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As a Matter of Rack
With all the excitement surrounding automation, robots, controls, and AI, pallet racks might seem less important. However, in our opinion, storage rack equipment remains the backbone of most warehouse and distribution operations. While automated storage systems do integrate with rack structures, let’s focus on standard pallet rack.
Designing pallet storage racks involves many decisions that can significantly impact cost, lead time, flexibility, and safety. This blog aims to guide those on a ‘simple’ rack journey to make the best choices for their operations.
Pallet Rack Type Review
Single Deep, 1 pallet deep – most flexible and common; 100% selectivity.
Push Back, 2-5 pallets deep – more costly than double-deep, LIFO, no double-deep reach required, but lift needs to be capable of the push back force at given height.
Pallet Flow, 2-8+ pallets deep – full pallet or case picking, FIFO, replenishment aisle required.
Drive-in, 5-10+ pallets deep – consistent high pallets/SKU, most underutilized.
Cantilever – storing longer/larger pallet loads, typically with side-loader.
Cold Rolled Racking
Cold rolled steel uprights are the most common used, supporting loads < 2,000 lbs.
Cold rolled uprights are typically designed with an open “C” shape for the uprights and a closed tube with a step for the beams.
Typically, “tear drop” holes are punched into the upright to allow connecting beams without the need for any additional hardware.
Cold rolled upright metal thickness – 12-gauge minimum; 10-gauge more durable.
Light/lower capacity bays – 13 to 14-gauge, but much less durable.
Cold rolled upright column width: 3″ to 4″.
Welded uprights vs. bolt together uprights – welded more common and durable.
Structural Racking
Structural steel uprights are thicker and heavier, often using C-channel profiles.
Holes are punched into the upright, so beams can be bolted to the uprights.
Structural column upright width: 3″ vs 4″.
Hybrid Rack Systems
Structural uprights and cold rolled load beams.
Cold Rolled vs. Structural Decision
The key factors in making this decision include the pallet load weight, load size, seismic forces, level of lift truck activity, and lift truck driver experience.
Typically, the heavier the loads and/or higher the throughput (i.e. forklift traffic) of a facility the more structural is appropriate. The lighter the unit load and/or slower the operations the cold rolled would be acceptable. For reference, a pallet load is considered ‘heavy’ when greater than 2,500 lbs.
Cold rolled is less costly than structural racking, but there are savings over time from fewer repairs overall the lifespan of structural rack.
Cold rolled strength and durability can be enhanced by using 10-guage metal thickness, adding column reinforcements, and upright protection.
Applying coatings or surface treatments such as galvanizing or painting can protect the steel from corrosion, thereby maintaining its strength over time.
Uprights
For standard 48” x 40” pallet storage in Single and Double Deep Rack, 42” & 44” deep uprights are most common. Pushback rack tends to be 52” or 54” deep.
The taller the opening per level the less capacity a given upright can support, or the stronger the upright must be designed for the same weight.
Leveling is critical during the installation of beams, which is greatly impacted by the building slab and proper installation of uprights.
Upright brace designs include:
K-Brace
Features diagonal braces forming a “K” shape.
Provides strong lateral support and is commonly used in standard pallet racking systems.
X-Brace
Diagonal braces intersect to form an “X” pattern.
Offers excellent stability and is ideal for heavy-duty applications.
Z-Brace
Diagonal braces form a “Z” shape.
Used for specific structural requirements and can provide enhanced support in certain configurations.
Footplates
Footplate designs depend on the column loads, slab, seismic zone and application.
Typical thickness ranges from 6mm to 10mm.
Size should match the dimensions of the upright column, expected load capacity, and application.
Secured using anchor bolts to the concrete floor.
Avoid anchoring into joints around building columns.
Avoid anchoring into slab expansion joints.
Load Beams
Typically, the longer the beams the “deeper” the beams for the same capacity.
The taller the opening per level the less capacity a given upright can support, or the stronger the upright designed for the same weight.
Most common lengths: 96”, 108”; Tunnels: 144”
Most common height: ~3” for half bays or shelving in full bays, ~4” for full bays, and ~6” for tunnel bays. Heavier loads may require deeper beams in all applications.
Leveling is critical during the installation of beams, which is greatly impacted by the building slab and proper installation of uprights.
Maximum deflection for selective rack load beams is typically / 180.
Accessories:
Pallet load supports (pallet support bars, wire mesh decking).
Waterfall vs. internal waterfall decking – internal good for case/each pick levels.
Pallet stops if required, common in double deep racking.
Rack capacity signage per row.
Protection:
End of aisle protection and tunnels.
Upright column protection.
In rack sprinkler systems may be required based on local codes.
We could elaborate further, but you got the idea. There are numerous factors to consider when retrofitting or designing a warehouse plan. Pallet rack designs play a significant role in this process, and we hope this information proves useful.
If you have any questions or need assistance, please let us know how we can help.
Illustration below stresses the importance of a proper rack structure design – it’s like have a small car in every position in the racks!
