Notranji portalni žerjav je mostni žerjav, pri katerem je most na obeh straneh podprt z nogami na tleh. Strukturno je sestavljen iz droga, pogonskega mehanizma vozička, dvižnega vozička in električnih delov. Nekateri portalni žerjavi imajo samo na eni strani opornike, druga stran pa je podprta na tovarniški zgradbi ali podstavku, kar se imenuje pol portalni žerjav. Portalni žerjav je sestavljen iz zgornjega mostnega okvirja (vključno z glavnim in končnim nosilcem), opornikov, spodnjega nosilca in drugih delov. Da bi razširili delovno območje žerjava, lahko glavni nosilec sega čez opornike na eno ali obe strani in tvori konzolo. Dvižni voziček z roko se lahko uporablja tudi za razširitev območja delovanja žerjava z nagibom in vrtenjem roke. Portalne žerjave lahko razvrstimo glede na strukturo okvirja vrat, obliko glavnega nosilca, strukturo glavnega nosilca in obliko uporabe.

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.