Last Updated: 6/11/2019
This safety alert concerns the collapse of a Callaghan 37 metre concrete placing boom and includes actions to be taken by boom owners to avoid similar incidents.
In June 2019, the first boom stage (truck end) of a Callaghan Model CCP 37ZX5 broke and the boom collapsed onto a house roof. It appears there was a crack which started in a weld on the top of the boom connecting a semi-circular stiffening section to the boom top plate. The crack spread through the parent metal of the boom and down the boom's side plates. The Callaghan concrete placing boom was manufactured by KCP Heavy Industries in Korea. At the time of the incident the placing boom was approximately two years old.
Photograph 1: Failure in first boom stage.
Photograph 2: Boom collapse onto house roof.
|Photograph 3 Close up of failed area, after boom has been separated.|
It appears the failure was the result of weld fatigue, though the full circumstances are still being investigated.
Owners of Callaghan CCP 37ZX5 concrete placing booms should carry out enhanced monitoring and inspection of these booms, in addition to the normal inspection specified by the manufacturer and discussed in the Concrete Pumping Code of Practice 2005. The enhanced inspection should focus on the first boom stage with special attention on the butt section.
Inspections should include checking for:
- the appearance of cracks and other defects, especially in welded connections and other high stress areas,
- deformation of the boom including buckling of boom plates, and impact damage
- indications of corrosion including internal corrosion.
If the inspection uncovers visual irregularities, advice should be sought from Callaghan Concrete Pumping or a Registered Professional Engineer of Queensland with experience in inspecting concrete placing booms.
Additional guidance on the safe use of concrete placing booms is listed below:
- Only operate placing booms in accordance with the manufacturer's instructions.
- Never use the placing boom as a crane to lift freely suspended loads.
- Only lift a drop hose with a maximum length and diameter specified by the boom manufacturer.
- Ensure that no workers, other than the line hand and concreters involved in the concrete pour, are under a concrete placing boom.