The crane boom is the load-carrying element that transfers the load from the hook to the tower or upper carriage. In tower cranes, a distinction is made between trolley booms (horizontal, with the hoist moving to the load position) and luffing booms (adjustable at an angle, for confined spaces). Mobile cranes typically use telescopic booms as standard — multiple box profiles nested together and hydraulically extendable.
Telescopic booms on modern mobile cranes are made from high-strength fine-grain steel (S960-S1300) with oval or polygonal cross-sections. A 5-section telescopic boom on a 300-ton crane can achieve boom lengths up to 80 meters. Lattice booms made from bolted angle profile segments enable even greater lengths (up to 200 m+) with lower dead weight — however, they require complex assembly.
Load capacity decreases significantly with increased reach: at double the reach, lifting capacity is halved (simplified). Therefore, crane booms are always a compromise between maximum reach and load capacity. Electronic load moment limitation calculates the permissible load for each boom position and prevents overloading.