Racks in your warehouse will invariably get damaged at some point. Although most rack damage happens because of forklift impacts, there are many other potential threats to the structural integrity of you racking system in a typical warehouse operation. 

Oftentimes damage is only cosmetic and nothing needs to be done if the rack passes inspection.  But how do you know when racks need to be unloaded and repaired, or completely torn down and replaced?  There are actually some industry guidelines that you can go by, set by the Rack Manufacturer’s Institute (RMI).

RMI Standards

The Rack Manufacturer’s Institute has two different calculations related to pallet rack structural components: the “Out-of-Plumb” ratio and the “Out-of-Straight” ratio. The higher the number on either of these two ratios, the more susceptible your racking system is to structural failure.

Out-of-Plumb Ratio

When a rack is “Out-of-Plum,” it means it is leaning beyond a certain acceptable level. RMI defines the Out-of-Plumb ratio as this:

“The maximum horizontal distance (inches or millimeters) from the centerline of the column at the floor to a plumb line that extends downward from the centerline of the column at the top shelf elevation divided by the vertical distance (feet or meters) from the floor to the top shelf elevation.”

The maximum Out-of-Plumb ratio for loaded pallet racking is ½ inch for every 10 feet of height. When the ratio exceeds this number (1/240, or .004166), the racking section must be unloaded and re-plumbed to prevent further damage and avoid potential collapse.

Out-of-Straight Ratio

A rack that is “Out-of-Straight” means that it is bowed beyond RMI standards. RMI defines the Out-of-Straight ratio like this:

“The maximum horizontal distance (inches or millimeters) from the centerline at any point on the column to a plumb line from any other point on the column divided by the vertical distance (feet or meters) between the two points.”

The Out-of-Straight calculation is identical to that for the Out-Of-Plumb ratio. For every 10 feet in height, a loaded rack cannot exceed ½ inch from the centerline.

There are several factors that can cause Out-of-Plumb or Out-of-Straight issues in columns. Such issues as forklift impact, beam height adjustments, faulty connections, and pallet impact can all affect the structural integrity of your system.

Rack Inspection

It’s a good idea to inspect your racks on a regular basis, and after any forklift impact or other event that could result in potential damage.  The Out-of-Straight and Out-of-Plumb ratios can be checked with laser lines, long levels or plumb bobs.

Any racks that are leaning or bowed beyond the acceptable ratios should be unloaded and either adjusted or replaced, depending on the extent of damage.   Any beam connectors should also be inspected in case the rack misalignment has caused bends or other deformities.

Of course, you can always call the trained professionals at Raymond West to inspect your racking systems. Our racking experts can quickly inspect your racks and give you a green light, or suggest what mitigation steps might be necessary to correct any damage.