Bulged sump
Load through the bottle rather than the posts, usually from mixed heights or misalignment. Permanent. The container becomes a rebottle candidate.
Logistics · 25 July 2024
Double-stacking empties, properly
Double-stacking empties halves your freight cost and is the most common way people destroy containers in transit. Both things are true, and the difference is about four inches of alignment.
- Sheet
- 59
- Revision
- 2026-10
- Scale
- 1:1
- Drawn at
- Peoria IL
80Empties in a 53' van
110 inInterior height needed
4Straps per row
3–5×Dynamic vs static load
A composite IBC carries load through four corner posts and nothing else. Every rule about stacking is a restatement of that sentence, and every failure is somebody having routed load somewhere else.
| Equipment | Single stacked | Double stacked | Interior height | Note |
|---|---|---|---|---|
| 53' dry van | 40 | 80 | 110 in | The standard empties move |
| 53' flatbed | 48 | Not advised | — | Tarped, single tier, better for mixed cages |
| 26' box truck | 18 | Not advised | — | Liftgate work, tight sites |
| 20' sea container | 9 | 18 | 89 in | 275s only; 330s will not double |
| 40' sea container | 20 | 40 | 89 in | Blocked and braced for export |
The four inches that matter
A 275 is 46 inches tall and a 330 is 53. Two 275s is 92 inches and fits a van with room to breathe. Two 330s is 106 inches, which fits a 110-inch van and does not fit a sea container at 89. Mixing them in a stack puts the upper container's posts somewhere between the lower container's posts, which routes load straight into the bottle. That is the whole mechanism behind nearly every bulged sump we take in.
- Same height containers only, in any one stack. No exceptions, not even for one pallet position.
- Posts over posts. Look down the stack from above before you strap — if you can see bottle shoulder under a post, restack it.
- Four straps per row minimum, corner boards at every strap-to-tube contact.
- Empties only. Filled containers travel one high, every time, regardless of the static rating on the plate.
Static rating is not a transport rating
The stacking load on a UN plate is measured standing still in a warehouse. Road transport imposes dynamic loads that run three to five times higher through potholes, rail crossings and hard braking. A container rated for two-high filled storage is not rated for two-high filled transport, and the plate does not say so because it was never claiming to.
Progressive creep
The one nobody notices: a filled double stack shortens slowly over weeks and then fails all at once. We have seen this in a warehouse, not just in transit.
Strap cut-through
A strap tensioned directly across galvanised tube at a corner abrades the coating and pulls the joint. Corner boards cost cents.
The five-minute pre-ship check
- Valve closed and capped — and the cap actually threaded on, not resting there.
- Top fitting sealed with the right gasket, tamper ring intact if the customer expects one.
- Cage square, posts aligned, nothing protruding past the pallet footprint.
- Placard legible and the UN plate photographed for the file.
- Four straps per row, corner boards at every contact, and a second walk after the first ten miles.
Our damage rate across 2023 was 0.4% of containers moved, and essentially all of it was cosmetic cage scuffing on loads where somebody skipped step five. There is no clever equipment behind that number — it is corner boards and a second walk.
Shipping containers yourself?
Ask us for the load plan for your trailer type. We will tell you what fits, how to strap it and what we would refuse to do.