Fundamentals of GMP Warehouse Design

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

Considering storage and retrieval methods

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 stock-keeping-units (SKUs), 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 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 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.

Considering building codes

In addition to these fundamental programmatic considerations for storage and retrieval of materials, key building code issues must be considered when designing GMP warehouse facilities.

Material classification. The first consideration for code compliance in a warehouse is understanding what is being stored. The materials must be identified, and their classification determined. Commodity Class is a classification system that is understood by fire protection engineers and is defined in several standards, most notably the National Fire Protection Agency’s NFPA 13 (1) and the International Fire Code (IFC), Section 3203 (2). When determining the Commodity Class, more than just the material stored needs to be considered. The packaging and pallets must also be included. In pharmaceutical warehouses, raw materials and finished goods usually fall into Commodity Classes III and IV, which include wood, paper, and certain plastics. The following comments, being focused on GMP warehouses, assumes a Commodity Class of III and IV.

Storage configuration. The next critical parameter in determining code requirements is the amount and configuration of the storage. As illustrated previously, pallets can be stored on the floor or even stacked. But racking of pallets is the most efficient form of storage and almost the definition of a warehouse. Providing racking configured to include a flue space behind the pallet load is important. Racks with a flue will eliminate the need for in-rack-sprinklers, which are expensive and an inefficient use of capital. 

Storing materials above 12 feet in height is a significant benchmark. Above this height, racking becomes defined as high-piled combustible storage. The IFC addresses high-piled combustible storage and defines it as “Storage of combustible materials in closely packed piles or combustible materials on pallets, in racks or on shelves where the top of storage is greater than 12 feet” (2). A result of the high-piled combustible storage found in warehouses is the requirement for fire apparatus access roads around the building. Because of the increased fire hazard that high-piled storage represents, ready access by fire trucks is crucial for life safety and property protection. To this end, the IFC requires that an access road configured for fire trucks with a minimum width of 20 feet must be located such that all portions of the exterior walls of the warehouse are within 150 feet of the road. This ensures that the local fire department is able to attack a potential fire from all sides of the warehouse exterior. 

The next benchmark relates to the size of the warehouse. Once the floor area of the high-piled storage reaches 12,000 ft², there are additional considerations that need to be met. Automatic sprinklers and fire detection systems are required as well as smoke and heat removal. In addition, access by fire department personnel are mandated. Above the 12,000-ft² threshold, the IFC requires, in Table 3206.2, that smoke and heat removal be provided (2). This can consist of smoke/heat vents or a mechanical smoke evacuation system. However, smoke and heat removal are expensive and often considered undesirable. When an early suppression fast response (ESFR) sprinkler system is provided, an option exists where smoke and heat removal can be avoided. Although an ESFR system also represents an expense, because it is so effective at extinguishing a fire, it is usually considered a sound investment. 

Exceeding the 12,000-ft² limit also mandates increased access by the fire department. In addition to accessibility for fire trucks, as previously mentioned, the increased hazard requires firefighting personnel have direct access to the building interior. Conventional three-foot-wide, swinging personnel doors provide this building entry. Along the exterior walls that face the fire truck access roads, doors for entry of fire personnel need to be located no more than 125 feet apart. Each of these doors must be clearly identified and a key box installed adjacent. This ensures that firefighters can easily get to and gain access to the interior when needed. It should be noted that loading dock doors are not as easily accessed, and therefore, the code does not allow them to be used as fire personnel access.

As discussed, rack storage can exceed 40 feet in height. But Chapter 32 of the IFC provides a dimensional limit of 40 foot for high-piled combustible storage. Above this height, the code redefines storage as extra-high-rack combustible storage. Extra-high-rack combustible storage is characterized by a significant increase in the fire-load and requires approval of the local fire code official. In addition, the code suggests the fire official call for additional engineered fire protection. Potential additional protection measures include fire-proofing of exposed steel columns, increase sprinkler density, in-rack sprinklers, or additional fire department hose connections. These kinds of heights are not usually seen with warehouses that are integrated into a manufacturing facility; however, they would not be exceptional for warehouses providing distribution of finished product. 

Conclusion

Warehouses have many common features and yet each one is unique. Understanding inventory and the demand for those materials is crucial to an optimized facility. In addition, to promote life safety and property protection, the code identifies unique measures needed to mitigate the inherent dangers found in these facilities. Warehouses are different from manufacturing and offices and require the appropriate knowledge. When designing or renovating a warehouse, it is important to consult the code and integrate the requirements from the start. 

References

1. NFPA, NFPA 13, Standard for the Installation of Sprinkler Systems (2019).
2. International Code Council, 2018 International Fire Code: Chapter 32: High-Piled Combustible Storage (2018), https://codes.iccsafe.org/content/IFC2018/CHAPTER-32-HIGH-PILED-COMBUSTIBLE-STORAGE, accessed 8 Jan. 2019.

Article Details

Pharmaceutical Technology
Vol. 43, No. 2
February 2019
Pages: 43–45

Citation

When referring to this article, please cite it as E. Bohn and "Fundamentals of GMP Warehouse Design," Pharmaceutical Technology 43 (2) 2019.

About the Authors

Eric Bohn, AIA and Magdalena Krapf, AIA, LEED AP, are both partners at JacobsWyper Architects, 1232 Chancellor St., Philadelphia, PA19107, tel: 215.985.0400.