Storage rack interchangeability

You can mix and match rack components from different suppliers, but you must take precautions, as MHMS president Fateen cautions.

By -- Modern Materials Handling, 11/1/2000

Editor's note: One of the goals of the Materials Handling & Management Society is to enhance the proficiency of the materials handling professional. In this respect, MHMS president Sal Fateen has written in this space earlier on storage rack standards and safety, an area in which he personally has specialized in his own professional career. This month he continues covering rack safety issues, following his columns in the October and June issues.

At the inception of storage racks, different manufacturers created unique column punching and beam-to-column connections. Most of these companies patented this connection and it became their trademark. You could spot the different manufacturers by first recognizing their standard colors and then their specific connection.

Over the years, as patents ran out, new manufacturers found it easier to copy a recognized column punching and the connection, which facilitated securing orders, especially repeat business.

Not to be outsold, some of the original rack manufacturers, which had their own special column punchings and unique connectors, also developed the more "generic" connections. Thus, they too were able to fulfill the requirements of repeat business.

With the market place being inundated with same-type connections from different suppliers, rack components from different manufacturers have been combined in the same installation at different times.

Also, used rack suppliers found it very advantageous having a lesser number of rack "brands" to inventory. However, not knowing who manufactured which column and who manufactured which beam, these suppliers tend to mix the components, as they look the same. When doing this, it is important for safety reasons to ensure that the new rack structure will have an adequately rated design value for the application.

One condition of being a member of the Rack Manufacturers Institute (RMI) is that members are required to test their components, which includes the beam-to-column connections. The test results are used in determining the beam end "fixity" (how fixed the end is) and hence its capacity. Since each connection behaves differently based on its tolerances, the values obtained are different. And thus the same beam will have a different capacity when used with a different connection.

Connections may look similar and may fit, but they could also cause local distortions and stress concentrations beyond the design stress. The beam-to-column locking device of one brand may differ from another and some may not function when intermixed with a different brand.

Stability of the racks in the down aisle direction is wholly dependent on the beam-to-column connection. Any looseness due to different tolerances of the manufactured parts will reduce the carrying capacity of the system, especially when lateral loads are imposed, by moving equipment or by seismic forces.

When buying replacement parts it is essential to inquire and investigate all connections to ensure that they are capable of producing the rated design values. Otherwise, de-rating the capacities will be necessary.

For more information on MHMS, visit the website www.mhia.org/mhms or contact Bobbie Curtis, Executive Dir. of MHMS, by calling 704-676-1183. The address is 8720 Red Oak Blvd., Suite 201, Charlotte, NC 28217-3935.