaving this to the judgment of the master and the competent authority at the port. P&I club guidance consistently recommends erring toward stopping loading early rather than waiting for rain to intensify.

Bilge well management during loading

Fine mineral concentrates can migrate into bilge wells during loading and during the voyage if the cargo becomes saturated. The resulting wet fines can block suction strainers, corrode steel bilge pipework, and compromise the bilge pump’s ability to remove drainage water. Operators should use suction plates covered with burlap or canvas at the bilge well openings, inspect the suction system regularly during loading, and record bilge sounding readings as a baseline before departure.

During the voyage, rising bilge levels are one of the few observable signs that moisture is migrating through the cargo. The IMSBC Code advises monitoring bilge levels continuously for Group A cargoes. Any significant increase in bilge levels not attributable to rainfall or condensation should prompt an investigation of cargo condition.

The master’s right and duty to refuse

Regulatory basis

SOLAS Chapter VI Regulation 2 requires the shipper to provide information about the cargo before loading. IMSBC Code Section 4.3 specifies that the master may refuse to load any cargo for which the required information has not been provided or is not satisfactory. This is both a right and, in many circumstances, a duty: a master who loads a Group A cargo knowing the moisture certificate is outdated, or in the absence of a valid TML certificate, cannot claim the certificate failure as a defence if the cargo subsequently liquefies.

The Code further states, in Section 7, that a Group A cargo with moisture content equal to or above the TML must not be loaded unless the vessel is a specially constructed or fitted ship meeting the Section 7 requirements and all conditions specified in the shipping country’s competent authority approval. Ordinary bulk carriers, the Handysize, Supramax, and Panamax vessels that carry the bulk of global concentrate trade, do not meet this exemption. Loading in violation of Section 7 is both a regulatory breach and, if a casualty results, a potential basis for invalidating the hull and cargo insurance.

Practical application

The master’s authority to refuse loading is well-established in law but not always easy to exercise commercially. Charter parties typically impose demurrage liability on the vessel if loading is delayed or refused for reasons that the charterer disputes. Exercising the right to refuse on moisture grounds requires clear documentary evidence, a valid TML certificate, a measured moisture content, and the master’s professional judgment that the gap between the two is insufficient.

Experienced masters dealing with concentrate cargoes document the exercise of authority carefully: a written communication to the charterer and shipper stating the regulatory basis for the refusal, a contemporaneous record of the can tests performed and their results, and a request for independent sampling by a surveyor appointed jointly by the master’s P&I club and the shipper’s interests.

If the master accepts the cargo under commercial pressure despite reserving concerns, the reservation must be noted in writing in the cargo declarations and in the mate’s receipt. This does not make the loading safe, but it preserves the documentary record for any subsequent investigation.

Special considerations for Group A and B concentrates

Sulphide chemistry and gas generation

Many mineral concentrates declared under the generic MINERAL CONCENTRATES schedule are sulphide-rich. Sulphide minerals, particularly pyrite (FeS₂), chalcopyrite (CuFeS₂), galena (PbS), sphalerite (ZnS), and molybdenite (MoS₂), oxidise in the presence of oxygen and moisture. The reactions are exothermic and produce sulphur dioxide, and in some conditions hydrogen sulphide, neither of which is immediately visible or easily detected without atmospheric monitoring.

The IMSBC Code designation MHB (Material Hazardous in Bulk) applies to these concentrates under the Group B provision. MHB (SH) means the cargo may spontaneously heat; MHB (TX) means it presents a toxicity hazard; MHB (CR) means it is corrosive. A polymetallic sulphide concentrate may carry two or all three MHB designations simultaneously.

Crew entering holds or enclosed spaces associated with sulphide concentrate cargoes must first test the atmosphere for oxygen content, hydrogen sulphide, and sulphur dioxide. The minimum acceptable oxygen level before entry is 19.5% by volume. Entry with oxygen below this level without appropriate self-contained breathing apparatus is prohibited and has caused fatalities in concentrate trade.

Self-heating and hold temperature

Sulphide oxidation is exothermic. Pyrite-rich concentrates in particular can generate measurable heat, and in extreme cases spontaneous combustion. While this is more commonly associated with coal than with mineral concentrates, the IMSBC Code schedules for Group A and B concentrates include cargo temperature monitoring requirements. Hold temperatures above the ambient norm during the voyage should prompt investigation.

The combination of self-heating and moisture near the TML is more dangerous than either hazard alone. Warming of the cargo increases the partial pressure of water vapour, can drive moisture migration within the cargo mass, and may produce local zones of elevated moisture in areas where condensation collects. This is one reason why the Code requires hatch covers to remain closed during the voyage for most mineral concentrate cargoes; ventilation, which might seem to reduce gas build-up, also introduces humid outside air that condenses on cooler surfaces.

Documented casualties and near-misses

Historical losses

Cargo liquefaction has been identified as the confirmed or probable cause of a significant number of bulk carrier losses since 1980. The documented record includes:

• Hui Long (2005): lost while carrying fluorspar mineral (a mineral concentrate type covered by the generic MINERAL CONCENTRATES entry). The vessel sank with 22 crew. The inquiry identified cargo liquefaction as the probable cause, making this one of the clearest pre-IMSBC-Code examples of a concentrate-class cargo leading to a loss.
• Asian Forest (2009): lost with 24 crew. Iron ore fines cargo; the investigation cited moisture content above TML. While iron ore fines has its own schedule, the liquefaction mechanism is identical to that affecting mineral concentrates.
• Black Rose (2009): lost in a similar period. Iron ore fines cargo, similar findings.
• Jian Fu Star (2010), Nasco Diamond (2010), and Hong Wei (2010): all lost in 2010 within months of each other, all carrying iron ore fines from Indonesian ports. The wave of losses prompted emergency IMO action on iron ore fines TML testing requirements and contributed to the development of the modified Proctor-Fagerberg procedure for that cargo class.
• Vinalines Queen (2011): lost with 22 of 23 crew, carrying nickel ore, another Group A cargo covered by IMSBC Code requirements similar to those for mineral concentrates. The single survivor’s account described the ship developing a severe list and capsizing within minutes, consistent with large-scale liquefaction.
• Bulk Jupiter (2015): lost with 18 of 19 crew, carrying bauxite. Bauxite was previously treated as Group C (non-liquefiable) but the Bulk Jupiter loss prompted IMO to reconsider its classification. The inquiry raised questions about whether the cargo’s fine fraction had been underestimated.

These casualties share a consistent pattern. The vessel departs port with certified documentation. In heavy seas, a list develops. The list increases despite attempts to correct it with ballast. Within hours, sometimes within minutes, the vessel capsizes. Survivors describe cargo that has turned to a slurry. The liquefaction had begun during loading, or shortly after departure, from a cargo that was at or above its TML.

Intercargo, the international trade association for dry bulk carriers, reported in 2024 that cargo liquefaction remains the leading cause of fatalities in the dry bulk sector, accounting for a disproportionate number of total-loss casualties relative to other incident categories.

Near-miss reporting and P&I club data

P&I clubs operating in the bulk carrier sector document multiple near-miss events involving mineral concentrate cargoes each year. Common patterns include:

• Cargo documentation provided after the vessel has already berthed and pre-loading inspections have begun, rather than in advance as required.
• Moisture certificates dated more than seven days before loading, which are technically invalid but frequently not noticed until the chief officer reviews them.
• Moisture certificates issued by laboratories that are not accredited or not recognised by the competent authority of the loading port.
• Cargo that passes the can test at the start of loading but fails it midway through, indicating that wetter cargo is being drawn from a different part of the stockpile as loading progresses.
• Bilge levels rising during the voyage at rates that can only be explained by moisture migrating from the cargo, in vessels carrying concentrates declared as compliant.

Each of these patterns is preventable. The IMSBC Code’s framework is not deficient in prescribing what must be done. The failures occur in the implementation: shippers who cut corners on testing, terminals that mix cargo batches with different moisture histories, and officers who accept documentation without adequate review under commercial time pressure.

Specially constructed ships

Section 7 exemption

The IMSBC Code’s Section 7 provides an exemption for ships specially constructed or fitted to carry Group A cargoes with moisture content above the TML. Such ships are rare in global trading. They must have:

• Reinforced double-bottom structure and tanktops designed to carry the additional hydrostatic loads from a partially liquefied cargo mass.
• Bilge systems capable of removing large volumes of moisture-laden material from the cargo spaces.
• Stability characteristics assessed specifically for the partially liquefied condition, not just the loaded solid condition.
• Flag state or classification society approval specifically covering the carriage of wet concentrate.

No standard Handysize, Supramax, Ultramax, or Panamax bulk carrier meets these requirements without specific modification and certification. A vessel presenting a general assignment of class or a standard bulk carrier certificate is not a Section 7 ship.

Practical consequence

The practical consequence of the Section 7 rule is that when a shipper cannot certify that the cargo moisture is below TML, there is no standard commercial bulk carrier that can legally carry it. The cargo must wait until it dries, or be blended with drier material, or be processed further to reduce moisture. The business pressure to ship on schedule is the single most important human factor in concentrate liquefaction casualties.

Limitations

The information in 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.

TML values are cargo-specific and cannot be generalised. Two concentrates from two different mines, both declared as polymetallic zinc-lead concentrate under the MINERAL CONCENTRATES BCSN, may have TML values differing by 3 to 4 percentage points because of differences in mineralogy, grind size, and clay content of the ore. The only reliable TML for a specific shipment is the value determined by an accredited laboratory on a representative sample of that specific batch within the validity window.

The can test screening procedure described here is the Section 8 method from the published IMSBC Code. It provides qualitative guidance only. Officers should not interpret a dry can test result as confirmation that the cargo is below TML.

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

The MHB provisions for Group A and B concentrates involve chemical hazard assessments that require professional classification expertise. Shippers dealing with novel or unusual concentrate compositions should seek competent authority guidance rather than relying on generic schedule references.

Regulatory requirements may differ between flag state and port state where the flag state has not yet implemented 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.

See also

• IMSBC Code
• IMSBC Group A cargoes: Cargoes that may liquefy
• Iron Ore Concentrate: IMSBC Code Schedule and Carriage
• Lead Concentrate: IMSBC Code Schedule and Carriage
• Zinc Concentrate: IMSBC Code Schedule and Carriage
• Copper Concentrate: IMSBC Code Schedule and Carriage
• Nickel Ore: IMSBC Code Schedule and Carriage
• Bulk Carrier

Related calculators:

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