A certificate of quality is the document your money is exchanged against. Reading it properly, before the contract goes firm, is the cheapest risk control available to a buyer.

Most disputes over petroleum cargoes are not arguments about honesty. They are arguments about specification — a buyer expecting one thing, a seller delivering another, and both pointing at the same certificate. The specification is the only place where "diesel" or "gasoil" acquires a precise meaning, and it is written in test methods rather than adjectives.

Every commercial grade is defined by a table of properties, each with a test method and a limit. The test method matters as much as the limit: sulphur measured by ASTM D2622 and sulphur measured by ASTM D4294 do not always return the same figure, and a contract that names one method cannot be settled with a certificate produced under the other. Before you agree a price, agree the method.

The properties that decide acceptance

Sulphur content is the first line most buyers look at, because it is usually the one written into law at the destination. A 10 ppm market and a 50 ppm market are different markets, and product blended for one cannot be sold into the other without reprocessing. If your destination has a statutory limit, the contract limit should sit below it with margin, not on it.

Density at 15°C matters for two reasons. It converts observed volume into standard volume, which is what you are invoiced for, and it interacts with the flash point and distillation range to tell you whether the parcel is really the grade it is called. A gasoil with an unusually low density has almost certainly been cut with something lighter.

Flash point is a safety and a carriage property. It governs how the cargo may be shipped and stored, and a parcel that fails flash point at load port may not be liftable at all. Cloud point and cold filter plugging point govern whether the product will flow in the destination climate — a summer-grade diesel delivered into a cold inland market will gel in the line before it reaches a customer.

• Test method named for every property, not just the limit.
• Sulphur limit below the destination statutory cap, with margin.
• Density at 15°C consistent with the distillation range.
• Flash point compatible with the carriage and storage plan.
• Cold-flow properties matched to the destination climate.
• Sampling and retention clause written into the contract.

Sampling, retention and the certificate itself

A certificate is only as good as the sample behind it. Sampling to ASTM D4057 at the load manifold, witnessed by an independent inspector, with sealed samples retained by both parties for an agreed period, is what turns a certificate into evidence. Without a retained sample there is nothing to re-test, and a quality claim becomes one party's word against the other's.

Check who issued the certificate and when. An inspection certificate dated weeks before the vessel loaded describes tank contents, not cargo. Certificates should be issued by a recognised independent inspector — SGS, Intertek, Bureau Veritas or an agreed equivalent — against samples drawn at the point the contract nominates, and they should carry the inspector's reference so they can be verified at source.

Finally, read the tolerance clause alongside the specification. Most contracts allow a quantity tolerance and some allow narrow off-spec bands with a price adjustment. Knowing in advance what is a discount and what is a rejection removes the worst outcome in this trade: a cargo alongside, a buyer refusing it, and demurrage running while the parties read the contract for the first time.

About the author

Regi Atlantic Trading Desk

Regi Atlantic Energy Limited

Notes from the people who source, trade, store and ship the cargo — written to answer the questions counterparties actually ask us before a contract goes firm.