Tower Crane Types, Components, and Configuration
Tower Crane Types, Components, and Configuration
Tower cranes are broadly classified by their configuration: hammerhead (horizontal jib with counter-jib and trolley), luffing jib (pivoting jib that raises/lowers), and flat-top (no cathead or pendant lines). Each has distinct operational characteristics: hammerheads are common for general construction; luffing jibs suit confined sites and can reduce swept radius; flat-tops ease erection and allow multiple cranes to overlap. Candidates must also know base types (fixed, rail-mounted, climbing) and tower assembly (mast sections, slewing unit, cab, jib, counter-jib, counterweights).
Key components include the mast, slewing ring, operator cab, hoist drum and rope, trolley, hook block, pendants (or tie bars), counterweights, and safety devices such as moment limiter, hoist limit switches, and anemometer. Traps often involve confusing luffing vs. hammerhead load charts, or assuming a flat-top has no load moment indicator-all tower cranes require overload protection. Another trap: counterweight is not ballast for stability alone; it balances the jib and affects backward stability.
Worked example / rule of thumb: For a hammerhead crane, the maximum capacity is at the shortest radius (near the mast); capacity decreases as the trolley moves outward. A common rule: never exceed the load chart for the actual radius, and remember that jib length and counterweight are fixed for a given configuration-changing them requires a new chart. Always verify the crane's configuration (jib length, counterweight, rope falls) matches the chart in use.