Is There a Difference in Strapping Joint Strength?

rv-evans-joint-strength-strappingA question that we hear a lot here at the R.V. Evans Company when discussing strapping is; “Is there a difference in joint strength between strapping materials?” This is often times brought on by the difference in appearance between steel strap and polyester strap. Naturally, you would think that the steel strap would be stronger, but in reality, the joint strength of strapping material is very similar.

Sealless Joint types

Sealless joints can be made with manual or pneumatic combination tools for steel strap. Using interlocking keys, the sealless joints provide static joint strength equal to that of notch-type joints. The reverse lock sealless joint features one reversed interlocking key for added security in impact conditions.

Basic seal joint types

Notch Joint

The most commonly used joints for steel strapping are down and reverse notch. One way to lock strap ends is to cut, or “notch” the seal and the strapping it joins to form tabs at the edges. These tabs are bent down (down notch joint) or bent up (reverse notch joint). The strength of the notch joint comes from the mechanical interlock between the seal and strapping. Notch joints are typically used on waxed steel strapping in packaging and unitizing applications.

Crimp Joint

Another way to seal the ends of strapping is to press or “crimp” undulations into the seal and strapping ends. The strength of the crimp joint comes from the deformed seal creating high frictional forces. Crimp joints produce high static and dynamic joint strengths and are used on applications in which the strapped load is subject to severe impact.  This style of joint is used in plastic applications as well.

Friction Weld

Polyester strapping uses friction seals to weld the strap, eliminating the need for metal seals. Additional savings can be gained via polyester’s low strap cost per foot and through reduced product damage from seals or staining. 

Summary

In conclusion, there is no strength lost from switching between steel and polyester strap with a properly specified strap recommendation. It is a general rule that you can expect 75-80% of the listed joint strength of strap. This rule holds true whether you are talking about battery powered hand tools or pneumatic hand tools for strapping. Though different types of strap are designed for different applications, there are benefits to each type and the joint type used. Contact the R.V. Evans Company to ensure that you are using the right type for you specific application.

For more information visit our website at www.rvevans.com or call us at 1-800-252-5894.

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Sources: http://www.rvevans.com/Packaging-Solutions/PDF/signode_catalog_spd_1445.pdf

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