Luffing all the way

 Two crawler cranes working on the New Street Square project in central London have demonstrated that there is a viable and cost-effective alternative to hiring tower cranes. Martin Cooper reports.

A large sprawling demolition project in the heart of the City of London would ordinarily require the services of an array of tower cranes. But Cantillon Demolition, working on the New Street Square project, says it has bucked the trend by using just two crawler cranes for all on-site crane duties.
As well as considerable time and cost savings, the two cranes, equipped with innovative luffing jibs, are said to have out-performed any viable alternatives and have also caught the eye of other contractors.
Cantillon commercial director Jim O'Sullivan says: "When planning got under way we anticipated hiring in the usual complement of tower cranes. However, we regularly rent from NRC Plant and its technical guys suggested using two crawler cranes."
These machines are a common sight on projects in continental Europe, but in the UK they have traditionally been thought of as too big and cumbersome for urban job sites.
Tower cranes, with their small footprint, are therefore the favoured crane for UK city-centre construction jobs.
"We wouldn't usually entertain the idea of using crawlers on an inner-city site, but on this project, space wasn't an issue," O'Sullivan says.
"The cranes NRC recommended weren't the ordinary run-of-the-mill machines."
NRC was finally commissioned to supply two crawler cranes. A 90t-capacity Hitachi Sumitomo SCX900-2, equipped with a 48m main boom and 18m fly-jib was initially brought on site. This was followed a few weeks later by a 100t Hitachi Sumitomo hydraulic crane fitted with special luffing equipment consisting of a 50m main tower and another 44m luffing jib.
O'Sullivan says the 100t luffer was the star of the show. "This was the first time either of these cranes had been used on a city project, but they saved us a lot of time and we'd use them again," he says.
Having the luffing jib feature enabled the 100 tonner to reach over the tallest building and dismantle and lift sections down. "With a conventional fly-jib option we would've needed to take a large chunk out of the building to reach the opposite side," O'Sullivan says.
Another advantage of the luffing option is its 9t lifting capacity compared to the 6t maximum capacity of the fly-jib version.
O'Sullivan says the 100t crawler crane was able to work on three adjacent buildings using its manoeuvrability and the extra reach afforded by the luffing jib. "The cranes could move around the site and thereby do the work normally done by four or five static tower cranes."

Coming down
New Street Square is, according to Cantillon, one of the largest demolition projects to take place in central London for many years. Seven post-war tower blocks, ranging in height from 17 storeys to six storeys, have been demolished.
In their place main contractor Sir Robert McAlpine is building a mixed retail and office development. The project, with four main buildings, will create 700,000m2 of office and 29,000m2 of retail space, built around what has been described as an inner-city pedestrian plaza.
With seven buildings to be demolished, Cantillon needed a versatile and cost-effective crane solution. O'Sullivan says ordinarily tower cranes would have been employed, but the crucial element of this project is that it is self-contained.
Bordered on all four sides by roads, the development was totally enclosed by dust and noise suppression sheeting and as each building came down the working area increased.
"By using the available space we were able to erect and use crawler cranes on a city project," O'Sullivan says. "And their greater versatility and manoeuvrability meant we only had to employ two machines."
O'Sullivan says the crawler cranes worked on different areas of the project and their mobility helped speed up the demolition process. They were used for a range of duties, he says, from lifting small demolition plant up to the higher floors, carrying man-lifts with personnel inside, to lifting large masonry segments. "They were all-round work-
horses," he says.
"When comparing them to tower cranes, the crawlers have the advantage of lower erection and dismantling costs," says O'Sullivan. "And, being diesel-powered there were no electric cables stretching across the site, which would have been the case had we used tower cranes."
However, O'Sullivan says the 100-tonner, with its luffing jib extension, was a new crane for him and he needed to be convinced. "Normally, we wouldn't have had the space for these cranes," he says. "But once NRC explained the capacity and workload capabilities of the cranes, we decided to hire them in."
The smaller 90t crawler was first to be delivered to site and involved a logistical feat as it required one lowloader and four flatbed trailers for transportation. As demolition had not started, the site was short of space and each delivery had to be unloaded before the next could arrive.
Erecting the 90t Hitachi Sumitomo was relatively easy as once the base unit was on the ground the machine could self-erect itself by lifting each boom length into position.
O'Sullivan says the 90t crane was immediately put to work and helped with the demolition of a nine-story building, which in turn made room for the second crane to be delivered.

Heavy duties
It then took NRC two days to erect the 100t crane, as the unit required another crane to aid its set-up. Once in position, it was put to work helping with the major part of the demolition project. The crawlers were used for all heavy duties including dismantling large segments of the condemned tower blocks.
"The largest lift never exceeded 8t, but the crane could reach three buildings without moving, lift down complete building sections and then deposit them in areas ready for pulverising," O'Sullivan says.
As the site is close to other occupied office blocks, noise and dust suppression were not the only pollution factors that had to be considered. To keep noise to a low level, Cantillon used the cranes to aid with on-site recycling of materials. "By lifting down large sections of the building we were then able to pulverise the material on-site, which was then re-used for pile mats," O'Sullivan says.
NRC managing director Rod Abbott says crawler cranes are usually viewed as large lumbering dinosaurs most suitable for large heavy lifting operations on sites with plenty of open ground.
But he believes today's crawlers are computer-controlled sophisticated items of kit and offer contractors an alternative to tower and mobile cranes.
So sophisticated in fact, that NRC usually rents the large crawler cranes with an operator. However, on this occasion, Cantillon had its own operator, an experienced plant and crane driver who was given two weeks on-site training by NRC.
"He drove both cranes as they normally didn't operate at the same time," O'Sullivan says. "Although at the beginning of the project, NRC sent us an operator while our man got up to speed."
"Most contractors wouldn't consider a crawler on an inner-city project, but I think there's a lot of potential for these machines in the UK," Abbott sums up.
"I can see these crawlers with luffing jibs taking a large chunk of the tower crane market once contractors realise their greater versatility."
"We've had a number of enquires from other contractors," says Abbott. "They noticed the cranes towering over the skyline and are intrigued about the alternative to towers."