Rack beam span and plastic pallets
Span is the open gap between beams. It changes the rating more than any other variable, and the sheet rarely prints it. Ask.
Why span matters
Bending in a beam grows with the square of the span, which is a standard result from engineering mechanics. Double the gap and the load a pallet can take across it falls by far more than half. The racking figure on a sheet is only correct for the span the maker tested.
| Pallet side across the beams | Beam gap (idealised) | What it means |
|---|---|---|
| 48 in | wider | More bending; the lower racking load applies |
| 40 in | narrower | Less bending, but the pallet's overhang changes |
Questions that settle it
- What span was the racking figure measured on?
- Is it for a 48 in or a 40 in side across the beams?
- Does the figure assume a flat, rigid load or a soft one?
- What happens to the figure after a long loaded period?
If the maker cannot answer, treat the rating as undefined for your rack. Rehrig Pacific lists a 2,000 lb edge rack figure and Nelson Company a 2,700 lb racking figure on named models; neither is a number for a rack with a different span.
A beam load worked out
Take a pallet with a 2,000 lb racking load. A loaded pallet of 1,170 lb uses 58.5 percent of it and leaves 830 lb; one of 2,788 lb is 788 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? |
|---|---|---|---|
| 1,170 | 58.5 percent | 830 | yes |
| 1,373 | 68.7 percent | 627 | yes |
| 1,576 | 78.8 percent | 424 | yes |
| 1,879 | 94.0 percent | 121 | yes |
| 2,182 | 109.1 percent | -182 | no |
| 2,385 | 119.2 percent | -385 | no |
| 2,788 | 139.4 percent | -788 | no |
A stack worked out
Take a stackable rated 8,000 lb static. The bottom pallet carries the pallets above it, so with each loaded pallet weighing 2,884 lb it can hold 2 above, a stack of 3. With 6,926 lb per pallet it can hold 1 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 |
|---|---|---|---|
| 2,884 | 2 | 3 | 5,768 |
| 3,391 | 2 | 3 | 6,782 |
| 3,898 | 2 | 3 | 7,796 |
| 4,405 | 1 | 2 | 4,405 |
| 4,912 | 1 | 2 | 4,912 |
| 5,919 | 1 | 2 | 5,919 |
| 6,926 | 1 | 2 | 6,926 |
Where span comes from
A rack beam is spaced for the pallets it was designed around. A 48 in pallet resting on beams set 42 in apart overhangs 3 in each side; the same pallet turned the other way, 40 in long across beams set closer, overhangs less. The racking figure on the sheet is for one such arrangement, and the further yours is from it, the less the figure tells you.
Ask the maker for the arrangement in writing. If it will not describe it, the figure is a marketing number. If it will, hand the description to the person who designed the rack, who can say whether it matches.
Measuring your own span
Measure the clear gap between the inner faces of the two beams that will carry the pallet, not the bay width, and note the beam depth too. The span you measure is the one to compare with the span printed beside the maker's racking load, and the two must be close for the figure to apply.
From the dock
- Overhanging a pallet past the beam is the quiet cause of dropped loads; check the overhang as well as the span.
- A pallet bridging two beams flexes at its centre; the more it flexes, the less margin it has left.
- Record the pallet model against each rack position, and a failure can be traced to its source quickly.
- Racks in cold storage are tightly spaced; confirm the pallet rating holds at that temperature.
- Rack inspectors look for bent uprights and overloaded bays; the pallet is a part of the load path they check.
- Shuttle and pallet-flow racks ask more of a deck than static rack; a conveyor-compatible base matters.
- Do not guess the racking load from the static one; the two numbers can differ by a large factor.
Words on this page
- Runner
- A continuous rail under a pallet. Runners lie flat across rack beams but stop pallets from nesting.
- 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.
- Edge rack
- A rack arrangement where the pallet rests on the edges of the beams. It is the common test case for a racking rating.
- Open deck
- A deck with slots or a grid, which drains water, sheds dust and weighs less than a solid one.
- Beam span
- The open gap between two rack beams. The longer the span, the lower the load the pallet can carry across it.
- Pallet jack
- A hand or powered truck with two forks, used to move a pallet short distances.
- Closed deck
- A solid deck that keeps small items and torn bags from falling through and wipes clean on top.
- Racking load
- The weight a pallet holds when it rests on two rack beams with an open gap between them. It is usually the lowest rating and only exists for pallets built for racks.
Tell us the footprint and how many stacks you move.
We work out the empty trailer, then take the request for a load.