Conflicting Signals on a Blind Lift
A 70-ton telescopic crane is setting a 4,500 lb steel beam into a rack inside a pre-engineered building. The operator can see the boom tip but not the load below the roof line. A signal person at the load has a two-way radio, but the battery indicator is flashing low and the channel is shared with a concrete crew. A second rigger at the landing point is visible to the operator and is giving hand signals, but those signals conflict with the radio instructions. The rigger at the load also steps behind a column, so the operator loses sight of both the load and that signal person. The lift is 60 ft radius and the beam must be rotated 90 degrees before landing. The site policy says radios are the primary communication method and hand signals are backup. The operator hears 'boom down' on the radio while the visible rigger gives 'stop.' The load is drifting toward a rack. No one has been designated as the signal person in charge.
1. What should the operator do immediately after hearing 'boom down' on the radio while the visible rigger gives 'stop'?
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The operator must stop all crane motion immediately. A stop signal from anyone must be obeyed, and conflicting signals are a reason to stop, not to choose the one that seems more convenient. The operator should hold the controls, sound the horn if that is the site's warning method, and not resume until one designated signal person gives a clear, unambiguous signal. The load drifting toward the rack increases the urgency; the operator should not boom down or swing while blind and receiving conflicting directions. If an emergency lowering is pre-planned, it should be performed only with clear communication and a confirmed clear landing area. The immediate priority is to stop, secure the load, and re-establish single-source communication.
2. Who should direct the lift, and what communication arrangement is required before resuming?
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One qualified signal person must be designated as in charge of the lift. That person must have a clear view of the load, the crane, and the intended path, or the lift must use a relay signal person who can see both the load and the operator. The designated signal person should be the one at the load if visibility can be restored, or a relay should be positioned so the operator receives signals from only one source at a time. The radio should be on a dedicated channel, tested before the lift, with a backup hand-signal method agreed upon. The visible rigger may give a stop signal at any time, but should not give directing signals unless designated. The operator follows only the designated signal person's signals, except that a stop signal from anyone must be obeyed. Before resuming, the signal person at the load must move out from behind the column or a relay must be established.
3. How should the low battery and shared radio channel be handled?
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The low battery and shared channel must be corrected before the lift continues. Replace the battery or use a fully charged spare radio, and confirm the radio is on a dedicated channel not used by the concrete crew. Perform a radio check at the actual lift position, including the boom tip and load area. Agree on an emergency stop word and a lost-communication procedure: if the radio fails or the signal is unclear, the operator stops and holds until communication is restored or a planned backup is in place. Hand signals can be the backup only if the operator and signal person can see each other; otherwise a relay signal person is needed. A cell phone should not be substituted as the primary signal method unless the site's procedures specifically allow it and reception is confirmed.