Reading a UN plate, character by character

1. Assuming the marking is current. A plate is permanent; test status is not. UN-marked plastic and composite IBCs in regulated service generally need a leakproofness test every 2.5 years and a periodic inspection every 5 years. Check the test dates, not just the manufacture date — see the regulations guide and check current regulations.
2. Assuming the plate survives rebottling. Replacing the inner bottle changes the assembly. The unit generally needs testing and re-marking by a qualified party before it carries regulated goods again; confirm documentation with the supplier.
3. Ignoring the gross mass limit. People calculate that their liquid fits volumetrically and never check the kilogram figure. A dense product can exceed the gross mass limit before the tote is full. Convert and compare every time you change product.

And one thing that is not a problem

A tote that is out of test, or never was UN marked, can still be useful for many jobs that are not regulated dangerous-goods transport: storage of non-hazardous liquids, water and site use. Check whether your product is actually regulated in transport, and check current regulations, before paying for marking you may not need.

Beyond the type code, the marking on a plastic or composite IBC carries several figures that people rarely read and that materially constrain what you can do.

Maximum permissible gross mass

In kilograms. Convert it — 2,000 kg is about 4,409 lb — and compare it against your calculated gross weight. A dense product can exceed this before the tote is full.

Test pressure

For example 250 kPa (about 36 psi). This is a design-type test figure, not an operating pressure. An IBC is not a pressure vessel and should not be pressurised in service.

Stacking test load

The superimposed load the design is marked to carry when stacked. Divide it by your gross weight per tote to see how many units can sit on top — which can be fewer than people assume for dense liquids.

Rated capacity in litres

The capacity the design was approved for.

Manufacture date

Month and year, and the starting point for the test and inspection cycle.

Inner receptacle date

Some manufacturers mark the bottle separately. On a rebottled unit the bottle date and the plate date will not agree, which is one quick way to identify one.

The UN packaging marking system comes from the UN Recommendations on the Transport of Dangerous Goods (the Model Regulations, often called the "Orange Book"), which harmonise packaging requirements internationally. Individual regimes implement it — for example 49 CFR in the United States, ADR for road transport in Europe, the IMDG Code at sea and the ICAO/IATA rules for air.

The structure is deliberately mechanical. For IBCs, the two digits describe the kind of IBC and its contents (11 and 21 for solids, 31 for liquids). The letter gives the material. In a composite IBC there are two letters: the inner receptacle, then the outer packaging. A trailing digit gives the category — for composite IBCs, 1 for a rigid inner receptacle and 2 for a flexible one.

So 31HA1 decomposes as: 31 (IBC for liquids), H (plastic inner receptacle), A (steel outer), 1 (rigid inner receptacle).

Similar logic runs through the wider system. A 1A1 is a non-removable-head steel drum. A 3H1 is a non-removable-head plastic jerrican. A 4G is a fibreboard box. Once you see the pattern, most markings decode on sight.

Why it matters to a tote buyer

Because the code is a statement about a tested design, not about the container in front of you. Two units with identical markings can be in completely different states depending on their test dates and whether either has been rebottled. The code tells you what the design was approved for; the dates tell you whether this unit is still in test. Check current regulations.