门式起重机主要用于室外的货场、料货场、散货的装卸作业。它的金属结构像门形框架，承载主梁下安装支腿，可以直接在地面的轨道上行走，主梁两端可以具有外伸悬管梁。门式起重机具有利用率高、作业范围大、适应面广、通用性强等特点，在港口货场得到广泛使用。

　　

　　Gantry cranes are mainly used for loadingand unloading of outdoor freight yards, freight yards and bulk cargo.lts metal structure is like a portal frame,legs are installed under the main beam,which can wallk directly onthetrack onthe ground,and the two ends of the main beam can have overhanging cantlever beams. Gantry crane is widely used in port freight yard because of its high utilization rate, wide working range, wide adaptablty and strong versatility.