Our “Warehousing Basics” series continues with a look at a pallet rack system’s fundamental material: steel.
As an integral material to the world of modern buildings, steel is the material of choice of engineers and architects because of it’s strength, reliability, versatility and it’s sustainable profile. Steel is not only extremely sturdy; it’s flexible, enabling structures to withstand high winds and even earthquakes.
It’s no surprise that steel is the building block of choice for all pallet rack systems today. But different manufacturers use different kinds of steel for their pallet rack components; and while all manufacturers of racking systems state the permissible loads on a racking section and on a pair of beams, sometimes this information is not sufficient for optimal decision-making. What characteristics about steel should you pay attention to while choosing a pallet racking system?
The key terms to understand regarding steel performance characteristics and how they affect your racking system are tensile strength, yield strength, grade, and gauge. When the values of these elements are matched to your system needs, the chances of pallet rack failures are greatly reduced.
Steel Tensile Strength & Yield StrengthThe term tensile strength refers to the amount of tensile (stretching) stress a material can withstand before breaking or failing. When a tensile stress is applied to a piece or bar of steel, it will stretch. Up to a certain point, the metal will revert to its original length. As force is incrementally applied, the bar will continue to return to its original length until a stress sufficient to cause permanent deformation is applied. The stress required to cause permanent deformation is known as the yield strength. When this stress point is reached, the bar’s cross-section will decrease and with further increasing stress the steel bar will rupture. The stress value at which rupture occurs is called ultimate tensile strength. The unit of measurement for ultimate tensile strength and yield strength values are expressed in tons per square inch, pounds per square inch or thousand pounds (KSI) per square inch.
Steel GradeAccording to the World Steel Association, there are over 3,500 different grades of steel, each encompassing unique physical, chemical and environmental properties. Different types of steel are produced according to the properties required for their application, and various grading systems are used to distinguish steels based on these properties. Steel grades to classify various steels by their composition and physical properties have been developed by a number of standards organizations. SAE International is one standards organization that maintains a numbering systems for steel grades. While SAE value are the most common, other countries have their own, including JIS (Japan), DIN (Germany), and GB (China).
The thickness of a sheet of metal is measured in a unit known as gauge. Counterintuitive to the way we normally think, gauge is determined on a retrogressive scale, meaning that the higher the gauge is the thinner the sheet of metal is. Thus, a sheet of 10 gauge steel is thicker than a sheet of 12 gauge steel, which is thicker than a sheet of 14 gauge steel, and so on. Pallet rack manufacturers offer a variety of gauges to accommodate different configurations and product loads.