Portal Crane (also known as gantry crane) is a kind of gantry crane which is supported by two legs on the ground.The structure consists of door frame, big car operating mechanism, lifting trolley and electric parts.Some gantry cranes only have a leg on one side and a leg on the other side running on the workshop or trestle bridge.The portal frame of gantry crane (including main beam and end beam), supporting leg, lower beam, etc.In order to enlarge the crane operation range, the main girder can extend out the legs to one or both sides, forming a cantilever.Also can use the crane with the arm frame, through the arm frame pitch and rotation to expand the crane operating range.