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Nine Constraints to Maximum Storage Space

Feb. 12, 2014
Analyzing and understanding the limitations of a building as they relate to the material handling systems you are evaluating will help maximize technology’s ROI.

When designing a material handling system and the associated operational work flows, the design of a facility itself can pose several constraints for the project managers to deal with. Added to these constraints is a company’s unique order profile (seasonality), the various sales channels (online and in-store) and the requirements of a wholesale network.  The solution to maximizing cubic space using material handling systems, reducing labor costs, expanding distribution capacity and improving quality typically starts with an understanding of those constraints.

The following are the chief constraints having to do with the relationship between a building and the material handling systems:

  • Building Shape – An Automated Storage and Retrieval System (AS/RS) would have a hard time being justified if the building shape did not allow for long aisles and appropriate overhead space to maximize storage density and minimize the number of crane aisles required. 
  • Dock Door Locations – A straight “flow through” building with shipping and receiving doors on opposing sides typically has the inventory storage (floor stack, pallet rack, shelving, etc…) rows perpendicular to the walls of the dock doors.  A “U-shaped flow” building with shipping and receiving doors on the same wall may or may not have the inventory storage rows parallel to the wall with the dock doors.
  • Clear Height – The height of the lowest ceiling obstruction will determine the height of the storage types and consequently the number of storage levels, as well as the number of levels a multi-level platform can accommodate. 
  • Column Spacing – This constraint is probably the number one source of frustration for material handling system designers.  Building column locations impact pallet rack rows, forklift aisles, pick module size, conveyor paths, and the locations of larger material handling units such as Vertical Lift Modules (VLMs), AS/RS, or carousels.   
  • Ceiling Joist Capacity – One of the best uses of vertical space as it relates to moving product around a warehouse or distribution center is to elevate the conveyor system by supporting it from the ceiling joists.  Sometimes, however, based on the live load and dead load of the conveyor and the products being conveyed, the ceiling joist capacity does not allow this strategy.  Many times, this can be overcome by structurally stiffening up the ceiling joists.
  • Fire, Building, & Safety Codes – All municipalities have their own ordinances and codes that must be adhered to.  Fire marshals have requirements that typically entail two unencumbered egress paths from anywhere inside the warehouse to an outward opening door within a certain distance.  Building inspectors place limitations on the overall square footage allowed by a mezzanine in a single room.   These requirements alone have major bearing on material handling system design strategy of maximizing the cubic space. 
  • Insurance – Premiums for insurance policies are largely dependent on the amount of inventory, the commodity classification of the inventory, the ways in which the inventory is stored and the ability to suppress any fire or smoke.  Additionally, documented OSHA violations or previous workplace accidents can also impact insurance premiums.  These factors have a major impact in storage system design and also the design of any multi-level equipment or system where personnel perform daily duties or inventory is typically stored. 
  • Lift Equipment –Forklifts, order pickers and any other mobile lift equipment all have height capacities as well as load limitations at their highest points.  This can become a game of inches and pounds, so priority should be placed on performing the due diligence on the storage system design and ensuring that it meets the planned lift equipment capacities.
  • Personal Preference –Automated Storage and Retrieval Systems (AS/RS), horizontal or vertical carousels, vertical lift modules, high bay racking, and multiple level pick modules and mezzanines work well in specific situations but not as well in others. We all live and learn, and develop preferences toward types of solutions, especially as it relates to specific applications.

John T. Phelan, Jr., P.E. is Chief Operating Officer of TriFactor, LLC, a material handling systems integrator based in Lakeland, Fla. This was excerpted from his new white paper, "Maximizing Cubic Space in the Warehouse,"  which can be downloaded here.