Replacing roof-mounted façade cranes in the heart of The Hague

Mammoet was approached by Façade Access Solutions, part of Alimak Group, to support with the replacement of roof-mounted Building Maintenance Units (BMUs) on two neighboring Dutch government buildings in The Hague. Each new Manntech BMU comprised sixteen parts - ranging from 200 kg (winches) to 3,500 kg (column and undercarriage) - that needed to be individually lifted.

Mammoet worked with Façade Access Solutions to determine the safest, and most efficient, method to support the removal of the old cranes and installation of the new ones. There were several challenges, including the extremely limited ground space that was available to assemble and operate a crane capable of doing the job. 

Mammoet was successful in finding the optimum crane, and setup position, to complete the project safely and with minimal disruption to the seat of Dutch political life.

Determining the best crane for the job  

Key to the solving this puzzle was selecting the correct type of crane, as it needed to achieve a 180-meter lifting height and work within a very limited space at street level. A crawler crane was considered initially but rejected due to concerns that its counterweight could collide with a nearby viaduct. 

After further analysis, a mobile crane was chosen instead - an LTM 11200 (with 1,200t maximum load capacity) fitted with a Y Frame on its main boom for added strength. 

Mobilising this crane - with the world’s largest telescopic boom - to the heart of the city would be no mean feat. The engineering team also determined that there was just one setup location that would make it possible for the crane’s boom to reach both buildings. "This was due to the Y Frame," explained Stefan Plugge, project manager at Mammoet. 

"We had to find a position that allowed us to stay clear of the buildings and the viaduct. From the one position we identified, the crane could service both buildings - thus avoiding the need to demobilise it to a different location, saving time and unnecessary disruption."

When it came to setting up the mobile crane, the team only used the space it needed, which minimised disruption further. 

For the first two days, a smaller assembly area was created. Only on the third day, when the boom had to be assembled on the ground, was this area temporarily extended. This allowed a key road to be closed for one day instead of three.  

Tall lifts in a complex city

The existing façade cranes were disassembled, lifted down and transported away. The components for the new cranes were lifted onto the roof of the buildings in a specific order, allowing assembly to happen simultaneously, again saving on time.

An adjacent street was used to store the old crane sections. It also served as a laydown area for the new components, which were delivered using a self-loading crane.

The team set up two lifting zones with different boundaries. This included an area for small parts (anything up to three meters), and another for larger items of up to 10.5 meters in length. 

Working within these zones enabled only the short-term closure of a nearby canal, and its neighboring road, during the lifting phase. Additional safety measures were also adhered to. "We discussed with the client that all items be attached using fixed lifting points," added Plugge. "Nothing would be lifted using slings or other lifting approaches. We also agreed that the maximum allowable wind speed would be low."

It was also determined that the roofs wouldn’t be strong enough to take the impact of the heavier components if one were to fall. Therefore, a crash deck was assembled on each roof before anything was lifted off or onto the buildings. 

As would be the case in any seat of government, The Hague is a complex city to perform heavy lifts at height, requiring detailed permitting, lifting and safety plans. Mammoet provided this information in a timely manner to keep everything on schedule. 

The team’s work kept disruption to a minimum, while successfully accomplishing these high lifts, safely and efficiently, in this challenging urban environment. 

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