So many customers spend too much time thinking about Pallet Rack Upright height, depth and Beam lengths. They often overlook Pallet Rack Beam capacity. For many, this is not an issue (as what they will be storing is relatively light) but for certain customers in certain industries it is a major factor that needs to be considered when sourcing Pallet Rack Beams.
Just as Pallet Rack Beams come in different lengths, each Beam length also comes in multiple capacities. The Pallet Rack Beam capacity, is generally calculated as a combination of the Beam length and the Beam height. For example, an Interlake 96″ long Teardrop style Beam that is 2.75″ high has roughly a 2,440 lbs. capacity. The same 96″ long Beam length in a 4.0″H face has a 5,370 lbs. capacity. Quite a difference! It is also important to remember that Beam ratings are calculated as an evenly distributed load.
A mistake we often see is a customer who purchases Beams on cost alone with no regard for related capacities. There are a couple of industries that immediately come to mind who have uniquely heavily concentrated loads… roofing, tile and feed & grain industries.
Case Study
We recently had the owner of a large feed & grain business in Lancaster, Ohio contact us about some Pallet Rack for one of their retail operations. We expressed our concern for the capacity of the Beams being purchased (due to weight of skids being stored) but in the end they purchased our least expensive 96″L Beam at 4,100 lbs. capacity per pair. Prior to pick-up, we once again mentioned that we did not think that this Beam would be adequate for the application, but they insisted it would.
A week or so after installation, we received a call (and subsequent photo above) with their concern for the way the Beams were deflecting with two, fully loaded skids on them. Note the excessive deflection (or bowing as it is commonly referred as) in the middle pair of Beams. We asked the customer to perform a simple deflection test.
We asked them to run a string from one side of Upright to the other and measure the “deflection gap” at the very center.
So what is an acceptable level of deflection on a pair of Beams?
It is important to note that some deflection is permissible, but not much. The maximum amount of deflection that is allowed in pallet rack beams is governed by the RMI-Rack Manufacturers Institute as well as ANSI Standards. The RMI deflection limit for a normal pair of Pallet Rack Beams is L/180 or the span divided by 180. A 96” Beam will have a deflection limit of 96/180 = 0.533”.
In more simple terms… Divide the length of the beam (from the inside of the columns) by 180. If the 96″ Beam length is divided by 180 for a result of .533, or about a ½ inch. If the deflection gap is equal to or greater than ½ inch, the beam is considered overloaded and unsafe.
Once they performed this simple test they realized that the Beams that they purchased were considerably under capacity for the loads they were storing.
What was interesting was they went from the lightest Beam we stocked at the time to the heaviest (8,560 lbs. cap. per pair). Unfortunately, we were unable to take back the overloaded Beams they never returned to their original shape.