Blind Set with Intermittent Radio and Load Rotation
A 6,000 lb precast panel is being set into a pocket in a wall. The crane operator cannot see the pocket; a signal person is at the wall edge with a clear view. Radio communication is intermittent, and the panel begins a slow rotation as it clears the wall. Two workers are guiding it with tag lines from the opposite side. The panel is 12 ft tall and has a 3 ft overhang past the pocket. Wind is 10 mph. The signal person's hand signals are visible to the operator only when the boom is not between them.
1. What is your immediate action when the panel starts rotating and radio communication is unreliable?
Read the worked answer
Stop the lift and hold the load. Do not continue a blind set with intermittent communication. The slow rotation is a warning that the load is not under control and may contact the wall or swing toward the tag-line workers. Keep personnel clear, maintain tension on the tag lines if it is safe, and have the operator hold hoist and swing until a reliable signal method is established. If the panel is drifting toward people or the wall, use the agreed emergency stop and lower or set it down in a clear area.
2. Establish a communication plan before restarting the set.
Read the worked answer
Designate one lead signal person and one alternate. If radio is unreliable, use standard hand signals with a clear line of sight, or station a relay signal person who can see both the lead signal person and the operator. Agree on stop, emergency stop, hoist, lower, swing, and dog-everything signals before the load moves. Test the radio and have a backup method. The operator must not act on conflicting signals; when in doubt, stop. No load movement should occur while the signal path is blocked by the boom.
3. What load-control measures are needed for the final alignment?
Read the worked answer
Use two tag lines from safe positions so the panel cannot rotate freely. Keep workers out from under the panel and away from the pocket pinch points. Control the panel with the tag lines and crane functions together; do not use workers' hands to stop a swinging load. Account for the 3 ft overhang and 10 mph wind, which can cause drift. Plan a safe set-down point if alignment cannot be controlled. Lower slowly, confirm the panel is fully engaged in the pocket, and only then release the rigging.