Sand is classified as Group C under the IMSBC Code in its ordinary silica and construction grades, meaning the cargo presents neither a liquefaction hazard nor a chemical hazard under standard commercial conditions. The practical hazards are primarily occupational: respirable crystalline silica dust is a confirmed carcinogen, and high-density heavy mineral sands raise distinct structural loading and radiation-protection concerns that construction sand does not.
The IMSBC Code, made mandatory under SOLAS Chapter VI by Resolution MSC.268(85) and entering into force in January 2011, schedules sand under several entries in its Appendix 1. The base SAND entry covers ordinary silica and construction sand as a Group C cargo. Separate entries exist for SAND (SILICA), INDUSTRIAL SAND, SAND (WASHED), ILMENITE SAND, and related schedules covering the heavy mineral sand family. Each entry carries distinct physical properties, hazard classifications, and handling requirements reflecting the substantial variation in sand commodities shipped by sea.
Sand is not a single material. The seaborne trade covers at least five commercially distinct product categories: construction sand for concrete and aggregate, high-purity silica sand for the glass and electronics industries, foundry sand for metal casting, frac sand for hydraulic fracturing in oil and gas production, and heavy mineral sands mined for their ilmenite, rutile, zircon, and monazite content. Each category has different particle size distributions, purity requirements, bulk densities, and hazard profiles. The IMSBC schedule structure reflects this: a shipper who declares only “sand” without specifying the product sub-type is likely under-declaring the cargo’s relevant properties.
What the IMSBC Code sand schedules cover
The main SAND schedule entry
The generic SAND entry in Appendix 1 of the IMSBC Code covers ordinary silica and construction sand. It specifies Group C, meaning the cargo does not liquefy under normal carriage conditions and presents no significant chemical hazard. The schedule records a bulk density range of approximately 1,250 to 1,920 kg/m3 and an angle of repose between 30 and 45 degrees depending on particle shape and moisture content.
The physical description in the Code notes that sand consists primarily of silica (silicon dioxide, SiO2) with variable amounts of feldspar, mica, and clay minerals depending on provenance. The term “ordinary sand” in the carriage trade encompasses river sand, beach sand, sea-dredged sand, and pit-mined sand, all of which share similar physical behaviour for carriage purposes despite differing in mineralogical detail.
Group C status does not mean the cargo is hazard-free. The Code’s generic schedule includes a specific note on dust generation and its health implications, referring carriers to the relevant sections of the Code covering protection of crew from cargo hazards. Respirable crystalline silica (RCS) is the primary occupational hazard, discussed in detail below.
SAND (SILICA) and processed sand variants
The IMSBC Code carries a separate schedule for SAND (SILICA), covering high-purity grades used in glass manufacture, ceramics, and the semiconductor supply chain. The schedule also records Group C but specifies tighter particle-size and chemical-purity requirements. A typical glass-grade silica sand contains 99.5 percent or more SiO2, with iron oxide below 0.02 percent by weight, and the particle size distribution is typically between 0.1 and 1.0 mm to suit the glass furnace batch requirements.
SAND (WASHED) and INDUSTRIAL SAND are further entries covering processed grades that have been screened, washed, and graded to meet industrial specifications. These grades are typically used in foundry moulding sand, filtration media, sports turf topdressing, and water-treatment filter beds. Their physical carriage properties are similar to ordinary silica sand, and both remain Group C in the IMSBC Code schedule, though the washed and dried nature of these products means their moisture content at loading is typically lower than construction sand freshly dug from a river deposit.
OLIVINE SAND is a distinct mineral entry in the Code, covering the magnesium iron silicate mineral olivine (Mg,Fe)2SiO4 used as foundry and refractory sand. Olivine sand does not contain free silica in the same proportion as quartz-based grades and its silicosis risk profile is different, though it still generates mineral dust. The IMSBC Code schedules it as Group C.
The heavy mineral sand schedules
The IMSBC Code schedules for the heavy mineral sand family are distinct from ordinary sand entries and carry different hazard classifications. The most traded heavy mineral products with individual IMSBC schedules are:
| Cargo name | Principal mineral | Bulk density (kg/m3) | Group |
|---|---|---|---|
| ILMENITE SAND | FeTiO3 (ilmenite) | 1,800 to 2,900 | A or C |
| RUTILE | TiO2 (rutile) | 1,500 to 2,500 | C |
| ZIRCON | ZrSiO4 (zircon) | 2,500 to 3,000 | C |
| ILMENITE | FeTiO3 (dense grade) | 2,200 to 3,200 | C |
Group classification for ilmenite sand depends on particle size. Fine ilmenite sand with a significant proportion of particles below 1 mm and elevated moisture content may liquefy and is classified Group A by the Code, subject to TML testing and MC certification under the same procedures that apply to mineral concentrates. Coarser ilmenite products, coarser rutile, and zircon are Group C.
Monazite, the rare earth phosphate mineral, does not hold a standalone IMSBC Appendix 1 schedule entry as a primary bulk cargo. It occurs as a minor constituent of heavy mineral sand concentrates and is separated from the primary titanium minerals at the mineral separation plant on shore. Raw heavy mineral sand concentrate, as loaded onto a vessel at a mine-site export terminal, typically contains a mixture of ilmenite, rutile, leucoxene, zircon, and small amounts of monazite, with the exact proportions depending on the deposit geology.
Ordinary silica sand: cargo properties and uses
Physical properties at sea
Construction and ordinary silica sand has a bulk density of approximately 1,400 to 1,700 kg/m3 in as-loaded condition, giving a stowage factor of roughly 0.59 to 0.71 m3 per tonne. Dry sand flows freely and has a fairly consistent angle of repose of about 30 to 35 degrees, which means loaded holds trim reasonably well and do not require bulldozer spreading for minor hatch access, though large shipments to multi-hatch Panamax or Capesize bulk carriers will require mechanical trimming equipment.
Wet sand behaves differently. Sand loaded at high moisture content, above about 12 to 15 percent by weight depending on particle size distribution, may compact under vessel motion and become difficult to discharge with grabs. Very fine, uniformly sized sand at high moisture has shown flow behaviour in the lower hold, consistent with early-stage liquefaction, though the IMSBC Code does not currently classify standard construction sand grades as Group A. The key physical variable is particle size: coarse angular river sand with a D50 particle diameter above about 0.5 mm drains rapidly and does not retain the pore-water pressures that drive liquefaction, while very fine well-sorted sand with a D50 below 0.1 mm has drainage characteristics that approach those of a fine mineral concentrate.
Sand is non-toxic, non-flammable, and non-self-heating. It is chemically inert with mild steel at ambient temperatures, though moist sand pooled in poorly drained bilge areas will promote moderate corrosion of the hold structure over time. Sand is abrasive: conveyor belts, grab bucket lips, and hold paint coatings all suffer measurable wear from repeated sand-loading cycles, and the abrasion damage to hold frames is a known maintenance item for vessels on regular sand routes.
Construction sand uses and trade
Construction sand is the largest-volume sand commodity by mass. Its primary use is as fine aggregate in concrete, where it occupies typically 35 to 40 percent of the concrete mix volume and contributes both to strength and workability. The concrete industry’s requirement is for sand with a particle size between about 0.075 mm and 4.75 mm, relatively clean of clay, organic matter, and salt, and with an appropriate particle-shape distribution.
Natural sand production is regionally constrained. River and floodplain deposits are the traditional source, but many of the world’s largest cities have exhausted accessible river sand within economic haulage distance of their construction sites. Southeast Asia is the most studied case: Singapore historically imported tens of millions of tonnes of construction sand annually for land reclamation projects, drawing supplies from Indonesia, Malaysia, Cambodia, and Vietnam under varied export-permit regimes. Indonesia banned sand exports in 2002, Vietnam restricted exports progressively from 2009, and Cambodia imposed an export ban in 2017, steadily narrowing Singapore’s supply options and pushing prices upward. The resulting trade disruptions drove both sea dredging of offshore sand deposits and increased interest in manufactured or recycled aggregate as substitutes.
Global seaborne trade in construction sand is large in tonnage but is dominated by short-sea and regional voyages. Deep-sea oceanic shipments of construction sand are economically marginal for most grades because the material is intrinsically low-value and freight costs are a high proportion of delivered cost. The exception is where destination countries face genuine supply scarcity and where the price premium over local alternatives is sufficient to support long-haul freight. Persian Gulf construction booms, island reclamation projects in the Pacific, and major infrastructure programmes in Southeast Asia have all at times supported deep-sea construction sand trade.
Silica sand for the glass and electronics industries
Glass-grade silica sand is a materially different product from construction sand, both in terms of specification tightness and in terms of trade economics. A glass-batch silica sand must be chemically very pure: iron oxide content below 0.015 percent is required for clear flat glass, below 0.005 percent for high-transmission optical glass, and total iron plus titanium oxide below 0.02 percent for solar panel glass. Particle size must be tightly controlled to ensure consistent melting behaviour in the furnace, and the particle shape should be angular rather than rounded to give good batch packing.
The major export sources of glass-grade silica sand include the Fontainebleau formation sands of France, the Lippe sands of Germany, the Loch Aline deposit in Scotland, Australian deposits in Western Australia and Victoria, and deposits in the eastern United States. These are traded in significant volumes to glass manufacturers in Asia and the Middle East where equivalent local deposits are absent.
Electronics-grade silica sand, used as feedstock for the production of high-purity quartz and ultimately silicon for semiconductors, is an even more specialized product requiring SiO2 content above 99.9 percent and sub-ppm levels of metallic impurities. The volumes are small, the material typically moves in bags or small parcels rather than bulk, and the cargo handling requirements focus on contamination prevention rather than on the bulk-carriage parameters addressed by the IMSBC Code.
Frac sand
Frac sand is high-purity silica sand used as a proppant in hydraulic fracturing operations for oil and gas production. The critical property is crush resistance under the closure stresses of the fractured rock formation, which can reach 7,000 to 14,000 kPa (1,000 to 2,000 psi) at typical shale reservoir depths. The API RP 19C and ISO 13503-2 standards define the test methods for proppant crush resistance, roundness, sphericity, and turbidity.
Commercially, frac sand is predominantly mined from the St. Peter Sandstone and Jordan Sandstone formations of the US Midwest, particularly in Wisconsin, Minnesota, and Texas. The shale revolution that began in the late 2000s drove demand from essentially zero to roughly 90 to 100 million tonnes per year in the United States alone by the mid-2010s, creating a substantial domestic rail-freight industry to move sand from the Wisconsin deposits to Texas and North Dakota shale plays. Seaborne export of frac sand has been more limited, but significant volumes have moved by sea to oil and gas developments in Argentina, China, and the Middle East.
Frac sand carriage by sea is Group C under the IMSBC Code, but the cargo requires special attention to dust suppression because frac sand is a well-sorted, very fine material with a high proportion of respirable silica. The silicosis risk for personnel loading and discharging frac sand is among the most intensely regulated aspects of the US domestic frac sand industry.
Foundry sand
Foundry sand is used to form the moulds and cores in metal casting. The sand must bind well with clay or resin binders, withstand the thermal shock of molten metal contact, and resist metal penetration. The primary material is silica sand, though chromite sand, zircon sand, and olivine sand are used for specific applications. New foundry sand is graded to close particle-size specifications, but a substantial fraction of the market is served by reclaimed spent foundry sand from metal casting facilities.
Seaborne trade in virgin foundry sand follows similar routes to glass-grade silica sand, with high-specification European and Australian deposits supplying foundry operations in Asia. Spent foundry sand is not a bulk commodity; it is managed as an industrial waste stream in most jurisdictions.
The silica dust health hazard
Respirable crystalline silica and silicosis
Crystalline silica occurs in three polymorphic forms: quartz, cristobalite, and tridymite. Quartz is by far the most abundant, making up most of the silica content in commercial sand. When silica-containing material is handled, dried, or conveyor-loaded, particles are generated across a wide size range. Respirable dust is defined as the fraction that penetrates to the gas-exchange region of the lung, namely particles with an aerodynamic diameter below approximately 10 micrometres (and particularly below 4 micrometres).
When inhaled, respirable crystalline silica particles deposit in the alveolar region of the lung. Silica is not inert at the cellular level: the crystal surface reacts with lung macrophages, triggering repeated inflammatory cycles. Over years of exposure, this produces a characteristic nodular fibrosis called silicosis. Silicosis is irreversible and progressive, and it increases susceptibility to tuberculosis by a factor of roughly 3 to 5 compared with unexposed workers. The International Agency for Research on Cancer (IARC) classified inhaled crystalline silica from occupational sources as a Group 1 human carcinogen in 1997, confirming that sufficient occupational exposure causes lung cancer independently of other risk factors.
The occupational exposure limit (OEL) for RCS in most jurisdictions is 0.025 to 0.1 mg/m3 as an 8-hour time-weighted average. US OSHA set its permissible exposure limit at 0.05 mg/m3 in 2016. The UK HSE applies a workplace exposure limit of 0.1 mg/m3. These limits are far below the concentrations that can occur at a sand terminal during active conveyor loading without dust control.
Dust exposure during sea loading and discharge
Sand terminals at major export points operate continuous conveyor-belt loading systems that discharge at rates of 500 to 3,000 tonnes per hour into open bulk carrier holds. At these discharge rates, a significant plume of airborne dust is generated at the point of material fall, in the hold during trimming, and at the belt transfer points ashore. The dust concentration in the hold atmosphere during loading can reach levels well above any occupational limit without engineering controls.
Crew members on board during loading operations, particularly those opening and closing hatch covers, trimming the cargo manually, and monitoring hold conditions from the deck edges, face episodic high-intensity RCS exposure. Dockers and terminal operators ashore also face exposure at the head of the shiploader chute and along the conveyor. Without a suppression system and respiratory protection, silica sand loading is one of the highest-risk dust-exposure scenarios in maritime port operations.
Engineering controls at modern sand terminals include enclosed conveyor transfer points, water-spray dust suppression at the loading chute, and, at the most advanced facilities, enclosed shiploaders with extraction ventilation. Where engineering controls are absent or insufficient, the appropriate respiratory protective equipment (RPE) is a P3/FFP3 filtering face piece or a half-mask with P3 filters, rated to remove particles at a minimum 99.95 percent efficiency. Standard surgical masks or FFP1/FFP2 dust masks do not provide adequate protection against RCS.
The SOLAS Chapter III provisions on personal protective equipment and the ILO Occupational Health and Safety Convention requirements both apply to RCS exposure during maritime cargo operations. Masters are responsible for ensuring that crew members working on deck during sand loading operations are equipped with appropriate RPE and are informed of the health hazard. This obligation is not contingent on whether the loading port’s national regulations have explicitly addressed maritime dust exposure.
Distinction between silicosis risk and the IMSBC Group classification
The silicosis hazard and the IMSBC Group C classification address different risks. Group C means the cargo does not liquefy and does not present a chemical hazard that threatens the vessel’s structural integrity or creates an immediately life-threatening atmosphere in an enclosed space. Group C says nothing about the long-term occupational health risk of dust inhalation during cargo handling.
A ship’s crew can safely carry Group C sand across the ocean in a fully loaded hold without any danger from the cargo itself. The silicosis risk arises only during the loading and discharge operations when airborne dust is generated. Masters, officers, and ship operators who understand the IMSBC Group C status of sand but do not understand the separate RCS health hazard may fail to implement appropriate dust controls, treating the cargo as entirely benign.
The Group A fines caveat
When fine sand may liquefy
The IMSBC Code’s general Group C classification for sand applies to typical commercial construction and silica sand grades with a mixed or coarse particle distribution and moderate to low moisture content. However, a specific category of sand requires additional attention: uniformly fine-grained sand with a particle size predominantly below 0.1 to 0.2 mm and a moisture content elevated by recent rain or inadequate drainage.
Fine-grained sand in this particle range can exhibit saturated pore-pressure behaviour under cyclic loading, fundamentally the same mechanism that causes Group A cargoes such as mineral concentrates to liquefy. The key physical parameters are permeability, compressibility, and the ratio of drainage path length to loading cycle period. Very fine, uniformly sorted sand has a permeability of roughly 0.001 to 0.01 mm/s, which is three to four orders of magnitude lower than coarse sand. At ship-motion frequencies of 5 to 15 seconds per cycle, fine sand cannot dissipate pore pressure between loading cycles, and the conditions for liquefaction are present if the moisture content exceeds a critical threshold analogous to the TML.
The IMSBC Code, in its provisions for Group C cargoes in Section 1.3, contains a general caveat that some materials ordinarily classified as Group C may exhibit Group A behaviour under specific conditions of particle size and moisture. Shippers and masters of consignments of fine processed sand, particularly washed and graded industrial sand, should verify that the cargo falls within the bulk parameters assumed for Group C or, if the particle size distribution and moisture content place the cargo in an uncertain zone, seek laboratory testing of the transportable moisture limit.
Practical moisture management
Sand loaded from river dredge or coastal sea-dredge sources often carries residual free moisture. Freshly dredged river sand can have a moisture content of 15 to 25 percent by weight before stockpiling and drainage. After 48 to 72 hours of free drainage on a level stockpile, most coarse to medium grades drain to a moisture content of 8 to 12 percent. Fine grades drain more slowly and may remain at 12 to 18 percent moisture for several days after dredging.
For ordinary construction sand, these moisture levels are generally below any liquefaction threshold, and the cargo is safe to load. For fine-grained processed grades, the moisture content should be checked against published or laboratory-determined TML values before loading, particularly if the cargo is to be carried in a deep hold where the overburden pressure from a 15-metre cargo depth would amplify any pore-pressure accumulation.
The practical advice in the IMSBC Code for all Group C cargoes applies: the master may require moisture content data from the shipper if there is reason to believe the cargo’s condition differs materially from that described in the schedule. Where the cargo has been exposed to heavy rain between stockpiling and loading, a prudent master will request a moisture content certificate issued within 7 days of the load date.
Heavy mineral sands: properties, trade, and hazards
What heavy mineral sands are
Heavy mineral sands are sedimentary deposits in which titanium-bearing and zirconium-bearing minerals have been concentrated by natural hydrodynamic sorting, typically in ancient beach ridges or river channel deposits. The term “heavy” refers to specific gravity: where ordinary quartz sand has a specific gravity of 2.65, the economically valuable minerals in heavy mineral sand deposits have specific gravities of 4.0 to 5.3, causing them to lag behind the lighter quartz during wave and wind reworking of beach deposits over geological time.
The commercially important minerals are:
Ilmenite (FeTiO3, specific gravity 4.5 to 5.0): the most abundant titanium mineral in heavy mineral sand deposits, comprising 50 to 90 percent of the heavy mineral fraction in most Australian, South African, and Indian deposits. Ilmenite is processed to produce titanium dioxide pigment via the sulphate or chloride process, or smelted to produce titanium slag and pig iron. The titanium dioxide pigment is the white opacity agent in paint, paper, and plastics.
Rutile (TiO2, specific gravity 4.2 to 4.3): a higher-grade titanium mineral with approximately 95 percent TiO2 content compared with around 45 to 65 percent for ilmenite. Rutile is the preferred feedstock for the chloride process, which produces higher-purity pigment grade TiO2. Natural rutile is increasingly supplemented by synthetic rutile produced by the selective leaching of ilmenite.
Zircon (ZrSiO4, specific gravity 4.6 to 4.7): the principal commercial source of zirconium and hafnium. Zircon is used in ceramic glazes, foundry sands (for its high thermal stability and very low coefficient of thermal expansion), zirconia refractories, and nuclear fuel applications. Australia produces approximately 35 to 40 percent of global zircon supply.
Leucoxene: an alteration product of ilmenite in which iron has been partially or wholly leached out, leaving a titanium-enriched pseudomorph. TiO2 content ranges from 65 to 90 percent. Leucoxene is a valuable intermediate between ilmenite and rutile in quality and price.
Monazite ((Ce,La,Nd,Th)PO4, specific gravity 4.6 to 5.4): a rare earth phosphate mineral and an accessory constituent of most heavy mineral sand deposits. Monazite is chemically complex: it is the primary host mineral for thorium in the Earth’s crust and contains thorium-232 concentrations that typically range from 2 to 10 percent ThO2 by mass in the pure mineral. The thorium content makes monazite a NORM (Naturally Occurring Radioactive Material).
Heavy mineral sand deposits and major trade routes
The principal heavy mineral sand producing countries are Australia, South Africa, Mozambique, Madagascar, India, Sri Lanka, Senegal, Sierra Leone, and, historically, the United States. Australia’s deposits, concentrated along the Western Australian coast from Eneabba northward and along the Murray Basin in Victoria and New South Wales, account for a large fraction of global ilmenite and zircon supply. The Richards Bay Minerals and Tronox Holdings operations in KwaZulu-Natal, South Africa, are among the largest single mineral sand operations globally.
Trade flows move from these producing countries to titanium dioxide pigment plants and ceramic manufacturers in Europe, China, Japan, South Korea, and North America. The cargo is shipped as a mixed heavy mineral concentrate directly from dredge operations in some cases, or as separated individual mineral products (ilmenite, rutile, zircon) from a mineral separation plant adjacent to the mine. The distinction matters for IMSBC purposes: a mixed heavy mineral concentrate with fine particle size and residual moisture from processing is more likely to be classified Group A than a coarse, separated, and dried single-mineral product.
A typical Australian heavy mineral sand operation loads ilmenite into Handysize or Supramax bulk carriers of 25,000 to 60,000 DWT at dedicated export terminals. The cargo’s high bulk density means that a Handysize vessel with a grain capacity of 35,000 to 40,000 m3 will be weight-limited, not volume-limited, when loading ilmenite at a bulk density of 2,200 to 2,500 kg/m3. A full cargo of ilmenite in a vessel with grain capacity of 38,000 m3 would theoretically weigh 84,000 to 95,000 tonnes, well above the vessel’s 28,000 to 30,000 DWT capacity. In practice, the vessel loads roughly 12,000 to 14,000 m3 of cargo to reach its summer deadweight mark.
Structural loading implications
The density of heavy mineral sands imposes the most operationally important constraint on carriage. Construction sand at 1,500 kg/m3 exerts a pressure of about 15 kN/m2 per metre of cargo depth on the tank top. Ilmenite at 2,500 kg/m3 exerts 25 kN/m2 per metre. Zircon at 2,800 to 3,000 kg/m3 exerts 28 to 30 kN/m2 per metre. These differences are not trivial at the cargo depths typical of a loaded Handysize hold.
SOLAS Chapter XII and the IACS Common Structural Rules establish maximum allowable tank-top loads for bulk carriers. Class societies express this as an allowable panel loading in kN/m2 at a specified hold filling level. For an older Handysize vessel without high-density cargo notation, the allowable tank-top loading may be as low as 15 to 18 kN/m2, which would limit the allowable filling depth for ilmenite to 6 to 7 metres rather than the 10 to 12 metres typical for coal. Masters and operators must check the vessel’s approved Loading Manual and class notations before accepting heavy mineral sand cargoes.
The practical approach for heavy mineral sand voyages is to load the cargo equally across all available holds to spread the load, maintaining the vessel’s longitudinal bending moment and shear force within approved limits as the cargo filling depth increases. The cargo draught survey on departure will confirm the total loaded mass, which combined with the grain capacity measurement from the vessel’s capacity plan allows cross-checking of the cargo’s actual bulk density against the declared value. A significant discrepancy between declared and measured bulk density is a flag that warrants investigation before departure.
NORM and monazite: the radioactivity consideration
Monazite is classified as a Naturally Occurring Radioactive Material because its thorium and uranium content, and the decay-chain progeny of those elements, emit gamma radiation and produce radon gas. The specific activity of natural monazite mineral is typically 70,000 to 200,000 Bq/kg for thorium-232 alone. To put this in context, the IAEA defines a clearance level of 1 Bq/g (1,000 Bq/kg) for bulk materials in its Basic Safety Standards; monazite in pure mineral form exceeds this by two to three orders of magnitude.
However, heavy mineral sand concentrates as loaded onto vessels contain monazite only as a minor constituent, typically 0.1 to 3.0 percent of the total cargo mass depending on the deposit. At 1 percent monazite content in a heavy mineral concentrate with specific activity of 150,000 Bq/kg, the activity concentration of the bulk cargo mixture is approximately 1,500 Bq/kg, which is above the IAEA clearance threshold but still relatively low in absolute terms. The dose rate to crew members standing on a loaded vessel carrying such a cargo is generally low and does not exceed occupational dose limits for a single voyage.
The regulatory position is more complex than the raw numbers suggest. Many national jurisdictions have adopted NORM regulations that require notification, documentation, or in some cases a formal radiation safety assessment before importing or handling materials that exceed defined concentration thresholds. Australia, the European Union, and South Africa all have NORM regulatory frameworks that apply to mineral sand cargoes. The operator, shipper, and receiving country’s port authority must collectively confirm the applicable thresholds and documentation requirements before the shipment is arranged.
Monazite itself, as a separated mineral product, is handled under much more stringent radiation safety controls. Pure monazite is not commonly shipped as a standalone bulk cargo. Where monazite concentrate is shipped, it typically moves under radioactive material transport regulations rather than the IMSBC Code alone, and the consignment requires radiation survey data, dose-rate labelling, and route pre-approval. The IMSBC Code does not include a standalone MONAZITE schedule; carriers of separated monazite concentrate should seek specialist radiation protection advice.
The practical takeaway for operators: a routine heavy mineral sand shipment from Australia or South Africa, declared as ilmenite, rutile, or zircon, is unlikely to present a significant radiation hazard to crew under normal carriage conditions. A cargo with unusually high monazite content, a product from a deposit known to be thorium-rich, or a separated rare-earth product from a monazite upgrading plant warrants a radiation survey before loading.
Hold preparation and cleaning
Before loading construction and silica sand
Construction sand requires relatively straightforward hold preparation. The holds must be clean, dry, and free of residue from previous cargoes. For construction-grade material destined for general aggregate use, the standard is a hold swept clean of previous cargo with no pools of water on the tank top. Bilge systems must be operational and bilge covers fitted and sealed; sand is highly effective at blocking bilge rose boxes and strum boxes, and a blocked bilge during a voyage where sand migrates into the bilge space can prevent effective bilge pumping in a subsequent emergency.
Glass-grade and electronics-grade silica sand imposes a much higher standard of hold cleanliness. Contamination with iron oxide scale from hold frames and plating, residues of fertilizer cargo, cement dust, or any chemical cargo can disqualify the entire parcel for its intended use. Holds destined for glass-grade silica sand must be wire-brushed or grit-blasted clean of rust scale, swept thoroughly, and inspected by the shipper’s or receiver’s surveyor before loading commences. A hold cleanliness certificate signed by the surveyor is standard commercial practice.
For all sand cargoes, bilge wells should be confirmed clean and pump-tested before loading. The primary drainage concern is not water egress from the cargo itself but rainwater ingress from an imperfect hatch cover seal during passage. A pool of water on a sand cargo surface after hatch covers close is a cosmetic problem for construction sand and a potentially cargo-damaging problem for glass-grade silica. Hatch cover weathertightness should be confirmed before loading sensitive grades.
Before loading heavy mineral sands
Heavy mineral sands do not require special hold treatment relative to their chemical properties: they are chemically stable, non-toxic in bulk carriage conditions, and non-reactive with mild steel. Hold preparation is broadly similar to that for construction sand. However, a few specific points apply.
First, holds must be clean of any residue that could contaminate the mineral product. Heavy mineral sands are processed to tight specifications after discharge: ilmenite and rutile enter a wet high-intensity magnetic separation process, and zircon enters gravity and electrostatic separation. Contamination with clay, cement, fertilizer, or organic material from a previous cargo can interfere with the downstream mineral separation and lower the product recovery, imposing a financial claim on the carrier. A previous grain cargo that left organic residue is a common source of specification problems for subsequent heavy mineral sand cargoes.
Second, the high density of the cargo means that the cargo mass concentrated in the lower sections of the hold during loading creates a significant hydrostatic pressure against the lower hold plating and tank-top structure. The tank top and the lower hopper plates should be checked for condition before heavy mineral sand loading, particularly in older vessels. Any known structural defects or repairs should be disclosed to the charterer and confirmed adequate for the planned cargo.
Third, for fine ilmenite sand classified as Group A, the holds must be examined for any condition that would compromise the hold’s ability to contain a cargo with Group A properties. The bilge systems must be operational, the hatch covers weathertight, and the vessel must have stability documentation adequate for the maximum expected cargo shift.
Loading, stowage, and discharge
Loading procedures
Sand is loaded by shore-side conveyor and shiploader at major export terminals. The loading rate varies from small coastal operations loading at 500 to 1,000 tonnes per hour to large modern terminal shiploaders delivering 2,000 to 5,000 tonnes per hour. The loading rate, combined with the cargo’s relatively high stowage factor compared with iron ore, means that a 30,000-tonne sand parcel on a Handysize vessel may take 12 to 24 hours to load.
Dust is the dominant loading hazard. At high loading rates, a significant plume of airborne sand and clay dust is generated at the point of material fall into the hold. The hold atmosphere during active loading typically has a very high dust concentration that renders the space unsafe for human entry. Crew members on deck near the hatch openings should wear appropriate RPE (FFP3 or equivalent). Where the cargo has been identified as high-purity silica sand, the RCS concentration in the dust plume is particularly high and the health protection requirements are strongest.
For heavy mineral sands, loading requires close attention to the vessel’s stability during the loading sequence. Because the cargo is substantially denser than coal or grain, the vessel’s metacentric height (GM) increases rapidly during initial loading, potentially reaching values above 3 to 4 metres on some vessel types. A high GM accelerates the vessel’s roll motion, creating a stiff, uncomfortable roll with short roll period. While not inherently dangerous, the stiff roll may cause some fatigue in crew and cargo securing gear. As holds fill and the cargo’s center of gravity rises, GM decreases toward more moderate values.
Trimming of heavy mineral sands is required to ensure even distribution across the hold and to satisfy the loading plan’s hold-by-hold weight limits. The cargo flows freely when dry and does not require mechanical spreading for normal fills, but hand-trimming at hold edges may be needed to achieve a level surface before the hatch covers are closed.
Draught survey and cargo quantity
Sand cargoes are routinely weighed by draught survey. The cargo draught survey measures the vessel’s displacement before and after loading (or before and after discharge) by reading freeboard marks on both sides of the vessel at six locations and correcting for trim, density, and deductibles. The difference in displacement gives the mass of cargo loaded or discharged.
Draught surveys for heavy mineral sands require careful density measurement of the surrounding water, because the cargo’s density is substantially higher than water and the displacement change per unit volume is proportionally larger. An error of 0.001 t/m3 in the density of the surrounding water, which might be unimportant for a coal cargo, translates to a meaningful tonnage discrepancy on a small heavy mineral sand shipment.
The cargo declaration for sand must state the bulk density. For construction sand, this is typically in the range 1,400 to 1,700 kg/m3, and variations in the declared value against the measured hold volume can reveal loading discrepancies. For heavy mineral sands, the declared bulk density is a critical parameter for verifying structural compliance, and the draught survey provides an independent check by comparing total mass against hold volumes used.
Discharge procedures
Construction sand is discharged by grab crane at the receiving terminal. Grab discharge is relatively straightforward for dry or slightly moist construction sand: the cargo is cohesive enough that grabs can take clean, full bites, and the hold clears progressively. Where the sand has become wet during passage (from hatch cover leakage or from cargo moisture), the grab may struggle to lift full loads from the hold corners, and the final tonnes may require bulldozer assistance.
For heavy mineral sands, discharge by grab is the standard method at most receiving terminals. The cargo’s high density means that a grab with a nominal 12-tonne capacity will reach capacity at a smaller volume of heavy mineral cargo than for coal or grain, and the cycle times should be adjusted accordingly. Some mineral processing operations receive cargo by pneumatic conveying or belt conveyor directly into the processing plant, but most offshore terminal-to-plant transfers are handled by road or rail after grab discharge.
Fine ilmenite classified as Group A presents a specific discharge concern: if the cargo has partially liquefied during the voyage, the lower hold may contain a fluid slurry zone that is invisible from above and hazardous to personnel entering the hold. The space entry procedure for any Group A cargo must assume the possibility of liquefaction in the lower layers and prohibit foot-traffic in the hold until the upper cargo surface has been fully removed by grab and the tank-top area inspected.
Limitations
The IMSBC Code schedules for sand entries are revised through biennial amendment cycles, and the Group C classification assigned to ordinary sand should be understood in the context of the standard commercial grades described in the schedule. Cargoes that deviate from the described particle size range, moisture content, or mineralogical composition may not fit the schedule parameters, and the shipper bears the legal responsibility under SOLAS Chapter VI to declare a cargo accurately under the correct BCSN.
This article addresses carriage under the IMSBC Code framework. Construction-grade sand is not regulated under the IMDG Code (which covers dangerous goods in packaged form), but specific sand types with chemical properties outside the ordinary range, including sands with elevated sulphide mineral content from ore-processing tailings used as fill, may require separate chemical hazard assessment.
The NORM discussion in this article addresses the general position for routine heavy mineral sand cargoes. It does not constitute radiation safety advice and does not substitute for a site-specific radiation survey or consultation with a qualified radiation protection adviser. NORM regulations differ by jurisdiction, and the applicable thresholds and documentation requirements must be confirmed on a shipment-by-shipment basis with the competent authority of the loading and discharge countries.
Vessel-specific structural limitations, including allowable tank-top loadings and high-density cargo notations, override the general guidance in this article. Masters must consult the vessel’s approved Loading Manual and the class surveyor’s confirmation before loading heavy mineral sands in vessels not previously cleared for the specific bulk density of the consignment.
See also
- IMSBC Code
- IMSBC Group C cargoes
- IMSBC Group A cargoes
- Mineral Concentrates: IMSBC Code Schedule
- Cargo Draught Survey: Bulk Carriers