B30.18 applies to the construction, installation, operation, inspection, and maintenance of hand-powered and power-driven overhead and gantry cranes that have a top or under running multiple girder bridge with a vertically guided carriage, with or without a top or under running trolley. The requirements included in this volume also apply to stacker cranes having the same fundamental characteristics, such as cantilever gantry and semi-gantry stacker cranes.