High-rise shelving consists of extended height uprights that support shelves to heights typically in the 14- to 21- foot range. Unlike mezzanine shelving, the aisles are clear of mezzanines, and upper elevations of the shelving system are accessed by use of a machine that elevates the warehouse personnel to the appropriate level. Two common machine are used to transport through the systems: order picking lift trucks and storage/retrieval (S/R) machines. Order picking lift trucks are free-path lift trucks with an operator's cab located in the front of the telescoping mast of the truck. As the forks of the truck are raised, the operator's cab raises in kind. The lift-truck operator is thus raised to the elevation required in the shelving to accomplish put/pick activities. A S/R machine is a device that rides on a rail at floor level. An operator's cab raises and lowers on a vertical mast. One of these devices, not found as frequently today, particularly in small parts systems, is the stacker crane. Basically an upside down lift truck, this machine is suspended from a crane bridge.
The high-rise configuration provides efficient vertical space utilization and increases labor productivity by increasing the speed with which warehouse personnel move within the system. Walking is replaced by riding. Additionally, the order picking lift trucks and S/R machine can be equipped with computer terminals to automatically transmit instructions to the operator.
