Unutarnji portalni kran je mosni kran u kojem je most poduprt na zemljinoj stazi pomoću nogu s obje strane. Strukturno se sastoji od jarbola, pogonskog mehanizma kolica, kolica za podizanje i električnih dijelova. Neki portalni kranovi imaju samo potporne nosače na jednoj strani, a druga strana je oslonjena na tvorničku zgradu ili postolje, što se naziva polu-portalni kran. Portalna dizalica sastoji se od gornjeg okvira mosta (uključujući glavnu gredu i krajnju gredu), potpornih nosača, donje grede i drugih dijelova. Kako bi se proširio radni raspon dizalice, glavna greda se može protezati izvan potpora na jednu ili obje strane kako bi oblikovala konzolu. Kolica za podizanje sa granom također se mogu koristiti za proširenje radnog raspona dizalice nagibom i rotacijom grane. Portalne dizalice mogu se klasificirati prema strukturi okvira vrata, obliku glavne grede, strukturi glavne grede i obliku 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.