Strapping Break Strength vs. Tensile Strength
Those who work with strapping know that there are two main types of strength to understand, which are break strength and tensile strength. Each play an important role in the security of your strapping, and therefore, the stability of your unitized load. Knowing how to measure these strengths and how to differentiate them is crucial if you want to apply your strapping successfully.
We’re going to go over each type of strength to help you gain a better understanding of where each fit into your packaging strategy. Keep reading if you want to learn more about break strength and tensile strength for strapping.
The break strength of a particular strapping is the measurement of tensional force required to break the strap. This is measured in pounds or Newtons, but more commonly in pounds.
A strapping’s break strength is affected by the width and gauge of the product, or the cross-section. This means that the break strength will increase as the gauge of your strapping increases. It will also be different based on the material of your strapping (steel, polyester, or polypropylene).
Most packaging professionals use the break strength as a guide to measure their applied tension because it is much easier to work with when determining the working range of your strapping. We’ll cover the working range of strapping after we talk about tensile strength.
The tensile strength is specific to each type of material, and it is derived using the break strength of your strapping. To find the tensile strength, you’ll take your measured break strength and divide it by the cross-section, or the width and gauge of the strapping. The final measurement is represented in pounds per square inch (psi). You can see an example of finding the tensile strength below.
Break Strength = 1,500 pounds
Cross Section = ½” by .020 = .5 x .020 = .010
Tensile Strength = 1,500/.010 = 150,000 pounds per square inch (psi)
The tensile strength is important because it allows you to compare the strength of the strapping materials themselves without a reference to the dimensions of the sample.
Working Range of Strapping
Although a strapping might have a high break strength or tensile strength, the working range of the strapping will limit the actual applied tension. Applied tension is measured in pounds and represents the actual tension given to the strapping during application. The applied tension you use will likely be a fraction of the break strength of your strapping. It also varies drastically between the different strapping materials available.
The working range of strapping determines how tightly the strap can be applied in order to perform to the best of its ability. This is typically considered the point where elongation has occurred, but not enough elongation to the point of no recovery. Another definition of working range is, “the range of applied tension where the minimum may be zero and the maximum is the highest level of tension that can be applied in actual situations.”
The working range of strapping is affected by the package, the types of seals and joints created, and the tools used to apply the strapping. Certain strapping tools limit the amount of tension that can be applied, so that will lower the working range of your strapping. Other tools can tension strapping to higher levels, so you’ll have to pick your supplies carefully to get the desired outcome of your strapping.
The strength of the sealed joints will also limit the working range. For example, if the break strength is 900 pounds, but the joint strength is only 600 pounds, the working range won’t be higher than 600 pounds.
The working range is also limited by the highest amount of tension the packages can handle. This means that the maximum working range is equal to the maximum tension of the packaging. If you apply strapping with a higher tension than what the packages can handle, you will crush the unitized containers and potentially damage products before they reach the customer.
Damaged products cost companies a lot of money, so you’ll want to do everything you can to get the applied tension within the correct working range. Any strapping applied within its ideal working range will product the products effectively in transit without damaging them or losing its hold.
To wrap up this article we’re going to highlight a few things for you to consider about different strapping materials.
- Steel strapping offers twice the amount of tensile strength as the strongest plastic strapping.
- Increasing the width and gauge of strapping with a lower tensile strength can yield a higher break strength than that of a higher tensile strength strapping.
- Strapping failure is often due to the application of the strapping rather than the strength.
We've got a huge selection of strapping supplies and tools here at The Packaging Group. Feel free to browse our strapping inventory to find quality products from Signode and other trusted manufacturers. We have both hand-grade and machine-grade strapping available.