Erection in a Tight Lane with a Powerline
A self-erecting tower crane is to be erected in a narrow service lane behind a row of shops. The lane is 4.5 m wide. The crane's transport trailer can only enter from one end, and the erection procedure requires the jib to unfold over the lane. An overhead low-voltage powerline runs along one side of the lane at about 5.5 m above ground, and the crane's fully erected jib height will be 9 m. The erection supervisor plans to use the crane's own self-erection sequence, which involves raising the mast and unfolding the jib, and says the powerline is 'only low voltage'. Two workers will guide the jib by hand during unfolding. The weather forecast is for gusts of 14 m/s during the planned erection window, and the crane manual states erection should not proceed above 10 m/s.
1. Identify the erection hazards and explain why the planned controls are inadequate.
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The main hazards are contact with the overhead powerline, insufficient lane width for the unfolding jib, manual handling of the jib during unfolding, and wind above the manufacturer's erection limit. The powerline is not safe because it is low voltage; any contact can be fatal, and the jib will pass within a few metres of it. Approach distances to overhead lines are set by the relevant electrical safety rules and must be maintained, and if they cannot be, the line should be isolated and proven de-energised, or the crane relocated. The 4.5 m lane is tight for a crane whose jib unfolds over the lane, and there may be insufficient room for the transport trailer, the crane and the personnel. Guiding the jib by hand during unfolding is dangerous because the jib can move unexpectedly and crush hands or trap workers; the manufacturer's procedure should be followed, which may require tag lines or controlled movement, not hands on the jib. The wind forecast of 14 m/s exceeds the manual's 10 m/s limit, so erection should not start. The supervisor's plan should be stopped and replanned.
2. Outline a safe erection plan for this location.
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The plan should start with a documented risk assessment and a check that the manufacturer's erection procedure is followed. The powerline must be isolated and proven de-energised with a permit, or the crane must be positioned so the jib and any load cannot approach the line within the required distance; if neither is possible, the lift should not proceed. The lane should be closed to traffic and pedestrians, with exclusion zones marked under the jib and around the crane. The transport trailer and crane should be positioned so the jib can unfold without obstruction, which may mean a different entry direction or a temporary road closure. Workers should not guide the jib by hand; use tag lines and the manufacturer's controls, and keep personnel clear of the jib's path. Erection should only proceed when the wind is within the manual's limit, with a anemometer on site and a stop-work trigger. A competent erection supervisor should sign off each stage, and the crane should be inspected and tested before use.