While it was once common for warehouse managers to purchase standard storage racks that were quick-shipped from manufacturers’ stocked inventory, this now occurs less often as racking becomes more specialized and regulations become stricter.
Today, storage rack systems are generally considered a building-like element. As a result, they are often subject to a variety of federal, state, and local regulations. These ordinances are continuing to evolve — perhaps none more so than seismic standards — and can become a pitfall for warehouse managers unfamiliar with them.
As a consequence, warehouse managers should seek expert guidance from a qualified design professional whenever the racking, foundation, or warehouse infrastructure must accommodate unusual stress, loading, function, or other nonstandard factors.
“Ordering quick-ship pallet racks is convenient, but should be limited to use with nonflammable, nonhazardous product stored inside buildings in low-risk seismic regions,” said Arlin Keck, an engineer at Steel King Industries.
The manufacturer has made warehouse storage racks, pallet racks, and handling/safety products since 1970.
“Usually, with quick-ship racks, there is a maximum pallet load limit that the racking can handle and a maximum bay load limit that the racking and the existing warehouse floor can handle,” added Keck. “There is also usually a 6:1 height-to-depth ratio placed on the racking. Any rack outside of these parameters typically requires a qualified design professional’s review.”
Even when the quick-ship rack is appropriate for a warehouse, there may be a need for expert input if there are special circumstances — for example, if rack installation occurs on a sloping floor.
Despite greater warehouse complexity and evolving regulations, understanding a few key distinctions about racking will help warehouse managers to keep their facilities cost effectively safe, compliant, and productive. These include seismic standards and environmental concerns for rack-supported buildings. For engineered systems such as pick modules, elevated platforms, and automated storage and retrieval systems (AS/RS), factors include travel distance, egress and access requirements, and safety protection and guarding.
SEISMIC AND ENVIRONMENTAL ISSUES
Because storage racks are considered building-like structures according to the International Building Code, and are represented as such in the Rack Manufacturer’s Institute (RMI) Standard, racks need to be designed to the local seismic requirements just like a building.
Since the RMI is the recognized U.S. specification for the design, testing, and utilization of industrial steel storage racks, responsible warehouse managers will want their racks to meet this recognized standard for seismic design.
RMI created the R-Mark Certification Program as a way for storage rack users to clearly identify those rack manufacturers whose components and design are in accordance with the RMI specifications.
While all U.S. states have some potential for earthquakes, 42 of the 50 states have a reasonable chance of experiencing damaging ground shaking from an earthquake in 50 years, which is generally considered the lifetime of a building.
Another reason for warehouse managers to seek a design professional’s input is the fact that seismic zone designations are changing. The U.S. Geological Survey (USGS) uses ground acceleration values, referred to as Seismic Design Categories (SDC) from A to F.
With seismic requirements increasing in many parts of the country and with a better understanding of structural performance during an earthquake event, standards will continue to evolve, placing more demand on the rack design.
“Seismic separation is another requirement for racks placed within an existing warehouse,” said Keck. “The rack needs to be a certain distance from the building columns so they will not collide during an earthquake. In high seismic regions, special inspection is typically required. An independent inspector will watch the installation and verify proper bolt tightening, especially the anchor bolt, along with checking for rack damage and missing or poor welds.”
Outdoor racking, and rack-supported structures, must also be designed to account for wind, rain, and snow loads.
In hurricane-prone regions, for example, outdoor rack and rack-supported structures must be designed to withstand the force of high-speed winds in addition to standard product and dead loads.
When heavy snowfall is prevalent, the outdoor rack and rack-supported structures must accommodate the accumulated weight of both snow and snow drifts, which occur when wind pushes snow up against taller structures or towers.
In all such unusual environmental conditions, of course, it is essential to consult with a professional about incorporating necessary safety factors into the rack design.
ENGINEERED SYSTEMS: PICK MODULES AND AS/RS STRUCTURES
By definition, an engineered system is any nonstandard storage rack that requires special design considerations. This can include a variety of rack types and safety equipment, semi-customized or actually custom-designed specifically to the warehouse application.
In terms of safety, racking, of course, must be designed for any unusual stresses, loads, or functions placed upon it. It must also meet applicable fire codes and insurance requirements. For instance, racking loaded with flammable products would require certain accommodations to ensure adequate fire detection, containment, and suppression.
Some of the most highly engineered systems actually involve pick modules, elevated platforms, and work platforms. In such engineered systems, a number of key factors must also be addressed to ensure safety, compliance, and permitting, according to Keck.
“To comply with the fire code, you need to address the means of egress (the path to exit a building), travel distance, and head clearance/exit width ... based on the number of people who have to evacuate the racking system,” he said.
In order to provide safe access and fall protection, the layout should include suitable stairs, ladders, and guarding throughout the engineered system. Because dropping off pallets or equipment at elevated levels may be required as well in such engineered systems, providing for safe drop zones (through an opening in the side railing to allow easy receipt) should be properly planned, too.
Ensuring that the engineered system functions as designed and that the employees working on an engineered rack structure feel comfortable is another consideration. Generally, this is referred to as serviceability. The term refers to how certain structural elements, like elevated walkways, must provide the desired support and stiffness for walking or cart use without unacceptable flex (bounce) or sway.
While such engineered systems require substantial input from a design professional, AS/RS structures — which can be over 100 feet tall and bear loads greater than 100,000 pounds per storage bay — require even more planning and integration.
In today’s warehouse environment, AS/RS systems are increasingly popular in big-box store distribution centers and large freezer companies for their ability to provide high-volume, high-turnaround storage with minimal labor.
“With AS/RS systems, there is a lot more interfacing between the equipment and the racking,” said Keck. “Because these systems use automated cranes and usually map each location on a coordinate plane via computer, the tolerances are a lot tighter. Since the machines stop at precise locations, each opening has to be at the exact location. So the racking must be very stiff, and the rack must be straight and plumb.”
SHORTCUTS NOW CAN MEAN HEADACHES LATER
While there is no denying that purchasing quick-ship racking is convenient for many standard applications, the truth is that many larger, more complex warehouse applications today require expert input from a design professional. This is almost always the case when it is necessary to coordinate with integrators as well as various safety and trade professionals under deadline. Troubles often occur when someone decides that it is quicker and cheaper to buy quick-ship racking when the application really calls for an engineered system.
So, when optimal storage, material flow, safety, and compliance is required in a warehouse, proactive managers will get the help they need up front to avoid costly surprises, delays, or retrofits.
Steel King is one of a select number of rack manufacturers that holds an active R-Mark License and is a licensed fabricator in Los Angeles County, which has some of the strictest seismic codes in the nation. For more info on optimizing warehouse storage and production, contact Steel King Industries, 2700 Chamber St., Stevens Point, WI 54481; call 800-826-0203; email firstname.lastname@example.org, or visit www.steelking.com.
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