Narrow-Aisle Form Follows Lift Truck Function

Converting from conventional to narrow-aisle storage seems a no-brainer. After all, an operation can store 20% to 25% more product in the same space by taking the narrow-aisle plunge. Even more impressive, switching to a very-narrow-aisle (VNA) system allows for 40% to 50% more product. And, with cost control being the Number One priority these days, we would expect today's storage aisles to be narrower than ever.

But that doesn't seem to be the case. According to David Morzella, warehouse products sales manager at Toyota Material Handling USA Inc. (TMHU), the trend to build up instead of out to limit a building's horizontal footprint and increase cube utilization has paradoxically caused aisles to become slightly wider.

The reason is based on simple physics and safety. “Higher heights require trucks with bigger footprints, so the trucks have become larger, and aisle width must follow,” Morzella explains. “In addition, ergonomics has resulted in bigger operator compartments, resulting in a larger lift truck footprint and, in turn, a larger aisle width.”

Traditionally, the narrow-aisle standard has been nine feet wide, and Morzella says, many material handling professionals still use that benchmark, which can create problems. “They lay out the aisles to be nine-and-a-half-feet wide, but the pallets create three inches of overhang,” he says. “And, that is often overlooked. So, they have to move the pallet rack to get space they need for the truck.”

Morzella says “clear aisle” is the amount of aisle space remaining after pallets are in the racks. “Narrow aisle has been redefined to nine-and-a half to 12-feet wide,” he says. Conventional aisles are 12-feet wide or more. “There's been some crossover between narrow and conventional,” notes Morzella. Because VNA configurations use guided turret trucks and other specialized vehicles, there hasn't been much change in that definition, he adds. Morzella defines VNA systems as less than eight feet.

Further complicating things is the fact that more companies are moving into existing buildings rather than constructing new ones. “They are working within existing parameters in many cases,” Morzella says.

The three main types of lift trucks designed to maneuver in narrow aisles and VNA systems are reach trucks, turret trucks and orderpickers. The Industrial Truck Association categorizes them as Class 2 industrial trucks. Class 2 also includes high-lift straddle trucks; reach-type outriggers; sideloaders, swing mast and convertible turret/stockpickers; and low-lift pallet and platform riders.

Truck Selection

The type of narrow-aisle lift truck to choose depends on how it will be used. Kevin Trenga, product marketing manager for Hyster warehouse trucks, says there are two primary functions of narrow-aisle lift trucks: rack interface and order picking.

“A reach truck is a rack interface truck,” he explains. “It does putaway and letdown of full pallet loads on either side of an aisle as narrow as 96 inches. Orderpickers are operator-up trucks designed for picking cases and units of product and are not for rack interface with pallet loads.”

“Reach trucks are designed to handle lots of putaways and letdowns at high heights plus have the maneuverability to work in the narrow aisle and transport product longer distances,” adds Maria Schwieterman, marketing product manager at Crown Equipment Corp. “Operator-up turret trucks are designed to work within an aisle.”