Inventory Management: Storage Considerations
The right combination of racks and shelving can maximize space and allow rapid access, location and checkout of essential parts
One major challenge facing maintenance and engineering managers in institutional and commercial organizations is developing a strategic approach to storing and managing the spare parts required to operate and maintain facilities.
Each facility requires parts that are unique to its operation. A school campus or hospital system faces additional challenges relating to: the number, location and age of buildings; the replacement of old technology with up-to-date technology; and the storage of the variety of parts for equipment that has changed over the years. For example, ceilings, lighting systems, plumbing systems and doors often feature products that have changed over the decades.
Overseeing the storage of supplies and parts becomes more complicated when several buildings are spread out geographically, as on a college or medical campus.
It is essential to store the variety of parts — many of the same family — in a manner that maximizes the use of available space, accents part-storage density, ensures a minimum yet sufficient quantity, and allows rapid access, location, and checkout.
Develop a Strategy
Because of the space limitations usually placed on parts storerooms that support maintenance, repair, and operations (MRO), it is essential managers develop an efficient parts-storage strategy.
Not surprisingly, one common question is, “What is the best method of parts storage for my facility?” In the manufacturing and industrial sectors, this question is easier to answer, as most of the parts are small enough to fit into modular drawer cabinets and 12-, 18-, and 24-inch shelving.
But it a school system or an administrative building complex, parts are generally larger. Also, each site has its own special requirements, depending on the number, size, and type of parts to be stored.
There is no across-the-board best method when it comes to MRO parts inventory management. But some general guidelines exist, offering steps to take and not to take, as well as storage systems to use and not to use.
Modular-Drawer Cabinets
Without a doubt, steel modular-drawer cabinets offer the greatest part-storage density of all available storage media, as well as the smallest possible footprint, because of their ability to store parts in three dimensions — height, width and depth. These cabinets are popular in the manufacturing industry because they can store a variety of parts, both generic and from the original equipment manufacturer (OEM).
They can store and organize very small parts, such as miniature light bulbs and overload heaters, up to the larger parts, such as circuit boards, air cylinders, and temperature and pressure gauges.
In other words, they can store parts as small as an aspirin up to parts as large as a 5-pound bag of sugar without difficulty. Adjustable partitions and dividers allow for varying part size, and supervisors can place a text or bar-code label for parts identification on the divider. Plastic bin cups are available for the very small parts.
Cabinets are about 30 inches square, stand about eye level, have up to 15 drawers and come in several colors. Drawer capacity is about 400 pounds each, and they vary in depth from about 2 inches to 13 inches. The number of drawers selected determines the price.
Modular-drawer cabinets reduce the amount of total square footage needed for storage, and they provide additional storage space on top of the cabinets for bulkier, lighter items. They present a layout that is efficient, cost-effective, attractive, and very professional, and managers can expand them neatly and easily. But they can be more expensive than standard, steel shelving.
Shelving Recommendations
Shelving provides effective parts storage if supervisors use both the horizontal and depth features completely and effectively. Otherwise, they can waste shelf space. Supervisors can adjust the distance between shelves according to the height of the part. Shelving units that are bolted together and the type available in retail hardware stores are not recommended for MRO spare-parts storerooms. When specifying shelving, consider the following recommendations:
• Buy closed shelving where the backs and side are solid, not open.
• Use shelving that is 36 inches wide. Shelving that is 42-48 inches wide is acceptable but more expensive.
• Use a common back panel for back-to-back shelving installations.
• Install cross-braces to increase stability.
• Use medium-duty, 22-gauge shelving that has a 600-pound load capacity.
• Consider using in-shelf drawer units at knee to shoulder level to increase the density of parts storage.
• Buy shelving that is 72-87 inches tall. Shelving taller than 6 feet requires a step-stool or four-wheel safety ladder.
• Avoid shelving taller than 87 inches. Parts-storage and retrieval, visibility, access, and safety are major concerns.
• Use metal or sturdy plastic bin boxes to increase part-storage density.
Measuring Shelving Depth
A number of applications use 12-inch shelving, but managers should avoid purchasing or installing such shelving, unless the clear majority of parts to be stored on them — more than 80 percent — are less than 12 inches long. In some storerooms, they work well, especially where parts can fit neatly on the shelf.
Such parts include common hardware, pipe fittings under 1 inch inner diameter, pneumatic and hydraulic fittings, quick-disconnect fittings, small electrical and conduit fittings, plugs, switches, bearings, and smaller OEM parts.
But often, when parts are too large or long to fit on 12-inch shelving, technicians place them on top shelf of the unit. This step presents a real danger of striking a fire sprinkler head if the ceiling is low. If other cases, technicians store parts longer than 12 inches lengthwise, wasting valuable storage space. Storage depth is restricted if the parts are 7 inches long or longer. Even if packaged, they require more horizontal shelving space.
In other cases, parts too large to be neatly stored on 12-inch shelving are stored on bulk storage or pallet racks. But this can lead to parts being lost or damaged, decrease consolidation and efficiency, and increase overall carrying costs.
If there were an industry-wide standard for parts storage, 18-inch shelving would measure up well. This depth provides the optimum storage depth for most parts that are maintained in MRO parts storerooms. Shelving that is 18 inches deep offers enough room for back-to-back parts storage, especially those parts in boxes. Supervisors can subdivide metal or plastic bin boxes with dividers or bin cups, further enhancing storage density.
In many installations of 18-inch shelving, part consolidation and organizing increased part-storage density, leading to a reduction in the number of parts requiring storage and lower overall inventory value.
Shelving that is 24 inches deep is the least useful for general parts storage. Considerable shelf depth space is wasted if parts are not 22-24 inches long. To store longer parts, consider setting up two of these units back-to-back with no back panel. The shelves both above and below the long parts had most of their shelf space wasted. For storerooms with long, or larger and lighter-weight parts, consider bulk-storage racks, 24 inches deep, 96 inches wide, and 72 inches high.
Bulk-Storage Racks
Bulk-storage racks are available in a range of lengths, depths, and heights. These racks can store parts too large, bulky or heavy for shelving. Products such as air filters, flexible ductwork, longer air or hydraulic cylinders, midsize gearboxes, conveyor belts, speed reducers, gear motors, and motors generally are stored on bulk-storage racks.
Crossbeams placed just above floor level enable parts storage off the floor. Or supervisors can store pallets on the floor under pallet racks to hold heavier, larger motors, gearboxes and machine parts.
Storerooms can use any combination of these fixtures to effectively and efficiently store parts. Well-organized storerooms give maintenance and engineering departments the support they need to keep equipment in the best possible operating condition. Perhaps most importantly, they enable technicians to make repairs more quickly and efficiently, and the organization remains more competitive and successful.
Frank Murphy, CPMM, is the founder and president of Inventory Management Services Inc. in Greenville, S.C.
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