The Great Debate: Bolted Pallet Racks vs Welded

The bolted framework of the Empire State Building is similar to bolted pallet rack. The steel framework of the Empire State Building is bolted together. The integrity of the building was not affected when a ten-ton B-52 bomber crashed into its 79th floor in 1945[/caption]  

The Truth About Bolted Pallet Rack

It has long been accepted on our continent that welded pallet rack is stronger and more reliable than bolted rack, but this is simply not true. Europeans have accepted bolted rack for decades, but North Americans have been slow to catch on. Due to misunderstanding and misconceptions about bolted racks’ strength and reliability, North Americans have not been so interested in this bolted product until recently. But people are finally beginning to discard their old prejudices against bolted rack, and it’s more and more becoming the rack of choice for many corporations in the US and Canada. The welded rack myth, however, is still touted by rack manufacturers and many distributors. Bolted rack is, in fact, somewhat less expensive to produce, is considerably cheaper to ship, and has other advantages which I will get to in more detail later, but there are structural advantages to bolted rack that no one talks about; and this is because almost all the North American rack manufacturers produce only welded rack. For this reason, the illusion that welded rack is superior endures.

Why bolted rack is structurally superior

Think about a building. A building constructed of steel–like a giant warehouse, or a huge retail structure (like Walmart or Home Depot) or better yet, a skyscraper. These buildings are constructed of steel posts and beams. And 90% of these posts and beams are bolted together. Not just because its more cost efficient to bolt than weld (which is true) but because a rigid structure can break. Large structures need to move. Bolted connections allow the structure to flex and give. This is how large buildings can withstand the forces of nature–from the earth shifting to high winds. A solid rigid structure is more likely to snap if it can’t “go with the flow.” The same is true for pallet rack. Strangely, many people believe that welded rack is the better choice for seismic areas, when in fact it’s the exact opposite!

Don’t just take my word for it

Unfortunately, manufacturers are notorious for skewing the truth to promote their products in a good light and since I represent a manufacturer, I thought it would be a good idea to get the facts from an unbiased, real engineer not associated with our firm.* I contacted a reputable engineer who doesn’t know me from Adam (or Eve), and I asked for an interview. Ken Klimas, with Hillman and Miley Consulting Engineers in White Plains, New York was kind enough to spend some time with me discussing the misconceptions as well as the merits of bolted rack. Mr. Klimas has a BS & MS in Aerospace and Applied Mechanics from Polytechnic Institute of New York, is a licensed Professional Engineer in New York and New Jersey and has been involved in the rack industry since 1973. As a past employee of several rack manufacturers, he served as an engineering delegate to the RMI (Rack Manufacturer’s Institute) and helped author the RMI Specification. Currently, Mr. Klimas serves as one of six engineers tasked with reviewing rack manufactures product submittals for compliance with the RMI Specification and issuance of “R Mark” certification. Here is what he wrote:

Rack frames are basically vertical trusses. Classic structural analysis assumes its members and connections are subject only to axial forces, both tension and compression. Bolted frame connections present a closer analogy to this classic assumption.

The welding of bracing members to the column section introduces secondary bending forces in the frame members which are not generally considered in the frames analysis and capacity rating. Additionally, for open lipped “C” shaped column sections, bracing is usually welded only to the “lips” of the section. Forces induced in the bracing, which can be produced by rack out of plumbness, forklift impacts and seismic events, will apply bending moments to those column lips. The impact of these bending forces on the frame’s capacity is unknown and not accounted for in current rack analysis. Bolted bracing members are not attached to the column lips and will not transfer moments across the joint since connections are made with a single bolt.

Finally, if field repairs are required, bolted connections can be visually examined easily. While welded joints may appear acceptable, the connection may not be adequate and its reliability can be confirmed only with further testing.

  So there you have it from a racking expert–the truth about bolted pallet rack and why it’s structurally superior to welded. But even if you don’t care about that, there are plenty of other reasons to choose bolted pallet rack and they all save you money.

Cost advantages of bolted pallet rack

Bolted pallet rack is less expensive to make.

One advantage of bolted rack is the material cost–it is cheaper to manufacture bolted rack and even if you ship the rack assembled, it is still less expensive because the labor costs associated with welding are much higher. Additionally, if you need a galvanized finish (such as for a food or pharmaceutical environment), bolted rack is a great choice because the uprights can be manufactured from galvanized components and then bolted together. Welding galvanized steel is not the best or easiest course because welding a galvanized product releases toxic fumes and destroys the integrity of the finish. Welded uprights are galvanized after construction or re-dipped, adding to the cost.

Bolted pallet rack is cheaper to ship.

If you ship the rack KD (knocked down), the freight savings is significant and usually far outweigh the cost of assembly. A 40 foot truck filled with welded uprights maxes out at about 20,000-25,000 pounds where a truckload of KD uprights will hold about 44,000-48,000 pounds of product–meaning the welded uprights will cost at least twice as much to ship.

Bolted pallet rack is easier (and less costly) to repair.

One of the biggest advantages is that you can easily unbolt and replace bent or damaged bracing. With welded rack, you must cut off or torch off the damaged piece. (You must unload the racks before replacing damaged bracing for both.) If you have a bolted base plate, you can make column repairs in the field with merely a ratchet and band saw. Furthermore, there is definitely such a thing as a faulty weld–if the weld is bad, or has been damaged you probably won’t know it until it’s too late. On the other hand, you can see if a bolt is missing. And unlike a bad weld, which can threaten the entire system’s integrity, if a nut were to come off (highly unlikely), the bolt would still hold.

Bolted pallet rack has shorter lead times (time is money!)

Bolted rack components can be made in advance and if you opt to ship KD, your product is out the door. Even if you choose pre-assembly, the time it takes to bolt your rack together is insignificant compared to the welding process.

What if the bolts loosen?

Many people think the bolts can become loose and need to be tightened occasionally. This is just not true. All Next Level FlexRack™ locking bolts are designed with a serrated lock nut and once the bolts are tightened they are locked in place and will not come loose, even if shipped assembled. This is true for all bolted rack that is properly assembled. But at Next level, we have taken it a step further–our upright columns are designed so that an installer easily knows when the bolts are properly tight–no second guessing, ever. The columns are straight and the braces slip right in. Tightening the locking bolt creates the necessary tension that holds the brace and assures the installer that he’s good to go. This is in contrast to a wedge-shaped column which must be pried open to force the braces in–making assembly more difficult and time-consuming in addition to the possibility of giving a false sense of security about the tightness of the bolts.

Conclusion

So, what’s not to love about bolted rack? When you understand how bolted pallet rack really works and can see the economic savings and even some “green” advantages (fewer trucks equal less fuel), the answer is nothing! *Since writing this article, Mr. Klimas has been retained by Next Level (August 10, 2013) to review and consult on the development of our bolted rack program. Next Level FlexRack™ meets or exceeds the standards set forth by the RMI (Rack Manufacturer’s Institute), AISI (American Iron and Steel Institute) and AISC (American Institute of Steel Construction). To learn more about Next Level FlexiRack™ visit our website–and also feel free to call us or contact us by email with any questions.
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