If a Heavy-Duty Plastic Box is rated 800 kg, can it hold 800 kg?

Answer: No. That is usually the distributed limit, so load it at about half; the concentrated allowance is typically thirty percent of it.

Are four stack layers enough?

Answer: Check clear height, weight and temperature. Above 35 °C in summer, design at three layers.

How much difference does 4 mm versus 5 mm make?

Answer: Bending capacity rises roughly with the square of thickness, so 5 mm is about sixty percent stiffer, but a wide rib pitch cancels much of that.

Can fork pockets be resized for existing pallets?

Answer: Within limits, but recheck insertion depth and foot position; raising the pocket also raises the centre of gravity.

The base has dipped after two years. Can it stay in the stack?

Answer: Beyond 5 mm the base has yielded, so cut the layer count or replace the box.

How to Choose a Heavy-Duty Plastic Box: 5 Criteria

Quick answer: Rate static load distributed and concentrated, count layers at real storage temperature, fix rib pitch and wall thickness, then check fork pocket depth against forklift practice. Four measured values decide whether the box sags in year three.

Five Criteria for a Heavy-Duty Plastic Box
Static Load and Safety Factor
Stack Layers and Creep Allowance
Wall Thickness and Rib Layout
Forklift Duty and Handling
FAQ

1. Five Criteria for a Heavy-Duty Plastic Box

Selection turns site forces into five numbers: load per box, layers, rib layout, fork entry and the surface under the feet.

Check	Number to obtain	Frequent mistake
Static load	Distributed, concentrated, deflection	Accepting one load figure
Stacking	Layers, weight per layer, temperature	Stacking empty boxes
Wall and ribs	Side, base, rib pitch	Asking for average wall
Forklift duty	Pocket size, insertion, dynamic factor	Applying static values
Feet and surface	Foot span, beam pitch	Ignoring beam gaps

Two 600 by 400 mm boxes with base ribs two millimetres apart behave differently by layer four. Three items are usually left vague: one load figure, an average wall, a pocket size without insertion depth.

2. Static Load and Safety Factor

Static load needs two figures. Distributed load covers the whole base, where 800 kg is a common rating for a 600 by 400 mm Heavy-Duty Plastic Box. Concentrated load uses a 100 by 100 mm steel block at the centre, where the same box often carries only 250 kg.

Heavy-Duty Plastic Box: closed off-white box on a galvanised rack, three white latches, recessed folding handles, rubber corner bumpers

Take the safety factor as 2.0: a 400 kg load calls for an 800 kg rating, and the margin absorbs offset loads and heat softening. A box specified at 1.5 looks fine for two years, then dips permanently.

Deflection is the neglected line on a Heavy-Duty Plastic Box: under a full base at 800 kg for 24 hours the pass line is 3 mm per metre, and 3 mm versus 8 mm decides whether a forklift can slide under the box.

3. Stack Layers and Creep Allowance

Layer counts for a Heavy-Duty Plastic Box cannot come from stacking empty boxes. Four full layers at 25 °C leave the bottom box carrying the three above it. In a 40 °C warehouse the walls soften and bow, and the upper base edge can drop into the lower rim.

One protocol covers it: 40 °C for 30 days at the real weight per layer, then measure height loss, which should stay under 3 mm, roughly a year of ambient storage.

Test one layer beyond the design count: the extra layer shows the room left in service.

4. Wall Thickness and Rib Layout

Report Heavy-Duty Plastic Box wall thickness in three places. For load-bearing boxes, 4.0 mm at the side, 5.0 mm at the base and 6.0 mm at the rim is a common spread. A 4.5 mm average reads better in a datasheet, but an unthickened base sags first.

Ribs move load to the corners. A 120 mm pitch, 12 mm rib height and R2 root radius is workable in injection moulding; past 150 mm the panel between ribs bows, and a rib without a root radius cracks as the part cools.

A cross pattern under the base, aligned with the feet, sends load straight into the rack beam. Vertical side ribs should sit above the feet so the force path stays vertical.

5. Forklift Duty and Handling

Forklift work is not static load. A 100 mm high, 200 mm wide pocket with fork insertion of at least three quarters of the box length decides whether a Heavy-Duty Plastic Box tips when lifted; enter halfway and the rear base has no support.

Use a dynamic factor of 1.3: lifting, braking and threshold impacts run about 1.3 times static, and a site handling forty boxes a day should ask for 2,000 drops from 300 mm onto concrete.

Duty	Key figure	How to check
Forklift	Pocket 100 by 200 mm	Insertion over three quarters of length
Pallet stacking	Foot span against beam pitch	Corners on beams, gap under 30 mm

Check feet against the surface too. Beams at 800 mm spacing under a 600 mm foot span leave 200 mm unsupported, which sags over months; add a slip sheet or choose a wider box.

Conclusion

Four numbers settle most of it: distributed and concentrated load, layers against temperature, wall thickness with rib pitch, pocket size with the dynamic factor. Written into the technical agreement, they replace feel with evidence. Get load, stack, ribs and fork entry aligned, and a Heavy-Duty Plastic Box holds up over three years.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.