Excavating machinery generally consists of a power unit, transmission unit, traveling mechanism, and working device. Single-bucket excavators and bucket wheel excavators also have a turntable, while multi-bucket excavators also have a material handling device. Power units include diesel engines, electric motors, diesel generator sets, or external power converter sets. Diesel engines and electric motors are mostly used in medium and small-sized excavators, driven centrally by a single prime mover; the two are interchangeable. Diesel generator sets and external power converter sets are used in large and medium-sized excavators, driven by multiple motors in a distributed manner. The traveling mechanism is mainly used to support the machine, change its working position, and move it to different work sites; additionally, the buckets of chain bucket excavators and ring wheel excavators cut the soil as the traveling mechanism moves continuously. Travel mechanisms include tracked, wheeled, walking, rail-mounted, floating, and trailer-mounted types.
Tracked excavators are used when the work site is fixed and requires a low ground pressure; wheeled excavators are used when the work site is variable; rail-mounted excavators are used when special construction conditions necessitate the installation of dedicated tracks; floating excavators are used for excavating underwater soil; trailer-mounted excavators are used when the walking device of a small single-bucket excavator lacks a power source; and walking excavators are used when the work site is fixed and the machine is heavy. Walking excavators are mostly used in large and medium-sized dragline excavators and bucket wheel excavators.
