Drive-in racking is an interesting technical solution to the problem: How can I get the space utilisation of block stacking without the crushing problems associated with this type of storage?
Drive-in racking is very simple. It comprises standard racking uprights arranged in a block without beams. The uprights are connected at the top to give the structure stability and by pallet support rails running from the front to the back of the block. Usually the uprights would be spaced one pallet apart. The depth of a scheme will be limited by operational constraints, normally the time it takes for a truck to drive into, and reverse out of, the lane. Typically a block of drive-in will be sized by the number of pallets being stored or handled, for example if you would normally ship 24 pallets in a vehicle, then it would be convenient for your racking to be three pallets high and eight pallets deep, or multiples thereof.
Drive-in racking can rise to heights in excess of twelve metres, the limit being the lift truck and the required speed of operation. Bear in mind that standard counterbalance trucks can lift to a maximum of around seven metres – modern reach trucks to over ten metres. Each lane will be wide enough for the truck to drive down with a pallet on its forks. Because of the pallet rails, any lifting of the load must take place before the truck enters the aisle.
Pallets are supported by pallet rails at each level above the ground. The width of the lanes is dictated by the pallet being used. In line with SEMA tolerances, the two critical dimensions are the lane width and the clear entry between pallet rails. When using a 1200mm wide pallet the lane width should be 1350mm, and the clear entry 1175mm. These dimensions are very important as they are designed to eliminate the possibility of pallets being mislocated and falling through. Completing the installation will be an aisle giving access to the block face.
Space utilisation and minimal product damage are the main benefits of drive-in racking. Typically 85% space utilisation is achievable. What you sacrifice is load selectivity. First-in, last-out is how it works so drive-in racking is ideal for batch production, and where stock rotation is not critical. Usually a lane is given over to a single product line and would store a typical order quantity. The illustrated soft drink’s installation shows this principle in practice.
An alternative is drive-through racking where the lanes are not blind. This has the benefit of increasing load selectivity and speed of operation. First in, first out stock rotation is easily achievable with a drive-through system. The down side of drive-through is that it uses more space because of the additional truck aisle..
Within drive-in or drive-through racking, load safety is excellent. Product is protected because it must be within the confines of the pallet to get in the storage system, and every pallet is supported. An interesting alternative, if your loads can support the weight, is to block stack two pallets in each bottom location, with the pallets above being individually supported. This has the benefit of increasing the manoeuvring space for the lift truck, slightly reducing the scheme cost and increasing space utilisation.
The real benefits of drive-in racking become apparent when comparing it to block stacking: selectivity, speed of throughput and storage stability are all better. It has no operational disadvantages, but pallets must be in a good condition and your truck drivers should be trained to work in smaller spaces. A small price to pay for a significant increase in storage efficiency.