Designed and engineered to store very long loads — such as building materials including piping, lumber, or bar stock — cantilevered storage rack structures incorporate central, vertical columns from which horizontal arms project perpendicularly on one or both sides, with no vertical column connecting the arms on the aisle face. Load placement should be down-aisle (or parallel to the load access face of the rack) on two or more arms designed to hold a specific, evenly distributed weight. To ensure the integrity of the storage system, it is critical that the load, for which the cantilevered rack structure has been designed, is placed on the arms in a uniform, symmetric manner.
For example, for a load that measures 180 inches and weighs 3,000 pounds, the racking design might incorporate three arms spaced 60 inches apart and each arm supporting a 1,000-pound load. To prevent overloading of any of the arms or columns, the forklift operator must place the load to ensure 30 inches of overhang (half of the column center-to-center distance) off the ends of the two outermost arms. This ensures a properly balanced load — side to side — across the rack arms.
Uniform Load Placement Best Practices
Uniform load distribution across the arms should always occur when placing a load into cantilevered storage rack. This is best practice, regardless of the number of arms (two, three, four or more) utilized to hold the stored items. Positioning the load too far to one side or the other of the outermost arms will place a disproportionate amount of stress upon the exterior arm(s). That could cause overloading and failure.
To avoid such a situation, it is critical to train forklift operators to place the load symmetrically on the cantilevered rack arms. Further, they should store a load only within the section of cantilevered rack designed specifically to hold it. That determination will be made by the professional rack engineer who designed the system based on a variety of details about the products to be stored, including sizes, dimensions, weights, and degree of rigidity or flexibility. Loads that are more flexible may need more arms to support them. Otherwise these types of loads may cause undesirable side pressure on the arms.
If the racking’s design is capable of holding different loads in specific bays of the system, train operators to recognize these individual product storage locations. Some operations use a color coding or alphanumeric labeling system. These systems identify each load and its corresponding storage location within the cantilevered racking by providing a visual cue for forklift operators.
Refer to Cantilevered Storage Rack LARC Drawings
Sometimes an operation will need to store a new load type with dimensions, weight, or other characteristics outside the scope of the cantilevered rack’s original design. Before making any changes to the rack’s configuration, it is important to consult the system’s load application and rack configuration (LARC) drawings first. The LARC drawings will show the different arm configurations and load capacities that the system’s components can safely support.
If the rack system’s owner desires a configuration different than the options shown in the LARC drawings, they should consult with the original rack manufacturer (preferably) or a qualified rack design engineer. These professionals can re-evaluate the capacity of the system and add new documentation to the package of LARC drawings. Making significant modifications to the structure’s configuration such that load capacities change necessitates updates to load plaques.
Want to learn more about the safe design, manufacture, and installation of cantilevered rack systems? Download RMI’s ANSI MH16.3 Specification for the Design, Testing and Utilization of Industrial Steel Cantilevered Storage Racks.