Earthing system creates conditions for normal operation of gantry crane and personal safety, thus avoiding electric shock and other danger.
A ring earthing system shall be provided on the gantry crane. Each and every electrical equipment shall be connected to this earthing at least at two points. It shall conform to general specification for earthing. 
Rubber matting shall be provided in front of the protective and control panels. All bonds between earth conductors and crane parts shall be welded if possible, or riveted and soldered. Where screwed bonds are made, care shall be taken that there is satisfactory contact surface and nuts shall be locked to prevent their loosening. Earth connections to equipment shall be made by means of multi strand flexible conductor to adequate section. 
The earth ring on the crane/ machine shall be connected to the plant earthing system through to gantry rails. Each end of each gantry rail shall be bonded to the plant earthing system.