Plastic pallet load capacity: static, dynamic and racking

In briefA plastic pallet has three load ratings: static (at rest on a surface), dynamic (moved on forks) and racking (suspended between the two beams of pallet racking). In racking the pallet is suspended and you read the racking load; on a shelf or the floor it rests on a surface and you read the static and dynamic loads, always for an evenly distributed load.

The data sheet of a plastic pallet gives three load ratings. Plastic pallet load capacity depends on the situation, and the three values are not interchangeable ^[3]. There is only one question to ask: where does the pallet rest?

Suspended or supported: the rule in one line

In racking the pallet is suspended: read the racking load. On a shelf or the floor it rests on a surface: read the static and dynamic loads.

In pallet racking the pallet rests only on the two beams, with empty space in between. The deck works as a bridge and sags in the middle. On a solid shelf or the floor, by contrast, the whole base is supported ^[2][11].

All three assume a load evenly distributed over the deck ^[3][4]. Only pallets designed for beam racking state a racking load: if it is missing, that pallet does not go on bare beams ^[4]. Orientation, drive-in, roller racking and nine-leg pallets are covered in the guide to rackable plastic pallets.

How they are measured: the ISO 8611 tests

The reference standard for flat pallets is ISO 8611. Part 1 sets out the test methods, Part 2 the performance requirements and the choice of tests, Part 3 the maximum working load tests ^[2]. The current edition of Part 1 is 2025, which replaces 2021 ^[1]. The deflection limits quoted below come from the 2011 edition of Part 2 ^[12]: if you need them for acceptance testing, check them against the current text.

Racking load: the bending test

ISO 8611 uses "racking" for storage on beams or in drive-in racking with an unsupported clear span, and checks it with the bending test ^[11]:

• Span. The supports sit 75 mm in from the edges of the pallet. On a 1200 mm side the clear span is 1,050 mm, on an 800 mm side 650 mm ^[11].
• Load. Two line loads at 0.18 times the span from each support: a distributed load, not a concentrated one ^[11].
• Deflection. Under load it must not exceed 2% of the span, about 21 mm over 1,050 mm. After unloading it must recover to within 0.7% ^[12]. The American ASTM D1185 allows 1.9% ^[2].
• Direction. One pallet is tested along its length and one along its width, and the weaker side is stated, unless the two values are within 15% of each other ^[11]. A 1,050 mm span and a 650 mm span give very different deflections.

Dynamic and static load

For the dynamic load, ISO 8611 lifts the pallet on forks about 100 mm wide. In the 2011 edition of Part 2 the allowed deflection is 20 mm under load and 7 mm after unloading ^[12]. For the static load, the compression of blocks and runners is tested on a solid surface, with a maximum deflection of 4 mm, and stacking is tested separately ^[12].

Nominal load and safety factor

The standard distinguishes two quantities.

• The nominal load is the lowest safe load obtained for a given support condition. It is used to compare pallets and excludes concentrated loads ^[2][11].
• The maximum working load applies only to the unit load it was tested with. If the packaging, layers or securing change, the result no longer applies ^[2]. How to secure the load is explained in the guide to load securing.

The safe load is the breaking load divided by a safety factor, which in ISO 8611 is at least 2 (about 2.84 in ASTM D1185). Stiffness is then checked against the deflection limits, and the lower of the two values is adopted ^[2][12].

Creep and 40 °C: why racking is hard on plastic

Under constant load, plastic keeps giving way slowly: this is creep. That is why ISO 8611 specifies creep tests of 24 or 48 hours for plastic pallets, against 2 hours in ASTM D1185 ^[2], and also measures deflection after unloading ^[12]. Racking is exactly that: a load that sits still for weeks.

The basic tests are carried out at 23 °C, but the maximum working load of plastic pallets is tested at 40 °C ^[12], a temperature reached in summer under an uninsulated roof. One maker of plastic products gives operating ranges of about −45/+77 °C for HDPE and −23/+82 °C for PP, with higher short peaks during washing ^[8]. There is no public temperature reduction factor: if the pallet works in a hot room, near an oven or in a container in the sun, ask the manufacturer for the load capacity at that temperature. The differences between materials are in the guide to plastic pallet materials.

How much they carry: data sheet values

The values below come from manufacturers' data sheets for 1200×800 and 1200×1000 pallets. They are values for individual models and should not be read as market averages.

For comparison, the EPAL wooden euro pallet has a working load of 1,500 kg and carries up to 5,500 kg as the bottom pallet of a stack on a flat floor ^[9].

In medium and heavy pallets the dynamic load is between a third and a sixth of the static load, and the racking load is lower still. Steel profiles mainly change the racking load: in a heavy pallet with runners it goes from 1,000 to 1,400 kg ^[6].

Even load and concentrated load

The stated ratings assume a load spread over the whole deck: cartons, sacks, drums evenly placed. One manufacturer, for example, tests the racking load with 25 kg sacks ^[3].

A concentrated load behaves differently. The same weight, placed on a small area or on a line, makes the deck bend much more. ISO 8611 excludes concentrated loads from the nominal load ^[2].

The typical case is a reel. A reel of film, paper or aluminium lying on a flat pallet touches the deck along a single line; on a saddle or cradle it puts its weight on two curved supports. In both cases it is a concentrated load, and the rating of a flat pallet is not enough to size it. How to choose a reel support by diameter, weight and core is explained in the guide to reel pallets.

How to read a data sheet

1. Check the test conditions: even load or not, which standard, which temperature. A rating without conditions tells you little.
2. Start from the lowest rating that applies to you. If the pallet goes on beams, the racking load decides, not the static load.
3. Look for the direction of the racking load: along the long side or the short side. If the data sheet does not say, ask the manufacturer.
4. Check whether the value needs reinforcement. The highest rating often belongs to the version with steel profiles, which costs and weighs more ^[6][7].
5. Look at the stack. Compare the static load with the weight of all the loaded pallets above the bottom one ^[3].

If you need to write these requirements into an order, the guide to specification and acceptance testing sets out what to ask for and how to check it.

Common mistakes when reading load capacity

• Using the static load for handling: a pallet rated 2,500 kg static may carry 800 kg on a forklift ^[5].
• Using the static load for racking: for the same pallet with runners, the data sheet can give 5,000 kg static and 1,000 kg in racking ^[6].
• Putting a nestable pallet with legs on beams: it generally states no racking load ^[5].
• Forgetting concentrated loads: the data sheet does not cover reels, moulds, motors or single drums ^[2].
• Ignoring time and heat: a pallet that holds overnight in racking can deflect beyond the limit after weeks of summer ^[2][12].
• Comparing data sheets based on different standards: an ISO 8611 value and an ASTM D1185 value come from different safety factors and creep tests ^[2].

Which designs can handle racking is explained in the guide to types of plastic pallet.

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