Do you know the difference between an out-of-plumb and out-of-straight rack upright?
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 relatively 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 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 can help us see and measure 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 and lasers help immensely in evaluating out-of-plumb and out-of-straight issues on pallet racks.
Some examples of what can cause out-of-plumb or out-of straight situations are:
- Beam height changes or alterations
- Type of beam connection used
- Insufficiently tightened bolts at the time of installation
- Impacts with forklifts or pallets commonly found near the base of uprights
- Overloading the beams and racks
If a pallet rack upright is out-of-plumb or out-of-straight, it must be unloaded and corrected to conform to the accepted tolerance. Always 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.
Damotech offers complete conformity inspections performed by engineers specialized in pallet racking and their safety.