Design Unit Loads for the Road

Sept. 1, 2010
New legislation may allow shippers to haul more weight, which means bigger unit loads. Until then, getting the most from your pallets and packaging is a best practice at any time.

Most of us are focused on lightening our loads if we know what's good for us. On the highways, bulking up could be a good thing, especially if Congress passes the pending Safe and Efficient Transportation Act (H.R. 1799/S. 3705). Under SETA, the federal vehicle weight limit would rise from 80,000 pounds to 97,000 pounds for vehicles equipped with a sixth axle.

New weight limits could put the spotlight on pallets and industrial packaging materials, like stretch and shrink wrap and strapping that make up the unit load. After all, new unit load designs may be needed to make the best use of the existing cube and take advantage of the new higher weight limits. However, getting the most out of a unit load is a best practice any time, regardless of whether Congress passes new laws.

In the past, too many companies approached unit load design the same way they approached safety stock levels in the warehouse: if some is good, more must be better. That results in wasted - and expensive - packaging on the load and in the landfill.

Forward thinking end users and suppliers are taking a system-based approach to the design process. This approach looks beyond the weight of the load to include how that load will be transported and handled at each node of the supply chain. The best companies are also including sustainability in that mix by considering how their packaging products will be reused or recycled at the end of their journey (see The Sustainable Unit Load).

Rather than throwing more packaging at the problem, a systems-based approach to unit loads uses software tools and lab testing to create a package that uses just the right amount of material to protect the product, make for safe handling and transportation and minimize the use of non-recyclable materials. Think of it as the scientific method for building the optimal load.

Let's take a look at some of the considerations that go into the optimal unit load.

Building the Better Pallet

The pallet is the basic building block of the unit load. The best design will safely handle a load throughout its journey through the supply chain at the lowest possible cost. The pallet is also unique in that the design has to work with both the material handling equipment that will move the load and with the stretch and shrink wrap or strapping that will unitize the load to the pallet.

Several considerations affect the ultimate design of the pallet, including:

Industry standards and customer requirements: The 48 × 40 GMA [Grocery Manufacturers Association] is the standard pallet for the grocery industry. Other industries, like the glass and can industries, also have pallet standards. Similarly, some customers, like club stores and big box retailers, have pallet and unit load specifications. In those instances, the pallet design is already decided for you.

One-time use or reusable: Whether a pallet is used once or is reused impacts the design. Many manufacturers, especially in the food and beverage industries, reuse the pallets they receive from their suppliers to ship their products. For them, a heavier duty pallet costs more up front, but has a long-term residual value. On the other hand, building materials like shingles are typically shipped to a construction site and thrown in the dumpster. Those pallets only need to be strong enough to support the weight of the product during storage and transportation.

Product matters: The type of product going on the pallet affects the design. Cartons, for example, require less deck board coverage than bagged or printed material that can sag between the deck board gaps and get damaged by lift truck forks.

Racked, stacked or floor loaded: A product that will be stored in an unsupported pallet rack may require a more substantial pallet than one that will be stored on the floor. Product that will be floor loaded in a trailer can be shipped on a lighter duty pallet than product that will be stacked two-high in the trailer or four-high in the warehouse.

What's on the customer's dock: Building a heavier unit load may cut down on a manufacturer's shipping costs, but those savings will be wasted if the distributor or retailer on the receiving end doesn't have a lift truck that can handle the extra weight.

Material Handling Counts

It's not just the weight of the load and how it will be stored that's important. A systems-based approach also recognizes that the type of equipment that will handle a pallet is also important. That is also too often overlooked because systems, pallets and packaging are designed in silos. A design change like an increase in the spacing of rollers on a conveyor may save $25,000 on a one-time capital investment, but it could also result in a $4 to $5 increase in the cost of every pallet — and that's a recurring cost.

Push-back rack, or flow racking, is an example of how the right pallet design can improve the performance of a materials handling system and save money at the same time.

How smoothly a pallet rolls across the narrow rollers can be critical to getting pallets in and out of the racking. At the same time, the high moisture content of the green hardwood lumber used in most pallets can cause them to warp or bend over time. If that happens, the pallet won't roll easily or may even get hung up in a rack, which can be a challenge in a rack system that is 20 pallets deep.

To solve that problem, one end user replaced its hardwood deck boards with southern yellow pine boards that were dry and stiff, allowing the pallet to roll without getting stuck. As a side benefit, using kiln-dried lumber allowed the customer to eliminate a corrugated sheet that was used as a moisture barrier between the pallet and its product, saving $1 per unit load in packaging.

Of course sometimes it makes more sense to consider changing equipment. One manufacturer was buying new pallets with high stringers because the facility had a dozen older pallet jacks on the dock that had been paid for and depreciated years ago. Replacing the pallet jacks with lower-profile equipment would have cost about $1,000 per unit. That investment would also have allowed the facility to use a recycled pallet with a 3-1/2-inch high stringer, saving about $3 per pallet. The manufacturer, however, was unwilling to make the capital investment.

The point is that when looking at unit load design, it's important to remember that the choice of equipment can have a significant impact on the cost per trip of a pallet.

Wrapping It All Up

Pallets and material handling equipment are two of the three components that go into an optimized unit load. Industrial packaging is the third component. While some users still get by with a bead of glue or an adhesive between layers, three materials are most commonly used.

Stretch wrap is the most versatile and the most common material. It provides a layer of protection from dirt, the first line of defense against theft, and it keeps the load together during shipment. It is adaptable: Stretch wrap can be used on mixed SKU loads that may not be perfect, neat or square.

Strapping, which is made from a variety of materials, is used on loads that need strategic security and vertical compression. Printed material is often strapped to a pallet, as are building materials like bricks or lumber.

Shrink wrap is the most expensive of the load unitization methods because it uses heat to shrink the film around the load. Shrink wrap also requires a neat and uniform load. But shrink provides five-sided protection from the elements for loads like rolled roofing or shingles that are heavy and may be stored outside.

Putting It All Together

How then do you put the three components of pallet, material handling and packaging materials together to optimize the unit load in a sustainable way? Increasingly, the answer is more science than art.

First, look for standards. Just as there are industry standards and customer requirements that dictate which pallet can be used, there are emerging standards that dictate how to build a unit load for some industries. The International Safe Transit Association, for example, has developed testing procedures and standards for shipments in a variety of situations and industries, like ISTA Project 3J for club store distribution. Anyone shipping a load of product into a club store needs to meet those standards.

Where there are no industry standards to follow, a good starting point is a pallet and unit load software design program. A unit load design system like the Cape Pack application from Cape Systems helps an end user build efficient pallet patterns and improve material and cube utilization. The system can also consider data such as a carton size and stack pattern to determine how much coverage needs to be on the top and bottom decks.

The next step is to use an application to design a pallet around those parameters. The Pallet Design System (PDS), available to pallet suppliers who belong to the National Wooden Pallet & Container Association, allows a pallet manufacturer to input a proposed pallet design plus performance parameters like the height and weight of the load. The system will determine whether the design will work. If the design isn't workable, the system will identify the component of the design that will fail first. A designer can change the height or weight of the load, the width and thickness of the boards or vary other components, like the nails, to design a pallet that will work.

Once a unit load is designed, the next step is to put it to the test at a unit load testing facility, such as the Center for Unit Load Design at Virginia Tech or an independent lab in the packaging industry. These facilities can perform vibration tests, compression tests and simulate the racking of a load. In addition, incline, or sled tests, can determine the gage of film or strapping or how many wraps of stretch film are required to keep a load contained on a pallet during transportation.

With software, independent lab testing and a systems-based approach to the design of a unit load, you can truly get the most value out of your unit load while ensuring that your product gets delivered from the end of the line to the end user intact.

Joe Pecchia is the director of strategic account & technology development for Millwood Inc., a provider of pallets, industrial packaging systems and solutions.

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