Plastic pallet racking and the span

What happens on the beams

A pallet on a rack sits on two parallel beams. Between them the deck is unsupported, and the load pushes it down. Plastic bends before it breaks, so a rackable pallet is judged by how much it sags and whether it recovers. The three-dimensional drawing on this page lets you turn a pallet across two beams to see where the gap is.

Because plastic creeps, a pallet loaded on a rack for months can bow further than one loaded for hours. Ask for the racking load and for what the maker says about long-term loading.

Checklist for a rack buyer

• Racking load on the sheet, in pounds, for the exact model.
• The beam span used in the rating.
• Pallet length across the beams: 48 in or 40 in. Racking a 48 x 40 pallet with its 40 in side across the beams halves the span and is a different case.
• Whether the rack has a safety rating of its own, which limits the load whatever the pallet can bear.
• Fire protection. A rack full of plastic can change the sprinkler design; see fire rated pallets.

A beam load worked out

Take a pallet with a 2,000 lb racking load. A loaded pallet of 840 lb uses 42.0 percent of it and leaves 1,160 lb; one of 2,458 lb is 458 lb over. Rack engineers also apply their own safety margins, so treat the figure as a ceiling.

A stack worked out

Take a stackable rated 10,000 lb static. The bottom pallet carries the pallets above it, so with each loaded pallet weighing 2,419 lb it can hold 4 above, a stack of 5. With 6,461 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.

Questions to put to the maker

• Does the pallet have runners or a cruciform base, and which way do they lie against the beams?
• Does the racking figure hold at the top of the temperature range?
• What beam span was the racking load measured across?
• Does the maker print a deflection limit, and is it met at the printed load?
• Which rack type was it tested on: edge rack, or a different arrangement?
• Does the maker publish the test method, so a second pair of eyes can read it?
• Does the rating assume the pallet's long side lies across the beams, or the short side?
• Is the racking load printed for this exact model, or only for a family of models?

From the dock

• Pallets are put on rack by forklift; a rack with tight clearance punishes any sloppy placement.
• Racks in cold storage are tightly spaced; confirm the pallet rating holds at that temperature.
• 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.
• Overhanging a pallet past the beam is the quiet cause of dropped loads; check the overhang as well as the span.
• Shuttle and pallet-flow racks ask more of a deck than static rack; a conveyor-compatible base matters.
• Rack inspectors look for bent uprights and overloaded bays; the pallet is a part of the load path they check.

Words on this page

Cruciform base

A base shaped like a plus sign under the pallet, which gives a stable footprint and slides well on conveyors.

Creep

Slow, permanent bending of plastic under a steady load. A pallet can hold a load for an hour and bow under it after a month.

Beam span

The open gap between two rack beams. The longer the span, the lower the load the pallet can carry across it.

Dynamic load

The weight a pallet holds while it is moved by a forklift, pallet jack or conveyor. It is lower than static because motion adds shock.

4-way entry

A pallet that forks or a pallet jack can enter from all four sides.

UL

Underwriters Laboratories, a safety testing body that publishes fire test standards, including one for storage pallets.

Open deck

A deck with slots or a grid, which drains water, sheds dust and weighs less than a solid one.

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.