UN plate archaeology: what a 2011 marking still tells you

Take a marking like 31HA1/Y/0311/USA/M4127. Every segment is doing a job.

What the date does and does not mean

The manufacture date is not an expiry date. It is the start of a testing schedule. For composite IBCs in regulated liquid service, the general requirement is a leakproofness test with external inspection at intervals not exceeding two and a half years, and a full periodic inspection including that test at intervals not exceeding five years from manufacture and from each subsequent periodic inspection.

So a 2011 container is not disqualified by age. It is disqualified by an overdue test, and an overdue test is a solvable problem. That is the entire distinction those three pallets turned on.

Verify the intervals that apply to your jurisdiction, transport mode and cargo before shipping. This is orientation, not regulatory advice.

The packing group letter

X approves the design for packing groups I, II and III. Y covers II and III. Z covers III only. Most composite IBCs you will meet carry Y, which is medium and low danger.

A container marked Y cannot be promoted to X by testing it more thoroughly. The letter describes what the design type was approved for when it was tested, and that does not change.

What kills a plate

• Overpainting. A plant repaints its fleet a corporate colour and the markings go with it.
• Close-range pressure washing. Four seconds at six inches will smooth a stamped plate to illegibility.
• Adhesive labels applied over the plate and then removed with a solvent.
• Corrosion under a plate that has trapped water against the frame.
• A cage repair that replaces the member the plate was mounted on, with the plate discarded.

What we do with an old plate

Transcribe it, photograph it, establish the design type and date, then inspect and test. If the container passes leakproofness and external inspection, it is marked with the test date and released with a written record against its serial number.

If it fails, we report the reason unit by unit rather than returning a count. Customers deserve to know whether they lost four containers to crazed bottles or to cracked welds, because those two answers imply completely different changes to how the fleet is being handled.

Of those three pallets — fifty-four containers — twenty-nine passed, eleven were rebottled and re-marked, nine went to reclaim, and five had plates too far gone to read and were sold into non-regulated water service. Nothing was landfilled.

Reading the secondary markings

The design-type code gets the attention, but a plate usually carries three more numbers that matter operationally.

The gross mass figure is the one people misuse most. It is a weight limit, not a volume limit, and for dense products it is reached long before the container is full.

The three fates of an old container

Once you can read a plate, a used container sorts into one of three futures within about a minute.

1. 01Legible plate, sound structure, testing due or overdue. Recertifiable. Inspect, test, re-mark, back into regulated service.
2. 02Legible plate, structural damage or a repair that departs from the design type. Not recertifiable. Perfectly good for non-regulated service.
3. 03Illegible or missing plate. Never recertifiable regardless of condition. Water, brine, non-regulated industrial or reclaim.

Sellers routinely price all three the same, which is why loads of mixed-plate stock are frequently a bargain and occasionally a disappointment. It is worth ten minutes with a torch before agreeing a number.

What we do with fleets

For customers with a hundred containers or more, we photograph and transcribe every plate at intake and build a schedule. It tells them which units come due in which quarter, which lets testing be batched rather than done reactively when somebody notices.

Batching matters more than it sounds. Testing twelve containers on one visit costs a fraction of testing one container twelve times, and the alternative to a schedule is almost always the second pattern.

One caveat about all of this

Regulatory requirements differ by jurisdiction, transport mode and cargo, and they change. Everything on this page is orientation to help you assess a container quickly, not a substitute for the current rules that apply to your shipment. Check them before you ship regulated material.

Questions about old stock

Is there an age at which a container is automatically unusable? No. There is a testing schedule, and a container that has been kept in test and remains structurally sound has no expiry. We routinely recertify containers over a decade old.

What if the container was repaired at some point? Repairs that restore the container to its approved design type are acceptable. Repairs that alter it are not, and the distinction matters — replacing a cage bar with equivalent tube is restoration, welding a reinforcement plate onto a frame is alteration.

Can a plate be replaced? Not by us, and not by you. A design-type marking is issued against a specific container by the approval holder. A container whose marking is lost has lost it permanently, which is the entire reason we are so insistent about protecting them.

Does the marking cover the fittings? The approval covers the assembly as tested, which includes the closures. Fitting a non-standard valve or cap to a rated container can take it outside its approval, which is why reconditioners fit like for like on regulated stock.