Our rack engineers are often asked by rack users if it is safe to remove bottom beam levels in a pallet rack system to store double-stacked pallets on the floor. UNARCO informs users that this practice is not safe because the capacity of the frame is dramatically decreased. Without hesitation, the rack user then asks, “How about if we just remove the beam in every other bay? Then we still have the same column span.”
The answer to this question is, “No!” The reason the answer is No lies in the fact that when every other beam is removed, one of the fundamental assumptions that is used to compute the frame table capacity value is undermined. The rack frame capacity tables are developed with the assumption that a column span is framed by two beam connections at the top and either a base plate or two beam connections at the bottom. When every other beam is removed, half of the top-span restraint of the column is gone and the frame model is no longer valid which voids the frame table capacity value. The practice of removing every other lower beam span in a pallet rack system is no safer that removing every other first story beam in a multi-story building.
Possibly the biggest and most regrettable mistake rack users make is to overlook the damage that the outrigger of a forklift truck can do to a pallet rack column. We see many cases where a significant percentage of warehouse aisle columns have been severely damaged due to forklift “bumps” during the first year. No matter how high your forklift driver accuracy is, history tells a consistent story of column damage from outrigger abuse even in some of the safest warehouses in America.
The best time to consider this issue and avoid this mistake is when you purchase the pallet rack and plan your warehouse layout. There are many ways to address this problem and probably the most obvious method would be to make sure the aisles and bays are wide enough to accommodate normal forklift activity. Because of site constraints, it is not always possible to keep the uprights out of harm’s way and we recommend that you add a “straddle” or outrigger guard on the aisle columns for extra insurance. Another simple precaution that prevents front column twist when the outrigger grazes the front column is to add a second anchor bolt. If the column is allowed to twist, damage to the column above the straddle protector can occur and easily defeat the purpose of the guard. It is not too late to check existing rack and make sure all anchors are installed properly and install an additional anchor on aisle upright columns.
You may be thinking, “I wish I had read this blog BEFORE I bought my pallet rack.” If this is the case, there are many ways to address this problem even after the rack is installed. Probably the best method is to add bolt-on, retrofit straddles that can do the job. A few dollars per column for a retrofit guard is a whole lot better than the cost of a repair piece or the replacement price of an upright frame. The straddle protector retrofit guards are easy to install with no disruption to warehouse operation. It is always a good idea to be proactive when it comes to warehouse safety and maintaining the pallet rack is as important as the initial design. If the current rack does not have proper equipment to ward off forklift damage, it may be a good time to address the abuse caused by daily operations and install some type of column protection.
As a pallet rack manufacturer, we are constantly asked to design rack systems of every magnitude. We have a large number of people who send in orders which would seemingly not require any engineering. However, there is one simple design principle that rack purchasers often overlook. Probably the easiest principle of pallet rack design in a complicated world of equations spanning from Phi and Lx is the height to depth ratio rule. The RMI defines the height to depth ratio for a single row of pallet rack to be “the ratio of the distance from the floor to the top beam level divided by the depth of the frame.” For the junior rack engineers out there, this simply means that a 24” deep upright should not have a top beam level higher than 144” (six times the depth). This easy fifth grade ratio computation is a welcome and simple approach to keep pallet rack from toppling over but is not as publicized as it should be.
With over fifty years of manufacturing experience, UNARCO Material Handling has partnered with the best and brightest companies in nearly every industry. Our engineering and manufacturing teams have worked with the majority of the current Fortune 500 list and helped develop some of the most advanced distribution networks in America. We are launching this blog to communicate on a number of topics in the world of pallet rack and warehouse storage solutions and weigh in with our views. After fifty successful years and as an industry leader, our views should be of some relevance in helping our past, present and future partners.