Crane Types, Components and Terminology
A self-erect crane raises and dismantles itself using its own mast sections and jib, usually with a ballast/erection frame, without a separate mobile crane. Candidates must know the parts by name and function.
Structure
- Base/ballast frame and ballast weights provide the counter-moment that keeps the crane stable; ballast is part of the stability calculation, not a convenience.
- Mast sections bolt or pin together; the slew ring transmits load from the slewing assembly into the mast and allows rotation.
- Jib carries the trolley and load; the counter-jib carries counterweight and often the hoist machinery.
- Trolley, hoist rope, hook block, and limit switches (hoist high/low, trolley in/out, slew) are the operating components.
Terminology traps
- Rated capacity is the maximum for a given radius and configuration; safe working load is the rated capacity after applying the relevant factors in the specific regime.
- Radius is measured from the slew centre to the hook, not to the jib tip.
- Out-of-service and in-service wind ratings are different figures; questions swap them.
- Free-standing height vs climbed/anchored height changes capacity dramatically.
Rule of thumb
If a question gives a configuration (ballast set, jib length, free-standing height) that differs from the load chart in front of you, the chart does not apply - the correct answer is "obtain the chart for that configuration".