27.06.2005

HSE publishes report on tower crane accident

The UK’S Health & Safety Executive has published the full report on the fatal tower crane accident at the HSBC bank building in Canada square on May 21 2000.

A Wolff 320BF self climbing tower crane, owned by Hewden tower cranes, was lifting its last 4.5 metre tower section into place when the top of the crane began to twist, buckling one of the top guide wheels of the climbing frame which led to the top of the crane toppling 120 metres into the site below. Three men working for Hewden’s, were killed while two others escaped.
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The Accident at Canada Square May 21 2000

As already announced at the inquest, the report concludes that in spite of a thorough investigation, involving tower crane experts along with metallurgical and engineering experts, it was not possible to determine exactly how or why the crane collapsed. As a result the HSE has decided that no prosecutions will be taken against anyone due to insufficient evidence.

During the investigation, the HSE found several unsatisfactory aspects to the arrangements for tower crane climbing; however, none of these issues can be said to have caused the collapse.

• The manufacturer’s instructions were not being followed closely in certain respects, e.g. in the arrangements for balancing the crane prior to climbing
• The special arrangements for supplying power to the hydraulic motor were not Used, so it would have been possible to slew the crane during a climb
• The crane was not fitted with an anemometer so there was no reliable indication of wind speed at the crane top prior to starting a climb
• The climbing frame had not been thoroughly examined and there were no formal arrangements for ensuring that the equipment was in good order and that defects were properly investigated
• The erectors seemed to be working unreasonably long hours of work with the potential to increase fatigue and errors
• Planning of specific climbing jobs was insufficient with inadequate assessment of risk and specification of control measures
• Erectors had not received formal training or instruction about the risks and the control measures required, although an experienced supervisor had led the team
• There was insufficient overall monitoring and supervision of climbing operations by senior management.
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Accident at Canada Square May 21 2000

Changes to the standards:

Action has also now been taken to develop a revision to British Standard BS 7121: Part 5, Tower Cranes, partly in order to give clear advice on the use of climbing frames.

Representations were also made to the relevant CEN and ISO standards committees about appropriate standards for the design of climbing frames.

The HSE has also worked with the CITB to establish, a new training course for tower crane erectors that includes the use of climbing frames. And has supported work by the Construction Industry Research and Information Association (CIRIA) concerning tower crane stability including the design and the safe use of climbing frames

While all this activity, suggest a major problem, a world wide investigation by the HSE into other similar accidents only unearthed on, in San Francisco in 1989, when a similar collapse was caused by the slewing of the crane during climbing.

After a legal battle between Hewden and the contractors Yarn Road and Cleveland Bridge, Hewden’s agreed a settlement in which they paid the two companies £4.875 million.

The report is available in a summary or full version format on the HSE web site Click here for the summary or here for the full report

A discussion paper is also available on the safe use of 'external' frames on tower cranes can be viewed at http://www.hse.gov.uk/construction/crane/discussion.pdf