Safe Operating Practices, Signals, and Communication
One voice, many stops
OSHA 1926.1419 through 1926.1423 cover hand, voice, audible, and radio signals. A single designated signal person directs the operator; the signal system must be agreed on before the lift. Any person may give a stop signal, and the operator must obey it. If a signal is unclear or the operator loses sight of the signal person, stop. Radio signals must be tested, and a relay signal person may be used when the operator cannot see the load.
Operating discipline
Keep the load low, avoid side pulls and dragging, use tag lines, and never let anyone ride the hook or the load. Do not lift over people. Use the anti-two-block system and never rely on feel to prevent two-blocking. Travel with the boom aligned and the load trailing, per the manufacturer. Never leave the controls with a load suspended; land it and relieve tension.
Worked example
A rigger who is not the designated signal person sees the load drifting toward a worker and gives the stop hand signal-arm extended, palm down, moving back and forth. The operator stops immediately. The designated signal person's radio call to 'hoist' does not override a stop from any person. The lift is not resumed until the hazard is corrected and a clear signal is given.
Traps
Thinking only the signal person can stop the lift; using an unqualified signal person; relying on a cell phone instead of a tested radio; wrapping a tag line around a hand; and free-falling a load are common failures. Also do not assume a hand signal means the same thing across every employer; confirm the signal chart.