Guide: Plastic pallet creep
Creep is slow deformation of plastic under a steady load. A pallet can carry a load for an hour and bow under it after a month, which is why a rating at rest is not a rating for storage.
What creep is
Nelson Company notes that plastic pallets can deform under heavy loads held for a long time. Metal and wood mostly spring back when the load comes off; plastic can flow, a little, under a steady stress, and the change is permanent. A deck that sagged a quarter inch in a week may sag half an inch in a month.
A short load test, which is how static ratings are usually taken, does not show the effect. That is why the maker's number is a number for a test, and why a long wait is a separate question.
Where it bites
- Racks: a loaded pallet sits on two beams for months, with the middle unsupported.
- Tall block stacks: the bottom pallet carries the weight for as long as the stack stands.
- Warm stores: heat makes plastic flow faster. See the cold guide for the other end of the scale.
- Uneven loads: concentrated weight deforms the deck sooner.
How to ask
- What load was the rating taken at, and for how long?
- Does the maker publish a long-term or storage rating?
- What deflection is allowed on a rack before the pallet is retired?
- Is the rating for new pallets only, or for reconditioned ones too?
Rotate stored pallets, unload long-held stacks, and inspect the decks. A pallet that has bowed on a rack should come off it.
A stack worked out
Take a stackable rated 30,000 lb static. The bottom pallet carries the pallets above it, so with each loaded pallet weighing 1,744 lb it can hold 17 above, a stack of 18. With 5,786 lb per pallet it can hold 5 above. This is a ceiling on a flat floor for a still stack, not a promise for a stack that moves or waits.
| Loaded pallet, lb | Pallets above the bottom | Stack height | Load on the bottom pallet, lb |
|---|---|---|---|
| 1,744 | 17 | 18 | 29,648 |
| 2,251 | 13 | 14 | 29,263 |
| 2,758 | 10 | 11 | 27,580 |
| 3,265 | 9 | 10 | 29,385 |
| 3,772 | 7 | 8 | 26,404 |
| 4,779 | 6 | 7 | 28,674 |
| 5,786 | 5 | 6 | 28,930 |
A beam load worked out
Take a pallet with a 2,700 lb racking load. A loaded pallet of 1,568 lb uses 58.1 percent of it and leaves 1,132 lb; one of 3,186 lb is 486 lb over. Rack engineers also apply their own safety margins, so treat the figure as a ceiling.
| Loaded pallet, lb | Share of the racking load | Left over, lb | Within the rating? |
|---|---|---|---|
| 1,568 | 58.1 percent | 1,132 | yes |
| 1,771 | 65.6 percent | 929 | yes |
| 1,974 | 73.1 percent | 726 | yes |
| 2,277 | 84.3 percent | 423 | yes |
| 2,580 | 95.6 percent | 120 | yes |
| 2,783 | 103.1 percent | -83 | no |
| 3,186 | 118.0 percent | -486 | no |
Words on this page
- Recycled content
- The share of a pallet moulded from reground plastic. Makers print it as a range, often by colour.
- UL
- Underwriters Laboratories, a safety testing body that publishes fire test standards, including one for storage pallets.
- Static load
- The weight a pallet holds while standing still on a flat floor, spread evenly across the deck. It is the highest of the three ratings.
- Nest ratio
- How many empty pallets fit in the height of one: pallet height divided by nest increment.
- Nest increment
- The extra height each additional empty pallet adds to a nested stack, measured in inches. A small increment means a short stack.
- Footprint
- The length and width of a pallet deck. It is chosen to fit the container, the drum, the bag or the receiving rack.
- HDPE
- High-density polyethylene, a tough resin used in many plastic pallets, valued for strength against its weight.
- Closed loop
- A route where pallets return to the sender after delivery, so the empty trip is a standing cost.
Tell us the footprint and how many stacks you move.
We work out the empty trailer, then take the request for a load.