How Are Corrugated Pallets Tested?

Posted by Jamie Watkins and Daniel Beighle on July 04,2018

There really are so many cool challenges that come up with designing and testing paper pallets on a day-to-day basis, and as an engineer, you stay busy with the science of it all.

This is what makes testing paper pallets unique from testing wooden pallets. There are all kinds of regulations and tests that have been done and perfected over the course of the past 120-year lifespan of wood pallets. The corrugated pallets we know now are relatively new.

Years ago, corrugated pallet designers focused on vertical flutes for strength. Therefore, most tests were done using the box compression test (BCT) to measure the maximum load a box could hold. To estimate the BCT of a paper pallet, engineers used the strength of a corrugated box with the same BCT and multiplied that by the number of corners on the pallet. That was supposed to give you the “strength” of the pallet.

As the corrugated pallet has evolved to take on different shapes, styles and compositions, testing has likewise evolved to ensure top-notch, safe and in-spec products are reliably delivered.

For example, one such instance in which our corrugated pallet evolved was with the addition of cores to the runners. This modification added stability and strength to the overall design. The concept for using round cores inside the corrugated pallets stemmed from the availability of surplus paper tubes from our warehouse. Since then, we have switched from recycled cores to manufactured cores, necessitating a new set of tests to be run.

Let’s look at some of the different tests, what engineers are looking for in each and what they mean for you as the consumer.


Testing the Components of a Corrugated Pallet

Pallets are like tiny bridges and follow a similar testing regimen. Even some of the testing machinery is comparable. First, it is important to test the different components of a paper pallet to gauge strength, sturdiness and reliability. If the individual pieces of the pallet don’t hold up to certain standards, engineers must make changes before they can assemble.

Engineers use these tests to gauge individual corrugated boards and paper cores that make up a corrugated pallet.


Edge Crush Test for Corrugated Boards

Engineers use the Edge Crush Test (ECT) to test individual corrugated boards. ECT measures cross-directional crushing of a corrugated board against a predefined measurement standard. This tells you how that board’s construction will stand up to crushing (also known as its edgewise compressive strength).

This standardized test helps ensure that if a pallet design uses a specific ECT board, manufacturers can replicate the design and the new pallet will perform the same regardless of where the corrugated board came from. This provides a higher level of continuity that doesn’t exist with wood.

Check out the ECT standards below:


 

Edge Crush Test

Maximum Load

Standard

32 ECT

40 lbs.

Heavy Duty

44 ECT

65 lbs.

Heavy Duty - Double Wall

48 ECT

80 lbs.

For more details on ECT, check out the ISO 3037:2007-03, Corrugated fibreboard - Determination of edgewise crush resistance.


Compression Test on Paper Pallet Cores

For our design, the compression test is very important because the strength of our corrugated pallet lies in the cores.

The compression test measures what pressure causes the core to crush by applying pressure to a paper core with either a motorized or pneumatic piston. This way, engineers get a very accurate measurement of the strength of our standard core.

Engineers repeat this test as they change the design and functionality of the cores.  


Testing Assembled Paper Pallets

Deflection Test for Paper Pallets

This is where engineers evaluate deflection across the pallet's horizontal frame while it is suspended. This tests the top deck's strength in the area between the runners. Engineers look for the least amount of deflection across the plane of the unsupported parts of the pallet.

This is part of Virginia Tech’s Center for Packaging and Unit Load Design’s process for determining the load capacity of the pallet. Specifically, this tests the overall functionality:

  1. Conduct a stiffness test
  2. Measure the deflection of the pallet under the test load at the end of the creep time
  3. Compare the deflection to the performance limit
  4. Adjust the test load to achieve deflection close to the performance limit
  5. Compare the test load to the maximum safe load (The smallest will be your safe load or load capacity)

There are ways to minimize this deflection. For example, engineers can change the spacing of the runners. If the runners are closer together, there is less of a chance for the top sheet to collapse.


Water Testing for Paper Pallets

Another important factor is how much moisture a paper pallet can take. Engineers test if a pallet's performance changes while holding the weight of a full load as it sits in water. The objective is for the top of the pallet and the product to remain dry and, in the instance of our design, for the cores to avoid wicking. If the top sheet remains dry, you can assume the pallet still can support the weight of the load as if it had never gotten wet to begin with.

For example, we conducted a test of a 1000 pound load in ¼ inch of water for two weeks. At the end of this time, the pallet had not collapsed and could still be lifted. The corrugated parts would flex and warp, but if allowed to dry, could retain shape. This isn't to say the pallet will "work" under these conditions, but will not collapse.

 

“Air Bladder Test” for Paper Pallet Strength, Stiffness and Durability

Prior to testing, engineers set an acceptable test limit of deflection for the pallet.

A pallet testing rig is set specifically to spread the pallet across the leakage point with a runner supported on a platform. The unsupported area between the runners is completely suspended. Above this they have an air bladder suspended on a rigid platen. The pressure from this air bladder acts as a general-purpose load uniformly applied to the pallet. The amount of deflection signifies the strength and stiffness of the corrugated pallet.

To give you some numbers for perspective: our three-runner corrugated pallet, with three cores per runner, is a standard 48 x 40 size. It was rated for 2500 pounds by Virginia Tech’s Center for Packaging and Unit Load Design.

Note: This air bladder test represents a more flexible load. A more rigid load, like a big wooden box, could hold much more weight. Since we endeavor to seek continuous improvement, recent research and development has yielded new updates to our current designs and are expected to test for even better strength and durability.


What about custom corrugated pallets?

Corrugated pallets are highly customizable. You can die cut them to fit your product or customize the top sheet into a tray to display your product. In addition, a custom-sized pallet may even provide a way to fit more product per truckload.

For a pallet manufacturer, it is imperative to get samples of these custom corrugated designs to the client as soon as possible while ensuring the updated functionality has been tested to meet the client's requirements.

The majority of the testing any pallet manufacturer does in-house will be for these custom designs. Because engineers keep component tests up-to-date, they can build custom designs pretty quickly to spec.

With corrugated, manufacturers have the capability to turn around a new pallet design in a day. A few days after that, they build a prototype. About 12 days later, pallet manufacturers can have a ready-to-test pallet sample at your facility where you can test it yourself under your specific circumstances and real-world conditions.


If you have questions about how corrugated pallets are tested or about paper pallets, in general. Let us know! Our team is always happy to help. CONTACT US HERE!

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