An Accident Involving Collision of Two Tower Cranes

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Figure 1: Two tower cranes that were involved in the accident

An accident occurred on 3 February 2009 at about 3.00pm at a construction site. The accident involved two tower cranes of luffing and hammerhead types. During the incident, the luffing tower crane was lowering down concrete formwork structures into the transporter lorry while the hammerhead tower crane was slewing. Both cranes were operating adjacent to each other when part of their working radius and crane height overlapped with one another. Investigation revealed that there was insufficient safety clearance distance for both cranes that led to the collision.

Several contributing factors have been identified. This includes failure of the employer to consider the planning, management and traffic control of tower crane operation.

Recommendations

1. Hazard identification, risk assessment and risk control(HIRARC) shall be implemented before performing any crane operation which has risk of collision. 2. Planning, management and traffic control shall be implemented if there are several tower cranes operating at a time. 3. Safety devices such as anti-collision and limit switches shall be installed and maintained to avoid collision between the tower cranes. 4. Signalman shall be given information, training and supervision in relation to collision hazard and he shall always give due attention to such hazard. 5. Employer shall communicate any changes to the tower crane height to crane operator, signalman and site supervisor and safety precaution shall be provided.

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