Petroleum Products: The Non-Bitumen Export Range

Four of these products come off a crude oil refinery, one comes out of a gas plant, one is recovered from the sulphur that had to be stripped out of the others, and one is not a petroleum product at all in the strict chemical sense. Urea is made from ammonia and carbon dioxide. It appears in this index because it moves on the same vessels, through the same terminals and against the same document set as everything else here, and because the buyers who ask for it are usually the same buyers who ask for sulphur.

Where each one actually comes from

• The vacuum distillate route — base oil. When heavy vacuum gas oil cuts are solvent extracted, dewaxed and hydrofinished rather than cracked, what is left has a controlled viscosity and a controlled response to temperature. That controlled response is what a lubricant blender is paying for; the oil itself is only the carrier.
• The bottom of the barrel — fuel oil and CST 180. Vacuum residue and visbreaker residue blended back with a lighter cutter stock until the mixture reaches a viscosity target. CST 180 is not a separate product from fuel oil; it is that blend adjusted to sit under a specific viscosity ceiling.
• The middle distillate route — EN 590 diesel. Hydrotreated gas oil. The hydrotreater is the whole commercial story: it is what takes sulphur from thousands of milligrams per kilogram down to ten, and it is why 10 ppm diesel and high-sulphur gas oil trade as different products rather than as different qualities of the same one.
• The gas processing route — LPG. Propane and butane separated from associated gas and from refinery off-gas, then held liquid either under pressure or by refrigeration. The ratio between the two is a commercial decision, not a fixed property.
• The by-product route — sulphur. Exactly what the hydrotreater removed, converted back to the elemental form in a Claus unit and then prilled, granulated or shipped molten. Sulphur is a by-product with a market rather than a product with a production plan, which is why availability tracks refinery and gas plant throughput rather than fertiliser demand.
• The ammonia route — urea. Ammonia and carbon dioxide reacted under pressure, then concentrated and either prilled or granulated. Natural gas is the feedstock, which is why urea and LPG frequently originate from the same national gas position.

The technical thread: every one is defined by a number, not a name

A bitumen buyer can get some way on a grade name alone, because 60/70 at least names a penetration band. That shortcut does not exist here. "Fuel oil" names no property whatsoever. "Base oil" names no viscosity. "LPG" does not say whether the cargo is propane, butane or a mixture, and the difference between those decides whether the product will vaporise at the destination in winter. In this range the specification is not an annex to the order; it is the order.

The category error that causes most of the trouble

The single most common failure in an enquiry for these products is treating a bracket as a product. CST 180 and CST 380 are viscosity brackets. High-sulphur and low-sulphur fuel oil are sulphur brackets. SN 150 and SN 500 are viscosity brackets. Agricultural urea and technical urea differ by one line, biuret, and by nothing else you can see. In every case the bracket is a ceiling or a band that a real cargo sits somewhere inside, and the batch Certificate of Analysis tells you where. Two cargoes that both satisfy the same bracket can behave differently in your plant, your engine or your reactor, and the way to control that is to specify the property you actually need rather than the bracket that contains it.

Base oil

Refined mineral oil produced from vacuum distillate, sold in solvent neutral grades where the SN number is a conventional viscosity label — approximately the Saybolt Universal Seconds viscosity at 100 °F — and not a viscosity index, and not a specification in itself. The classification that matters commercially is the base stock categories in API 1509 Appendix E, which sort base stocks into groups on three criteria read together, never on one alone: saturates content, sulphur content and viscosity index. Group I holds sulphur above 0.03 % m/m and/or saturates below 90 % with a viscosity index of 80 or more but under 120; Group II holds sulphur at or below 0.03 % m/m and saturates at or above 90 % in the same viscosity index band; Group III meets the Group II purity limits with a viscosity index of 120 or higher. An offer that names a group on the strength of one number is not evidence of anything: saturates are determined to ASTM D2007, viscosity index to ASTM D2270, and the sulphur figure by whichever of ASTM D2622, D4294 or D4927 the producer's laboratory runs. Acceptance turns on kinematic viscosity at 40 °C to ASTM D445, because that is what defines the grade and what the blender's formulation is built around. Two other lines cause more disputes than they should: viscosity index to ASTM D2270, which decides which API group the oil can legitimately be sold as, and colour to ASTM D1500, which is the only property a receiving blender can assess by eye and therefore the one that triggers the first phone call. See base oil for the grade-by-grade tables.

Fuel oil

Residual fuel is the heavy end of the barrel blended back to a viscosity target with a lighter cutter stock. Two standards govern it depending on where it is burned. For marine use it is ISO 8217, whose Table 2 covers the RMA to RMK residual grades and fixes not only viscosity and density but the contamination limits that actually protect machinery. For stationary burner use it is ASTM D396, whose Grade No. 6 is defined by kinematic viscosity of 15.0 to 50.0 mm²/s at 100 °C with a flash point minimum of 60 °C and water and sediment capped at 2.00 % V/V. Acceptance is decided by viscosity at 50 °C and sulphur content together, because those two set both the price and the legality of the cargo. The line that does the most damage when it is ignored is aluminium plus silicon, the catalyst fines carried over from a fluid catalytic cracker: they are abrasive, they survive purification if the purifier is set up badly, and they wear fuel pumps and liners in a way no other contaminant does. ISO 8217 caps aluminium plus silicon at 60 mg/kg in the RMG and RMK grades, and that ceiling is written on the assumption that the fuel will be settled and purified on board rather than burned as delivered. Full tables are on the fuel oil page.

CST 180

CST 180 is not a distinct product. It is residual fuel oil blended to sit under a kinematic viscosity ceiling of 180.0 mm²/s at 50 °C, corresponding to the ISO 8217 grades RME 180 and RMG 180. The CST in the name is centistokes, and a centistoke is exactly one mm²/s, so 180 cSt and 180.0 mm²/s are the same quantity written two ways — the older symbol survives in the product name while the standards themselves have used mm²/s for decades. The number is a maximum, not a target, and a cargo testing at 140 mm²/s is fully compliant even though it is noticeably thinner than one testing at 178. Two points cause confusion. First, the 50 °C reference temperature is part of the definition: an older figure quoted at 100 °F or in Redwood seconds describes a different measurement and cannot be compared directly. Second, RME 180 and RMG 180 share a viscosity ceiling but not their contamination limits, and RME 180 is the tighter of the two on carbon residue, ash and vanadium. Naming the viscosity without naming the ISO 8217 grade leaves half the specification undefined. The CST 180 fuel oil page carries the grade comparison.

EN 590 diesel

Automotive gas oil manufactured to the European standard EN 590, which is the most tightly written document in this range and the reason it is the easiest of the seven to buy safely. Acceptance turns on two lines read together: cetane number of 51.0 minimum to EN ISO 5165, which governs ignition quality, and sulphur of 10.0 mg/kg maximum, which is what the phrase "10 ppm" refers to and what makes the fuel legal in a market with modern emissions equipment. Beyond those, the standard fixes density between 820.0 and 845.0 kg/m³ at 15 °C, viscosity between 2.000 and 4.500 mm²/s at 40 °C, FAME content at 7.0 % V/V maximum and lubricity at a corrected wear scar diameter of 460 µm maximum. The line most often forgotten in an export enquiry is the cold filter plugging point grade, which is climate and season dependent: a temperate grade shipped into a cold market will wax and block filters even though every other line on the certificate passes. See EN 590 diesel.

LPG

Liquefied petroleum gas is propane, butane or a defined mixture of the two, held liquid under its own vapour pressure or by refrigeration. The reference specification for commercial grades is ASTM D1835; automotive LPG in Europe is governed by EN 589. Acceptance turns on vapour pressure at 37.8 °C together with composition, because those two decide whether the cargo is what it says it is and whether it will behave in the destination climate. Propane boils at about -42 °C and will vaporise from a cylinder in a cold winter; butane boils at about -0.5 °C and will not, which is why mixture ratios are seasonal in most markets and why an unnamed "LPG" specification is a genuine commercial risk rather than a formality. The special duty grade usually written HD-5 adds a composition floor of 90 liquid volume % propane with propene capped at 5 %. The LPG page sets out the grade differences and the pressure vessel implications.

Sulphur

Elemental sulphur recovered from refinery and gas plant hydrogen sulphide in a Claus unit, then formed into granules, prills, pastilles or slate, or moved molten in heated tankers. There is no single international product specification equivalent to ISO 8217 or EN 590 that fixes the limits; solid sulphur trades against a commercial specification built from purity, moisture, ash, acidity and organic carbon. The individual properties do have published methods — moisture to ISO 3426, ash to ISO 3425, acidity as sulphuric acid to ISO 3704 — so the gap is in the limits rather than in the measurement, and it is the contract that has to supply them and name the referee laboratory. Acceptance turns on purity on a dry basis, typically 99.8 to 99.9 % m/m, with one structural point behind it: purity is not measured directly at all, it is calculated by difference from those measured impurity lines, so a purity claim on a certificate that does not report them has nothing behind the subtraction. Purity alone is also not enough: moisture drives corrosion and weight disputes, and friability drives the dust that causes both handling losses and a real fire hazard. Shipment is controlled by the IMO IMSBC Code, which carries separate cargo schedules for formed solid sulphur and for crushed lump and coarse grained sulphur, and the declaration is a loading requirement rather than a document you can produce later. See sulphur.

Urea

Urea is produced by reacting ammonia with carbon dioxide under pressure and is supplied prilled or granular. Acceptance turns on total nitrogen of 46.0 % m/m minimum, determined by titration after distillation to ISO 5315, against a theoretical maximum of about 46.6 % that fixes how little room a producer has to move. The second line, and the one that separates the two commercial grades, is biuret: a condensation product formed when urea is held too hot for too long, determined spectrometrically to ISO 2754. Broadcast agricultural urea normally carries a biuret ceiling of 1.0 % m/m, and biuret is precisely the line that separates that grade from low-biuret foliar urea at about 0.25 % m/m. Biuret is actively toxic to the crop rather than merely inert, and the difference between the grades is one of dosing route: spread on soil it is diluted before the plant ever sees it, sprayed on the canopy it arrives undiluted on the leaf. Technical grade for diesel exhaust fluid is a third case, and the arithmetic there is worth doing rather than assuming. ISO 22241-1 caps biuret at 0.3 % m/m in the finished AUS 32 solution, and because that solution is only 32.5 % m/m urea, the limit corresponds to roughly 0.9 % m/m on the solid — so agricultural urea sitting at its 1.0 % ceiling fails, but only just. What actually excludes it are the limits ISO 22241-1 sets alongside biuret on aldehydes, insolubles, phosphate and trace metals. Granular urea is preferred for bulk blending and mechanical spreading because it is harder and less prone to attrition; prilled urea is smaller, softer and cheaper to produce. The urea page covers both grades and the packing options.

LPG — the vapour, not the liquid

One volume of liquid propane becomes roughly 250 to 270 volumes of gas on vaporising, and that gas is heavier than air — propane vapour is about one and a half times the density of air and butane vapour about twice. That combination is the whole hazard: a leak does not disperse upward, it flows downhill and collects in trenches, pits, basements, bilges, cable ducts and the bottom of a cargo hold, where it will sit at an ignitable concentration long after the leak has stopped. Propane is flammable in air over roughly 2 to 10 % by volume, which is a narrow window that a modest leak reaches quickly in a confined space. LPG is odourless as produced, so an odorant such as ethyl mercaptan is added specifically so that a leak is detectable below the lower flammable limit; a cargo delivered without odorant, where the destination requires it, is a safety defect rather than a specification variance. Liquid LPG also expands substantially with temperature — propane by roughly 0.3 % per degree Celsius, more than ten times the rate of water — so cylinders and tanks are never filled liquid-full. Filling is controlled by a maximum filling ratio, and the ratio is set by mass against the vessel's water capacity, not by volume: 0.42 kg per litre for propane and 0.51 kg per litre for n-butane under ADR packing instruction P200. Charged on that basis a propane cylinder still retains a vapour cushion of roughly a fifth of its volume at normal filling temperature, and that cushion is the only thing standing between the liquid and the shell when the vessel sits in the sun. Overfilling removes that margin, the relief valve becomes the only thing between the vessel and hydraulic rupture, and a vessel engulfed in fire can fail catastrophically as a boiling liquid expanding vapour explosion. The filling ratio is set against the vessel and the product, and is the one number on an LPG shipment that must never be treated as a target to be rounded up. For transport, propane is UN 1978, butane is UN 1011 and liquefied petroleum gases are UN 1075, all Class 2.1.

Residual fuel oil and CST 180 — heat and hydrogen sulphide

Residual fuel has to be heated to be pumped and heated further to be atomised, and every one of its hazards follows from that. The temperatures are not arbitrary, they are set by viscosity: a fuel is stored warm enough to stay mobile, brought to the pump at a viscosity the pump can lift, and heated at the burner or injector until the viscosity falls into the narrow band that will atomise. In round terms, storage of a 180 mm²/s grade sits around 40 to 50 °C and always at least 10 °C above the cargo's own pour point; transfer and pumping sit around 45 to 60 °C; and a centrifugal separator inlet runs near 98 °C. Final heating is set by what the equipment needs, and that is not one figure: a diesel injector wants 10 to 15 mm²/s, which takes a 180 mm²/s fuel to roughly 115 to 125 °C and a 380 mm²/s fuel to roughly 135 to 145 °C, whereas a boiler burner wants a thicker 15 to 25 mm²/s and a 180 mm²/s fuel reaches that lower, around 95 to 115 °C. Treat those as the shape of the problem and take the actual figures from the equipment manufacturer and the batch viscosity, because heating past what the fuel needs is not free: it cracks the fuel, cokes the heater surfaces and drives the vapour space hazard below. Hydrogen sulphide partitions out of the liquid into the vapour space of a heated tank and concentrates there; the ISO 8217 limit of 2.00 mg/kg applies to the liquid phase to IP 570 and is not a measure of headspace concentration. Opening a heated residual fuel tank, or entering one, is confined space work requiring gas testing, ventilation and a permit, and hydrogen sulphide deadens the sense of smell at exactly the concentrations that matter. The 60 °C minimum flash point in ISO 8217 is not an arbitrary commercial line either: SOLAS restricts oil fuel used in machinery spaces to a flash point of not less than 60 °C, so a cargo below that figure is a statutory failure. Water in a hot tank is the other classic incident: free water reaching a heating coil or a hot layer flashes to steam and can foam the tank over.

EN 590 diesel and base oil — the flash point sets the rules

Diesel to EN 590 has a flash point above 55 °C and travels as UN 1202, Class 3, packing group III. It is not a low-flash product, but it accumulates static charge during high-velocity loading into a tank or a drum, and the standard controls are bonding, earthing and a reduced initial fill rate rather than anything exotic. Base oil is a low acute hazard material with a flash point from about 200 °C upward, and its real risk is not the bulk liquid but oil mist: a fine mist of a high flash point oil ignites far below the flash point of the liquid, which is what makes leaking high-pressure lines in a blending plant dangerous. For both, the significant health exposure is repeated or prolonged skin contact rather than a single incident.

Sulphur — dust, acid and the IMSBC Code

Solid sulphur is a combustible solid and its dust is the problem. Suspended sulphur dust has one of the lowest minimum ignition energies of any industrial dust — low enough that an electrostatic discharge is a credible ignition source, not a theoretical one. Sulphur is an excellent electrical insulator, so it accumulates charge readily as it is poured, conveyed, screened and blown, and the charge has nowhere to go. That is why bonding and earthing of chutes, conveyors, hoppers, bagging heads and the operators themselves is a control rather than a courtesy, why free-fall discharge heights are kept short, and why dust is suppressed at the point it is generated rather than cleaned up afterwards. Burning sulphur produces sulphur dioxide, which is acutely irritant, heavier than air and will therefore follow the same low ground the dust settled on. Friability matters for safety as well as for weight loss: a product that abrades during handling generates the dust that creates the hazard, which is one reason granular product is often specified over prilled. Molten sulphur evolves hydrogen sulphide and hydrogen polysulphides into the tank vapour space, where it can reach concentrations that are immediately dangerous while the liquid below still tests clean, so heated sulphur storage carries the same confined space discipline as heated fuel oil: gas test, ventilate, permit, and never rely on smell, because hydrogen sulphide destroys the sense of smell at exactly the concentrations that matter. Sulphur wetted with water forms acid and is corrosive to mild steel, so cargo hold coatings, bag liners and stowage away from moisture are practical requirements rather than preferences. Shipment in bulk is governed by the IMO IMSBC Code, which carries distinct cargo schedules for formed solid sulphur and for crushed lump and coarse grained sulphur. Solid sulphur carries UN 1350, Class 4.1, packing group III, though in practice that classification bites on crushed lump and coarse grained material rather than on the export mainstream, because Special Provision 242 lifts shaped product out of the dangerous goods regime entirely. Molten sulphur is a separate entry again, UN 2448. The shipper's cargo declaration is required before loading, and it cannot be produced retrospectively.

Urea — ammonia on decomposition, and water damage

Urea is not flammable and is not classified as a dangerous good for transport, which is why it is the easiest of the seven to move and the one whose hazards are most often dismissed. It melts at about 133 °C and decomposes above that, releasing ammonia and forming biuret; a fire in a urea store therefore produces an irritant ammonia atmosphere and destroys the product quality at the same time. The dust is an eye and respiratory irritant. The dominant commercial risk, though, is moisture: urea is hygroscopic, and a cargo that takes on water cakes into solid lumps that no spreader will handle, which is the standard damage claim on this product. Stow it away from moisture, keep the bag liners intact, and treat a torn liner as a quality issue rather than a packaging one. Urea and its solutions are also corrosive to copper and copper alloys, which is why diesel exhaust fluid systems are built in stainless steel and why a copper-lined tank is the wrong tank.

Every one of these products has a Safety Data Sheet, and on this range the SDS is a working document rather than a filing requirement. Several destination customs authorities request it at import, many terminals will not accept a cargo without it, and for LPG and sulphur it carries the transport classification the carrier needs before the booking is confirmed.

The certificate carries more weight than the conversation

On every one of these products, the batch Certificate of Analysis is the instrument that decides acceptance. Not the offer, not the technical data sheet, not the assurance given by a salesperson. That makes the structure of the certificate worth as much scrutiny as its contents. A usable COA is tied to a specific tank, lot or batch number; carries a sampling date and a sampling point; reports actual measured values rather than the specification range copied down the column; and names the test method beside every result. A certificate whose figures land on the specification limit on every line, on every shipment, is reporting the specification rather than the batch. That is not automatically dishonest, but it is the single most useful thing to notice before a cargo loads.

Independent inspection is the mechanism, and it differs by product

Quality is only half of it. On this range, quantity disputes are at least as common as quality disputes, and the quantity method changes with the physical form. Liquid cargoes are determined by shore tank or vessel ullage measurement with temperature correction to a standard reference; bulk solids are determined by draft survey or by weighbridge; bagged product is determined by count and by check-weighing a sample of bags. Each method has a tolerance, and the tolerance belongs in the contract rather than in a later argument. A load-port inspection by an independent firm covers sampling, testing, quantity determination and packing condition in one report that a bank, an insurer and a buyer's technical department will all accept, which is why it is normally cheaper to commission than the first disagreement it prevents.

Sealed retained samples, held by both sides

Every number argued about later comes from a sample, and a sample nobody can place is a number nobody has to accept. The chain that makes a figure hold up is procedural rather than technical: drawn under the inspector's supervision, drawn from the right point for the physical form — running sample through a loading line, spot samples at three tank depths, bag sampling spread across the stow rather than taken from whatever is nearest the door — then sealed, numbered against the seal record, and split so that buyer and seller each walk away holding one. Marine fuel makes this a legal obligation rather than good practice: MARPOL Annex VI requires the bunker delivery note to be kept for three years and a representative sealed and labelled sample of the delivered fuel to be kept for at least twelve months. The other six products carry no such requirement, which is exactly why writing the same routine into the contract is worth the paragraph it takes — when a retained twin exists, most quality disputes are settled by opening it rather than by arguing about whose laboratory to believe.

The document set, and what is product-specific

The common core is the same across all seven: commercial invoice, packing list, bill of lading, certificate of origin, Certificate of Analysis, Safety Data Sheet and, where agreed, the third-party inspection certificate. What varies is the product-specific layer. Bulk sulphur needs the shipper's declaration required by the IMSBC Code before loading. LPG needs a dangerous goods declaration and a carrier booking that matches the UN number and class. EN 590 diesel bought against a national fuel regulation may need a conformity statement naming the specific EN 590 edition and the cold filter plugging point grade. Urea sold as fertiliser is frequently subject to a destination import registration that has nothing to do with the quality of the cargo and everything to do with whether it can be cleared.

Terms that prevent arguments rather than settle them

Four clauses do most of the work. Name the Incoterms 2020 rule in full, with the named place, so that the transfer of risk and the allocation of inspection and discharge costs are unambiguous. State the quantity tolerance explicitly, because these products load to a vessel or tank rather than to a purchase order. Say who pays for inspection and who appoints the inspector. And name the referee laboratory in advance, because appointing one after a dispute has started is significantly harder than agreeing to one before.