Fundamentals of GMP Warehouse Design: Considering Storage and Retrieval Methods

Warehousing is a critical yet often-overlooked need of the pharmaceutical industry. Although GMP warehousing can have some specific requirements (e.g., cleanliness, temperature control), in this article, the author discusses some of the basic questions and criteria that drive warehouse design for both GMP and conventional warehouses.

An effective warehouse must be appropriate for the materials being stored. Likewise, a sound understanding of the inventory is necessary to create an efficient and successful operation. Not only do the materials anticipated need to be identified, but the frequency, quantity, and sequence of retrieval must be considered. 

Choosing a pallet rack type

The key attribute of warehousing is the method of storage; in other words, the type of pallet rack that is used. There are many options available; some of the common types are known as “single or selective,” “double deep,” “push back,” “drive-in,” and “flow racks”. Fundamentally, however, the decision for the most appropriate rack focuses on the number of pallets stacked within a horizontal lane of the rack. 

Placing pallets one deep on a multilevel rack is the traditional and most common approach. This approach provides the greatest flexibility because it gives access to all pallets, at all times. The relative low density of pallets, however, limits the quantity that can be stored. Greater density is achieved by increasing the height of the racks or by placing pallets one behind the other within the same lane. Verticality is a function of the height available; lane depth is driven by the materials stored and the rate of their use. For any given height, stacking pallets more than one deep eliminates aisles and increases both the pallet density per square foot and the amount of storage. 

When stacking pallets one in front of the other, however, a condition referred to as “first in, last out” is created. The pallet in front must be used before the one behind is available. To justify this method of storage, all the material in that lane must be the same, and the quantity and rate of use needs to be such that the “last” pallet is taken in a timely manner. To store pallets that are never used is an obvious waste of space, inventory, and money. The number of SKUs (stock-keeping-units), the throughput, and inventory turnover all play into this decision. A warehouse, of course, does not need to have only a single type of racking. An analysis of the inventory will also provide the data necessary to determine the diversity and appropriateness of multiple types of rack.

Considering forklifts and aisle spacing

In selecting racking, the type of fork truck must also be factored. There are numerous types of trucks, each with different performance characteristics and capital costs. Characteristics include height and depth of reach; sit-down, standing, and “man-up” models as well as the space required for maneuvering. Conventional, sit-down, counterbalance forklifts require a turning radius of up to 13 feet. To allow turning and placement of loads in the racks, this maneuvering dimension must be provided in front of the racks. But there are other options. At the other extreme, a special turret truck is offered that allows very narrow aisles of as little as six feet between racks. In large facilities, considerable density can be achieved through these smaller aisles.

When considering aisles, however, the width needs to work in concert with the column bays. For those fortunate enough to build a new facility, it is possible to optimize these three factors: rack types, forklift, and column spacing. When working in existing facilities, however, the column spacing is a given, and some compromises are often required. 

Automated systems

High-density warehousing with an automated storage and retrieval systems (AS/RS)offers a solution for many warehousing challenges. These computer-controlled systems use neither aisles nor forklifts. Each pallet is automatically placed and retrieved from defined storage locations on robotic carriages. AS/RS maximizes storage within a given footprint, reduces labor costs, reduces product damage, and increases the accuracy of inventory management, but capital costs are significant.

The physical storage of pallets, as basic and simple as it appears, has not been overlooked by the digital revolution. Software to manage and control inventory can greatly reduce costs. It is easy to assume that more storage is better. Large inventories, however, require money tied up in idle materials that are not adding value, and the capital costs to construct and operate larger warehouses must be considered. Contemporary supply chain strategies try to balance the quantity stored to the throughput of the facility. With barcoding and radio-frequency identification, it is possible to know every item in an inventory as well as its real-time status. Production planning and historical data can be used to reduce the time that materials are stored before use. This “just-In-time” approach contrasts with the traditional “just-In-case” philosophy. Efficiency is increased and waste decreased by receiving goods only as needed. Less space is used, smaller inventory investments made, minimal inventory obsolescence occurs, and responsiveness for accommodating product changes is increased.

Conclusion

The design and operation of modern warehouse facilities has many tools at its disposal. All are focused on creating effective and efficient operations. Understanding inventory and the demand for those materials is crucial to an optimized facility. With less money tied up in inventory, a well-organized and well-run facility frees up resources for use elsewhere, increasing the value that the warehouse operation delivers.

About the Author

Eric Bohn is partner at JacobsWyper Architects, 1232 Chancellor St., Philadelphia, PA 19107,  tel: 215.985.0400.