The short version
- The manufacture date does not expire; the periodic test dates do.
- A rating says nothing about chemical compatibility with your specific liquid.
- No plate, no rating — and no inspection can create one.
- Keep pressure washer nozzles away from plates; that is how most of them are destroyed.
The marking, segment by segment
Take a representative marking and walk through it. Every group means something specific and the order is fixed, which is what makes it readable at a glance once you have done it a few times.
| Segment | Example | Meaning |
|---|---|---|
| UN symbol | UN | Certified against the UN model regulations |
| Type digit | 31 | 31 = IBC for liquids; 11 = solids by gravity; 21 = solids under pressure |
| Material code | HA | H = plastic; HA = rigid plastic inner in an outer casing (composite) |
| Category digit | 1 | 1 = designed to be stacked; 2 = not designed to be stacked |
| Packing group | Y | X = groups I, II, III; Y = II and III; Z = III only |
| Manufacture date | 03 26 | Month and year — March 2026 |
| Country | USA | State that authorised the design type |
| Manufacturer code | M5678 | Assigned to the maker or reconditioner |
| Stacking load | 1500 | Maximum permitted stacking load, kilograms |
| Gross mass | 2400 | Maximum permitted gross mass, kilograms |
The two numbers at the end are the ones operators actually use day to day. Gross mass tells you the heaviest the container may legally be when full — which, converted, is where the "do not fill this with sulphuric acid" conversation starts. Stacking load tells you what may sit on top of it.
The dates that expire, and the one that does not
The manufacture date in the marking never expires. What expires are the periodic test dates, which are marked separately on or near the plate. Under 49 CFR 178.813 a composite IBC in regulated liquid service needs a leak test at least every 2.5 years and a full periodic inspection every 5.
The clock runs from manufacture, not from when you bought the container. This trips up buyers constantly: a tote purchased last month may have eighteen months left on a five-year cycle, or none. Check the plate before you assume you have time.
The five-year wall
Three things the rating does not tell you
This is where most of the real-world risk sits, because a UN marking is easy to over-read.
- It does not tell you the container is chemically compatible with your liquid. The design-type tests are physical — drop, leakproofness, hydraulic pressure, stacking, vibration. Nothing in them involves your product. Send us the safety data sheet and we check resin and gasket compatibility separately.
- It does not tell you the container is clean, or what was in it before. Those are entirely separate records, and a Grade C container can carry a perfectly current UN rating.
- It does not transfer between cages. The design type covers the container as an assembly, so moving a bottle into a different frame breaks the chain unless it is done under a reconditioner marking scheme.
Legibility is the whole game
A plate that has been painted over, corroded or scoured away is, functionally, no plate at all. That container is limited to non-regulated service permanently, and nothing anyone can do restores it.
The most common way plates die is a pressure washer nozzle held too close. It is quick, it is irreversible and it happens in yards that are otherwise very careful. We photograph every plate at intake precisely because we have watched them degrade over successive visits.
One other pattern worth flagging: if a plate's stated gross mass does not match the container it is attached to, or the manufacturer code does not correspond to a real approval holder, the plate has probably been moved between frames. We treat that as an automatic rejection, and so should you.
Written by Priya Raghunathan, wash chemistry & compliance at IBC Totes San Francisco. Published September 30, 2024. Spotted something wrong? Tell us — we would rather fix it than defend it.