Every composite IBC tank carries a UN marking stamped into the steel cage or printed on a durable label. This string of letters and numbers looks cryptic, but it encodes critical information about the container performance rating. Here is how to read it.
The UN Marking Format
A typical UN marking on a composite IBC tank looks like this:
UN 31HA1/Y/12 24/USA/M1234/2500/1200
Each segment has a specific meaning:
UN — United Nations. Indicates the container has been tested to UN performance standards.
31 — Container type code. 31 means "rigid intermediate bulk container." Other codes: 11 = flexible IBC, 21 = metal IBC.
H — Material code for the outer packaging. H = plastic. A = steel. B = aluminum.
A — Material code for the inner container. A = plastic. In a composite IBC (steel cage plus plastic bottle), the code reads "HA" — plastic outer structure with plastic inner bottle.
1 — Category. 1 = fitted with a bottom discharge valve. 2 = no bottom discharge valve.
So "31HA1" means: rigid IBC, composite construction (plastic in metal cage), with bottom discharge valve.
Y — Packing group performance level. X = suitable for Packing Groups I, II, and III (most dangerous). Y = suitable for Packing Groups II and III. Z = suitable for Packing Group III only.
12 24 — Month and year of manufacture (December 2024 in this example).
USA — Country where the performance tests were conducted.
M1234 — Manufacturer code or authorization number.
2500 — Maximum gross mass in kilograms when carrying liquids with a specific gravity of 1.0.
1200 — The test load weight in kilograms used during the stacking test.
Packing Groups Explained
The packing group indicates the degree of hazard:
- •Packing Group I (PG I): Great danger. Requires the most robust container (X-rated).
- •Packing Group II (PG II): Medium danger. Requires a Y or X-rated container.
- •Packing Group III (PG III): Minor danger. Any rating (X, Y, or Z) is acceptable.
Most standard composite IBC tanks carry a Y rating, which covers the majority of industrial chemicals classified under Packing Groups II and III. Only the most hazardous materials (strong oxidizers, highly corrosive substances) require PG I containers.
Why Ratings Matter
If you are shipping hazardous materials via public roads, rail, sea, or air, the container MUST carry a valid UN rating that matches or exceeds the packing group of the contents. Using an improperly rated container for hazmat transport is a federal violation carrying substantial fines — and creates genuine safety risks.
For non-hazardous storage and non-regulated transport, the UN rating is less critical but still serves as a useful quality indicator. A tank with a valid UN marking has been manufactured and tested to internationally recognized standards, which speaks to overall build quality.
Reconditioned Tanks and UN Ratings
When an IBC tank is professionally reconditioned, it can receive updated UN markings if it passes the required performance tests. The reconditioning mark is added below the original manufacturing mark and includes the reconditioning date, facility code, and the letter "R" to indicate reconditioned status. At our facility, tanks that pass our highest-tier inspection protocol receive updated UN 31HA1/Y ratings, certifying them for continued hazmat transport.