Pallet Rack Load Distribution Guide
How to profile your loads for safe, reliable storage
Pallet racks are probably the most common warehouse storage equipment in the world, and for good reason: they’re safe, versatile and use the vertical cube of high-bay warehouses when correctly specified, loaded, unloaded and used within the rack’s tolerance. Load distribution–the way a load sits on your racks–is a critical factor for safe usage. Here’s how to get it right.
Types of loads and how to define them
Most racks you see have published their capacities for evenly-distributed loads. When racks fail, one of the primary reasons is overloading. Mis-loading is a form of overloading in many cases, so you must take the way your rack is loaded into account as you use it.
- Evenly-distributed (or universally distributed) loads are the ideal load and will utilize the full capacity of your rack beams. Rack beam capacities are almost always listed assuming even load distribution. When correctly specified, decking can help you reach evenly distributed load status, even if the load does not fully sit on both the front and rear beams. If a unitized, uniform load sits squarely on both sets of beams, it should reach the beams’ listed capacity ratings.
- Concentrated loads aren’t evenly distributed across beams or any rack decking. Oddly-shaped loads or loads that are too small to sit over both beams tend to be concentrated loads. Longer, heavy loads might be considered concentrated loads. Concentrated loads do not utilize the full strength of your rack beams.
- Point loads focus the weight on small feet or other “points.” When your load concentrates its weight on points, it’s a point load. Examples may be a wire bin with feet, or a specific component that does not lie on a large, flat surface. A pallet with individual feet is also a point load. Point loads cannot use the full beam capacity and should be evaluated for safe usage.
Read more: An Illustrated Guide to Rack Load Types
Loads of similar weights can dramatically differ in weight distribution, shape or profile–which has serious implications for rack integrity
Standard pallet rack specifications tell you that the listed capacity is for evenly distributed loads that sit on a pair of beams. Capacities are listed by the pair, not per beam.
If your load spreads its weight across the full surface of the support beams (or its decking), you can usually rely on the listed capacity. Point or concentrated loads on those same beams don’t share that rating. This is why you must carefully evaluate all the loads that could be placed on your rack system in advance. A load like a unitized and cross-stacked pallet of, say, full containers of liquids tends to be very heavy –but are safe to store at the listed capacity if your rack is specified to hold that weight. It’s evenly distributed and the calculation is relatively simple.
What if your load isn’t uniform and unitized?
Above: these two loads may weigh the same, but will exert different types of force on the load beams. Unbalanced, off-center, or oddly shaped loads require design and engineering work to safely store on pallet racks.
Bulk machine components in footed bins, or a long compressor that weighs 3,000 pounds–but is twice as heavy on one side. Even if these loads are palletized, their weight will alter beam capacities. Having a thorough understanding of all the load factors lets us build a safe, stable solution.
Load factors
- Weight: per unit and per bay.
- Weight: distribution of weight for the load.
- Dimensions: Height, width, depth of the load and the pallets to be used.
- Shape: is the load unitized? Does it vary in shape?
- Uniformity: will the rack hold the same items consistently?
- Pallet type: All pallets don’t affect the rack similarly. Is your pallet GMA, skids, slipsheets, etc. Two or four way entry? All the pallet factors count.
- Container type: If you’re using bins or containers, what type are they? Do they have feet? Do they sit flat on decks or across beams?
- Other factors: If any motion or friction will act on the rack (such as on a reel rack) or dangerous loading needs should be considered.
When you’re storing a very heavy, oddly-shaped, or nonstandard load, you should always know these details–and make sure your rack provider knows as well. A solution can be engineered for virtually any load if its profile is taken into account in advance. If your rack is expected to hold more than one type of load, specify it for the heaviest, difficult load it could host to help ensure its stability and integrity.
Read more: Pallet Rack Storage Ideas for Difficult Loads and Situations
The bottom line
The more you know about your load, environment and how the rack will be used, the better your rack design will be–especially when it comes to very heavy, unbalanced, concentrated or point loads. Profile the load before you specify your rack system for stable, safe and longterm operations.
Download our Pallet Rack Guide
Pallet rack enhances your warehouse and improve overall facility performance when correctly specified, laid out and installed for the right load in the right positions. Check out our guide to specifications, styles, accessories and applications with expert tips from our employee-owners. You’ll find quick, useful information on racks and how you can use them more effectively.
Download the guide today
Tags: warehouse storage, pallet racks, rack safety, RMI
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.