Seaworthy packaging is packing built to survive an ocean voyage and the handling at each end: crane lifts, heavy motion, stacking, condensation and salt air. For machinery and heavy goods, that means a strong wooden base or crate, cargo fixed to it with no play, a sealed moisture barrier with desiccant or corrosion inhibitor, and clear lifting points and markings. Two reference documents are widely used: the HPE packing guidelines and the GDV packaging handbook.
Why sea transport is demanding
A container or breakbulk shipment is not simply "stored" while it travels. It is lifted several times by cranes, spreaders and forklifts, and it sits in trucks, rail wagons, terminals and vessels. At sea, ships roll, pitch and heave, loading the cargo in all directions, and stacked containers experience further forces. Packaging must therefore resist not only vertical load but also lateral and longitudinal forces.
The second major hazard is moisture. Air inside a container carries water vapor, and when temperature falls, for example when a ship moves from warm to cold regions or at night, that moisture condenses on cold surfaces and can drip on cargo, a phenomenon often called container rain. Unprotected steel and electrical equipment corrode quickly under these conditions. This is why seaworthy packaging is as much about climate control as about mechanical strength.
Key reference documents
| Document | Publisher | What it covers |
|---|---|---|
| HPE packing guidelines (2nd edition, 2010) | HPE, German federation for wooden packaging, pallets and export packaging | Crate and case types, skid design, timber specification, ISPM 15, corrosion protection |
| Packaging handbook | GDV, German Insurance Association | Loads on cargo, crates, corrosion protection, handling with cranes, across transport modes |
| CTU Code (2014) | IMO, ILO and UNECE | Voluntary code of practice for packing and securing cargo in containers and other transport units |
The GDV handbook is explicit that it accepts equivalent national or international standards if they protect the cargo equally well, so it works as a flexible technical reference rather than a rigid rulebook. The CTU Code is also non-mandatory but is widely used as the basis for national guidance and contractual requirements. Crate construction is covered in export crates and the German guideline in the HPE packaging guidelines.
Mechanical protection
Good seaworthy packing starts with the base. For heavy goods, the HPE guidelines describe skid-based cases with at least two runners no more than 100 cm (39 in) apart, fork openings at least 10 cm (3.9 in) high and secondary points for crane lifting. The same document distinguishes cases for goods up to 500 kg from heavier designs on runners.
Practical points for machinery:
- Fix the cargo to the base with bolts, straps or steel brackets. Friction alone is not reliable at sea.
- Spread the load across runners or cross members rather than on single points.
- Mark the center of gravity and the lifting points on the outside, using symbols compliant with ISO 780.
- Block and brace inside the crate or container so nothing moves; see dunnage, blocking and bracing.
- Use dry, graded timber to avoid shrinkage, mould and loosening of joints.
When crates are loaded into containers, the container's own limits and securing points apply; see pallets in shipping containers and load securing standards.
Corrosion and moisture protection
Three methods are described in the HPE guidelines, often combined:
| Method | How it works | Notes |
|---|---|---|
| Desiccants in a sealed barrier | Silica gel or similar bags absorb moisture inside a welded or heat-sealed foil enclosure | The guidelines call for relative humidity of 40% or lower inside the sealed polyethylene film, film at least 0.2 mm thick, for up to 12 months |
| Protective coatings | Oil, wax or lacquer layer applied to clean, dry metal surfaces | Must be removed or tolerated at destination |
| VCI (volatile corrosion inhibitors) | Chemicals release vapor that forms a protective molecular layer on metal | Used in paper, film or emitters inside sealed enclosures |
For all three, surfaces must be clean, dry and free of fingerprints and salts before packing. Sealing quality is critical: a small hole in the barrier foil defeats the desiccant. Packaging should not be opened for inspection without resealing, and the humidity indicator card inside the foil lets the receiver check conditions. Dehumidifying and VCI methods suit different goods; mixed-metal assemblies and electronics need specific inhibitor selection.
Lifting and handling
Heavy cargo is lifted by crane, forklift or sling. The GDV handbook includes guidance on loads occurring when general cargo is handled with cranes. Good practice:
- Provide purpose-built lifting lugs, rope slots or sling points rather than relying on improvised lifting.
- Make sure slings do not crush the crate or the cargo; use spreader bars where needed.
- Mark the lifting points and the permitted sling angle.
- Declare accurate gross weight, including packaging. Containers shipped internationally require a verified gross mass.
ISPM 15 and documents
Any solid wood in the packaging, including runners, frames and dunnage, must be treated and marked according to ISPM 15 when shipped across borders; see ISPM 15 explained and dunnage and ISPM 15. The HPE guidelines note that solid timber of 6 mm or thicker is covered and that heat treatment means a core temperature of at least 56 °C for 30 minutes.
Checklist before shipping
- Cargo clean, dry, treated against corrosion.
- Barrier foil sealed, desiccant quantity calculated for the volume and the transit time.
- Cargo fixed and blocked, with no movement when shaken.
- Crate strong enough for stacking or marked "do not stack".
- Lifting points and center of gravity marked.
- ISPM 15 mark and handling symbols visible.
- Weight and dimensions declared accurately.
Frequently asked questions
What is the difference between seaworthy and domestic packaging?
Seaworthy packaging is designed for repeated crane lifts, long storage, ship motion and humidity changes. Domestic packaging often only has to survive a short truck journey.
How much desiccant is needed?
It depends on the volume of the sealed foil enclosure, the foil's permeability and the transit time. Desiccant suppliers publish calculation methods, and the HPE guidelines set a target of at most 40% relative humidity inside the sealed film.
What is VCI?
Volatile corrosion inhibitor. It is a chemical that releases vapor in a closed space and forms a thin protective layer on metal surfaces, often supplied as treated paper or film.
Is the CTU Code mandatory?
No. It is a voluntary code of practice from IMO, ILO and UNECE, but it is widely used as a basis for national rules and contracts.
Sources
- HPE 2010 guideline for packing — HPE Bundesverband Holzpackmittel, Paletten, Exportverpackung
- GDV packaging handbook — German Insurance Association (GDV)
- IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units (CTU Code) — International Maritime Organization
- CTU Code: a quick guide — International Plant Protection Convention
- ISPM 15 (2018): Regulation of wood packaging material in international trade — International Plant Protection Convention