Unit Load Design: Commercialization

National Wooden Pallet & Container Association

WelcomeMessage

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Unit Load Design is the recognition that the cargo sitting on a pallet supports some of it’s own weight.

Kristen DeLack, PEStructural Engineer

• Introduction• Commercialization• Distillation• Question & Answers

Outline

Types of unit loads

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Roadmap

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Extensive Testing

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• Nearly three years of testing unit loads of boxes is wrapping up.

• Long-term creep tests will be complete in another two months.

• Exploratory testing.• Full scale lab testing of stringer and block

pallets with unit loads of boxes.• Box crush testing.• High humidity testing.• Vibration during transportation tests.• Stretch wrap containment force

characterization.

Computer Modelling

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Distillation

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Box edge loading is a function of the pallet stiffness.

Stiffer Pallet lower box stress

Less Stiff Pallet Higher box stress

When does it matter most?

When racked. Especially in a weak direction!

Assuming that the pallet is designed according to best practices:• Gap between deckboards isn’t too high• All box corners are supported by deckboards• Be careful with bottom deckboard layout for

stacked > 1 high

Introducing PDS Unit Load

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Ability to layout and specify common unit loads

LoadSynctm – Can be used by clients to specify unit loads

and provide the design details to PDS pallet professionals

Perform basic corrugated box design calculations

Determine box load factors

Predict unit load displacement

Specify pallet stiffness required to produce a desired box

load factor

Design a pallet to meet desired stiffness and box load factorEvoke a cultural shift that encourages end users to recognize important interactions between the load & pallet and begin specifying pallet stiffness.

Are we there yet?

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Baby Steps

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• PDS limitations• Regular Slotted Containers (RSC)’s• Column stacked – interlock stacked tends to be

better for the pallet and worse for the boxes• Symmetrical layouts in two planes• 80% pallet coverage• No overhang

• Support conditions• Racked across length• Racked across width• Stacked (maybe)

What can you do with it?

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• Gain insight into how boxes and pallets interact and use this to optimize the entire unit load.

• The box on the left sustained damage during a month-long creep test (just sitting there) as the load began to concentrate on the outside edge.

Why does it matter?

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• Packaging failure may still occur even though the pallet is OK.

• This could cause rejection of the unit load or an expensive cleanup.

• Design optimization – only use the needed material where it is required and save what is not necessary.

Design Optimization

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$ $$$$

National Wooden Pallet & Container Association

A tool to help you build a relationship with your clients

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Thank You.