Figure 1 - Crawler crane position within sulphur pit after incident

PTP-AC201201 Projects and Technology – Major Projects March 2012

Crane Operator Fataly Injured

Target audience for this alert ¡ Project Managers

¡ Project Engineers

¡ Turnaround Managers

¡ Authorised Persons – Lifting and Hoisting

What happened During construction work on the BUGIS project at the Pulau Bukom Site - Singapore, a crane operator used a crawler crane to position a steel H-beam for piling with a vibro-hammer in an excavated pit. In the process, the crane fell into the excavation pit and the operator was fatally injured. No other persons were injured.

Why it happened ¡ The 50 ton crane was being used to position two H-

beams using a vibro-hammer. The total load (vibro hammer and beam) has been established to be 8.7tons. The load was assumed at the time of the incident to be 7.5 tons.

¡ The safe working radius for a 9.0 ton load was 12m according to the manufacturers load charts. The toppling radius would have been 14m.

¡ The first H-Beam was successfully put in position at a 10.15m working radius which was within the crane manufacturer’s 12m safe working radius.

¡ The intended final position for the second H-Beam, at 14.6m, was outside the safe working radius. The second beam was to be ‘parked’ temporarily, close to the first beam (at a radius of 11.15m), to allow the crane to be moved to a new location. See Figure 2.

Figure 2 – showing the layout of job, the intended parking

position for second H-beam and the safe working radius of the

crane

¡ The operator was instructed to lower the H-beam (wire down) at its temporary position. He responded by lowering the crane boom rather than by ’wiring down’ and did not respond to instructions to stop lowering the boom.

¡ The boom continued to be lowered past the tipping point of the crane (14m), passing both the intended temporary, and final locations for the H-Beam. The final impact point of the H-Beam was found to be at a radius of16.35m.

On further investigation it was found that:

¡ The work was being carried out under a generic method statement for the sheet piling. The positioning of the H beams and the safe working distances were not mentioned in the method statement. The lift was treated as a Low Risk Routine lift when in fact it was High Risk lift as the crane was required to move with the load.

¡ The Lifting and Hoisting SME appointed by the Project Management Contractor was not fully aware of the Bukom lift procedures and requirements.

¡ The underestimation of the load weight meant that the safe working radius and tipping point were over estimated by 2m.

¡ The safety devices on the crane failed to prevent the crane from toppling. The most likely explanation is that the safeguarding was functioning correctly and triggered an auto-cutoff when overload conditions were reached but the momentum of the boom and load being rapidly lowered caused the crane to topple into the excavated pit.

¡ The deceased was an experienced crane operator and had worked at Bukom in the past. He had not been passed as ‘Fit to Work’ as a crane operator but he had been passed as fit to work as a foreman.

Underlying causes on why the operator continued to lower the boom and why he failed to respond to instructions are unknown.

Lessons learned For this type of operation, the quality of the risk assessment and method statements is critical and adequate time and resources needs to be given to developing the work plan and communicating it to the lifting crew. The Contractor treated sheet piling as a routine activity with routine lifting and consequently did not develop a lifting plan.

Interviews with other operators found that vibrations from a vibro-hammer can be transmitted to the boom causing nuisance trips of the safeguarding system. Consequently safety devices are frequently overridden by operators. A safer alternative is to use an excavator with a long arm and vibro-hammer fitted.

For safety critical positions, such as crane operators, sites need to ensure that they cross reference the Fitness to Work information provided by contractors against the actual activities that their employees will carry out.

Figure 3 - Second H-beam was lowered using boom and passed

the tipping point