More is More: Estimating Pallet Rack Upright Capacities
Racks with less space between beams tend to have higher capacities, but this must always be evaluated for load characteristics
There are two types of pallet rack capacity to take into account: beam and upright. Getting those capacities right is a critical factor in safe, efficient rack operations, so understanding why they are very different numbers is important.
Beams are simple…
To calculate beam capacity, it’s a simple number. Almost any beam sold has a standard capacity per pair. To be clear, that means that this rack beam has 5,080 pounds capacity per level (two beams) not for each beam. There are rules for load distribution (it has to be evenly distributed), but essentially that’s a rather easily understood number. You can have two pallets of up to 2,540 pounds each on that beam level.
…But it’s more complicated for uprights
Upright frames depend on the vertical space between beams, also called the “unsupported span”. Essentially the more air between levels, the lower the capacity of the rack due to fewer beams, which act as horizontal ties between the uprights. This makes the rack structurally more stable and capable of holding more weight.
If you have a very tall light load, the distance between beam levels can be greater, but you should always have this evaluated. For dense, heavy loads, you tend to need tighter beam spacing. I
Above: in this drawing, the left rack bay tends to have heavier capacities than the right bay because it has more beams and less vertical space between them.
All rack manufacturers post their upright capacity tables online, or provide them in printed form. The tables compare the type of upright to the vertical beam spacing, and tell you how much the frames can hold in total. This is pretty much independent of what the beams can hold, but will obviously need to be stout enough to carry fully loaded beams.
Every rack is a little different
All major manufacturers publish upright capacity tables that compare vertical beam spacing to the upright type. While a listing of every potential rack upright capacity table out there would take days to read, in general you can find these on manufacturer websites, or you can contact any rack vendor for assistance locating this information. You’ll need that table to compare to your situation for any rack installation.
Below: Steel King SK2000 upright capacity table. Most tables will read something like this one:
Scott Stone is Cisco-Eagle's Vice President of Marketing with more than thirty years of experience in material handling, warehousing and industrial operations. His work is published in multiple industry journals an websites on a variety of warehousing topics. He writes about automation, warehousing, safety, manufacturing and other areas of concern for industrial operations and those who operate them.