September 18, 2015
material handling update | AS/RS

Freeze frame!

Freeze frame!

Despite the sub-zero temps, no one's complaining about working conditions in the freezer of North America's largest refrigerated warehouse. That's because it's "staffed" by a sophisticated mega-AS/RS that performs virtually all of the work.

By David Maloney

Working in a freezer for an eight-hour shift is among the most difficult jobs in the supply chain world. In order to spare workers (and forklifts) from having to toil in adverse conditions—think temperatures that dip to a frosty minus 10 degrees Fahrenheit—a new warehouse in Richland, Wash., is instead relying on an automated storage and retrieval system (AS/RS) from Dematic to handle most of the work. The AS/RS is believed to be one of the largest ever built in a freezer. It offers over 36 million cubic feet of storage capacity and can handle throughput volumes in excess of 250 trucks and 20 railcars a day.

The Richland facility, which opened in July, is owned and operated by Preferred Freezer Services, a New Jersey-based company with 35 refrigerated warehouses in the U.S. and a handful of others in Asia. As a public warehouse company, Preferred Freezer Services built the facility to serve the needs of a specific group of clients, primarily potato growers in the Pacific Northwest. One of the facility's larger customers is Lamb Weston, a supplier of frozen vegetable products that is part of ConAgra Foods.

The new facility offers 455,000 square feet of refrigerated space, with 312,000 of it dedicated to the automated freezer. The AS/RS within measures 116 feet high and features deep-lane racking served by 15 storage/retrieval cranes. The system provides very dense storage for more than 117,000 pallets of frozen french fries, hash browns, and other frozen products. The steel pallet racks, supplied by Frazier Industrial, also serve as the main structural support for the freezer's roof and walls.


A majority of the goods handled at the new facility arrive in Preferred Freezer Services' company-owned trucks, rather than vehicles operated by its clients or outside carriers. Preferred Freezer has learned that the more of its supply chain it handles itself, the lower the risk that products will be damaged or will jam up its automated handling systems. Therefore, about 65 percent of incoming goods are transported in Preferred Freezer's trucks.

"We want to make sure we control the flow, so we made the decision to use our own people," says Burnie Taylor, director of major capital projects and general manager in Richland.

The trucks pick up finished goods at production plants located within 50 miles of Richland. The vehicles that transport these goods are equipped with conveyance systems inside the 53-foot reefer trailers. Upon arrival at the Richland facility, they're directed to one of four automated docks, where the pallets are conveyed off the trailers and loaded onto a pallet monorail system for transport to the AS/RS. The monorail consists of hanging carts with roller beds. The pallets simply roll off the conveyor and onto the carts. A scanning system then records each pallet number and captures the load's dimensions to ensure it can be handled by the automated system.

The remaining 35 percent of inbound goods (those not arriving on company trucks) enter the facility via commercial trucks. There are six rail doors in the building and 14 other inbound truck docks in addition to the automated doors. Most of the products not delivered by company trucks are either floor stacked, rest on other pallets, or reside on slipsheets. These have to be manually transferred to slave pallets that are suitable for use in the automated system. The pallets are then loaded onto the monorail for transport to the AS/RS.

The AS/RS is spread out over three separate 104,000-square-foot freezer rooms, with five aisles and cranes per room. It features 18 possible points of entry and exit. Typically, nine are assigned to incoming goods and the other nine to outgoing products, though all 18 can serve either purpose. The monorail usually delivers the pallet to the entry point closest to the assigned storage location, where it is automatically discharged onto pallet conveyors to enter the system. From there, a storage/retrieval crane picks up the pallet and ferries it to the assigned lane, Where a deep lane cart know as the "Supercap Cart" (supplied by Automha) takes over and carries the load down the lane to the next available position.

From two to six pallets are stored in each lane, with most lanes devoted to a single stock-keeping unit (SKU). Product is put away in multiple aisles to create redundancy throughout the warehouse. This assures that all SKUs are accessible when a crane is down for maintenance and provides for easy access to faster-moving products.

"We have a lot of flex built into the system to manage inventories," says Taylor. He adds that customers often have different rotations for their goods. Some rotate stock according to first in/first out principles, while others rotate products based on expiration dates.

Full pallets are retrieved from the system via a process that's essentially a reversal of the entry process. The moles retrieve the goods and then transfer the pallets to the storage/retrieval cranes for transport to output stations. From there, the monorail system picks up the pallets for transport to outbound docks.

In addition, Preferred Freezer builds "rainbow" pallets of mixed goods for customers. For these, the monorail delivers pallets to four picking stations, where a Tygard Claw layer picker attachment on a Crown sit-down lift truck is used to assemble the pallets. It removes a layer from the source pallet and deposits it onto an order pallet, building rows of mixed SKUs in the process. Individual cartons are also picked by hand and added to the order pallets. When a completed pallet is ready to ship, it is conveyed to the docks via either the monorail system or lift truck.

Many of the mixed pallets are picked in advance of shipment to balance workflow. In this case, the mixed pallets enter the monorail system for transport back to the AS/RS, where they're held until the shipment date. They are then picked in the same manner as standard full pallets.


By allowing the AS/RS to do most of the work in the freezer, Preferred Freezer can assign its human employees to areas away from the cold, such as the dock, where temperatures hover at a relatively balmy 40 degrees Fahrenheit. "When you look at the labor force and being an employer of choice in the freezer business, it is an advantage not to have people needing to access the freezer," says Taylor.

While the AS/RS's bone-chilling conditions would make it quite uncomfortable for people to work there, other factors make it downright inhospitable. This is the first freezer system in the country (and the second in North America) to incorporate a low oxygen environment for fire prevention. Nitrogen is introduced to the atmosphere inside to virtually eliminate any chance of combustion. Furthermore, the new installation is a lights-out system.

At present, operations are continuing to ramp up in the new building, which is expected to house 200 million pounds of inventory by next month (it's designed to hold up to 250 million pounds). When it reaches full capacity, the facility is projected to have a throughput of 2 billion pounds of products a year.

About the Author

David Maloney
Editorial Director
David Maloney has been a journalist for more than 35 years and is currently the editorial director for DC Velocity and Supply Chain Quarterly magazines. In this role, he is responsible for the editorial content of both brands of Agile Business Media. Dave joined DC Velocity in April of 2004. Prior to that, he was a senior editor for Modern Materials Handling magazine. Dave also has extensive experience as a broadcast journalist. Before writing for supply chain publications, he was a journalist, television producer and director in Pittsburgh. Dave combines a background of reporting on logistics with his video production experience to bring new opportunities to DC Velocity readers, including web videos highlighting top distribution and logistics facilities, webcasts and other cross-media projects. He continues to live and work in the Pittsburgh area.

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