A complex process

Three huge tower cranes were used to move construction materials up to level 156 of Burj Dubai, and crane operators worked at heights of more than 700 metres, almost double the height of the Empire State Building, said the developer Emaar.

The last high altitude crane used to build the tower was dismantled in November 2009 and work focused on interiors and landscaping, it added.

Installation of the cranes was relatively straightforward, as sections of the cranes could be moved up the tower with the completion of new levels. But as the tower grew in height, the floor plates and working area became smaller and smaller, providing insufficient room to fit the three cranes at the top of the construction. Again, dismantling them was a considerably more complex process.

The first crane was removed in November 2007 and installed at level 99 in order to serve as a future recovery crane. For the next 11 months, the two remaining cranes continued their climb up the tower until October 2008, when one of them was removed due to the small size of the tower's floor plate. This left one final crane to continue with the rest of the exterior work.

In May 2009, Greg Sang, Project Director at Emaar Properties, told Emirates Business that the cranes atop the Burj Dubai will be dismantled by August.

"The building has more than 160 floors. The tiers above the floors starting from Tier 24 are the maintenance areas for the spire. We are still working on the project and the cladding is still not finished. The last crane is coming down slowly because it is still working while it is lowering itself down. It is lifting up cladding panels," said Sang.

"During construction, we had three big tower cranes of 25 tonne capacity, which we called M1, M2 and M3. The building is tapering in size as you go up and it reached a certain point where they would not fit anymore. We took two of them down and they were dismantled component by component. The last one is still up there and it needs to come down. Right now, it is 700m above ground."

Sang spoke to this newspaper in May, when the process of taking the top-most crane down was yet to begin. "The first process is to bring it to Level 159 (see graphic), where there is a recovery crane called R1. The crane can climb itself down by removing sections of masts – it has a hydraulic system within it.

"The R1 crane will start to dismantle it component by component. The boom is in sections – around two to three metres long each. It will lower the pieces down to the transfer level 99, which has a deck. The M3 crane will lower them down to the ground. It is the one that was at the top and we moved it down to L99 to help with the operations," said Sang.

A second recovery crane called the R2 is at SDD5/15. "Once M1 is gone, R2 takes down R1 same way down to 99 and then down to the ground. The R2 will take it down in the hoist to level 99," said Sang. "At Level 99, it takes down the M3 and then lowers it down to the ground. The R2 goes down the hoist to the ground level and the cranes will be off the Burj Dubai."

In June 2009, the final crane had to be removed in order to allow the exterior cladding and finishing works to progress in the area it occupied. This longest-serving crane had been in operation since the start of construction in March 2005.

A small recovery crane was lifted up and installed at level 159. With recovery cranes now positioned at levels 99 and 159, the task of removing the last crane was ready to begin.

The process started with the crane climbing down from its working height of more than 700 metres. The crane removed its own mast sections and lowered them to the ground until the boom and power pack were at the position of the Level 159 recovery crane. From there, the Level 159 recovery crane dismantled the remainder of the main crane, lowering the pieces of boom, mast and power pack to the recovery crane at level 99, which further lowered them to the ground. A team of 35 skilled technicians manned the cranes.

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