Can a case rated 500 kg be stacked five high?

No. That figure is static load on a face; stacking passes through corners for months. Recalculate with unit weight times tiers minus one, then allow for creep and heat.

Does a thicker wall make a heavy-duty protective case more drop-resistant?

Up to a point, and the gain fades past eight millimetres. Corner blocks, continuous ribs and preload matter more.

Are more ribs always better?

No. Excess density adds mass, slows release and leaves shrink marks. Continuous ribs along the load direction beat an even grid.

What changes between two latches and four?

Pressure across the joint. Past a metre, two latches leave the gasket under-compressed in the middle. Four divide the load but open slower. ---

Heavy-Duty Protective Case: Load Ratings and Wall Thickness

Quick answer: Three numbers describe the strength of a heavy-duty protective case, and they are not interchangeable: static load on a flat face, dynamic load from a drop, and stacking load held for months. Wall thickness is one input only, set by shot weight rather than by the mould, and it varies by roughly twenty percent across a part. Rib direction, corner blocks and hardware placement decide more. Ask for the test conditions behind any figure.

Heavy-duty protective case loads: static, dynamic and stacking
Wall thickness and shot weight: what rotomoulding can hold
Where ribs and boss blocks belong
How latches, hinges and hardware carry load
Reading a specification table
FAQ

1. Heavy-duty protective case loads: static, dynamic and stacking

A load figure for a heavy-duty protective case means little without its qualifier. A shell that holds a tonne with its base flat may carry a fraction on two bearers. A dynamic rating with no drop height, attitude or temperature cannot be repeated. An unqualified number is a rank, not a capacity.

Close-up of a steel latch and rivets on the dark moulded shell

All three travel one path: base to walls, walls to corners, then keepers and hinges back to the shell. The rivets along the keeper's edge are where impact enters a heavy-duty protective case first. Stacking is the slow figure: unit weight times the tier count less one, times 1.5 to 2, with creep doubling deflection.

2. Wall thickness and shot weight: what rotomoulding can hold

Wall thickness in a heavy-duty protective case is an outcome, not a setting. Shot weight across the mould surface sets it, and four to eight millimetres covers most heavy builds. Below four, drop performance falls off; above eight, mass and cooling time climb.

Grey case open, ring-shaped metal parts set in round foam pockets

The arithmetic: surface area times thickness times density. Two square metres at six millimetres takes about eleven kilograms of polyethylene at 0.94 g/cm³. Foam sits inside, so each extra millimetre of wall costs a millimetre of cavity and a new liner. Ask for minimum wall and measuring points; nominal figures hide corners.

3. Where ribs and boss blocks belong

Ribs stop a heavy-duty protective case from bowing under vacuum or stack load. Boss blocks take point loads. Both go where load enters.

Olive heavy-duty cases stacked two tiers on a pallet, corner blocks aligned

The olive cases stand two tiers on a pallet, corner blocks meeting. Load runs down four corners; shift the upper case half a width and the wall turns from compression to shear. Ribs follow a ratio: 0.6 to 0.8 times wall, height six to eight times wall, root radius at least half.

4. How latches, hinges and hardware carry load

Hardware closes the load chain, and on a heavy-duty protective case it usually fails first. One latch per 300 to 400 millimetres is a working rule. Past a metre, four is the floor.

Olive-drab case closed on a steel shelf, lid ribs and latches

Four latches, two folding handles and a pressure valve line the front, with lid ribs above. Ribs resist bending, the edge abrasion, latches bulging and handles lifting. Latch preload must match gasket compression of 25 to 35 percent: tighter flattens the seal, looser lets water past. Hinges see lid weight times centre distance, so a wider lid needs a larger pin.

5. Reading a specification table

A specification table for a heavy-duty protective case is a screening tool, not a ranking. Only size and mass compare directly. Load and ingress need test conditions.

Field	Usual entry	Ask instead
Internal size	L × W × H	To liner or shell
External size	Hardware included	Latches folded, handles stowed
Wall	One figure	Nominal, minimum, where measured
Load	Kilograms	Face or point support, time, temperature
Stack tiers	A number	Full or empty, pallet included
Ingress	IP67	Test state, valve refitted

Internal and external sizes share one basis.
Confirm whether wall is nominal or minimum.
Fix the support method behind the load.
Confirm how ingress was tested.

Self-weight with or without liner, load per case or per base area, tiers with or without a pallet: each moves the answer a grade. Where a heavy-duty protective case is listed without a basis, take the conservative reading. Ask which basis applies.

Conclusion

Read a heavy-duty protective case in this order: support method, duration, then temperature. Static figures answer for deflection, dynamic ones for drop height and attitude, stacking for tiers and creep. Accept wall thickness only as a minimum, check ribs run into the corners, count hardware against the length it holds.

This article covers container-side specifications and design implications only.