WorkSafe has attended many incidents where articulated mobile cranes, known as pick and carry cranes, have overturned. Contributing factors include:
- operating on surfaces that cannot support the weight of the crane and suspended load
- failure to derate the crane's lifting capacity as per manufacturer's requirements
- excessive boom angle and boom extension
- uncontrolled load sway (pendulum motion)
- moving up, down or across a slope
- changing direction (articulating) or manoeuvring around obstructions
- excessive speed
- under-inflated tyres
Risk increases significantly if more than one of the above factors is present.
Overturning articulated mobile cranes can expose the operator, dogman, rigging crews and others to the risk of death or serious injury.
The lifting capacity of cranes is reduced when traversing slopes or changing direction, failing to derate the crane may result in the crane overturning
Standard load charts can only be relied on when traversing minor variations in surface gradient or for minor crane articulation during lifts.
Recommended control measures
Employers and self-employed persons must, so far as is reasonably practicable, eliminate the risk of overturning. If it is not reasonably practicable to eliminate the risk, it must be reduced so far as is reasonably practicable.
Plan for a safe lift
Duty holders should ensure that a competent person plans the lift, taking into account:
- the load/s to be moved
- the travel path, including slopes to be traversed
- changes in surface gradient (camber, gutters etc.)
- changes in the surface (soft spots, uncompacted material, backfilled trenches etc.)
- any manoeuvres or changes of direction
- the crane manufacture's operating recommendations for maximum slope and deration of rated capacity
- weather conditions and any potential for wind tunnelling by surrounding structures, and
- even though the crane operator must be licensed to operate the crane they may not be familiar with the specific crane and its operating limitations
Ensure the pick and carry operation is within the manufacturer's specification for the crane. If that is not possible, ensure the lift is undertaken as a designed lift.
Consider alternative plant or use engineering controls
In some situations, it may be reasonably practicable to eliminate the risk of overturning by selecting another type of plant more suitable to moving the load. If you cannot eliminate the risk you should reduce it by using engineering controls, such as a crane with operator aid devices that automatically derate the cranes lifting capacity for slope and articulation.
Support controls with safe systems of work
Even when high order controls are implemented they should be supported by safe systems of work, such as:
- checking crane tyres are properly inflated and in good condition
- keeping loads near the ground, close to and up-hill of the crane (eg reverse down slopes)
- keeping the boom tip as low as possible by using minimal boom extension and the lowest boom angle
- keeping the articulation angle to a minimum by using large radius or multiple point turns to change direction, or landing the load and repositioning the crane instead of traveling with the load through turns or on slopes, and
- using tag lines to limit load sway while moving the load
The duty holder should establish an exclusion zone to keep non-essential people out of the potential overturning area, including for any uncontrolled movement of the suspended load should the crane overturn.
If the crane lift includes high risk construction work, the hazards, risks and controls must be documented in a safe work method statement (SWMS), which must be followed while the lift is being undertaken.
- AS 2550.1-2011 – Cranes, hoists and winches – Safe use – General requirements
- AS 2550.5-2011 – Cranes, hoists and winches – Mobile cranes
Crane Industry Council of Australia
- Crane Industry Council of Australia, position paper, CICA-PA-0009-B, Articulated Crane Operator Requirements