Planning for bulk pile storage

Block or bulk pile storage is a practical alternative in a number of cases; here are some considerations to optimize this kind of handling layout.

-- Modern Materials Handling, 1/1/2001

In theory, planning should be easy for a block or bulk pile storage layout in which pallets or unit loads are stacked one on top of another without the use of supporting racking. Unlike most storage systems this one has very few fixed elements except for the building columns and aisle lighting in the storage area. Block or bulk pile storage also provides a much higher degree of flexibility to adapt to a changing business environment than with many materials handling systems.

Even so, there are a number of factors to be considered in optimizing a block storage layout. Chief factors include:

• Determining your unit load handling needs.

• Establishing the tradeoff necessary for your situation between accessibility of stored loads and the degree of storage density you require.

• Developing the best means for replenishing products you store in bulk.

• Determining maximum unit load stability and stacking heights; for example, how high can we safely pile the product, especially in hot, humid months.

• Establishing the order picking requirements for your layout.

• Deciding how you will handle remnant or out-of-season lots of stored product or materials.

Column space does not permit a detailed examination of each factor, so we will only illustrate how your planning might proceed with the first two bullet point items.

Unit load handling needs have an impact mainly on travel aisle width and storage row clearance requirements. For standard pallet handling, the dominant influences are set by the turning and clearance needs of the lift trucks you'll be using. In situations where your lift trucks handle large, non-standard unit loads (for example, lawn or garden tractors) or in cases where load handling requires use of forklift attachments like carton clamps or forkless, top-handling devices, special clearances for the lift truck and attachment are needed. In these cases, check with your attachment supplier and/or lift truck dealer.

Establishing the tradeoff between load accessibility and storage density refers to your specific needs to access various products by stock keeping units (SKUs) and to design a layout so that multiple SKUs are not found in the same row. Finding the right tradeoff includes determining the average quantity of unit loads per SKU divided by the stacking height. That calculation gives you the average number of unit load piles per SKU. As a starting point this calculation helps determine the average storage lane depths initially.

You should also run an ABC and Pareto analysis of SKUs to determine if a combination of short rows and longer rows gives you the most efficient layout. Remember that one of the big advantages with a block storage layout is that short storage rows can be created adjacent to major cross aisles by turning the rows 90 degrees to the main aisle layout.

To reduce storage honeycombing within the lanes, use the same general rule of thumb that applies in deep lane systems (such as drive-in and push-back rack): provide at least three storage lanes per SKU.

With some products, transportation needs (for example, making the depth of an aisle equivalent to a truckload quantity) as well as fire prevention requirements can also influence aisle depth.

Block storage is a practical layout alternative in a number of cases. It is particularly ideal when you have a tight fisted boss who likes to invest in real estate but not equipment.