Blind lift over a live traffic lane
You must lift 2.4 t of formwork panels from a laydown area on the landward side of the wharf to a barge on the seaward side. The crane is positioned so the operator cannot see the barge deck; the slew path crosses a wharf road used by trucks, and there is a 6 m gap between the crane and a row of stacked containers that blocks the line of sight. Two doggers are available, one with a radio and one with hand signals only. Wind is 15 knots across the slew path. The barge moves 0.5 m vertically with the swell.
1. Design the communication and control arrangement for this lift, and justify each element.
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The lift is blind, so the operator must rely on a single designated signal person and a controlled exclusion zone.
One dogger should be the sole signaller, positioned where they can see both the load and the landing point and can be seen or heard by the operator. The second dogger can act as a spotter at the road but must not give signals, because two signal sources create conflicting commands.
Use the radio dogger as signaller, with an agreed channel, a radio check before the lift, and a fallback hand-signal code in case the radio fails. Agree in advance: who stops the lift, the stop signal, and the phrase for "load moving blind".
Control the road: stop trucks with barriers or a flagger before the load crosses, and keep the exclusion zone under the load for the whole slew. The containers block sight, so the signaller must give continuous position calls, not just start and finish.
For the barge, the 0.5 m swell means the landing point moves. Agree a landing procedure: hold the load clear, wait for the swell to settle, lower on the signaller's command, and never chase the deck. Account for the 15 knots across the slew path by keeping the load low and using a tag line.
2. Halfway through the slew the radio fails. What do you do, and what should have prevented the problem?
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Stop the slew immediately and hold the load. Do not continue blind on assumption. If the load is over the road, hold position and keep the exclusion zone; if it is clear of people and traffic, lower it to a safe resting place only if the signaller's fallback signal is visible and unambiguous.
The fallback matters: with the containers blocking sight, hand signals may not be visible to the operator, which is exactly why a radio check and a backup plan were needed before the lift. If no signal can be established, the operator should hold and wait for the signaller to reach a position of visibility or for a replacement radio.
Prevention: a pre-lift radio check, a charged spare battery or second radio, and an agreed lost-communication procedure - hold, do not move, re-establish contact. The lift plan should have identified the blind zone and specified that the operator must be able to see the signaller at all times, or that a relay signaller is used.