Maximizing Space Vs. Accessibility

Brian Schiavo
Created:

Product mixes are helping to determine racking strategies.


Sadowski says his company looked at its product portfolio when it was evaluating its racking options and decided how much inventory it would be able to bulk store with three-high deep racks.

"Then we looked at the rest of our inventory," he explains, "and decided we needed to do some selective pushback as well. We took the time to figure out the percentages that we needed to operate efficiently."

 

Finding The Best Racking System

Racking systems come in configurations suited to a variety of applications. Here's a look at systems commonly found in grocery warehouses:

  • Single-deep selective racks offer the most efficient selection and movement of product. Typically, the aisles in-between the racks are 10 feet to 12 feet. While this provides for maximum accessibility and less congestion, it takes up more space in the warehouse than other storage modules. Thus, the density of this storage module is the lowest. This system is useful for faster-than-average moving product. "It's also good for slow-moving case pick operations, where you've got a lot of SKUs that only move in pick quantities of one to five pallets a day," says Dwight Dbeery, vice president of engineering services for Next Generation Logistics.
  • Double-deep racks are selective or pushback pallet racks arranged back-to-back, allowing for two or more pallets of the same SKU on one level. Double-deep rack increases density by reducing the number of aisles required for storage and retrieval. In most cases, switching to double-deep can produce a 50 percent space savings. "Double-deep select rack needs a reach truck that has a double-deep reach pantograph attachment to get back to the second location," Dbeery explains. "I'd pay the extra money for the pushback, rather than the select."
  • • Narrow aisle racking can be used for heavy duty and high density storage systems. The aisle width needs only to be slightly larger than the pallet load, therefore utilizing maximum warehouse space. It also offers direct accessibility to each individual pallet.
  • Pushback racking is a higher density storage module for products that have greater than five pallets/SKU in inventory. The trade-off is lower selectivity for higher density. Pushback systems follow the "last in, first out" inventory methodology. Thus, it is not the best storage medium for product rotation, especially if the product is date sensitive.
  • Flow-through rack supports "first in, first out" inventory. This is a good choice when product rotation is important. The system operates on gravity. When product is input from the back, it flows by gravity to the front, insuring that there is always product at the front pickface. This storage module is also higher density, meaning that less square footage is required in the warehouse to store more pallets than selective racking. "It's good if you're talking about mechanizing very high pallet inventory items," notes Dbeery.
  • Drive-in racking offers the highest density storage. It is a good choice when space is at a premium, such as refrigerated or freezer applications. While it provides much more density than selective rack, the application is limited since drive-in rack is best used for large quantities of pallets (usually 10 or more). "Drive-in racking makes good sense for cold storage," says Dbeery, but because of the high cost, "it's not for food distribution."

Sources: Tompkins Associates; Next Generation Logistics

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