Drive-in rack, pushback rack enable Zero Mountain to increase national capacity, enhance logistics
The nation’s network of frozen and refrigerated distribution centers forms a logistical supply chain that is vital to food safety. Yet because of the high operational costs of freezing or cooling pallets of product within confined areas, every square inch of storage and every movement of product must be efficient. A challenge occurs, however, when frozen storage must be expanded across an irregular landscape that makes traditional, space-efficient, rectangular warehousing impossible.
To continue the growth of its distribution centers in the national logistics supply chain, Zero Mountain had to expand its frozen storage and cooler capacity at its Fort Smith AR facility. As a premium cold storage warehousing services provider to the food industry nationwide, the company freezes, stores and ships an estimated two billion pounds of frozen food and meat annually for many Fortune 500 companies.
“We needed to expand our warehouse 100,000 square feet between two existing buildings,” said Joe Rumsey, Zero Mountain’s president and chief executive officer. “But the landscape didn’t allow for a traditional rectangular-shaped warehouse, so one side was built at a sloping angle. Still, because of the operational cost of frozen and cooler storage, the design had to maximize storage density, capacity, efficiency and durability.”
Looking to achieve these goals, Rumsey turned to Cisco-Eagle, a materials handling, automation and storage systems integrator; and Steel King Industries, a storage system and pallet rack manufacturer.
For freezer storage, the companies chose drive-in rack for its cost-effective, high-density storage capacity that requires fewer aisles and provides better cube utilization than selective rack. Drive-in rack enables storing up to 75% more pallets than selective racking and is ideal for high-traffic and cooler/freezer installations.
To maximize efficient freezer storage design with the warehouse’s untraditional shape, the companies varied racking depth from two to nine pallets deep. They also varied pallet opening heights, including some for 100-inch-high pallets for retail and some for 2,000-lb double-stacked pallets for export.
The result: an area of approximately 71,000 square feet holds more than 8,000 pallet positions, plus almost 300 pallet positions for blast cells, which are enclosed areas where product is flash-frozen at –30° F for frozen storage.
The drive-in rack used required exceptional strength. This was not only to support up to 4,000-lb pallet loads of frozen poultry, but also the weight of HVAC equipment for six rack-supported blast cells.
With drive-in rack, forklifts drive directly into the rack to allow storage of two or more pallets deep. Because forklifts drive directly into the rack, they tend to take more abuse than other rack structures. Rumsey was concerned that the industry’s typical, light gauge, roll-formed rack would be prone to forklift damage and costly replacement.
As a solution, Cisco-Eagle recommended and Zero Mountain chose SK3000 drive-in rack, a rugged bolted rack with structural channel columns, by Steel King. A number of rack features helped the company meet its strength, capacity and durability goals.
Compared with typical racking, the pallet rack constructed of hot-rolled structural channel column with full horizontal and diagonal bracing offers greater frame strength, durability and cross-sectional area. All Grade-5 hardware provides greater shear strength, and a heavy 7-gauge wrap-around connector plate ensures a square and plumb installation with a tighter connection and greater moment resistance.
“For the application, the SK3000 drive-in rack provides the most pallet positions per cubic foot, with the highest per pallet and overall capacity,” said Amanda Miller, a Cisco-Eagle engineer on the project, who adds that 2-inch vertical rack adjustability also helped to optimize efficient storage for a range of pallet sizes.
“Since it is structural, not roll-formed, it offers a lot more rigidity and is able to better withstand any potential forklift impact,” said Miller.
With the drive-in rack, various features came standard that help with longevity. For strength, the load rails are constructed of durable structural angle steel, and they feature a flared entry design that eases bay access and minimizes potential forklift impact. Space-saving low-profile arms increase clearance and decrease possible product damage.
Welded rail stops also prevent loads from being pushed off the racks and improve safety. To further increase rack clearance and reduce forklift impact with the rack, an offset leg design option was also chosen.
“The structural drive-in rack provides us with the strength, capacity and durability we need to withstand decades of use, where forklift impact is expected,” said Rumsey.
For almost 600 pallet positions of additional cooler storage in a smaller room in a dock area, the companies also chose a two-deep pushback rack arrangement around the perimeter of the room. Bolted tubular SK2500 pallet rack was chosen for economical strength and durability. Its columns, made of high-strength (55,000-psi minimum) steel, have up to 44 times more resistance to torsional fork truck impacts than open-back roll-formed columns.
Pushback pallet rack offers up to 90% more product storage than selective rack systems and up to 400% more selectivity than drive-in racks. Unlike static, single-pallet-deep selective racks, a dynamic pushback rack system allows pallets to be stored two to five deep while providing easy access to a variety of different SKUs.
With pushback rack, pallets are stored behind each other in a series of nested carts and are loaded from the same side of the system, eliminating separate aisles for each function. Composed of a stable rack along with a series of inclined carts and rails, when one pallet is pulled, the one behind it rolls forward.
“The pushback rack gave us quick loading and unloading with good storage density in a dock area where most people do not usually have storage capacity,” said Rumsey. “Together with our drive-in rack, our warehouse expansion has helped to maximize our capacity and materials handling efficiency.”
For more info on optimizing warehouse storage and production, contact Steel King Industries, 2700 Chamber St, Stevens Point WI 54481; access www.steelking.com; call 800-826-0203; or email [email protected]. ♦
Del Williams is a technical writer based in Torrance CA.
