As distribution centers and manufacturing facilities perpetually chase increased efficiency, they often stop short of considering major changes to their warehouse’s core design itself. This is certainly understandable given the costs and disruptions that design-level changes entail, but in many cases, the potential efficiency gains that design enhancements can unlock are well worth the effort. Very Narrow Aisle (VNA) warehouse designs are a great example of this concept, as we’ll explain below.
Very Narrow Aisle warehouse design describes a layout and equipment scheme that specifically balances near-maximum density with ample selectivity short of going to full blown automated warehouse storage. The tenants of VNA design include:
- Pick Operations – a VNA warehouse design utilizes static racking and operator-driven industrial trucks to pick and pull materials.
- Density – the core differentiator for a VNA design is to increase storage density by trading less traffic space for more storage space, to an extreme degree.
- Aisle Width – to free up more space for storage, forklift aisles are reduced from the traditional 12′-14′ width to a very narrow 5′-6′ width. In this way, VNA designs can often achieve 30% to 50% higher density levels than a traditional wide-aisle layout.
- Storage Height – to further increase storage density, VNA designs promote increasing storage heights often up to 40′-60′.
- Selectivity – achieving such high densities with VNA designs naturally constrains the speed of pick missions and vehicle traffic, making VNA preferred for highly selective, moderate volume operations (as opposed to bulk volume operations).
- Pick Equipment – the concept of such narrow, tall aisles is based on the premise that fork trucks will no longer maneuver in the aisles, and instead will only travel forwards and backwards down aisles. This facet of the design requires a whole new category of specialized pick equipment, which becomes the key to making VNA designs work.
VNA Material Handling Equipment Types
As we just learned above, very narrow aisle fork truck equipment is the lynchpin that holds VNA warehouse designs together. Understanding what makes VNA equipment special begins with reviewing the position of the operator.
VNA fork truck equipment changes the position of the operator entirely compared to standard forklifts, placing the operator at fork level where they now move vertically with the forks to the height of the pick. This position gives the operator the best vantage point to the goods being picked and also opens up a whole new world of high elevation unit picking as well.
There are two main types of Very Narrow Aisle Trucks:
Turret Trucks
Turret trucks are intended to pick entire pallets by rotating the forks to align with pallet positions instead of rotating the entire truck. These vehicles feature forks attached to a rotating turret, which can independently rotate the forks towards pallet positions on the right or left of the aisle while the truck itself remains parallel to the aisle. Once the turret has rotated to the desired side, the mast then slides into the racking to pick and pull a pallet.
Order Pickers
Order picker trucks are not intended to pick entire pallets, but instead to allow operators to pick individual goods from elevated racking positions. Like turret trucks, order pickers travel down narrow aisles, stop at the desired storage location, and raise the operator up to the elevation of the desired goods for them to grab by hand all without needing to turn the lift at all. In this fashion, operators can pick multiple products across many varying rack positions and heights to build orders. Order pickers may or may not have forks – those that are equipped with forks hold a single pallet or bin that is meant to retain picked goods while building orders.
Key Considerations when Evaluating Very Narrow Aisle Options
Here are a handful of key considerations that warehouse managers should keep in mind when evaluating VNA options.
Man-Up versus Man-Down
VNA designs utilize “man-up” forklift truck styles by default, which elevate the lift truck operator up to racking heights to make their picks. Alternatively, “man-down” lifts are available in which the operator stays seated at ground level and uses advanced vision systems and semi-automated pick mechanisms to complete picks remotely.
Specialized Operator Training
Very narrow aisle applications come with many unique safety and functional nuances. As such, VNA warehouse operators must complete specialized training programs that specifically address these nuances, especially for extended heights and mixed aisle environments.
Vehicle Guidance Systems
As fork truck aisles get narrower, the chance of accidental racking strikes gets exponentially higher. VNA truck operators have very little room for error, making manual operation of VNA trucks inherently risky. To protect against such impacts, VNA lift trucks are available with optional vehicle guidance systems that remove the need for manual steering, usually consisting of a fixed wire or rail installed down the length of an aisle to which the VNA truck aligns.
Racking Selection
VNA warehouse designs typically utilize single selective pallet racking or shelving, as these applications tend to need the highest level of selectivity. For applications that approach bulk-type storage, VNA designs can easily accommodate different racking selections such as push-back and mixed-format racking.
Costs
Very narrow aisle warehouse designs usually come along with an associated price premium (spanning racking costs, truck costs, and the associated operational costs). With that said, VNA designs are selected for their clear overall cost savings and cost avoidance benefits, such as by decreasing carrying costs (via increasing density) and avoiding construction of expanded warehouse space.
Construction and Code Implications
Further to the above point on costs, very narrow aisle warehouse designs do impact construction and code costs in the form of structural, fire protection, emergency egress, and mechanical heating, ventilation and air-conditioning (HVAC) elements. A few examples: floors will require higher tolerance flatness to assure lift stability given the heights involved, and fire, lighting, and ventilation systems will all need to increase in coverage given the increase in product storage density.
Safety
VNA trucks offer many safety benefits both directly and indirectly. Direct safety features include dead-man floor controls, multi-point operator restraints, semi-enclosed cabs, light detection and ranging (LiDAR) assisted positioning systems, and ergonomic controls. Indirect safety benefits include design attributes such as reduced rack strikes, slower travel speeds, reduced operator strain, and saving whole pallet pulls to grab a single unit.
Mission Speeds and Total Throughout
Individual VNA lifts typically operate at slower speeds than traditional lifts, which drives many warehouses to increase the amount of VNA lifts they’re using to keep overall mission rates high. As more VNA lifts are deployed together with fixed guidance systems and compound diagonal travel functionality (raising/lowering the cabin while automatically moving up or down the aisle), VNA designs can achieve higher total throughput overall.
We hope that this discussion has been helpful for your commercial material handling needs. Fairchild Equipment is the Upper Midwest’s premier Material Handling Equipment and Service resource, with headquarters in Green Bay, Wisconsin, and numerous locations in five states ready 24/7 to serve your needs. For more information or to discuss which Warehouse Optimization solution might be best for you, please send us a message or call us at (844) 432-4724.
