Do you know the accepted column verticality tolerance for pallet racks ? Understand the difference between out-of-plumb and out-of-straights?
Montreal’s Olympic Stadium, the Tower of Pisa and the Parliament Clock Tower “Big Ben” in London have something in common. These famous buildings lean. The Olympic Stadium leans intentionally by about 45 degrees, the Tower of Pisa by 3.99 degrees and Big Ben leans by a mere 0.26 degrees. If these towers were pallet racks, would they conform to standards?
US and Canadian standards are quite straightforward when it comes to pallet racking stability. The tolerance when the rack is loaded is 1/240, which amounts to ½ inch over a height of 10 feet or 12.5mm over 3m (this holds true for both front-to-back and side-to-side leaning). This is equivalent to less than 0.24 degrees of tilt. Anything above this is considered out-of-plumb and does not conform to standards.
The Tower of Pisa’s non-conformity, for instance, is understandable since it very clearly leans; anyone would doubt its stability. However, most of you probably didn’t even know that “Big Ben” leaned. It’s not even noticeable to the naked eye, yet it falls outside of tolerance. Therefore, it is recommended to use electronic levels to inspect an upright’s inclination because they see things our eyes can’t.
The same column verticality tolerance is used for pallet racking stability. While out-of-plumb racks are ones that are straight but lean, out-of-straight racks are ones that have unintended curving. Regardless of the reason for the curvature, the same tolerance of ½ inch over 10 feet (12mm over 3m) still applies. This equates to a curvature of 1/20th of an inch per foot. Again, electronic levels help immensely in measuring the pallet racking stability.
Some examples of what can cause Out-of-Plumb or Out of Straight situations:
- Beam height changes or alterations.
- Type of beam connection used.
- Insufficiently tightened bolts at time of installation.
- Impacts with lifts or pallets, common at base of upright.
- Overloading the beams and rack.
If your pallet rack is out-of-plumb or out-of-straight, it must be unloaded and corrected to conform to standard column verticality tolerance. Look for the cause or the damage affecting your racks to lean or curve to better correct the issue and prevent it from occurring again.