Racking comes in many guises but there are just two basic cost elements that underpin any decision to choose a particular type — the cost of static space and operational costs. On the former, the cost per pallet stored will vary according to location and specific industries but a figure of £2 to £3 per week would cover most applications. But choosing a particular racking format, or combination, will be governed by other factors like the dynamics of products stored. Some fast-moving products, for example, may need instant selectivity and therefore would rule out block stacking, which is the simplest form of storage but offering 65% of usable storage space. Each business, therefore, must find the optimum solution to suit its operational requirements.
There is one caveat, however, that should be borne in mind, and that is racking’s interface with handling equipment, like forklifts. While APR is the most commonly used racking and offers 100% instant selectivity the amount of storage space lost through aisle spaces will depend heavily on the type of forklifts used. Such racking when used with conventional counterbalanced trucks enables only about 40% of useable storage space. Reach trucks will raise that to 46% and very narrow aisle trucks to 59%. Storage can be further maximised if the forklifts in question are fitted with attachments like pantographs to allow double-deep pallet storage. If the trucks used are the articulating type then more space can be saved at aisle ends when moving from aisle to aisle. Compared with a counterbalanced truck an articulating machine can store 50% more pallets and about 30% more than a reach truck in the same cube, which explains why many warehouse operators design their racking around these trucks. Drive in/drive through racking, while limiting accessibility, raises the bar even further to 65%, gravity fed or live racking to 80% and aisle-free, high density systems offer 85%. Other variants within the high density racking sector include push-back, but this is usually limited to five-pallet deep storage lanes.
Whatever racking format is chosen, operational and safety procedures, governed by delivery times, will strongly influence choice. Where sub-pallet loads, like totes, are handled, a growing trend in e-tailing, then order picking time and accuracy are important and this is where apparently dumb racking/shelving take on a new coat. To save much time walking around, order pickers can wait for goods to be delivered to them by mini robots, stacker cranes or shuttles in a paperless operation based on pick-to-light or voice picking, which virtually eliminates picking errors. Obviously, such automated systems are costly to install and maintain but as with most MHE it is not the initial cost that should dominate buying decisions but the life cycle costs, including how the chosen racking impacts interface costs like rent, rates, utilities and building construction costs. Radio-controlled shuttles, in particular, like those from BT, can save significant labour costs because more than one shuttle can be controlled by only one forklift driver and so he can handle multiple loads at the same time.
Energy cost in certain applications, like cold stores, can be so high, typically 20-30% of total store running costs, that high storage density is often specified, usually either mobile or drive-in. Mobiles, typically three times as costly as APR initially, offer 100% selectivity but with a time delay because each aisle must be opened first before truck ingress. Drive-in is also commonly used in cold stores but has poor stock selectivity and high accident rates against it. Cold stores can, however, to some extent have the best of both worlds – 100% instant stock selectivity and high density storage thanks to the effective cold store cabs that can now be fitted to articulating forklifts.
In a fast-moving logistics world where online shopping is transforming warehouse operations, time compression techniques to enable next-day delivery to the consumers’ homes emphasise the need to pay the utmost attention to how racking/shelving can combat the tyranny of time. Shorter customer delivery times are crucial because they cut stock dwell times, and therefore inventory costs, and they improve customer service levels, which helps to retain their loyalty. Those who neglect the power of carefully-chosen racking to deliver competitive edge do so at their peril.
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