Crane operation, communication, hand and whistle signals
Safe operation depends on smooth, predictable control inputs and unambiguous communication. One person, the dogman or rigger, should direct the lift, and only one. The operator must obey signals from the designated signaller, but must stop immediately for a stop signal from anyone. If communication is lost, stop. If the operator cannot see the load or the signaller, use radio or a relay signaller.
Know the standard hand signals: raise and lower load, raise and lower boom, slew left and right, extend and retract boom, stop, emergency stop, dog everything. Whistle signals follow the same intent: one short for raise or hoist, two short for lower, a long for stop. Signals must be clear, distinct and given from a position visible to the operator.
Operational discipline includes avoiding rapid slewing that swings the load, avoiding side loading the boom, keeping the load as low as practicable, using taglines, and never leaving the controls with a load suspended. Watch the load, the radius and the capacity indicator. Beware of wind acting on large sail-area loads.
Traps: accepting signals from an unknown person, continuing after a radio failure, and confusing slew signals. Another trap is slewing too fast and inducing load swing that increases radius and capacity demand.
Rule of thumb: one signaller, clear line of sight, radio backup, and stop for anyone. Worked example: the radio fails mid-lift. Correct action is to stop, lower the load safely if possible with the assistance of a relay signaller in sight, then re-establish communication before continuing.