Parts of a Tower Crane


The construction industry has the capabilities to build some impressive structures reaching ever-increasing heights. The work in building these utilizes a variety of construction equipment, with tower cranes typically providing the means to lift and move tools, materials and building parts around a site. The design of a tower crane includes a few different components.


  • The base of a tower crane typically has a steel unit, with this connected to a custom-built concrete pad. It provides the structure with stability, therefore needs to be well-designed and well-constructed.


  • The mast provides a tower crane with its height, and comprises individual steel sections connected together. The number of sections determines the height of the crane, and a tower crane typically has a design which enables the mast to grow during construction by adding further sections. This ensures it has adequate height to safely and efficiently carry out the work required.

Slewing Unit/Top Climber

  • A slewing unit sits at the top of the mas. This houses the motor and machinery which enables the crane to rotate. A top climber sits just below the slewing unit and this piece of equipment enables the mast to grow. The slewing unit disconnects from the mast, with hydraulic rams in the top climber raising it higher. On completion of this process, the crane can hoist and insert a new section of mast, with the slewing unit then reconnected.


  • The boom is the working arm of a tower crane. Formed of individual steel sections connected together, it extends out from the top of the slewing unit parallel to the ground. A small trolley attached to the underside can run the length of the boom, and this holds the hoisting mechanism. The movement of the trolley, in combination with the rotation of the crane, enables accurate positioning for pick-up and set-down of loads.

Machinery Arm

  • The machinery arm also extends out from the top of the slewing unit, in the opposite direction to the boom. Shorter in length and formed of steel sections, it houses machinery and electrics needed for the operation of the crane. Large counterweights on the machinery arm balance the weight of the boom and loads.

Chain and Hook

  • The chain and hook sit below the small trolley on the boom. Raised and lowered by the hoisting mechanism, it picks up loads and places them in the required location.

Operating Cab

  • The driver of a tower crane sits in the operating cab, which houses the controls needed to operate the equipment. Typically located on top of the slewing unit, it has enough space for one person to sit comfortably and use the controls. The cab has large windows fitted on front and sides to provide a good all-round view for safe operation.


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