Slewing, Travelling, Trolleying and Precision Load Placement
Smooth control is a safety skill. Slewing accelerates the load outward through centrifugal effect, so the load swings wide of the jib line; a sudden stop reverses the swing. Trolleying in or out changes radius and therefore load moment, so trolleying out with a heavy load can overload the crane even if the load was within capacity at the original radius. Travelling (for rail-mounted cranes) adds rail condition, track alignment, stops, and the need to keep the load low and controlled. Hoisting must avoid shock loading: take up slack gently, lift clear, then move.
Precision placement requires anticipation. Plan the path before the lift: clear of people, structures, powerlines and other cranes; know where the load will land and who will guide it. Use tag lines to control rotation, but never let a person stand under the load or hold a tag line wrapped around a hand. Approach the landing point slightly high, lower slowly, and set down only when the dogger signals and the landing area is clear. Avoid side loading the jib by dragging loads; never use the crane to pull.
Traps: assuming a load within capacity at one radius is safe at all radii; using the slew brake as a positioning tool; rapid reversing that shocks the structure; and letting the load swing toward people because the signal was unclear. Another trap is forgetting that wind pushes the load and the jib differently, changing the swing behaviour.
Rule of thumb: slow is smooth, smooth is safe - plan the path, lift clear, travel low, land gently.