Storage racks are an essential part of any warehouse, their layout and design a considerable undertaking no matter what a facility’s size or purpose. As systems become more complex to handle growth in e-commerce and a generally faster-paced business environment, they are also taking on a higher profile when it comes to safety and efficiency. A poorly designed rack system can fail on many fronts, including potentially causing worker injury if it can’t properly support the items it’s designed to hold. A well-designed system, by contrast, can protect workers from the danger of falling items or rack collapses and also help streamline the flow of products through the facility.
“[Storage] racking went from being almost a commodity to now being highly engineered,” observes Arlin Keck, corporate R&D engineer for rack manufacturer Steel King, emphasizing worker safety as the main reason for the change. “Everything has evolved over time.”
Today, racking system designers must take into account a range of factors when planning a system, including the geographic location of the project, maximum pallet size and the weight of the items being stored, facility layout and design, and the customer’s preferred style or type of racking. Doing so allows designers to create the best possible system for the operation.
Here’s a look at some key considerations to keep in mind when designing or redesigning your storage rack system with an eye toward safety and efficiency.
DESIGN FOR EFFICIENCY
Designing a storage rack system begins with some important questions, according to Joe Rooney, vice president of Baker Industrial Supply, a Texas-based supplier of retail and warehouse storage products. The process starts with an assessment of the type of facility you’re running—a retail operation, warehouse, manufacturing facility, or e-commerce distribution center, for instance—as well as the types of products being stored and moved, referred to as “loads.” Loads can include products stored on pallets as well as hand-stacked items and boxes. As an example, a typical eight-foot-long rack shelf usually has two pallets stored on each shelf; the combined weight of those two pallets and the product on those pallets makes up the “load” on that shelf.
This catwalk uses Hannibal Industries' TubeRack, which is designed specifically to withstand the dangers of seismic events, according to the company.
Next, designers must take into account various specifications and guidelines. Dave Olson, national sales manager for racking system manufacturer Ridg-U-Rak, says designers must base their design on specifications from the Rack Manufacturers Institute (RMI), an industry group within the material handling trade association MHI that provides guidelines and standards for storage racks. In addition, he says, they must ensure the design meets both local and international building codes.
Rooney adds that workflow is another important consideration.
“We also have to consider how [the customer] wants to move [the items]. For a distribution center, it’s about speed. For manufacturers, speed and throughput are not as important,” he explains. “Design has gone from ‘I’ve got this 48-by-40 pallet and I need to store 600 of them and put them on this wall’ to having more of a process. Today, we say ‘Let’s look at your space and see how you can effectively and efficiently move this material.”
Depending on the operation, that may entail a basic pallet rack design, or it may require racking that is part of an automated storage and retrieval system (AS/RS). Either way, the planning and preparation begin with the same initial questions.
“The key thing for any rack system design is the customer’s knowing its product, the mix and usage of SKUs (stock-keeping units), and how it wants to operate its warehouse,” explains Olson, adding that designers and warehouse operators must also consider the type of material handling equipment used in the facility, the type of loads being handled, and the volume of product moving in and out daily. “The customer knowing his needs is critical to formulating the proper rack system and layout—that’s where you start.”
PUT SAFETY FIRST
Designing for safety means ensuring that your rack system will stand up to internal operational damage from forklifts and other material handling equipment as well as external threats, such as earthquakes or hurricanes. Both types of threats require attention in the early stages of design to ensure both an adequate and a safe rack system.
“If [you go] back far enough in the history of racking, racking was treated like an off-the-shelf commodity with few if any design or safety regulations,” explains Steel King’s Keck. “Today, racking is a highly engineered and regulated product with design and safety requirements listed in all state building codes.”
To meet those requirements, designers must account for all loading conditions, which include the size and weight of items being stored and moved, the complexity of the racking structure being used, and seismic conditions and the location of the racking itself (indoors or out, for instance). More complex racking structures can sometimes include a mix of different structures like pick modules, multilevel platforms, and stairways—all of which can affect the load on the entire system.
In addition to adhering to building codes, rack system designers and installers will often recommend extra safety measures to protect against other types of damage and injury. Special structures can help protect against internal damage from forklifts, for example. These can include a variety of rack column protectors, end-of-aisle protectors, free-standing guard railing, pallet support bars, beam safety locks, safety netting, load plaques (affixed to racks as a reminder of their load capacity), and so on. Wire-guided vehicles can help as well; these are very narrow-aisle (VNA) forklifts that use an electromechanical system to control steering. The system is guided by an energized wire secured in the floor. Such systems help boost forklift driver confidence in narrow aisles at increased heights, helping to reduce the risk of a forklift’s hitting and damaging the racking, according to Rooney.
Reinforcing racks to withstand external threats is trickier and can involve advanced rack designs. Today, designing for seismic conditions is a part of almost every project, explains Olson. Extra steps can include using base isolation systems, which help dissipate the seismic energy exerted on a rack system during an earthquake. Olson points to Ridg-U-Rak’s “Pellegrino” base isolation system as an example. The system includes a base isolation unit that is positioned between the upright frame and the floor. The frame is attached to the base isolator, which is in turn anchored to the floor, allowing the rack structure itself to move relative to the floor. The aim is to add flexibility and allow dissipation of the seismic energy exerted on the rack system during an earthquake.
“Designs that incorporate flexibility [are important],” Olson explains, adding that structures that can provide both flexibility and strength help the entire system to flex and move. Such design features can help keep racks from “shedding” their loads, a term used to describe items falling off of a racking system.
Tubular design structures are the newest innovation to add the flexibility needed to withstand seismic events. Andrew Kirby of Hannibal Industries created a product called TubeRack specifically to withstand the dangers of seismic events; he says it was designed to save lives and was inspired by the continuously changing building codes that make it hard for warehouse operators to meet both safety requirements and profitability goals.
“We needed to change something,” says Kirby, an engineer and 30-year industry veteran. “So we came up with a solution to use a system that is flexible yet capable of supporting [a system’s] design weight when displaced. The best way to protect yourself from an earthquake is to allow the product and the pallet racking to move together. That’s what kills people—falling product.”
“The best way to protect yourself from an earthquake is to allow the product and the pallet racking to move together,” says Andrew Kirby of Hannibal Industries.
TubeRack is made from structural steel tubing and is designed to support heavier loads with less steel on lighter slabs. Its modular design eliminates the diagonal braces that connect the front and rear columns of a traditional system, helping to dissipate the energy exerted on the racking during an earthquake. This creates a less rigid system that allows the entire rack to move and flex in the direction of the seismic waves.
“With TubeRack, we take out those diagonals so we add flexibility. We let [the rack] move in the direction that the load is applied,” says Kirby, using a simple example to illustrate his point: The force of an impact between two people walking toward each other down the street is considerably stronger than the force of an impact between two people walking in the same direction. Removing the rigid diagonal beam essentially creates the latter scenario.
“The difference is in how the energy is dissipated,” Kirby says, adding that TubeRack lowers the potential for product shed during a seismic event or impact by up to 70%.
Kirby says it’s also important to leave enough space between the racking and the building to allow for movement. Other seismic recommendations include storing your tallest and heaviest loads at or near the bottom of the rack and avoiding low-friction pallets, such as those made out of plastic, to keep things from sliding around.
INSPECT FOR DAMAGE
Regardless of the threat, experts point to regular inspection and repair of damage as an essential part of maintaining rack system integrity.
“Problems can be exacerbated substantially with damaged frames or beams not properly engaged and locked,” Olson explains.
Keck adds that forklift operators should report any impacts or damage to racking immediately to allow for inspection and repair. Such policies should be encouraging, not punitive, to avoid incidents going unreported.
“If someone damages a rack, they can’t be reprimanded all the time. You have to have a program that ‘eases’ the reporting of those incidents,” Keck explains. “Workers should be encouraged to report any damaged parts or missing hardware. At a minimum, a complete rack walk-through/inspection should be done once a year.”
Many companies will do more frequent formal inspections—quarterly or even monthly—but the experts emphasize that continuous monitoring by all warehouse or distribution center staff is important. On top of that, Kirby recommends conducting a complete re-evaluation of a system every three years to make sure it continues to be safe and meet a business’s changing demands.
In the end, it all circles back to safety.
“These things are important,” he says. “[You need to] safeguard the product, and by safeguarding the product, you safeguard the people.”
Gartner, Inc.