Effective Unitized Loads: Connections Between Packaging, Pallets, and Material Handling Equipment

An archived Pallet Enterprise article provides an excellent case study demonstrating the relationship between packaging, pallets and material handling equipment.

Boxed bottles of antifreeze were stored on pallets in overhead racks.  After several months of storage, facility managers found themselves cleaning up leaking antifreeze that had covered the warehouse floor.  The boxes could have supported the antifreeze on certain pallets and the pallets could have performed properly on certain racks, but together, the result was an expensive mess.  Should the box manufacturer bear the costs of the cleanup, or was the pallet supplier at fault?  The Virginia Tech Center for Unit Load Design was consulted to develop a unit load design for future shipments to the facility.

Background Information
The antifreeze was shipped in one-gallon HDPE (high density polyethylene) plastic bottles designed for containment only.  The bottles lacked the structural integrity to support compressive stresses.  The bottles were placed into a 275 pound, single wall, C-flute corrugated box.   Each unit load consisted of 36 boxes (nine boxes per layer, stacked four layers high) resting on a 48” x 40” grade A GMA hardwood pallets with decking that ranged from ½”-3/4”.  The approximate weight of each unit came to 2,100 pounds.  Each loaded pallet was racked across the 40” deck boards in drive through racks that spanned 36”.  Upon examination, the boxes were wet and crushed and many of the bottles failed due to the weight of the load.  A significant number of the pallets sustained bowing of 1-2” that persisted even after the boxes were removed.

Key Findings
A load audit determined that individually, the pallets and racks were adequate for the application, and that the boxes were strong enough assuming they were placed on a flat deck.  Problems arose after 4 months of storage in the drive through rack.  Consultants from Virginia Tech found that many of the pallets were capable of supporting 2100 pounds when racked across the stringers, but failure occurred when racked across the deck in the drive through rack.  Overloading caused pallet deflection to increase over time, which changed how the compressive stress was distributed across the load.  The end result was bottles and box failure, which resulted in leaks.

Potential Solutions
Pallet Options–A hardwood 48”x40” GMA pallet with 13/16″ decking would adequately support the load, but at a significant cost increase. Grade A recycled pallets with at least ¾” thick deck boards were also considered due to the lower price point.

Box Design Considerations—New boxes with corrugated internal supports would enhance compression strength and spread compressive stresses over a greater surface area.  This strategy would be particularly helpful in tandem with the use recycled pallets due to their propensity for random decking placement.

Improved Bottle Specification —Use of a thicker bottle with more substantial shoulder design was also considered but not implemented due to cost considerations.

Storage Rack Design—Stiffer pallets should be used with a drive through storage rack.  Switching to a different storage system requires a larger initial investment than other options, but is often the most cost effective solution over time.

Captive Pallets—Placing shipping pallets on captive pallets prior to storing the loads on the rack system would add rigidity to the load, but this practice is more cost effective in situations with fast turns or repeat sales over time rather than long term storage scenarios.

The available data suggested used of recycled 48” x 40” grade A pallets with ¾” decking combined with C-Flute boxes with corrugated winged H inserts rated at 200 pounds.  Although this new, combined unitization method comes at a slightly high price point than the previous load configuration, it is still more cost effective than solutions addressing single variables.

By examining the connections between packaging, pallets, and material handling equipment, safer, cost effective unit loads designed to prevent product loss and damage are achievable.  Remember, effective unitized loads can reduce costs, minimize product damage, and have a significant impact on your company’s bottom line.  Contact the domestic and international shipping experts at Litco International to learn more about effective strategies to safely Carry your products on through the most demanding supply chains.

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Effective Unitized Loads: Connections Between Packaging, Pallets, and Material Handling Equipment