TOPIC COMMENTARY

Cranes and precast panel erecting

Article contributed by JOHN HUMPHRIES – CICA

Working with or around precast concrete panels is a high-risk operation. The collapse of any concrete panel, even a small one, can have catastrophic consequences for workers, the public and property.

Recently published accident statistics reflect a high representation of incidents involving precast elements. In light of this, here is a list of the top 6 causal factors of incidents involving this kind of lift and it’s not all in the craneage.

Clutch and Insert Compatibility. Turning up on site with the wrong clutches is an easy mistake to make. Take the time to ensure the crew heading to the job has compatible clutches for the lifting inserts cast into the elements to be lifted. It is recommended that the same manufacturer for the insert and clutch are used or a letter obtained from the manufacturer about compatibility.

Incorrect Rigging for Panel Rotating. Load equalising snatch blocks are crucial and, along with the chains and shackles, need to be of sufficient capacity and correctly tagged with up to date inspections.

Panel Birth Certificates and Shop Drawings need to be provided and

reviewed prior, to confirm lifting points, masses/dimensions, curing time and the need for strong-backs. Often, the crane company will be assigned blame if a panel breaks mid lift. Crane operators need to be aware of this as, sometimes panels are designed incorrectly and are inherently unstable! If in doubt don’t lift.

Tail-swing Clearance and Crane Setup

Sufficient clearance to slew is obvious, yet often overlooked and the panel installation sequence and position of temporary panel bracing (props), often causes issues here. Also, the Crane needs to be of adequate capacity with a current CraneSafe Green Sticker and set up on suitable ground with adequate timbers or mats.

Panel Trucks need to be positioned in line with the crane boom to allow for rotation in line the boom, with the skids/ legs lowered to provide stability. Stacking or sequencing needs to be in the right order, alternating from side to side so the trailer is not unbalanced at any stage of unloading. If the trucks are not positioned correctly a second crane should be used, rather than attempting to horizontally rotate the panels, which will side-load the sheaves on the boom.

Temporary Leaning. If the panel sequencing is wrong, never lean a panel on the crane or another structure. The panel should be properly positioned elsewhere on dowels and braced, as per a normal installation.

While seemingly obvious, these points are often overlooked. The best way to ensure this doesn’t happen is adequate planning, a good lift plan and site-specific SWMS will capture the multiple high-risk work triggers:

Involves tilt-up or precast concrete

Has a risk of a person falling two metres or more

Requires temporary support to prevent collapse

Movement of powered mobile plant

Adjacent to roadways.

The lift plan will determine if load share calculations are required. If the mass of the load is within the minimum rated capacity of both the main and the auxiliary hook, load share calculations are not required for the lift plan, however, a lift procedure is still required, and should specify the risk management process of the entire operation. If the load mass is greater than the minimum rated capacity of either hook, you can either use a bigger crane or calculate the maximum load share for each hook as part of your lift procedure. According to AS2550.5, the minimum rated capacity of each hoist must be at least 1.2 times the maximum calculated share of the load for that hoist. This is carried over from the Dual Crane Lift Standard and acts as a safeguard against complexities and uncertainties of coordinating two cranes at once. CICA’s position is that this is not mandatory for a single crane dual hook lift if it’s a ‘Designed Lift’ planned by a

professional engineer as the ‘competent person’ mentioned in the standard. The site should be inspected with the builder or supervisor well in advance to determine: If this information is available from the beginning of the project, then many of the issues mentioned previously are avoided or mitigated early.

“While many problems originate outside a crane crew’s sphere of influence, we fail in our duty of care when we try and ‘make do’ with a less than ideal situation

that we detected far too late.”

Trenching and backfilling hazards and the need for geotechnical ground studies

Other works occurring on the day of lifting

Electrical hazards and site constraints

Propping and access issues

Material delivery points and orientation This article cannot possibly cover every detail of precast erection, but rather, highlights the more common oversights and draws attention to the many simple elements that can prevent a large incident.

Be wary of making economic or efficiency decisions rather than safety decisions when presented with an unforeseen hazard.

CICA Membership provides members access to the Australian Standards, guidance notes, safety bulletins, resources and tools to facilitate compliance and safety. Go to www.cica.com.au for more information on how to join.

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