Other Voices: Getting the most from your pallet design

What’s the most crucial piece of material handling equipment? Some might argue that it’s the lift truck or conveyor, both of which are ubiquitous. I think an argument can be made that the pallet is at the top of that list.

After all, everything moves on a pallet. In all likelihood, the coffee you drank this morning, the clothes you’re now wearing and the dinner you will eat tonight moved from Point A to Point B on a pallet. At the same time, a collapsed pallet can cause significant product damage, worker injuries and shut down operations if product is spilled. Getting the right pallet is as important as choosing the right lift truck or specing out the right conveyor.

At first blush, the design of a pallet seems pretty basic. For that reason, the pallet usually gets short-changed in the design of an overall materials handling process. However, there are several opportunities to make changes to its fundamental building blocks that can extend its useful life and improve protection of the products riding on a pallet deck. Spending a little more time upfront on your pallet design will lower your pallet operation costs in the long term.

Of course, there are many factors to consider when choosing a pallet, including matching its footprint to your product footprint and selecting a design that will maximize cube utilization. Additionally, there are numerous options for the type of material used in the pallet. However, 92 percent of the 1.9 billion pallets used in the U.S. are wooden pallets. This article will focus on three key elements of wooden pallets that have been tested and measured extensively at the Center for Packaging and Unit Load Design at Virginia Tech: strength, stiffness and durability.

Strength and stiffness are critical to supporting pallet load

It is critical that you select a pallet with enough strength to support the unit load, as well as withstand forklift operations and tolerate racking. Here are the three most common designs that support racking and forklift use in order of most to least durable.

• The block pallet, popular for its full four-way entry capabilities, has a square or rectangular spacer between the top and bottom decks. True four-way entry makes it easier for a forklift to access from any/all four sides. It is most commonly seen with a perimeter base design which provides optimum stress distribution. However it can be designed as a unidirectional or cruciform (plastic) base as well.

• The second option is a two-way pallet. It has stringers (support beams, usually 2x4s) that run the length of the pallet to support the top deck. Although more durable than the last option, it is only accessible from 2 of the 4 sides (front and back).

• The partial four–way is the most popular pallet for racking. It can be accessed by a forklift from any of the four sides; however access on two of the sides is enabled by notches in the wood; rather than an opening between two solid stringers 2x4s. These notches compromise the load-bearing capacity. Also be aware that square notches compromise load-bearing capacity more than rounded ones.

Strength and stiffness go hand in hand; however, most pallet buyers don’t consider stiffness when making their selection. Stiffness, and not strength, is the factor that keeps pallet boards from sagging and bending (referred to as deflection). If a pallet is not stiff enough, it will sag and create unstable unit loads that collapse or topple. Often, the loss is greater than just the product that is damaged. For example, product tumbling 30 feet down a racking system can cause serious injuries to workers. Broken tomato jars moving on a conveyor system can contaminate a wide area of a manufacturing plant and shut down operations until thorough sanitation has been achieved. The potential for injury and the cost of shutting down operations and cleanup are much more than the expense of buying a better pallet with greater stiffness.

Determining if your pallet has the right stiffness for your operations is not an easy task because numerous factors are involved. There are commercially available pallet design software packages (such as Best Load™) that can help you determine the stresses experienced by your product as a function of the pallet stiffness. If you don’t have access to a software package, make sure that you run extensive laboratory tests and field trials with your new pallet design before committing to a large purchase.

Improvements to lead edge board and fasteners extend life of pallet

Durability refers to how long your pallet will perform well over a specified number of trips. Making a small increase in your investment upfront will extend its useful life considerably.

The most common points of failure on wooden pallets are the lead edge board, fasteners and splits in the stringer or blocks. The lead edge board is the first line of defense against the forklift and it is the most crucial component on a wood pallet. This is the piece of lumber at the very front or back of the pallet. The vast majority of all wood pallet damage happens at the forklift entry points. Also, damage to the lead edge board is the most likely to cause product destruction and loss.

There are cost-effective ways to reinforce the lead edge board. Following are the measurable results that can be achieved by making changes to its design. These results are based on testing done at Virginia Tech:

• Attaching a pallet protector, such as the pointGUARD®, to the front of the pallet reduces the severity of impacts on blocks and stringers and lead edge boards. In testing, it increased lead edge durability by 100 percent and block durability by 400 percent.

• Butting lead edge deckboards yields a 38% improvement.
•  Incorporating split-inhibitors in leading edge deckboards results in a 48% improvement.
 
Other best practices for the lead edge board include using butted, double nominal 6-inch boards as lead edge boards, using hardwood boards for the lead edge of the pallet and using better nails.
The following design changes in the overall construction of the pallet have also been confirmed to improve durability:

• Using dense hardwood instead of medium density hardwood yields a 38% improvement.
• Using dense hardwood instead of Douglas Fir yields a 165% improvement.
• Using air-dry or kiln-dried wood instead of green yields a 43% improvement.

Another common point of failure is the fastener. At our center in Virginia Tech, we’ve been given pallets that have fasteners that are so cheap they fall apart before we get our testing under way. Be sure that your fasteners are multiple use or limited grade based on the grading system published by ANSI MH1 standard – they are worth the extra cost. Don’t use repair grade fasteners. A mere 5 to 6% increase in the number of fasteners yields a 56% improvement. Also, a simple design change that does not require any additional cost yet increases durability is placing pallet boards closer to each other, minimizing the space between them.

Conversely, don’t design or invest in a pallet for longer than you can retain ownership. I don’t recommend designing for a life longer than 10 years. At the end of a decade, even the strongest pallet will be filled with dirt and too unsanitary to use any longer. Also, your product and unit load footprints will likely change over the course of 10 years.

Before investing in your next load of wooden pallets, make a careful review of available design changes and do not make a selection based solely on price. These proven metrics demonstrate that a small additional investment greatly increases your return on investment over the life of the pallet. Additionally, a stronger product results in less product damage, adding to the savings.

Laszlo Horvath is the Director of the Center for Packaging and Unit Load Design at Virginia Tech University. He can be reached by email at [email protected]. This content was originally presented at the Reusable Packaging Association Reusables Learning Center at PACK EXPO 2014. Click here, to read the entire presentation.