The importance of ensuring the strength of a box for shipping cannot be understated, especially if you've experienced receiving damaged goods due to inadequate box strength. But how can we accurately measure box strength and what steps can be taken to guarantee the appropriate box strength for the items being shipped?
We may have to dive in history to answer the above queries
For a significant period, the regulatory authority responsible for overseeing the truck and rail freight sector relied solely on the Mullen Burst Test as the benchmark for evaluating box strength. This test was widely recognized as the industry standard, and no other options were available or utilized.
By utilizing a pressurized diaphragm, the Mullen Burst Test assesses the maximum amount of pressure, measured in pounds per square inch, that a corrugated box can withstand before collapsing. A helpful comparison for this method would be determining the amount of force required to punch through the side of a box. In essence, the stronger the box, the more force it can withstand, plain and simple.
In 1990s, a change was taking place
Although the Mullen Burst Test ratings underwent modifications, a few individuals observed that the vertical tensile strength of the boxes remained robust. This implied that the boxes could still be stacked to the same height, bearing the same load, provided that the contents inside were stationary and did not exert pressure on the sidewalls. In essence, the corrugated material may burst more readily, but it would not collapse or be crushed.
ECT - Edge Crust Test
Subsequently, the National Motor Freight Traffic Association (NMFTA) revised the industry standard to incorporate the Edge Crush Test (ECT) method. This test evaluates the strength of corrugated boxes in a distinctive manner, unlike the Mullen Burst Test, which relied on the "punch strength" of the material. Instead, the ECT measures the amount of weight that can be placed over the edge of the corrugated material before it collapses. This can be likened to determining the maximum weight a box can support before being crushed, much like sitting on it.
The NMFTA recognized that the crucial aspect in shipping boxes is their ability to be stacked to a certain height. The ECT method proved to be more relevant to this aspect, as it measures how much weight a box can withstand on top of it before collapsing. In essence, ECT provides a straightforward metric that determines the maximum weight a box can carry without being crushed, making it more directly linked to the stacking height of the boxes.
Which test is relevant when?
When packaging goods that will remain stationary during transportation, without exerting any lateral pressure on the box's sides, and will undergo minimal handling and transit nodes, the ECT becomes the most applicable metric. In this scenario, the primary concern is the box's stacking strength, and the critical aspect is determining the weight capacity of the box before collapsing, as represented by the ECT measurement.
If the items being shipped are prone to movement inside the box, such as ball bearings, plastic beads, and round fruits, or if they exert pressure on the sides of the box, the Mullen Burst Test becomes more relevant. Additionally, this test is more appropriate for boxes being shipped along a route that involves multiple handling and transit points, such as loading and unloading onto a truck, rail car, and shipping container. The Mullen Burst Test accounts for the box's strength when under lateral pressure, which is a vital consideration for boxes undergoing repeated loading and unloading and handling at different points along the shipment path.
All the boxes supplied by Logipack Technology are tested for ECT and Bursting strength to ensure the customer requirements of performance are met. We even go ahead and suggest the design update in your boxes based on the applications.
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