Packing is the part of an enclosure order that nobody designs and everybody pays for. A cargo of powder-coated cabinets that arrives with scuffed door faces and a rust bloom along the cut edges is not a supplier problem — by then the goods have passed three terminals, a customs inspection and forty days of humidity, and the damage is yours. The rules below are the ones that keep enclosures arriving in the condition they left in, whether the order is two crates going to Germany or forty going to Texas.
What actually damages enclosures in transit
- Vibration. A container under road and rail transit sees continuous low-frequency vibration. Fasteners back out, stitch welds fatigue, and any place where two coated surfaces touch will chafe through the paint.
- Impact and handling. Forklift tines, dropped crates, terminal stacking. Damage clusters at corners and on the door face, because those are the least supported areas.
- Condensation — the one that surprises people. A steel container and a steel enclosure have a high thermal mass. At night the container cools faster than it can exchange air, so its internal surfaces drop below the dew point and water runs off the ceiling onto the cargo. This is called container rain, and on a humid route it can be litres, not drops.
- Stacking load. Crates stacked two or three high press down on the topmost panel. An enclosure is stiff in shear but weak in the flat panel between stiffeners, and doors deform first.
- Salt and humidity. Coastal routes and sea spray attack every uncoated edge, scratch and thread. A 60 µm powder coat survives; a laser-cut edge with no post-treatment does not.
Crating: ISPM 15 is the detail that stops your shipment
Wood packaging entering most countries must be ISPM 15 compliant: heat treatment to a 56 °C core for 30 minutes, kiln drying, or fumigation, with the IPPC stamp showing the country code, producer number and treatment code (HT for heat treated).
- Plywood, OSB and processed board are exempt from ISPM 15 because the manufacturing process removes the pest risk. This is why almost all export crates are built from plywood rather than solid timber.
- The stamp matters more than the crate. Solid timber skids without a valid IPPC mark are the single most common cause of shipments being held, fumigated at destination or returned — at a cost many times the price of the crate. If your supplier uses solid wood for a base, ask for the IPPC stamp number and keep it on file.
- Base design. A three-runner skid base with 100 × 100 mm timber, 12–18 mm plywood deck and 100 mm minimum fork clearance underneath. Provide fork entry from both directions, and mark lifting and centre-of-gravity points on crates above roughly 1,000 kg.
- Panel thickness. 9–12 mm plywood for sides and lids on enclosures up to about 500 kg; 12–15 mm above that; add corner battens on any crate that will be stacked.
- Clearance. Leave at least 50 mm between the enclosure and the crate wall on all sides, and fill it with foam rather than leaving it as an air gap — a loose cabinet inside a crate self-destructs from vibration.
- Reusable and steel-framed crates are worth quoting when the same enclosure repeats, and they sidestep the ISPM 15 question entirely.
Moisture control: desiccant maths and container rain
Moisture is the failure mode that gets missed because it is invisible at loading and obvious at destination — a fine orange bloom on machined faces, white rust on the galvanized brackets, water marks inside the cabinet. There are three levels of protection, and picking the right one is a cost decision, not a technical one.
- VCI film. A volatile corrosion inhibitor film or bag releases vapour that forms a monomolecular protective layer on steel. Effective for 12–24 months and the usual choice for enclosures with machined or unpainted surfaces.
- Desiccant. Calculated on the enclosed volume, not on the weight of the goods. A working figure for a sealed cargo space is 0.3–0.5 kg of desiccant per cubic metre of volume. That gives roughly 10–16 kg for a 20 GP container (about 33 m³) and 23–38 kg for a 40 HQ (about 76 m³) — take the upper end for tropical routes and the rainy season.
- Barrier bags. Aluminium foil laminate bags, heat sealed around the unit, with desiccant inside and a humidity indicator card visible through a window. For high-value or long-voyage shipments this is the only method that reliably holds internal humidity below 40% RH.
- Container desiccant placement. Hang container desiccant bags from the ceiling rails so they intercept moisture before it drips. Desiccant laid on the container floor does very little for the cargo above it.
- Do not seal damp goods. If packing happens on a humid day, the air sealed inside the crate carries the water. Measure the relative humidity at packing; below 50% is the working target before you close a barrier bag.
Surface protection: coated, stainless and machined faces
Most visible damage claims are surface claims — scuffs, transfer marks and chafe on a face that will be seen by the end user. Protection here is cheap and specific.
- Separate every unit. 10–20 mm of EPE or PE foam between stacked cabinets, and never metal-on-metal contact. Foam at corners and along door edges.
- Match the film to the finish. PE film is safe on cured powder coat. PVC stretch film can migrate plasticiser and leave a mark on a freshly cured coating, so avoid it on visible faces.
- Stainless needs a removable film, and a written removal deadline. Protective film left on stainless for more than about three months bakes the adhesive on and creates a worse problem than the scratch it prevented.
- Protect threads and connectors. Caps on threaded studs, plugs on cable glands, and covers on connectors. A dented thread on a ground stud fails an inspection at the far end.
- Cut edges are the corrosion start point. Where a laser-cut or sheared edge will be exposed to weather, either touch it up with zinc-rich paint before packing or specify edge treatment on the drawing.
Bracing and container loading
Blocking and bracing is where a container load either behaves as one unit or tears itself apart. The physics is simple: the cargo must not be able to move in any direction, and no strap or brace may load a door face or a flat panel.
- Restrain at three points minimum. A unit lashed at only two points can pivot. Lashing straps should run at roughly 45° and attach to the container's lashing rings, not to other cargo.
- Total lashing capacity must exceed the cargo weight. As a working rule, the sum of the lashing working load limits should be at least equal to the cargo weight for the transverse direction, because that is the direction a container moves most.
- Fill the voids. Timber dunnage or inflatable dunnage bags between units and from the last unit to the container wall. Voids are what allow a load to build momentum.
- Keep cargo off the doors. Leave a gap at the door end and put a barrier or dunnage frame in place. Container doors are the weakest part of the structure and cargo that leans on them damages both the goods and the container.
- Heavy items on the floor. Never stack a heavy crate on top of an enclosure crate. Load the heavy units first, distribute weight evenly side to side, and keep the centre of gravity low.
Marking, documents and test standards
- Shipping marks on at least two faces of each crate: consignee, order or PO number, item number, case number in the form 1 of 5, gross and net weight, and external dimensions. Add the standard handling symbols to ISO 780 — keep dry, this way up, fragile, and centre of gravity on heavy cases.
- A packing list that matches the crates. One line per case, listing contents, quantity and weight. This is what a damage surveyor will work from.
- Test standards worth quoting. ISTA 3E covers unitised loads in truck and container distribution, ASTM D4169 provides a distribution cycle with assurance levels, and ISTA 1A or ASTM D5276 drop tests apply to individual heavy cases. If you have a recurring damage problem on a lane, ask for a test rather than another layer of foam.
Packing options at a glance
| Risk | What it damages | Mitigation |
|---|---|---|
| Vibration | Paint chafe, loose fasteners, fatigued stitch welds | Foam separation, no metal-to-metal contact, tight bracing |
| Impact | Corners, door faces, thin panels | Corner battens, 50 mm internal clearance, no loose hardware |
| Container rain | Machined faces, galvanized parts, cabinet interiors | VCI film, 0.3–0.5 kg/m³ desiccant, barrier bags for long voyages |
| Stacking load | Top panels, door alignment, seal compression | Stack only crates rated for it, never on a door-up unit |
| Salt and sea air | Cut edges, threads, scratches, unpainted steel | Edge touch-up, VCI, thread caps, barrier bag |
Choosing the packing level for an order
| Order profile | Packing specification | Why |
|---|---|---|
| Air freight, small enclosure, short transit | Plywood crate with foam, no barrier bag | Transit too short for condensation to matter |
| FCL sea freight, powder-coated cabinets | Plywood crates, foam, 0.3 kg/m³ desiccant, lashing at 3 points | Standard export protection |
| Anything unpainted, machined or plated | Add VCI film or a foil barrier bag | Bare steel rusts in days, not months |
| LCL shipment | Full crate, perimeter base, barrier bag, corner battens | Multiple handling and restacking events |
| Repeat order of a standard enclosure | Steel-framed reusable crate, returnable | Avoids ISPM 15 entirely, pays back over shipments |
The short version: foam between every unit, VCI or a barrier bag with a calculated desiccant load on anything unpainted, a valid IPPC stamp on the timber, and bracing that stops movement. Those four decisions prevent most transit claims on enclosures.
Xingyuan Electric (Suzhou) Co., Ltd. is based in Lili Town, Wujiang District, Suzhou, China, and manufactures sheet metal enclosures and electrical assemblies for energy storage, EV charging, advanced manufacturing and power distribution customers worldwide. The company runs a 52-person team in a 5,000+ square metre production facility with more than 20 laser cutting, CNC bending and welding machines, delivering standard orders in 7–15 days and building every order to drawing or to sample. Export packing is planned at quotation stage rather than bolted on at the end: crate construction, desiccant load, VCI or barrier bag selection, lashing plan and shipping marks are all specified per order and confirmed against the destination port and route. Send your drawings, quantity and delivery port for a packing proposal and quotation.