What you need to know about clearances in the warehouse.
Have you ever felt uneasy when someone gets a little too close to your personal space? In our day to day lives, there are no strict rules about what is too close for comfort. Some people go through life blissfully unaware that they make people uncomfortable by intruding on their space. Pallet racking clearance, however, has more specific rules and guidelines that dictate just how close they can get to any pallet rack component.
Pallet racks are structures designed to be self-sufficient and freestanding. Building components (i.e., walls, building columns, beams, etc.) are not typically designed to support additional loads from neighboring structures. Connecting pallet racks to building components allows forces to transfer between them, which could have unintended consequences. Unless a structural engineer specifically designed the structures to interact, it is not recommended to connect pallet racks to building components.
Figure 1. Example of a pallet rack connected to the building structure (not recommended)
Ensuring that pallet racks are not connected to a building component is not enough. To prevent contact between building components and pallet racks through vibrations (caused by operation, impact or a seismic event), pallet racks should have a minimum clearance from the building's structure. Current standards call for a minimum pallet racking clearance equal to:
- 5% of the racking height with the building in the down-aisle direction
- 2% of the racking height with the building in the cross-aisle direction
The hatched area in Figure 2 represents the required clearance between a rack and the building structure.
Figure 2. Plan view of building/racking structure separation
In the event of an impact or seismic activity, a pallet rack could damage a building component if it’s too close, compromising its load carrying capacity. Figure 3 shows an example of an upright that does not respect the recommended pallet racking clearance.
Multiplying the height of your pallet rack times 0.05 for down-aisle or 0.02 for cross-aisle directions will allow you to determine the necessary clearance for your pallet rack. For example, if your pallet rack is 240 inches tall (20 feet), the required clearance would be 12 inches (5% of 240) in the down-aisle direction and 4.8 inches (2% of 240) in the cross-aisle direction.
If you are certain that the topmost beam elevation will not be modified over time, the topmost beam height can be used instead of the rack's height to determine the required pallet racking clearance.
Figure 3. Upright in close proximity to a building column
Figure 4. Minimum down-aisle and cross-aisle clearances
Other recommended clearances
Aside from pallet rack and building component clearances, there are other clearances to keep in mind in your warehouse. Storing pallets within the recommended clearances will reduce damage to pallet rack components and ensure safe and efficient operation.
Minimum clearances for proper handling and protection of pallet racks are recommended. Required general clearances for single deep/double deep pallet racks are listed in Table 1 below.
Table 1. Recommended clearances for single deep and double deep pallet racks
|
# |
Clearance |
Recommended space |
|
1 |
Between two loads and between one load and the upright frame |
At least 3 in. |
|
2 |
Between the load and the overhead beam |
At least 3 in. (and more for top levels safe handling) |
|
3 |
Pallet overhang |
Between 2 and 4 in. over the front and back beams |
|
4 |
Between two loads in back-to-back cells |
At least 4 in. |
|
5 |
Service aisle |
|
|
6 |
Main aisle |
According to the lift truck manufacturer’s recommendations |
|
7 |
Between load and an automatic sprinkler system |
At least 18 in. |
|
8 |
Walkways |
|
As shown in the table above, to avoid damage or unintended impacts with rack components, pallets should have a minimum clearance of 3 inches between two pallets or one pallet and the upright frame. Lift truck drivers should pay close attention and make sure there is adequate space on both sides of the pallet when placing them. Figure 5 shows a pallet stored directly against a column. Disregarding the recommended clearances can result in damage to pallet rack components.
Figure 5. Improper pallet storage
Pallet racks are efficient structures for storing large quantities of merchandise, but standards must be followed to ensure they are used safely and remain free of damage. Following the recommended clearances from building components and other objects is an Important one.
