LPG is not one substance. It is a family of light hydrocarbons that are gases at ambient conditions but turn liquid under modest pressure, and the proportions inside the cargo are what the buyer is really specifying.
The two components that matter commercially are propane (C3H8) and butane (C4H10, present as n-butane and isobutane). Both liquefy at ambient temperature under pressures a steel cylinder handles easily, which is what makes the product portable at all: as a liquid it occupies roughly a two-hundred-and-seventieth of the volume it would occupy as a gas. Smaller quantities of ethane, propene and the butenes are normally present depending on where the stream came from.
Two cargoes can both be called LPG, both pass every purity line on the certificate, and behave completely differently in the receiving market. A 30/70 propane–butane mixture landed in a country with sub-zero winter nights will leave liquid butane sitting unvaporised in the bottom of the cylinder while the customer complains that the gas ran out early. The same mixture in a Gulf or South Asian market performs perfectly and gives the user more megajoules per cylinder than a propane-rich alternative.
The ratio also governs the pressure rating your storage and your ship must carry. Commercial propane develops roughly 1270 kPa gauge at 40 °C; commercial butane develops roughly 280 kPa at the same temperature. A receiving tank or ISO container designed around butane service cannot take a propane cargo. This is the single most common mismatch in first-time LPG transactions, and it is settled by writing the ratio, with a tolerance and a test method, into the contract.
LPG reaches the market by two routes, and the route shapes the composition. Gas processing recovers propane and butane as natural gas liquids when raw associated or non-associated gas is stripped and fractionated; this material is essentially saturated, with very low olefin content. Refinery production yields LPG from crude distillation overheads, catalytic cracking, reforming and hydrocracking; these streams carry propene and butenes, and refinery-derived LPG therefore needs closer attention to diene content, evaporation residue and odour stability. A buyer specifying LPG for petrochemical feed rather than fuel almost always cares about this distinction, because the olefin content is either the point of the purchase or an impurity in it, and nothing else on a standard certificate reveals it.
The word LPG covers all three, but the acceptance criteria diverge sharply. Automotive LPG in Europe is controlled by EN 589, which adds a motor octane number floor and a diene ceiling that no fuel-gas specification contains. Cylinder and bulk fuel gas is normally bought against ASTM D1835 or a national equivalent derived from it. Petrochemical feedstock is bought against a composition envelope by gas chromatography and is very often supplied unodorised, which is a safety-critical difference that must be stated on the face of the contract rather than assumed.
ASTM D1835 is the specification most export LPG contracts outside Europe are written against. It defines four grades and, unusually for a petroleum specification, it does not fix composition by percentage for the commercial grades — it fixes behaviour, through vapour pressure and the 95 percent evaporated temperature.
| Property | Test method | Unit | Commercial propane | Commercial butane | PB mixtures | Special-duty propane (HD-5) |
|---|---|---|---|---|---|---|
| Vapour pressure at 37.8 °C, max | ASTM D1267 / D6897 | kPa gauge | 1434 | 483 | 1434 | 1434 |
| Volatile residue — temperature at 95 % evaporated, max | ASTM D1837 | °C | −38.3 | 2.2 | 2.2 | −38.3 |
| Residual matter — residue on evaporation of 100 mL, max | ASTM D2158 | mL | 0.05 | 0.05 | 0.05 | 0.05 |
| Oil stain observation | ASTM D2158 | — | pass | pass | pass | pass |
| Copper strip corrosion, 1 h at 37.8 °C, max | ASTM D1838 | class | No. 1 | No. 1 | No. 1 | No. 1 |
| Total sulphur, max | ASTM D6667 / D2784 | mg/kg (= ppm by mass) | 185 | 140 | 140 | 123 |
| Hydrogen sulphide | ASTM D2420 | — | pass | pass | pass | pass |
| Free water content | visual examination | — | none | none | none | none |
| Moisture content — valve freeze test | ASTM D2713 | — | pass | not specified | not specified | pass |
| Propane content, min | ASTM D2163 | liquid volume % | — | — | — | 90 |
| Propene (propylene) content, max | ASTM D2163 | liquid volume % | — | — | — | 5 |
EN 589 is the European specification for LPG used as a vehicle fuel. It carries every purity line a fuel-gas specification carries and then adds two that only matter in an engine: a motor octane floor and a diene ceiling. The edition matters more here than on most specifications, because the sulphur ceiling and the diene requirement have both moved. The figures below are the current EN 589:2024 edition, with the superseded values identified.
| Property | Test method | Unit | Limit |
|---|---|---|---|
| Motor octane number, MON, min | EN 589 Annex B (calculated from composition) | — | 89.0 |
| Total diene content, including 1,3-butadiene, max | EN 27941 / ISO 7941 | % (m/m) | 0.5 |
| 1,3-butadiene content, max | EN 27941 / ISO 7941 | % (m/m) | < 0.10 (limit introduced by the 2024 edition) |
| Hydrogen sulphide | EN ISO 8819 | — | pass (absent) |
| Total sulphur content after odorisation, max | EN 17178 / EN ISO 20846 / EN ISO 20884 | mg/kg (= ppm by mass) | 30 (editions before 2024 allowed 50) |
| Copper strip corrosion, 1 h at 40 °C, max | EN ISO 6251 | class | class 1 |
| Evaporation residue, max | EN 15470 / EN 15471 | mg/kg | 60 |
| Gauge vapour pressure at 40 °C, max | EN ISO 4256 / EN ISO 8973 | kPa | 1550 |
| Gauge vapour pressure, min, at the temperature of the applicable climatic class A to E | EN ISO 4256 / EN ISO 8973 | kPa | 150 |
| Water content — free water | EN 15469 | — | absent |
| Odour | — | — | distinctive and unpleasant, detectable below the lower flammable limit |
An LPG certificate is short. Every line on it is there because something specific went wrong often enough to justify a standard, and a certificate is worth reading for what it omits as much as for what it reports.
This is the master analysis and the one line a buyer should never accept a certificate without. It reports the component breakdown — ethane, propane, propene, isobutane, n-butane, the butenes, pentanes and heavier — from which almost everything else can be predicted. It is what proves the propane-to-butane ratio you paid for is the ratio in the tank, and it is what reveals a pentane-and-heavier tail that will not vaporise at all and will simply accumulate in the customer's vessel as unusable liquid. Where a contract names a mix ratio, D2163 is the method that makes that clause enforceable.
Measured at 37.8 °C in the ASTM system and at 40 °C in the European system, so check which temperature a figure refers to before you compare two certificates. ASTM D1267 uses an LPG sampling cylinder and a pressure gauge; ASTM D6897 is a mini-method expansion technique. This value is the one that must be matched against the design pressure of the receiving tank, the ISO container or the ship. ASTM D2598 provides a calculation route to vapour pressure and relative density from the gas chromatography composition, which is useful for checking a certificate for internal consistency: if the reported composition and the reported vapour pressure do not agree, one of the two numbers is wrong.
The single most common specification error on this product is quoting one sulphur ceiling for everything. ASTM D1835 sets 185 mg/kg for commercial propane, 140 mg/kg for commercial butane and for propane–butane mixtures, and 123 mg/kg for special-duty propane HD-5. EN 589:2024 sets 30 mg/kg after odorisation for automotive LPG, tightened from the 50 mg/kg that earlier editions allowed and that a great many published tables still repeat. Milligrams per kilogram and parts per million by mass are the same unit; parts per million by volume is not, and a figure quoted without saying which is unusable. Sulphur matters for corrosion in the customer's equipment, for emissions in engine and burner applications, and increasingly for national fuel-quality regulation at destination. Note the phrase after odorisation in EN 589: the odorant itself is a sulphur compound, so the limit is applied to the product as delivered, not to the base gas before the odorant was injected, and at a 30 mg/kg ceiling the odorant contribution is no longer a rounding error.
A polished copper strip is exposed to the liquid LPG for one hour and then compared against a reference standard. A class 1 result means the product will not attack the copper and brass in valves, regulators, gauges and burner trains. It is a fast, cheap test and it is the most direct evidence you have that corrosive sulphur species are not present in a form the total sulphur figure alone would not reveal.
A measured volume of LPG is allowed to evaporate and whatever is left behind is measured — a maximum of 0.05 mL per 100 mL under ASTM D1835, and a maximum of 60 mg/kg under EN 589. Recent editions of D1835 also permit the residue to be determined chromatographically to ASTM D7756 instead, which reports a mass concentration rather than a volume, so the two routes are not directly comparable numbers. The residue is heavy hydrocarbon, compressor oil carried over from the plant, or plasticiser picked up from unsuitable hoses. It does not evaporate in the customer's vessel, so it accumulates, fouls regulators and vaporisers, and eventually has to be drained and disposed of. The oil stain observation reported alongside it under ASTM D2158 is the qualitative check for exactly that carried-over oil.
Free water in LPG is a freezing hazard rather than a quality nuisance. As liquid LPG expands through a regulator or a valve orifice it cools sharply, and any free water present freezes at that point and blocks the flow — which is precisely what the ASTM D2713 valve freeze test is designed to detect. Free water also sits at the bottom of a vessel, where it promotes internal corrosion and where it will be drawn off first on a bottom-outlet tank. Both the ASTM and EN systems require free water to be absent, and antifreeze agents such as methanol are sometimes added in cold climates. Ask whether any has been added, because it changes what the vessel drains.
A pass or fail against a lead acetate paper. Hydrogen sulphide is acutely toxic, corrosive, and it deadens the sense of smell at concentrations well below those that harm you, which makes it the one contaminant whose presence undermines the entire odorisation safety case.
These are the published physical properties of the two principal components. Commercial grades sit close to them, and a mixture sits between them roughly in proportion to its composition.
| Property | Unit | Propane | n-Butane | Why a buyer cares |
|---|---|---|---|---|
| Boiling point at 101.325 kPa | °C | −42.1 | −0.5 | Butane stops vaporising usefully near and below freezing |
| Liquid relative density at 15 °C | — | about 0.51 | about 0.58 | Converts contract tonnes into loaded cubic metres |
| Vapour relative density, air = 1 | — | 1.52 | 2.01 | Vapour sinks and pools — the core safety hazard |
| Liquid to gas expansion at 15 °C | volume ratio | about 270 : 1 | about 235 : 1 | A small liquid leak produces a very large gas cloud |
| Gauge vapour pressure at 15 °C | kPa | about 630 | about 80 | Winter draw-off and regulator inlet pressure |
| Gauge vapour pressure at 40 °C | kPa | about 1270 | about 280 | Sets vessel, cylinder and hose design pressure |
| Gauge vapour pressure at 50 °C | kPa | about 1610 | about 400 | Summer stock standing in an unshaded yard |
| Gross calorific value, mass basis | MJ/kg | about 50.3 | about 49.5 | Nearly identical — mass buys the same energy |
| Gross calorific value, liquid volume basis | MJ/L | about 25.5 | about 28.9 | Butane carries roughly 13 % more energy per litre of tank |
| Flammable limits in air | volume % | 2.1–9.5 | 1.8–8.4 | A leak reaches the flammable range very quickly |
| Auto-ignition temperature | °C | about 470 | about 370 | Hot surfaces ignite the cloud without any spark |
| Flash point | °C | about −104 | about −60 | The product is always far above its flash point in service |
| Stoichiometric air requirement | m³ air per m³ gas | about 24 | about 31 | Burner, appliance and vaporiser sizing |
The pressures below are calculated from the pure-component saturation pressures on an ideal-solution basis and rounded. They are for orientation when matching a mix ratio to a climate and to a receiving vessel's design pressure.
| Propane / butane, liquid volume | Gauge vapour pressure at 15 °C | Gauge vapour pressure at 40 °C | Bubble point at atmospheric pressure | Where the ratio is normally used |
|---|---|---|---|---|
| 100 / 0 | about 630 kPa | about 1270 kPa | about −42 °C | Cold climates, exposed outdoor tanks, winter-grade autogas, HD-5 engine fuel |
| 70 / 30 | about 480 kPa | about 1000 kPa | about −36 °C | Winter autogas grades and general-purpose export mixture |
| 50 / 50 | about 370 kPa | about 810 kPa | about −30 °C | The most widely traded domestic cylinder mixture |
| 30 / 70 | about 260 kPa | about 600 kPa | about −23 °C | Warm-climate cylinder and bulk fuel supply |
| 0 / 100 | about 80 kPa | about 280 kPa | about −0.5 °C | Aerosol propellant, lighter fuel, warm-climate industrial fuel, petrochemical feed |
LPG has an excellent safety record when the physics is respected and a very unforgiving one when it is not. Everything in this section follows from three facts: the vapour is heavier than air, the liquid expands enormously on release, and the liquid also expands substantially with temperature inside a closed vessel.
Propane vapour is about 1.5 times the density of air and butane vapour about 2.0 times. Unlike natural gas, an LPG release does not rise and disperse. It sinks, spreads across the floor as a shallow layer, and accumulates in any low point — inspection pits, cable trenches, drains, sumps, basements, lift shafts, the bilges of a vessel, the floor of a closed shipping container. It will travel along the ground away from the leak and can reach an ignition source at a distance with nothing visible in between. Every practical control follows from this: LPG is stored outdoors or in a ground-level store with low-level ventilation, never below ground; cylinders are kept away from drains and pits; and where fixed gas detection is installed the detector heads go near floor level, because a head mounted at ceiling height will sit in clean air while the room fills underneath it.
One litre of liquid propane produces roughly 270 litres of vapour. The lower flammable limit is 2.1 percent by volume. Those two numbers together mean that one litre of escaped liquid can bring about 13 cubic metres of air into the flammable range. A single 12 kg cylinder emptied into a closed space releases around 24 litres of liquid, roughly 6.4 cubic metres of vapour, and enough to carry something in the order of 300 cubic metres of air into the flammable range — a room considerably larger than the one most cylinders sit in. This is why LPG incidents are so often building-destroying rather than localised, and why any smell of gas indoors is an evacuate-and-ventilate event rather than a maintenance call.
Commercial propane and butane are essentially odourless. Ethyl mercaptan (ethanethiol) is added specifically so that a leak is detectable by smell well before the mixture reaches the lower flammable limit — the accepted design intent is detection at about one-fifth of the LEL, roughly 0.4 percent by volume for propane. NFPA 58 recognises an addition rate of 1.0 lb of ethyl mercaptan per 10,000 US gallons of LPG, about 0.45 kg per 37.85 cubic metres, as sufficient for that purpose. Three limitations must be understood by anyone relying on it:
Odour is a warning device, not a detection system. Where people work around LPG in enclosed spaces, fixed low-level gas detection is the control that actually does the job.
Liquid LPG has a coefficient of cubical expansion far higher than water — propane expands roughly 0.3 percent per degree Celsius, well over ten times the rate of water. A vessel filled completely with liquid has no vapour space to absorb that expansion, so a modest temperature rise produces a hydraulic pressure increase that will burst the shell or lift the relief valve and discharge liquid rather than vapour. Filling is therefore controlled on a mass basis against the vessel's water capacity:
In practice this leaves a propane cylinder about 82 percent liquid-full by volume at a 15 °C filling temperature — 0.42 kg per litre divided by a liquid density of about 0.51 kg per litre — and the remaining space is what absorbs the expansion as the cylinder warms toward the 50 to 55 °C design case. NFPA 58 sets equivalent volumetric filling limits for bulk containers, tightening the allowance as ambient temperature and container type require. Two operational consequences follow. First, a cylinder or tank must never be filled by volume alone, and never by pressure — it is filled by weight or by a fixed maximum liquid level device. Second, overfilling is not a paperwork error; it converts a pressure vessel with a designed vapour cushion into a hydraulically solid one.
The failure mode that defines LPG firefighting doctrine is the boiling liquid expanding vapour explosion. When flame impinges on a vessel, the portion of the shell in contact with liquid is cooled from the inside and survives. The portion above the liquid line is not: the vapour carries heat away poorly, the steel there loses strength, and it does so while the internal pressure is rising and the relief valve is discharging. The shell tears, the pressure drops to atmospheric instantaneously, the entire liquid inventory flashes to vapour, and the result is a fireball plus vessel fragments thrown a long distance along the axis of a horizontal tank. Relief valves do not prevent this — they protect against overpressure, not against loss of shell strength.
The practical rules that follow are specific:
Liquid propane leaves a fitting at around minus 42 °C. Skin contact causes an immediate cold burn, and the injury is often worse than it first appears; gloves and eye protection are required for any transfer or disconnection work where liquid can be released. LPG is not toxic, but it is a simple asphyxiant that displaces oxygen, and because it collects at low level the oxygen-deficient layer is exactly where a person who has collapsed will be lying. Confined space entry procedures apply to any pit, tank or hold that has contained LPG.
Static electricity is a credible ignition source during transfer. Road tankers must be bonded and earthed to the fill point before hoses are connected, engines are stopped, and mobile phones and other non-certified electrical equipment stay outside the transfer zone. Hoses, couplings and emergency shut-off arrangements are inspected before each transfer, and excess flow valves are there precisely because a hose failure during transfer is the highest-consequence routine risk in LPG distribution.
Cylinders are stored and used upright, without exception, so that the pressure relief valve sits in the vapour space; a relief valve discharging liquid instead of vapour discharges roughly 270 times more material into the atmosphere. Cylinders are kept out of direct sun, off wet ground, secured against falling, away from oxidisers and away from any drain or opening leading below ground level. A cylinder is only refilled if its periodic inspection is in date — commonly up to a ten-year interval for domestic steel cylinders under EN 1440 and the European transportable pressure equipment regime, with different requalification cycles applying to DOT-specification cylinders in the United States. Cylinder construction is covered by EN 1442 and ISO 4706 for welded steel LPG cylinders, and valves by EN ISO 14245.
LPG is a Class 2.1 flammable gas in every international transport regime. The UN numbers a shipper will see are UN 1965 for hydrocarbon gas mixture, liquefied, n.o.s. (the usual entry for commercial propane–butane mixtures), UN 1075 for petroleum gases, liquefied (the generic LPG entry, used where the mixture is not further identified), UN 1978 for propane, UN 1011 for butane and UN 1969 for isobutane. Sea carriage in packages and portable tanks follows the IMDG Code, road and rail in Europe follow ADR and RID, and bulk carriage by sea falls under the IGC Code for gas carriers. Segregation from oxidising substances and from sources of ignition is mandatory, and the dangerous goods declaration accompanying the cargo must carry the correct UN number for the actual composition rather than a generic one.
The receiving infrastructure decides the supply mode, not the other way round. This is the question to settle before anything else in an LPG inquiry.
Welded steel cylinders to EN 1442 or ISO 4706, valves to EN ISO 14245, commonly in nominal net contents from 5 kg to 45 kg. Filled by weight or fixed maximum liquid level, never by pressure. Periodic inspection to EN 1440 or the applicable national regime.
Pressurised road transport to ADR for domestic and commercial bulk tanks, with bonding and earthing, excess flow protection and emergency shut-off at the transfer point. Suits customers with a fixed bulk vessel and a metered delivery arrangement.
Pressurised portable tank under IMDG portable tank instruction T50, intermodal on road, rail and container ship. The practical choice for parcel-size volumes to a market without a refrigerated import terminal.
Cargo carried at ambient temperature in cylindrical or spherical pressure tanks, with design pressures in the region of 17 to 18 barg, that is 1700 to 1800 kPa gauge in the units used elsewhere on this page. Small regional and coastal parcels. No refrigeration plant needed at either end, which is the whole point of the mode.
Partial refrigeration at reduced pressure, typically down to around minus 48 °C, with a reliquefaction plant aboard. The flexible middle option, able to discharge into either a pressurised or a refrigerated shore facility.
Propane carried at about minus 42 °C and butane at about minus 0.5 °C at near-atmospheric pressure in insulated prismatic tanks. Efficient for large parcels, but only usable where the receiving terminal has refrigerated storage and a vapour handling system.
An LPG transaction is settled on three things: the composition, the quantity determination method and the compatibility of the shipment mode with the receiving facility. Getting any of the three wrong is expensive after the cargo has sailed and cheap to fix before.
The choice is not primarily about the ship. It is about what the buyer has ashore. Pressurised shipment carries the cargo at ambient temperature, which means the receiving side needs pressure vessels rated for the vapour pressure of the actual product at the hottest temperature it will see — for propane that is a design case in the region of 1600 kPa gauge at 50 °C, and a facility built for butane service will not have it. Refrigerated shipment carries the cargo cold at near-atmospheric pressure, which is far more efficient per tonne on a long voyage but requires insulated storage, a boil-off and vapour return system, and materials qualified for cryogenic service at the receiving terminal.
The mismatch cases are the ones that cost money. Discharging refrigerated cargo into a pressurised shore tank means warming it and accepting the pressure that results. Loading pressurised cargo into a refrigerated tank means flashing a fraction of it on entry and having somewhere for that vapour to go. Semi-pressurised, semi-refrigerated tonnage exists precisely because it can serve both sides, which is why it dominates the flexible parcel trade. For a first shipment into a new market, the honest sequence is: confirm the discharge facility's design pressure and temperature capability, then choose the ship, then fix the mix ratio — not the reverse.
LPG cannot be gauged with a dip tape. Quantity is established by closed measurement: liquid level from the tank gauging system, liquid temperature, vapour space pressure and temperature, and a density figure. Density comes either from direct measurement by pressure hydrometer to ASTM D1657, or by calculation from the gas chromatography composition using ASTM D2598 or ISO 8973. Observed volume is corrected to 15 °C using the light hydrocarbon correction procedures in API MPMS Chapter 11.2 and ASTM D1250. The vapour in the tank ullage carries real mass and is accounted for separately.
Two commercial points follow. First, decide in the contract whether the invoice quantity is ship's figures or shore tank figures, and what tolerance triggers a joint investigation — this is the single most common quantity dispute in the trade. Second, sampling for the certificate must be by a purpose-built closed pressure sampling cylinder taken under supervision. An LPG sample cannot be drawn into an open container, and a certificate produced from an improperly taken sample is not defensible whatever the laboratory says.
Pricing in this product is normally formula-based against published monthly or daily index quotations rather than fixed, so the pricing clause, the quotation period and the quantity basis together determine what is actually invoiced. Fix all three in the same document.
LPG is the family name. Propane and butane are the two members of it that are traded in volume. Propane boils at about minus 42 °C and carries a high vapour pressure, roughly 1270 kPa gauge at 40 °C. Butane boils at about minus 0.5 °C and carries roughly 280 kPa at the same temperature. Most of the world buys a propane–butane mixture and specifies the ratio, because the ratio is what determines cold-weather performance and the pressure rating the receiving equipment must have.
Match it to the coldest ambient temperature the product will be used at and to the design pressure of the receiving vessel. A propane-rich mixture such as 70/30 vaporises reliably in cold weather but demands a higher-rated tank. A butane-rich mixture such as 30/70 gives more energy per litre of storage and lower pressure, but in a market with cold nights it will leave unvaporised liquid in the cylinder. Note also that as vapour is drawn off, propane depletes first and the residual liquid becomes progressively more butane-rich, so the practical cold limit is always warmer than the initial bubble point.
ASTM D1835 is the general commercial specification for propane, butane, propane–butane mixtures and HD-5 propane, and it is what most export fuel-gas contracts outside Europe are written against. EN 589 applies specifically to LPG used as an automotive fuel in Europe and adds two requirements no fuel-gas specification contains: a minimum motor octane number of 89.0 and a maximum total diene content of 0.5 % (m/m), now backed by a separate 1,3-butadiene limit below 0.10 % (m/m). EN 589 is also much tighter on sulphur — 30 mg/kg after odorisation in the 2024 edition, against 185 mg/kg for commercial propane under D1835. If the product will be sold as autogas in Europe, EN 589 governs, and the contract should name the edition because both the sulphur and the vapour pressure requirements have moved. If it will be burned in appliances or industry, ASTM D1835 or the national equivalent is the reference.
Because liquid LPG expands with temperature at roughly 0.3 percent per degree Celsius, more than ten times the rate of water. A vessel with no vapour space has nowhere to absorb that expansion, so a hot afternoon produces a hydraulic pressure rise that can burst the shell or force the relief valve to discharge liquid. Filling is controlled by mass against water capacity: 0.42 kg per litre for propane, 0.51 kg per litre for n-butane and 0.49 kg per litre for isobutane under ADR packing instruction P200. For propane that leaves the cylinder about 82 percent liquid-full by volume at a 15 °C filling temperature, and the vapour space above it is what absorbs the expansion as the cylinder warms.
Propane vapour is about 1.52 times the density of air and butane vapour about 2.01 times, so a release sinks and spreads rather than dispersing upward. It fills pits, trenches, drains, basements, ship holds and the floors of closed containers, and it can travel along the ground to a remote ignition source. LPG is therefore stored outdoors or at ground level with low-level ventilation, never below ground, away from drains and openings leading downward, and any fixed gas detection is mounted near floor level.
HD-5 is the special-duty propane grade in ASTM D1835, intended primarily for engine fuel. On top of the requirements common to all grades it sets a minimum propane content of 90 liquid volume percent and a maximum propene content of 5 liquid volume percent, both determined by gas chromatography to ASTM D2163. The propene ceiling is what distinguishes it: propene burns differently, affects octane, and is far more likely to be present in refinery-derived than in gas-plant material.
For fuel use, yes in practice, and it should be stated on the certificate. Commercial propane and butane are essentially odourless, so ethyl mercaptan is added so that a leak is detectable by smell at roughly one-fifth of the lower flammable limit. NFPA 58 recognises an addition rate of 1.0 lb per 10,000 US gallons, about 0.45 kg per 37.85 cubic metres. Petrochemical feedstock parcels are frequently supplied unodorised by design, which is a legitimate requirement but changes the entire gas detection case at the receiving site. Odorised or unodorised must be written into the contract, not assumed.
It depends entirely on what the discharge facility can accept. Pressurised shipment arrives at ambient temperature and needs shore vessels rated for the product vapour pressure at the hottest temperature it will see. Fully refrigerated shipment arrives cold at near-atmospheric pressure and needs insulated storage plus a vapour handling system. Semi-pressurised, semi-refrigerated tonnage can serve either side, which is why it carries much of the flexible parcel trade. Confirm the terminal capability first, then choose the mode.
Send the grade or the propane-to-butane ratio you need, the quantity, whether you require cylinders, bulk, ISO tank or a vessel parcel, the destination port and the Incoterm. State the design pressure and temperature capability of the receiving facility and whether the product must be odorised, and the offer will be checked against those constraints before it is priced. If you are buying against EN 589, name the edition, because the sulphur ceiling and the cold-end vapour pressure requirement both changed in 2024. Enquiries are handled on WhatsApp at +971 56 144 5733.