The boom is the primary working tool of hydraulic excavators and cranes. On excavators, it connects the upper carriage to the stick and together determines the maximum digging depth and reach. Standard designs distinguish between monobloc booms (single piece, rigid) and articulated booms (adjustable, two-piece with hydraulic articulation).
Articulated booms enable deeper digging directly in front of the machine and are particularly popular in canal construction. For demolition work, there are special high-reach booms (high-reach demolition) with reaches up to 40 meters; for waterway maintenance, long-reach booms with up to 24 meters reach at reduced digging forces.
Boom construction is a compromise between weight, rigidity, and reach. High-strength fine-grain steel (S690-S960) enables thinner wall thicknesses with equal strength. On cranes, boom length together with load capacity determines the performance class — for example, a Liebherr LTM 1300-6.4 achieves 80 meters of outreach.