Services · S-07
UN/DOT testing
& certification.
Short answer
- Leakproofness, hydrostatic, stack and vibration testing
- Our own reconditioner registration code since 2023
- Test records retained and reissued on request
- Fleet-wide periodic scheduling from plate dates
Book testing
Read your plate
UN31HA1/Y/1120/26/USA/M1234, decoded
Every character is a certified fact, not branding. This is the single most useful thing to learn in bulk liquid handling, and it takes about four minutes.
The United Nations packaging symbol. Everything after it is a certified specification, not marketing.
Category and construction: 31 = composite IBC for liquids. 11 = rigid for solids, 21 = rigid for solids under pressure.
Inner receptacle material: H = plastic. A = steel, B = aluminium, N = other metal, L = textile, M = paper, G = fibreboard.
Outer packaging: A = steel, 1 = with structural equipment (the cage). A2 would be steel without.
Packing group authorisation: Y covers PG II and III. X covers I, II and III. Z covers PG III only.
Hydrostatic test pressure in kPa, or stacking load in kg depending on position — read against the rest of the string.
Year of manufacture (2026). Composite IBCs for hazmat have a 5-year service life from this date, re-testable at 2.5 years.
Country of certification and the manufacturer or reconditioner registration code.
Full walk-through with worked examples: UN markings decoded.
The schedule
What is required, and when
| Interval | Requirement | What it catches | Our turnaround |
|---|---|---|---|
| Initial certification | Design type approval, hydrostatic, drop, stack, vibration | Design and manufacturing defects | Manufacturer |
| Every 2.5 years | Visual inspection + leakproofness at ≥3 psi | Seal failures, gasket degradation, bottle stress cracks | 4 business days |
| Every 5 years | Visual + leakproofness + hydrostatic to the plate rating | Wall thinning, crazing, weld fatigue | 4 business days |
| End of 5-year life | None — the unit leaves hazmat service permanently | — | Regrade to non-regulated or recycle |
| After repair | Re-test appropriate to the repair, plus re-marking | Repair quality | 4 business days |
| After rebottling | Leakproofness, then re-mark with a fresh date | Seating and new-bottle integrity | Included in rebottling |
Short answer
- Service life is absolute — no retest extends it
- Read the two-digit year in the marking and count
- An out-of-life IBC is fine for non-regulated liquid
- Fleet audits catch this before a DOT inspector does
Our test bay
Four tests, one record
- 01
Visual inspection, inside and out
Cage welds, upright geometry, base fixings, bottle crazing, stress cracks at the bottom radius, marking legibility. Most failures are found here rather than under pressure.
- 02
Leakproofness at 3 psi minimum
Air pressure held for the specified dwell with all closures fitted as they will ship. Pass/fail recorded against the serial, with the gauge trace retained.
- 03
Hydrostatic test to the plate rating
Required at initial certification and the five-year periodic. Tests the bottle wall and the closure seating under the actual pressure the marking claims.
- 04
Stack and vibration, on request
Stack load testing for design verification and vibration testing where a customer qualification programme calls for it. Reported with the raw data, not just a pass stamp.
Questions
Certification questions
How often does an IBC need retesting?
For hazmat service, a composite IBC has a five-year service life from the moulding date on the plate, with a leakproofness retest and visual inspection required at 2.5 years. Hydrostatic testing is required at initial certification and at the five-year point. Non-hazmat service carries no regulatory retest requirement, though sensible operators test anyway.
What does the 2.5-year periodic involve?
A visual external and internal inspection, a leakproofness test at a minimum of 3 psi held for the specified dwell, verification that the marking is legible and complete, and a record retained by the party performing the test. We re-mark the test date and our registration code on completion.
Can an expired IBC be recertified?
An IBC past its five-year service life cannot be returned to hazmat service by retesting — the service life is absolute. It can be used for non-regulated liquid indefinitely if it is sound. This surprises people every week, so check the moulding year before you plan a fleet around it.
Do you hold your own reconditioner code?
Yes, since 2023. That is why re-marking takes four business days after test rather than the three weeks a third-party queue used to cost us. The code appears in the marking string so the certification is traceable to us.
What test pressure is required?
Leakproofness is a minimum of 3 psi (20 kPa) air pressure. Hydrostatic test pressure depends on the packing group and the design, and is stamped in the marking string in kPa. Always read the plate rather than assuming a standard figure.
Fleet audit
What a fleet audit finds, and what it costs you not to run one
We audit customer fleets regularly and the findings are consistent enough to publish. Nobody in these fleets was being careless — the plate is small and nobody owned the schedule.
| Fleet size | Past service life | Periodic overdue | Illegible plate | Wrong packing group |
|---|---|---|---|---|
| 180 units | 6% | 14% | 2% | 1% |
| 420 units | 11% | 22% | 5% | 0% |
| 95 units | 19% | 31% | 8% | 3% |
| 640 units | 8% | 9% | 3% | 1% |
| Weighted average | 9.4% | 16.1% | 4.1% | 0.9% |
Roughly one unit in ten in a typical fleet has quietly left hazmat service. Those containers are perfectly legal for non-regulated liquid and completely unusable for the regulated product they are probably still carrying. An audit is photographs of plates and an afternoon of reading.
Running the schedule yourself
How to build a periodic schedule from your own plates
You do not need us for this. If you would rather do it in-house, this is the method we use.
- 01
Photograph every specification plate once
Square on, close enough to read the full marking string. A phone is fine. Do it when the units are stationary rather than chasing them later.
- 02
Extract the moulding year from each string
Two digits, usually after the test-pressure segment. That date starts the five-year hazmat service clock and nothing resets it.
- 03
Calculate two dates per unit
Moulding year plus 2.5 years is the leakproofness retest. Moulding year plus 5 is the end of hazmat service — an absolute stop, not a test interval.
- 04
Flag the packing group letter
Y covers packing groups II and III; X covers all three; Z covers III only. A Y-marked unit cannot legally carry a PG I material regardless of condition.
- 05
Sort by end-of-life date, not by retest date
Units approaching five years should be planned out of regulated service rather than retested. Testing a unit that leaves service in four months is wasted money.
- 06
Separate the illegible plates immediately
An illegible marking means uncertified, full stop. Those units either come out of regulated service or go through full re-testing and re-marking.
Short answer
- Service life is absolute — no test extends it
- Retest at 2.5 years, hydrostatic at 5
- An illegible plate means uncertified
- Plan by end-of-life date, not by retest date
From the Yard Journal
Longer pieces from the people who run the wash line, the test bay and the trading desk.
14 September 2023 · 4 min
What the 2.5-year retest actually catches
Three years of test bay records, sorted by failure mode. The periodic leakproofness test is not a formality, and what it finds is not what most people expect.
Priya Raghunathan · Head of reconditioning
Read12 June 2025 · 3 min
What changed when we got our own reconditioner code
Before 2023 a UN re-marking took three weeks in somebody else's queue. Now it takes four days in ours. The interesting part is what the delay was actually costing.
Priya Raghunathan · Head of reconditioning
Read
Next move
Send us the marking strings from your fleet.
Photograph the plates — even phone photos work — and we will build you a periodic schedule showing which units are due, which are approaching end of life, and which left hazmat service last year without anyone noticing.