~Four-link type portal crane has been extensively applied to loading and unloading at port and materiel handling at dockyard and metallurgy industry, The main structures are composed of steel frame, lifting mechanism, luffing mechanism, slewing mechanism, crane travel mechanism, spreader device(grab, container spreader, and hook and electromagnetic disk), electrical equipment and other accessory equipments for safety. Steel structures include jib and A-frame, slewing platform and gantry frame.
  Referenced standards: GB17495-1998 Harbor portal crane technical specifications, GB6067-85 Lifting equipments Safety specification, GB3811-2008 Crane design standards,   ISO standards,   FEM standards and JIS standards.