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The crate spec for a transformer going by container is not the same as the crate spec for the same transformer going break-bulk. Most exporters get this wrong because the container forgives a lot of design sins — its steel walls bear half the load — while a break-bulk crate has to stand on its own through lifting, lashing, decking, weather and customs handling.
Here's how to spec it right both ways.
What changes between the two modes
| Load case | Container (FCL) | Break-bulk (BB) |
|---|---|---|
| Lifting events | 2 (stuff + de-stuff) | 4–6 (factory → truck → port → vessel → port → consignee) |
| External weather | Box walls block rain | Direct sea spray + sun |
| Lateral g-load | 0.6g (container handling) | 1.2–1.5g (vessel roll, wave slap) |
| Stack height | 1 box (rarely double-stack) | 2–3 crates (on-deck or hold) |
| Handling temperature | Indoor + container interior | Direct sun, –10 to +55°C |
Spec rule 1: Board thickness
For container shipments, IS 710 BWP plywood at 12 mm panels with 18 mm runners is enough for most engineering loads up to ~1,200 kg. For break-bulk, step up to 18 mm panels with 25 mm runners on anything above 800 kg — the doubled g-load means board flex becomes the failure mode.
For the heaviest loads (transformer cores, CNC headstocks, turbine shafts) the call is always 28 mm panels with 50 mm runners, regardless of mode. At that load class the cost delta is rounding error.
Spec rule 2: Lashing pattern
Container shipments rely on the box's lashing rings — most exporters use diagonal cross-lashing with 4 ratchet straps per crate. That's adequate up to 800 kg per crate.
Break-bulk shipments lash to the deck or hold rings, which means the crate itself becomes a load path. The crate needs continuous bottom skids running the full length of the load, not segmented blocks. Skid construction:
- Up to 2 tonnes: 75 × 100 mm hardwood skids spaced max 600 mm apart
- 2–5 tonnes: 100 × 150 mm skids spaced max 500 mm apart, with 18 mm load-spreader plywood on top
- 5–10 tonnes: 150 × 200 mm skids continuous under the load, with welded lifting eyes through-bolted via 16 mm bolts
Spec rule 3: Wind load (for on-deck staging)
Break-bulk cargo often spends 24–72 hours on the port apron before loading. IS 875 Part 3 gives basic wind speeds for Indian ports — for Mundra, Pipavav, JNPT and Chennai, design for 47–55 m/s gusts. For Tuticorin and Vizag, 50–60 m/s.
What this means in practice: any crate over 1.5 m tall with a surface area greater than 2 sqm needs to be either anchored to deck rings during apron staging or weighted with a 200+ kg ballast skid. Otherwise it walks. We've seen 800 kg crates slide 4 metres during a single afternoon at Mundra during a pre-monsoon storm.
Spec rule 4: Lifting eyes vs forklift slots
Forklift slots are cheaper. Lifting eyes are necessary above 3 tonnes — most port cranes operate via top-lift, not fork-lift, and you can't safely top-lift a flat crate.
Spec: through-bolted 16 mm eye bolts at four corners on the top frame, rated for 1.5× crate gross weight per eye. For crates above 5 tonnes, double the eye bolts to eight (two per corner) and add intermediate ones at the midpoint of each long edge.
The cost crossover point
For loads under 8 tonnes per crate, container shipping is almost always cheaper end-to-end. The crate spec is lighter, lashing simpler, demurrage exposure shorter.
Above 8 tonnes per crate, break-bulk often wins on freight cost but loses on crating cost. The breakeven point shifts with destination — for Middle East routes, break-bulk wins above 6 tonnes; for Europe, the crossover moves to 12+ tonnes because of dwell-time penalties at transshipment hubs.
Three failure modes we've seen
1. Skid splitting under crane lift
Soft pine skids on a 4-tonne crate, lifted at the four-corner method instead of via under-load forks. The skid fibers crushed under the lifting load and the crate split lengthwise. Fix: hardwood skids (jackwood, gurjan or rubberwood) on anything above 2 tonnes, full-length not segmented.
2. Container floor punch-through
A 6-tonne crate with concentrated load on a 100 × 100 mm point — the container's 28 mm flooring took a depression but the crate's bottom skid was 75 mm wide and crushed into the floor. Fix: load-spreader plywood (18 mm minimum) under the skids, sized to keep contact pressure below 4 kg/cm².
3. Lashing failure on a break-bulk hold
4-tonne crate lashed to deck rings via webbing only — no D-ring on the crate itself. During a 4-metre swell, the webbing chafed through against the crate's plywood edge in 14 hours. Fix: through-bolted D-rings on the crate, never lash directly to plywood edges.
Quoting checklist
When you ask us for a crate quote, give us:
- Gross weight per crate (loaded)
- External dimensions L × W × H
- Center of gravity location (if not centred)
- Mode: container, break-bulk, or unsure (we'll quote both)
- Destination port
- ISPM-15 status — destination country and whether HT stamps are mandatory
With those six items the Cochin Wood group's crating line returns a finished crate spec — board thickness, skid construction, lashing pattern, lifting hardware — within one business day. Send the spec here.