11.06.2007

Tower crane dismantle goes wrong

The dismatling of a tower crane, belonging to Irish Cranes went seriously wrong on Saturday but fortunately caused little more than some damage to the tower cranes jib and a few red faces.
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Saturdays 'incident' in Lurgan

The Terex Comedil crane was being dismantled at a site in Castor Bay, Lurgan Co Armargh by tower crane specialist Irish Cranes, for Farrens Construction.

The jib of the flat top crane was being lifted by a Liebherr LTM500 telescopic crane belonging to McNallys crane hire, when the slings which had been incorrectly attached to the jib caused it to rotate rapidly to a vertical position causing considerable damage.

The resulting shock caused the jib to part and appear to wrap itself around the boom of the mobile crane.

UPDATE

Since posting this story, we have received more detailed facts on what happened with a key message of the dangers of working on tower crane dismantling and the need to verify that they know what they are doing.

McNallys Crane hire was asked to provide a 250 tonne crane to help dismantle a Terex/Comedil CT331 tower crane at the Castor Bay Water Treatment Works, near Lurgan Co Armagh.

McNallys dispatched one of its 500 tonne Liebherr LTM 1500’s which was working in the area.

The crane began by removing the tower cranes counterweights, having completed this task it prepared to remove the bulk of the cranes jib.

Tower crane specialists employed by Irish Crane & Lifting who were responsible for taking the crane down, attached the slings to the tower cranes jib and allowed the mobile crane to take its weight.

The pins connecting the jib to the tower were then removed. As soon as the jib was freed from the tower it rotated rapidly from the horizontal to the vertical, with the jib tip pointing up and the base down.

Subsequent investigation of the jib section revealed a major error had been made in the calculation of the jibs centre of gravity for slinging purposes.

McNally says that it has a policy when working with tower crane dismantling to oversize all of the components it uses, including the use of slings that have twice the safe load capacity of that required.

Thus if, as in this case, one of the legs in a two leg sling set, ends up taking all of the load it still has the full safety margin.


McNally’s says that within four hours of the accident being reported it had mobilised a 300 tonner, a 250 tonner and a 100 tonne crane to the site.
A detailed lift plan and method statement were drawn up and the jib was removed safely from the 500 tonner late on Saturday night.