室内门式起重机是桥架由两侧支腿支撑在地面轨道上的桥式起重机。结构上由桅杆、小车运行机构、起升小车及电气部分组成。有的门式起重机一侧只有支腿，另一侧支撑在厂房或栈桥上，称为半门式起重机。门式起重机由上桥架（包括主梁和端梁）、支腿、下梁等部件组成。为了扩大起重机的作业范围，主梁可向一侧或两侧延伸超出支腿，形成悬臂。带臂架的起重小车也可用于通过臂架的俯仰和旋转来扩大起重机的操作范围。门式起重机可按门架结构、主梁形式、主梁结构、使用形式等分类。

Gantry cranes are widely used in various industries of the national economy such as metallurgy, electric power, ports, logistics, machinery manufacturing and marine engineering. They are important process equipment for industrial production and are related to the safety of people's lives and the safety of national economic operations. and social stability are important components of public security in all countries. The development momentum of my country's hoisting machinery industry is strong. As of the end of 2017, the number of hoisting machinery in my country reached 2.2375 million units. According to the "Notice of the State Administration for Market Regulation on the Safety Status of National Special Equipment in 2017", the accident rate and fatality rate of cranes in my country rank first among the eight categories of special equipment. Therefore, there is an urgent need for an effective means to ensure the safety of in-service cranes. Safe and reliable operation of machinery.