Understanding Upright Load Capacity

Understanding upright load capacity is key to avoiding safety risks in your warehouse.

The configuration of your pallet racking controls the strength of your uprights.

Considering how commonly many users reconfigure their beams, it is important for them to realize that they may be effectively weakening their uprights from what they were originally rated for.

We want to shed light on the subject, so you can anticipate the ramifications of your racking’s configuration.

Fundamentals of Upright Capacity

Unlike beams, which have fixed capacity ratings, uprights are severely weakened if the spacing between beams is too great. Upright load capacity charts are primarily built around this factor, called “Maximum Unsupported Length” (or HbL). It all relates to bending (or buckling), easily overlooked but crucially important.

An upright is made of two vertical posts, tied together with cross-struts. A steel vertical post can be extremely resistant to a perfectly vertical load, but if it is too tall, without side support, it will begin to bow. Add the unexpected horizontal force, such as a bump from a forklift, and that bow becomes a bend. Once a bend occurs, the upright is compromised and cannot achieve it’s full strength.

This potential weakness can be compensated for with more robust upright posts.

However, the most effective way to assure uprights retain sufficient capacity is by placing beam levels relatively close together. For example a 36″ to 60″ distance (top-of-beam to top-of-beam) is reasonable. Most uprights will perform well under normal loads.

A Quick Strategy

Considering vertical loads only, the lowest part of an upright always carries the most load because it is transfering all the weight from above, down to the ground. These portions are also more susceptible to forklift damage. Knowing this, it is smart to incorporate shorter beam heights (hence shorter unsupported length) near the floor.

Upright Load Capacity Charts Are Manufacturer and Model Specific

Unfortunately, there is no one chart to tell you the fixed capacity of any given upright. Each manufacturer creates their own upright capacity charts, with figures validated by engineers.

Reading Upright Load Capacity Charts

Before reading the charts we need the:

• Upright Manufacturer & Model – this gives us the post type and key dimensions

• Maximum Unsupported Length (HbL) – measuring in field or as specified in design

1. Upright Manufacturer & Model

Usually marked on the upright, this informs us of key measurements such as post width and depth, and steel gauge. This also tells us which chart to reference.

2. Maximum Unsupported Length (HbL)

The Maximum Unsupported Length could be the distance from floor to top of first beam or the distance between any adjacent beam levels. Be aware that an upright does not need beam support on both sides (see diagram).

In theory each upright in your racking system could have a different HbL and corresponding capacity. Often we break a system into section groups, where beam levels and components are uniform. In this way, we can find the most extreme HbL within a group and determine whether the lowest possible capacity is sufficient for the highest possible load.

3. Reading the Upright Load Capacity Charts

Upright capacity charts vary, but often represent upright models in column, often going from smaller to larger dimensions left to right. Manufacturers may have several post types (although not nearly as many as beam profiles). Carefully inspect your uprights specs to determine the right model.

Unsupported length is often represented on horizontal rows, going from short to long length, top to bottom.

With these two figures, we arrive at a weight capacity for a single upright.

Notice a few things about this ficticious, example chart. The upright post dimensions are usually the key information differentiating the upright models. Moving left to right, the upright profile typically is more robust, and the capacities also become greater. Moving top to bottom, the HbL becomes longer, weakening the upright, and the capacities become lower.

CAUTION: Upright capacity charts are not universal. Manufacturers have many profile lines, and capacities vary, even among uprights of the similar dimensions. Profiles may be differentiated based on other factors in addition to post width, depth, and steel gauge. 

Extra Strength

What if you need a stronger upright, but need to maintain a long unsupported length of post? There are ways to “beef” up an upright. Manufacturers can make double-posts, or reinforced posts, that add stiffness and increase capacity. Usually these are fabricated at the lower portion of the upright, since the lower portion almost always is subject to the most forces.

Summary

Upright capacity charts are not as straightforward as those for beams due to the variability of Maximum Unsupported Length. For accurate capacities, it is important to use measure components correctly and reference manufacture specific charts. Remember, each manufacturer creates their own charts.

Did you find that helpful? We’ll be following this article up with one on reading beam capacity charts. If this all seems like too much engineering, no worries. We read the charts so you don’t have to.