IMSBC Group C: the residual solid bulk cargo group

IMSBC Group C is the residual classification in the International Maritime Solid Bulk Cargoes Code : under the group definitions at section 1.7, a solid bulk cargo is Group C when it is neither liable to liquefy or dynamically separate (Group A ) nor possessed of a chemical hazard in bulk (Group B ), so the group is defined entirely by what a cargo is not.

The classification is an outcome of two failed tests rather than a positive finding, and nothing in it certifies that a cargo is safe to load. A Group C cargo still needs a shipper’s declaration under section 4, still has to be trimmed under section 5, and still has to be loaded inside the tank top load limit in the ship’s loading manual, which for iron ore lump, pig iron and the ferroalloys binds long before the hold is full. Group C is also the largest group in the Code: 115 of the 223 individual cargo schedules in appendix 1 of the 07-23 consolidated text carry Group C in the hazard classification cell, 51.6 percent.

What section 1.7 says, and why Group C is decided last

Group C is assigned by elimination, and the Code says so in one sentence. Section 1.7, the unnumbered alphabetical definitions list, reads:

Group C consists of cargoes which are classified as neither group A nor group B.

Its two siblings on the same page carry the positive tests. Group A consists of cargoes which possess a hazard due to moisture that may result in liquefaction or dynamic separation if shipped at a moisture content in excess of their transportable moisture limit . Group B consists of cargoes which possess a chemical hazard which could give rise to a dangerous situation on a ship. Neither test met, and the cargo is Group C.

What amendment 06-21 changed about the definition

The wording is newer than most secondary sources record. The 05-19 text, adopted as IMO resolution MSC.462(101), defined Group C as cargoes which are neither liable to liquefy (group A) nor to possess chemical hazards (group B). Amendment 06-21, IMO resolution MSC.500(105), replaced that with the current text.

The change is not cosmetic. The old wording defined Group C by the absence of two physical facts; the current wording defines it by the absence of two classifications. Under the text in force, a cargo is Group C because the classification process placed it nowhere else, not because anyone established that it is harmless. That distinction is the whole of what follows.

What Group C does not certify

Group C removes nothing from sections 2, 3, 4, 5 and 6 of the Code. Section 1.2.2 is explicit that a cargo listed in appendix 1 shall be transported in accordance with the provisions in its schedule in addition to the provisions in sections 1 to 10 and 11.1.1, and section 1.2.1 warns that the schedules are not exhaustive and that the properties attributed to the cargoes are given only for guidance.

The Code supplies its own counter-example. SUGAR is Group C, and its Hazard block reads:

As sugar dissolves in water, ingress of water may result in the creation of air pockets in the body of the cargo with the ship’s motion. The hazards are then similar to the hazards presented by cargoes which may liquefy.

Its Carriage cell is the control on that hazard: after loading, the hatches of the cargo spaces shall be sealed to prevent water ingress, as necessary. A Group C classification and a liquefaction-like failure mode sit on the same page of the same schedule.

Group A, Group B and Group C compared

The comparison is what makes the residual logic operational. A surveyor confirming a Group A cargo asks for a test result; one confirming a Group B cargo asks for a class or an MHB code; one confirming a Group C cargo can only ask what the cargo was tested against and found not to be.

Where the Group C schedules live, and how many there are

The schedules are in appendix 1 of the Code, not in section 9. Section 9 sets the classification criteria for group B cargoes; appendix 1 carries the 223 individual cargo schedules ; appendix 4 is the index of Bulk Cargo Shipping Names and their synonyms; appendix 5 is the trilingual BCSN list, which section 1.4.2 makes mandatory alongside appendix 1.

Counting the hazard classification tables in the 07-23 text gives 223 schedules, of which 115 read Group C, 59 read Group B, 32 read Group A, 16 read A and B, and one, COAL, reads B (and A). Appendix 4 lists 116 Group C names rather than 115, because the index splits BORAX, ANHYDROUS into crude and refined while appendix 1 carries one schedule headed BORAX, ANHYDROUS (crude or refined).

The index carries one live inconsistency worth knowing about. The synonym row for triple superphosphate is still marked Group C, while the Bulk Cargo Shipping Name it points at, SUPERPHOSPHATE (triple, granular), reads Group B with an MHB CR code. Where the index and the schedule disagree, the schedule governs.

Which cells of a Group C schedule are mandatory

Section 1.4.2 lists what remains recommendatory or informative, and inside a schedule that is: the Description, the Characteristics other than the hazard classification block, the Hazard section, and the Emergency procedures. Everything else binds.

Nine operational fields bind, plus the hazard classification row. The consequence catches people out: the bulk density and stowage factor printed in the schedule are informative and are not the figures the ship loads to. The binding numbers are the shipper’s declared stowage factor under 4.2.2.6 and the declared bulk density under 4.2.2.7. The IRON ORE schedule prints a bulk density range of 1,250 to 3,500 kg/m3, which is far too wide to plan a stow against, and that is exactly why it is informative.

What a Group C schedule says, and what it omits

Across the 115 Group C schedules the language is highly repetitive, and the repetitions are worth knowing because a departure from them is a signal. 112 of the 115 carry the sentence that the cargo is non-combustible or has a low fire risk. 81 open the Hazard block with “No special hazards.” The two schedules with no low-fire-risk sentence at all are AMMONIUM NITRATE BASED FERTILIZER and SUGAR.

Three cells carry more obligation than the group’s reputation suggests:

• Weather precautions. 42 of the 115 carry the standard formula requiring the cargo to be kept as dry as practicable, not handled during precipitation, and all non-working hatches of the cargo spaces closed during handling. This is a mandatory field, so a Group C cargo can carry a full no-handling-in-rain obligation despite having no moisture hazard classification.
• Precautions. 59 of the 115 carry a bilge-well clause. The ALUMINA form is the model: bilge wells clean, dry and covered to prevent ingress of the cargo, machinery and accommodation spaces protected from dust, and persons who may be exposed to the dust wearing goggles or equivalent eye protection and dust filter masks. That is mandatory personal protective equipment on a Group C cargo.
• Discharge. Most read “No special requirements.” SCRAP METAL does not: where the cargo is discharged by magnet or spider grab, the deck and deck machinery shall be protected from falling cargo and damage to the ship shall be checked after completion of discharge. It is the Code’s only express grab-damage provision, and it sits on a Group C schedule.

What every Group C schedule omits is the Emergency procedures block. None of the 115 carries one. Because section 1.4.2 makes that block informative in any case, the omission costs nothing legally, but operationally it means there is no cargo-specific emergency guidance printed for any Group C cargo, and the ship falls back on section 3 and on its own contingency plans. The presence or absence of that block is the fastest way to tell a Group C schedule from a Group B one at a glance.

The Group A boundary is set schedule by schedule

There is no general particle-size or moisture threshold in the IMSBC Code separating Group A from Group C. Section 1.7 defines Group A by the moisture hazard and Group C residually, and every actual number lives in an individual schedule’s applicability clause. Any statement of a single site-wide threshold is wrong, and the widely repeated 6.3 mm sieve figure is the common instance of that error: 6.3 mm appears nowhere in the Code as a group criterion.

Iron ore and iron ore fines

The IRON ORE schedule, Group C, applies to iron ore cargoes containing either less than 10 percent of fine particles less than 1 mm, or less than 50 percent of particles less than 10 mm, or both. IRON ORE FINES , Group A, applies to cargoes containing both 10 percent or more of particles under 1 mm and 50 percent or more under 10 mm. Both criteria must be met for Group A; either one failing puts the cargo on the IRON ORE schedule.

There is a second route back to Group C that has nothing to do with particle size. Iron ore fines where the total goethite content is 35 percent or more by mass may be carried in accordance with the IRON ORE schedule, provided the master receives from the shipper a declaration of the goethite content determined according to internationally or nationally accepted standard procedures. Goethite is a hydrated iron oxide that binds moisture within its crystal structure, so a high-goethite fines cargo does not behave as a liquefaction risk in the way its particle size distribution would suggest.

Bauxite and bauxite fines

The bauxite thresholds are different numbers on different sieves, and conflating them with the iron ore pair is a common error. BAUXITE , Group C, applies to cargoes containing either 30 percent or less of fine particles less than 1 mm, or 40 percent or less of particles less than 2.5 mm, or both. BAUXITE FINES , Group A, applies where the cargo contains both more than 30 percent under 1 mm and more than 40 percent under 2.5 mm.

Bauxite also carries the Code’s clearest example of a document, rather than a measurement, deciding the group. Where the shipper provides the master with a certificate, in accordance with the result of a test approved by the competent authority of the port of loading, stating that the moisture of the cargo freely drains so that the degree of saturation is not liable to reach 70 percent, the cargo may be carried as a group C cargo under the BAUXITE schedule. Appendix 2 paragraph 1.6.1.4 carries the underlying rule that a free-draining sample means the cargo is not classified as group A, and section 7.2.2 supplies the physics: liquefaction does not occur when the cargo consists of large particles or lumps and water passes through the spaces between the particles without an increase in water pressure.

Manganese ore, and the coal case that looks similar but is not

MANGANESE ORE , Group C, carries no applicability clause at all; its boundary is written entirely from the fines side. MANGANESE ORE FINES , Group A, uses the same 10 percent at 1 mm and 50 percent at 10 mm pair as iron ore, and then adds its own escape: manganese ore cargoes which do not exhibit a flow moisture point are not liable to liquefy and shall be shipped as a group C cargo under the MANGANESE ORE schedule. A cargo with no measurable flow moisture point returns to Group C regardless of how fine it is.

COAL uses the identical particle-size pair and lands somewhere else entirely. Coal is classified group A and B unless classified group B only, either by a test determined by the appropriate authority or where it carries not more than 10 percent by weight of particles under 1 mm and not more than 50 percent under 10 mm. The coarse limb of coal drops out of Group A into Group B only. There is no Group C limb for coal, for direct reduced iron , or for any zinc cargo.

Every Group A and Group C threshold in the Code, in one table

The Group B boundary runs through section 9.2.3, not section 1.7

A cargo leaves Group C for Group B on one of three routes, all of them in section 9. Section 9.1 states that solid bulk cargoes which may possess chemical hazards during transport, because of their chemical nature or properties, are in group B, and splits the group into dangerous goods without additional hazards, materials hazardous only in bulk , and dangerous goods that also possess MHB hazards.

Section 9.2.2 routes dangerous goods to part 2 of the IMDG Code and enumerates the classes it uses at subsections 9.2.2.1 to 9.2.2.8: 4.1, 4.2, 4.3, 5.1, 6.1, 7, 8 and 9. Class 5.2, organic peroxides, is not among them; class 7, radioactive material, is.

The seven MHB codes, read from the Group C side

MHB is not a subset of dangerous goods but its complement. Section 1.7 defines materials hazardous only in bulk as materials which may possess chemical hazards when carried in bulk other than materials classified as dangerous goods in the IMDG Code. The MHB criteria are in sections 9.2.3.2 to 9.2.3.7, with the notation table at 9.2.3.1.5:

Two further routes carry no test at all. Section 9.2.3.1.3 allows a material to be classified as MHB by analogy with similar cargoes with known hazardous properties or by records of accidents, and 9.2.3.1.4 is the open catch-all. A cargo is Group C only after none of these has caught it.

One Bulk Cargo Shipping Name, two schedules, one test

The cleanest worked example of the boundary in the Code is seed cakes . Two schedules carry the identical name, SEED CAKES AND OTHER RESIDUES OF PROCESSED OILY VEGETABLES. The Group C schedule applies to cargoes substantially free from flammable solvents or other flammable chemicals which do not meet any of the criteria on dangerous goods or materials hazardous only in bulk specified in 9.2.2 or 9.2.3. The Group B schedule applies to cargoes substantially free from flammable solvents which meet the criterion for self-heating solids specified in 9.2.3.3 and do not meet any 9.2.2 criteria.

The 9.2.3.3 self-heating test result, and nothing else, decides which schedule the same consignment loads under. The name on the declaration is identical either way, which is why the group cell rather than the cargo name is what a loading officer has to read.

Scrap, sulphur and the fertilizers

SCRAP METAL is Group C, and its Hazard block carries the boundary in a single sentence: the cargo is non-combustible or has a low fire risk except when it contains swarf, that is fine metal turnings liable to spontaneous combustion, in which case the applicable schedule is FERROUS METAL BORINGS, SHAVINGS, TURNINGS or CUTTINGS UN 2793, class 4.2, Group B. The distinguishing feature is swarf, not oil contamination, and neither schedule sets an oil-content threshold or requires an oil-content certificate.

Sulphur splits on a process rather than a size. SULPHUR (formed, solid), Group C, covers sulphur recovered from sour gas processing or refinery operations that has been through a forming process converting it from a molten state into prills, granules, pellets, pastilles or flakes of 1 to 10 mm. SULPHUR UN 1350 (crushed lump and coarse grained) is class 4.1, Group B. Fine grained sulphur, flowers of sulphur, is prohibited in bulk altogether.

The fertilizers split on composition. AMMONIUM NITRATE BASED FERTILIZER is Group C where it is a straight nitrogen fertilizer with less than 2 percent chloride and either not more than 70 percent ammonium nitrate with other inorganic materials, or not more than 80 percent ammonium nitrate with calcium carbonate, dolomite or mineral calcium sulphate and not more than 0.4 percent total combustible organic material calculated as carbon. The shipper must declare the ammonium nitrate content and the chloride content in accordance with section 4.2. The UN 2067 and UN 2071 versions of the same commodity are Group B, class 5.1.

SODIUM NITRATE, POTASSIUM NITRATE and their mixture are each Group C in a granulometrically defined non-friable prill or granule form, with 95 percent at or above 1.0 mm, at most 2.5 percent between 0.85 and 1.0 mm and at most 2.5 percent below 0.85 mm. Their UN-numbered twins, UN 1498, UN 1486 and UN 1499, are Group B class 5.1. SUPERPHOSPHATE is Group C, while SUPERPHOSPHATE (triple, granular) is Group B with an MHB CR code and a mandatory instruction to be separated from alkali and urea.

What a Group C cargo does not attract from section 9

Nothing. Sections 9.3.1.4 and 9.3.1.6 both key on group B cargoes, and both mandatory segregation matrices are written for group B. Where a Group C schedule restricts stowage, it does so in its own Stowage and segregation cell, which for most Group C cargoes reads “No special requirements.”

What the shipper has to declare for a Group C cargo

Section 4.2.1 requires the shipper to provide the master or their representative with appropriate information on the cargo sufficiently in advance of loading to enable the necessary precautions to be put into effect. The section 4 declaration lists eighteen information items, and a Group C cargo attracts roughly half of them.

The items that apply regardless of group are the Bulk Cargo Shipping Name, the cargo group, the total quantity, the stowage factor at 4.2.2.6, the bulk density at 4.2.2.7 as required by SOLAS regulation XII/10, the need for trimming and the trimming procedures at 4.2.2.8, the likelihood of shifting including the angle of repose where applicable at 4.2.2.9, whether the cargo is harmful to the marine environment under appendix I of MARPOL Annex V at 4.2.2.17, and anything national authorities require at 4.2.2.18.

The declaration form at section 4.2.3 carries four tick boxes for the group: A and B, A, B, and C. There is no unclassified option, which matters more than it looks: a shipper who cannot place a cargo in a listed schedule is on the section 1.3 route and is not free to write Group C because nothing else fits.

Item 4.2.2.17 is the one most often left blank. The MARPOL Annex V harmful-to-the-marine-environment declaration is group-blind, it governs what can be done with hold washings on passage, and a Group C cargo attracts it exactly as a Group B cargo does.

What falls away, and what does not

A Group C cargo needs no transportable moisture limit certificate. Section 4.3.2 requires a signed TML certificate and a certificate or declaration of moisture content only when a group A cargo is carried, and the related machinery at 4.3.3 to 4.3.5, the sampling intervals at 4.5 and the whole of section 8 are Group A provisions.

It needs no dangerous-goods documentation either. Section 4.8.3 requires a Document of Compliance for the carriage of dangerous goods of ships carrying dangerous goods in solid form in bulk, and a Group C cargo carries no IMDG class, so the whole of section 4.8, including the special list or manifest under SOLAS regulation VII/7-2.2, does not attach.

What does not fall away is sampling . Section 4.4 requires the shipper to arrange for appropriate sampling and testing and to provide the master with the results, and 4.4.4 lets the ship’s interests reject unfit portions of a consignment identified during that process. Note the section number: sampling for a Group C cargo is section 4.4, while 4.3 is the certification regime that Group A triggers.

What the master can actually do

The IMSBC Code contains no general right for the master to refuse a cargo. It gives two express powers, and they are narrower than the folklore:

• Section 5.1.3: the master has the right to require that the cargo be trimmed level, where there is any concern regarding stability.
• SOLAS regulation VI/7.5: the master may suspend loading or unloading where the ship’s stress limits are exceeded or are likely to be, with an obligation to notify.

A refusal power comes from national law or from the contract, and one jurisdiction supplies it by name. Section 115 of the Canadian Cargo, Fumigation and Tackle Regulations , SOR/2007-128, requires a shipper loading solid bulk cargo in Canadian waters to comply with SOLAS regulations VI/2 and XII/10 and the applicable appendix 1 schedule, and requires the authorized representative and the master to refuse the cargo where the shipper does not provide the required documents. Elsewhere the practical route runs through the charter party and the overriding authority the ISM Code gives the master on safety grounds.

Trimming applies to every solid bulk cargo, including Group C

Section 5 is not group-specific and applies in full to a Group C cargo. Section 5.1.1 states that trimming a cargo reduces the likelihood of the cargo shifting and minimizes the air entering the cargo, and requires cargoes to be trimmed reasonably level, as necessary. The near-universal Group C Loading cell says exactly that: trim in accordance with the relevant provisions required under sections 4 and 5 of this Code.

Section 5.1.2 adds the structural half: cargo spaces are to be filled as full as practicable without resulting in excessive loading on the bottom structure or tween deck, the cargo is to be spread as widely as practicable to the boundary of the space, and alternate hold loading restrictions required by SOLAS chapter XII may also need to be taken into account.

The section 5.4 ladder

For a non-cohesive cargo the requirement is keyed to the angle of repose, and the categorisation into cohesive and non-cohesive is made for trimming purposes under 5.4.2.

The 5.4.3 rung produces the article’s neatest result. GRAIN SCREENING PELLETS is a Group C cargo whose printed angle of repose is less than 30 degrees and whose Description says the cargo flows freely like grain, so it is carried under the grain stowage provisions even though grain itself is outside the IMSBC Code entirely. POTASSIUM CHLORIDE, printed at 30 to 47 degrees, straddles both 5.4.4 and 5.4.5, so a single consignment can require either the 1.5 m or the 2 m unevenness limit depending on what it actually measures at.

Which Group C cargoes carry an angle of repose, and which do not

22 of the 115 Group C schedules print a numeric angle of repose, and the population is almost entirely fertilizers, industrial salts and slags: the nitrates at 26 to 32 degrees, UREA at 28 to 45, AMMONIUM SULPHATE at 28 to 35, SUPERPHOSPHATE and DIAMMONIUM PHOSPHATE at 30 to 40, POTASSIUM CHLORIDE at 30 to 47, POTASH at 32 to 35, BORAX at 35 and FERRONICKEL SLAG (granulated) at 36 to 56.

Not one Group C ore, mineral, metal or aggregate schedule prints an angle of repose. IRON ORE, BAUXITE, MANGANESE ORE, CHROMITE ORE, CEMENT , SAND , LIMESTONE , GYPSUM , PIG IRON and SALT all read “Not applicable”. Section 5.3.2 explains why: the angle of repose is not an indicator of the stability of a cohesive bulk cargo and it is not included in the individual schedules for cohesive cargoes. The cell is not an omission, it is a statement that the measure would be meaningless.

Section 6 gives the two measurement methods where one is needed: the tilting box method at 6.2.1, suitable for non-cohesive granular materials with a grain size not greater than 10 mm, and a shipboard test method at 6.2.2 giving an approximate angle in the absence of a tilting box apparatus. Both procedures sit in appendix 2 , which section 1.4.2 makes informative.

High density, the 0.56 threshold, and the tank top

Section 1.7 defines a high-density solid bulk cargo as a solid bulk cargo with a stowage factor of 0.56 m3/t or less. The definition is expressed as a stowage factor, not as a density, and the phrase 0.56 m3/t appears 32 times in the Code: once in the definition and 31 times in schedule Loading cells.

Group C owns the dense end of the trade. Ranked on the dense end of their printed stowage factor: FERROCHROME and FERROMANGANESE at 0.18 m3/t, COPPER GRANULES at 0.22, FERRONICKEL and LEAD ORE at 0.24, SILICOMANGANESE (carbo-thermic) and COPPER MATTE at 0.25, PIG IRON at 0.28, IRON ORE at 0.29, ILMENITE (ROCK) at 0.31, MANGANESE ORE at 0.32, CHROMITE ORE at 0.33 and BARYTES at 0.34. Section 2.1.2 puts that in perspective with the Code’s one design figure: a general cargo ship is normally constructed to carry cargoes in the range of 1.39 to 1.67 m3/t when loaded to full bale and deadweight capacities.

What the Code requires at or below 0.56 m3/t

The dense-cargo Loading cell is a mandatory field, and its text is identical across the dense Group C schedules:

When the stowage factor of this cargo is equal to or less than 0.56 m3/t, the tank top may be overstressed unless the cargo is evenly spread across the tank top to equalize the weight distribution. Due consideration shall be given to ensure that the tank top is not overstressed during the voyage and during loading by a pile of the cargo.

Section 2 adds four more requirements. Under 2.1.3.3 high-density cargoes shall as far as practicable be loaded in the lower hold cargo spaces in preference to tween deck spaces. Under 2.1.3.4, where a high-density cargo has to go higher, due consideration is given that the deck area is not overstressed and that stability is not reduced below the ship’s stated minimum. Under 2.2.4, because of the velocity at which some high-density cargoes are loaded, special care may be needed to protect the cargo space fittings from damage, with sounding the bilges after loading named as the detection method. Section 2.1.3.2 requires shifting divisions and bins of adequate strength wherever cargoes suspected of readily shifting are carried in tween-deck spaces or in partially filled spaces.

The trap here is which stowage factor triggers the cell. It is the actual stowage factor of the consignment, which is the shipper’s declared value under 4.2.2.6, and not the schedule’s printed range, which is informative. IRON ORE prints 0.29 to 0.80 m3/t, so one schedule covers consignments on both sides of the 0.56 trigger.

Where the tank top limit actually comes from

Not from the IMSBC Code. The number lives in the booklet required by SOLAS regulation VI/7.2, which must be in a language the responsible officers are familiar with and must contain, as a minimum, the stability data required by regulation II-1/5-1, the ballasting and deballasting rates and capacities, the maximum allowable load per unit surface area of the tank top plating, the maximum allowable load per hold, general loading and unloading instructions with regard to structural strength, any special restrictions imposed by the Administration or a recognized organization, and where strength calculations are required, the maximum permissible forces and moments on the hull during loading, unloading and the voyage.

That booklet is endorsed under SOLAS regulation XII/8.1, any operational restriction is recorded under XII/8.2, and a ship carrying such a restriction is marked under XII/8.3 with a 500 mm equilateral triangle whose apex sits 300 mm below the deck line. The class basis for the permissible loads themselves is IACS Unified Requirement S1, Rev.7, and UR S1A, Rev.6.

Above that sits the loading plan. Under SOLAS regulation VI/7.3 the master and the terminal representative agree a plan ensuring the permissible forces and moments are not exceeded, covering the sequence, the quantity and rate of loading, the number of pours and the deballasting or ballasting capability, and that plan is lodged with the appropriate authority of the port State. Under VI/7.6 loading is monitored continuously, draught and tonnage observations are recorded in a cargo logbook, and cargo or ballast operations are adjusted where significant deviations from the plan are detected. The practice behind all of it is the BLU Code , IMO Assembly resolution A.862(20).

The load relation, and why the hold is never full

For a level stow on the inner bottom the relation is arithmetic. The uniformly distributed load is the product of the cargo bulk density and the stow height, and the maximum fill height is the permissible load divided by the density, which is the same as the permissible load multiplied by the stowage factor. A cargo at 0.28 m3/t reaches a given tank top load at roughly one fifth of the height that a cargo at 1.39 m3/t does. This is why a Capesize loading iron ore weighs out with the holds visibly part empty, while the same ship cubes out on coke at 1.25 to 2.93 m3/t long before the deadweight is used.

The general relation holds only where the cargo surface is level. The IACS Common Structural Rules treat the inner bottom as a horizontal panel, so the geometric factor drops out and the pressure reduces to density times gravity times height; on a sloped hopper panel it does not, and the angle of repose re-enters the calculation. A pile left untrimmed under a loading spout concentrates the load exactly where the rules assume it is spread, which is why the mandatory Loading cell says evenly spread rather than simply within the limit.

SOLAS chapter XII, and the two density numbers that get confused

The 1,780 kg/m3 figure quoted alongside the Code’s high-density definition appears nowhere in the IMSBC Code. It belongs to SOLAS chapter XII , and the two numbers should never be run into one sentence.

Regulation XII/10 works in two limbs. Regulation XII/10.1 is universal: the shipper declares the density of the cargo to the master before loading on every bulk carrier of 150 m in length and upwards, whatever the cargo and whatever the group. Regulation XII/10.2 is narrow: for bulk carriers to which regulation XII/6 applies and which do not comply with all the chapter XII requirements for cargoes of 1,780 kg/m3 and above, a cargo declared in the 1,250 to 1,780 kg/m3 band must have its density verified by an accredited testing organization. The verification method is in MSC/Circ.908 , and what the limb triggers is third-party verification, not a structural requirement.

Alternate hold loading is where dense Group C cargo meets the ship’s longitudinal strength. IACS Recommendation No. 46 records that alternate loading raises the ship’s centre of gravity, that the cargo weight in a loaded hold is approximately double, and that the empty holds have not been reinforced, so ships not approved for the practice must not adopt it. The approval is carried as a class notation and its operational output is the hold mass curve , which gives the permissible cargo mass in each hold against draught.

What actually goes wrong with Group C cargo

The Code’s own general accident statement is at section 2.1.1 and it is group-blind: a number of accidents have occurred as a result of improper loading and unloading of solid bulk cargoes, and solid bulk cargoes have to be properly distributed throughout the ship to provide adequate stability and to ensure that the ship’s structure is never overstressed.

The honest framing of the casualty record is that Group C hazards do not appear in it as a named cause of loss. The INTERCARGO Bulk Carrier Casualty Report 2026, published 7 July 2026 and covering 2016 to 2025, records 17 bulk carriers of 10,000 dwt and above lost with 71 lives, with cargo liquefaction the leading cause of loss of life at 37 fatalities and grounding the leading cause of ship losses at 41.1 percent of cases. Liquefaction is a Group A hazard and grounding is not a cargo hazard at all. Group C risk does not show up as sinkings; it shows up as structural damage, cargo damage and claims.

Five failure modes, each with its control

1. Tank top overloading. The mechanism is the arithmetic above, and the controls are SOLAS VI/7.2, the agreed plan under VI/7.3, the suspension right under VI/7.5 and the monitoring duty under VI/7.6. The schedule-level control is the mandatory even-spreading sentence.
2. Cargo shift. Section 7 does not apply to a Group C cargo, so the only control is section 5 trimming and, for a cargo at or below 30 degrees, the grain stowage provisions via 5.4.3.
3. Dust. 64 of the 115 Group C schedules mention dust. Sections 2.2.5 and 2.2.6 require ventilation shut down or screened and air conditioning on recirculation during loading and discharge, and dust kept off moving parts of deck machinery and external navigational aids. Section 3.3 requires breathing protection, protective clothing and washing facilities, and section 3.4.1 notes that the dust explosion risk is minimized by ventilating and by hosing down rather than sweeping .
4. Hold contamination and cargo damage. The Code sets almost nothing here for Group C, which is precisely why the standard is contractual. The ship’s duties are section 2.2.1, cargo spaces inspected and prepared for the particular cargo, and 2.2.2 to 2.2.3 on bilge wells , strainer plates, bilge lines, sounding pipes and service lines. Everything above that comes from the charter party and the receiver, which is where dry cargo shortage and damage claims begin.
5. Water ingress. 42 of the 115 Group C schedules carry the mandatory keep-as-dry-as-practicable weather precaution. SUGAR and SALT are both highly soluble and both schedules address ingress directly, SUGAR with the free-surface warning and the sealed-hatch requirement.

Oxygen depletion deserves separate mention because it crosses the group line. Section 3.2.3 names ferrous metals among the cargoes liable to cause oxygen depletion in a cargo space, and SCRAP METAL is a Group C ferrous metal. That pulls in 3.2.4 on enclosed space entry and 3.2.5, which requires instruments for measuring gas and oxygen concentration to be provided.

Discharge damage

Grab and bulldozer damage is the dominant Group C loss mechanism on the ship side and it is largely unregulated by the Code. SOLAS regulation XII/6.5.1 is the statutory hook, requiring that cargo can be loaded and discharged by standard loading and discharge equipment and procedures without damage which may compromise the safety of the structure. Class carries the rest: the GRAB notation in the IACS Common Structural Rules is mandatory on BC-A and BC-B bulk carriers, at 35 t for ships of 250 m and above, 30 t from 200 m to under 250 m, and 20 t otherwise, and the rules warn that the notation does not negate the use of heavier grabs and flags the possibility of early renewal of inner bottom plating.

The Group C cargoes a practitioner meets

The figures below are each schedule’s own Characteristics table in the 07-23 text. They are informative under section 1.4.2 and are given here to show the shape of the group, not to plan a stow: the binding numbers are always the declared ones. “Not applicable” in the angle of repose column is the schedule’s own wording, and under section 5.3.2 it means the cargo is cohesive.

Three things fall out of the table. The density spread inside Group C is more than an order of magnitude, from COKE at 341 kg/m3 to FERROCHROME at 5,556, so no operational generalisation about the group survives contact with a specific cargo. The ferroalloys, not the ores, are the densest cargoes in the Code. And most of the group is cohesive, which is why the angle of repose column is mostly empty. A finder such as the IMSBC cargo finder on ShipCalculators.com is the quickest way to pull a specific schedule’s cells; the Code itself remains the authority.

The cargoes that are not in the group at all

Two large classes get filed under Group C by people who should know better, and neither belongs.

Grain has no IMSBC group. SOLAS regulation VI/1-2 requires the carriage of solid bulk cargoes other than grain to comply with the IMSBC Code, and grain is governed by SOLAS chapter VI part C and the International Grain Code, IMO resolution MSC.23(59). There is no WHEAT, MAIZE, RICE, SOYA BEANS, BARLEY, OATS or RYE schedule in appendix 1. The only grain-derived Group C entries are GRAIN SCREENING PELLETS and DISTILLERS DRIED GRAINS WITH SOLUBLES, and the maize, rice and soyabean names that do appear in appendix 4 are all cross-references to the seed cake family, that is to processing residues rather than to the grain.

Steel products and metal ingots are not solid bulk cargoes. Section 1.7 defines a solid bulk cargo as material loaded directly into the cargo spaces of a ship without any intermediate form of containment, and a coil in a cradle with bolsters and lashings is the opposite of that. Appendix 4 contains no steel, slab, billet, coil, ingot or cathode Bulk Cargo Shipping Name. Those cargoes are governed by SOLAS regulation VI/5, the Cargo Securing Manual and the CSS Code , IMO Assembly resolution A.714(17), with the structural side of steel coil loads in bulk carrier holds handled separately in the IACS Common Structural Rules. The Group C non-ferrous entries that do exist are the ferroalloys and mattes, not refined metal shapes.

A cargo with no schedule is not Group C by default

Section 1.3 governs a cargo that is not listed in appendix 1, and the route it takes depends on the hazard assessment rather than on the shipper’s preference. Under 1.3.1 the shipper provides the competent authority of the port of loading with the characteristics and properties of the cargo in accordance with section 4, and that authority assesses acceptability.

The split then matters:

• Section 1.3.1.1, where the cargo may present hazards as defined by group A or B: advice is to be sought from the competent authorities of the port of unloading and of the flag State, and the three competent authorities set the preliminary suitable conditions for the carriage.
• Section 1.3.1.2, where the cargo presents no specific hazards for transportation: the carriage shall be authorized, and the competent authorities of the port of unloading and of the flag State shall be advised of that authorization.

A cargo assessed as presenting no specific hazards is authorized by the loading-port authority alone. The other two are notified, not consulted, and that is the operative practical difference between proposing a Group C cargo and proposing a Group A or B one. The word tripartite appears nowhere in MSC.539(107); it is trade usage for the 1.3.1.1 route, and the cargoes-not-listed procedure covers both limbs.

Either way, section 1.3.2 requires the loading-port authority to provide the master with a certificate stating the characteristics of the cargo and the required conditions for carriage and handling, and to submit an application to IMO within one year to have the cargo incorporated into appendix 1. The format for that submission is section 1.3.3, and it is the same 13-field structure every schedule follows. Section 1.5 exemptions run on a separate track and apply to Group C cargoes as they do to any other.

The Code defines the competent authority as any national regulatory body or authority designated or otherwise recognized as such for any purpose in connection with the Code, and adds one sentence that is often dropped: the competent authority shall operate independently from the shipper.

Regional overlays on a Group C carriage

The IMSBC Code applies through SOLAS regulation VI/1-2 wherever SOLAS applies, and four regional instruments add to it in ways that matter for Group C specifically.

European Union. No instrument transposes the Code itself, but Directive 2001/96/EC of 4 December 2001 makes BLU Code loading and unloading practice binding at terminals in Member States for bulk carriers of any flag: agreed loading plans, terminal suitability, terminal representative duties, ship and shore information exchange, and an authority power to halt operations. Because Group C risk is concentrated in the loading operation rather than in the passage, this is the most consequential regional overlay the group attracts anywhere.

United States. 46 CFR part 148 covers the carriage of bulk solid materials that require special handling, and incorporates the IMSBC Code by reference at 46 CFR 148.8. Section 148.55(b) permits a bulk solid material classed, described, stowed and segregated in accordance with the Code to be offered, accepted and transported within the United States. Part 148 is written for materials requiring special handling, so a Group C cargo generally sits outside its substantive requirements while still being carried under the Code by virtue of those two sections.

Australia. Marine Order 34 (Solid bulk cargoes) 2016 , made under the Navigation Act 2012 and commenced on 1 January 2017, gives the IMSBC Code and the BLU Code effect in Australian law and adds AMSA approvals, a notice of intention to ship, a notice of fumigation, and the domestic route for a cargo not listed in appendix 1.

Canada. The Cargo, Fumigation and Tackle Regulations, SOR/2007-128, section 115, requires compliance with SOLAS regulations VI/2 and XII/10 and the applicable appendix 1 schedule, and requires the authorized representative and the master to refuse the cargo where the shipper does not provide the required documents.

Port state control on a Group C cargo is therefore mostly a documentary inspection: the cargo declaration and its group cell, the density declaration under SOLAS XII/10, the loading plan and the cargo logbook entries under VI/7.3 and VI/7.6, the stability information, and the ship’s approval for whatever loading pattern is in use.

Which amendment governs, today and from 2027

The amendment set in force today is 07-23, adopted as IMO resolution MSC.539(107) on 8 June 2023, deemed accepted on 1 July 2024, and mandatory since 1 January 2025. Its annex replaces the complete text of the Code, so it is a consolidated edition rather than a set of deltas, and no count of schedules added by it is derivable from the resolution itself. 07-23 governs carriage until 31 December 2026.

Amendment 08-25, adopted as IMO resolution MSC.575(110) on 26 June 2025 and deemed accepted on 1 July 2026, is not yet mandatory. It may be applied in whole or in part on a voluntary basis from 1 January 2026, and it governs carriage from 1 January 2027. It inserts eleven new schedules in alphabetical order: ALUMINIUM SULPHATE GRANULAR, APATITE CONCENTRATE, ASPHALT GRANULATES, CRUSHED GRANODIORITE COARSE, FERRIC SULPHATE GRANULAR, FISH MEAL (FISH SCRAP) STABILIZED, IRON ORE BRIQUETTES, PEA PROTEIN CONCENTRATE PELLETS, PHOSPHATE ROCK FINES (uncalcined), TUFF COARSE and ZINC SLAG (coarse). It also removes the word MHB from the second column of the 9.3.3 segregation table and adds division 1.6 to the fourth column heading, neither of which affects Group C.

Because a voluntary-application window is open, the practical question during 2026 is which edition the ship is carrying and which the load port is working to. The amendment cycle runs on two years and tacit acceptance, and a consignment loaded under one edition and discharged under the next is routine rather than exceptional.

Between the 05-19 and 07-23 editions Group C grew from 110 schedules to 115. Seven Group C names are new: BROWN FUSED ALUMINA, CLAM SHELL, DUNITE, POTASSIUM NITRATE, the Group C limb of SEED CAKES AND OTHER RESIDUES OF PROCESSED OILY VEGETABLES, SODIUM NITRATE, and SODIUM NITRATE AND POTASSIUM NITRATE MIXTURE. One name left the group entirely: SUPERPHOSPHATE (triple, granular), now Group B with an MHB CR code on the eye-corrosion limb of 9.2.3.7. A cargo’s group is not a permanent property of the commodity.

Amendment 09-27 is in preparation, with cargoes agreed in principle at the eleventh session of the Sub-Committee on Carriage of Cargoes and Containers in September 2025. It has no resolution number and no dates.

Limitations

This article states what the IMSBC Code as amended by 07-23 requires. It is not a substitute for the Code, for the individual schedule, or for the ship’s own documents, and four limits should be read with it.

The schedule figures here are informative. Every size, angle of repose, bulk density and stowage factor quoted is from the schedule’s Characteristics table, which section 1.4.2 makes informative other than the hazard classification block. The binding figures for any consignment are the shipper’s declared values under section 4.2.2, and a cargo can and does fall outside its own schedule’s printed range.

No tank top load figure is given for any ship or ship class. The permissible load per unit area of tank top plating and per hold is a ship-specific number in the booklet required by SOLAS regulation VI/7.2, approved by the Administration or a recognized organization. Any generalised t/m2 rating for a size class would be wrong on some ships in that class, and the load relation given above is the method, not a result.

The schedule counts are a parse of the 07-23 consolidated text. The 115 of 223 figure was produced by reading the group cell of every hazard classification table in appendix 1, and it reconciles with appendix 4 to a single documented difference, the BORAX split. Counts published elsewhere differ, usually because they count index rows rather than schedules.

The group assigned to each of the eleven schedules inserted by 08-25 is not stated here. Those groups were not read from MSC.575(110) for this article, and several of the names invite an assumption that would be worth nothing if wrong. Confirm each against the resolution before relying on it.

Two further points of practice. The Code carries at least one internal inconsistency of its own, the triple superphosphate index row discussed above, so where an index entry and a schedule disagree the schedule governs. And a Group C classification says nothing about the commercial standard the hold has to meet: the hold cleanliness standard for most Group C cargoes is contractual, and “No special requirements” in the schedule is where the Code stops, not where the obligation stops.

Related Articles

• IMSBC Code : the instrument itself, its SOLAS hook and its structure
• IMSBC Group A cargoes : the liquefaction and dynamic separation group across the boundary
• IMSBC Group B cargoes : the chemical hazard group and the MHB regime
• IMSBC individual cargo schedule : the 13 fields and how to read one
• IMSBC schedule mandatory and informative fields : what section 1.4.2 binds
• Shipper’s cargo declaration for solid bulk : the section 4.2 information items
• High-density solid bulk cargo : the 0.56 m3/t definition and what it triggers
• Tank top strength and loading limits : where the permissible load comes from
• Angle of repose of solid bulk cargoes : measurement and the trimming ladder
• Broken stowage in bulk cargoes : the gap between stowage factor and hold volume
• Bulk carrier loading plan and sequence : SOLAS VI/7 and the pour sequence
• Cargo hold preparation standards : the commercial standards above the Code
• Cargo draught survey for bulk cargoes : quantity determination on a Group C load
• SOLAS Chapter VI: carriage of cargoes and oil fuels : regulations 1-2, 2, 6 and 7
• Bulk carrier : the ship type that carries the group
• Bulk carrier size classes : Handysize through Capesize and the trades each serves
• Minor bulk trades : the long tail below the five majors, most of it Group C