Luffing further

As time passes, the ambitions of developers and architects have grown. Construction projects have become higher and have demanded larger and heavier loads to be lifted to everincreasing heights. At the same time, space for construction—and for siting the cranes that are needed for construction—has become increasingly congested.

The paradigm example for this is the city of New York. New skyscrapers are rising to new heights; streets are narrow, and closing them off to allow a crane is appallingly expensive—and if the crane is to be in position for months, becomes economically prohibitive. Neighbouring buildings, also possibly rising to great heights, have airspace rights that both legally and for safety reasons severely limit the radius of operation of the jib of a traditional flat-top or hammerhead tower crane. It would seem a circle that is impossible to square.

There is, however, a solution. The luffing tower crane can offer the same reach as a fixed-jib; but, when its jib is raised, occupies far less space. The challenge has been to make them of large enough capacity to be useful and economical on veryhigh- rise projects.

As this article was being laid out, we received news of a new entrant to the class, the Jaso J780PA (shown on p30). The first of these cranes is currently on its way to Australia for its first job; a second is currently being assembled for testing in Spain.

The crane comes in two versions: a 75t-capacity model, with an entirely new winch, and a model using Jaso’s existing largest winch, but configured to lift 64t with four falls of rope.

At the original time of writing, only three companies had risen to the challenge and have produced very large luffing jib tower cranes of 700tm capacity or more and able to lift loads as great as 64t.

Liebherr offers two versions of their 710 HC-L, the 25/50 and the 32/64. The 25/50t has bigger lifting capacity at the jib head; the 32/64t has greater maximum lift capacity. Both versions come with two hoist gears and a new tower system of 2.45m external dimensions which can climb inside or outside a building, and up to 1,100m hook height. Wolffkran produces the 700B, with 30m basic jib reaching up to 70m with extensions. And just over a year ago, in April 2017, Linden Comansa introduced their LCL700.

We have said that New York provides ideal conditions and incentives for such large luffing tower cranes. Is that city big enough to support three separate providers? And have these companies found a market for them outside that city?

“There are not many manufacturers that offer luffing-jib cranes of this size” says Mariano Echávarri, sales director of Linden Comansa. So why did Linden Comansa become one of them?

“Some of our customers were starting to demand larger sizes of luffing-jib cranes,” he says. “Our largest luffer a few years ago was the 24t or 30t LCL500 so we needed to complete our range to meet the market’s demands. We requested some information from those customers and with that input we decided to design and launch the LCL700.”

Travis Felchlin is in charge of Linden Comansa’s sales and rentals for the north-west. “The thinking behind the luffing tower cranes is that in some cities there is no room to go wider—so you have to go taller,” he says. “A rigid jib moves in a fixed-sized circle, of say 200ft radius, which of course can hit neighbouring buildings; a luffing jib can go upwards and take up no space outside its own site. It takes up very little room, especially when it is parked in a near-vertical position at night.” The LCL700’s ‘out-of-service’ jib radius is actually between 20.4m and 16m, depending on the maximum reach.

The LCL700 comes available in 50t and 64t versions; here we are concerned with the larger 64t. Has it advantages over the competition? “It is very easy to erect” says Echávarri; “One of its main features is that the luffing reevings come pre-installed from the factory, which eases and speeds up the erection of the crane.”

The design of the crane was a challenge. Some design changes were incorporated over previous, smaller luffers. “This crane is the first luffer from Comansa whose jib is square-shaped rather than triangular,” he says. The change is to give better stability. “It includes new features which no Comansa crane has had before. An auxiliary winch is one: it is a very important help for the erection team when they are assembling the crane at a jobsite.”

New York has strict emission and safety controls for cranes. “Our models are all electric” says Felchlin. New York’s infrastructure, with ageing network of cables under busy streets, is not everywhere ideal for supplying it.“We usually take an 800KVA generator to supply the power. We don’t always need that much power: sometimes it is enough to switch to half load, when the crane is not lifting its maximum.”

Duncan Salt, head of sales and service of Wolffkran, agrees: “We entered the New York market at a time when there was a move away from the old-fashioned diesel powered cranes. Electricity powered cranes give you a lower power requirement—it only uses power when the crane is actively lifting, unlike diesel, which is on tick-over all the time. We prefer to use mains power, but in New York that can be quite difficult—though the infrastructure for that has improved in the years we’ve been there.”

“Our luffers were not developed specifically for New York” says Salt. “We have always been making them, and they have been one the strengths of Wolffkran through the years. Our hoists are typically very fast with good payloads, and these are what customers want, so they became popular as a crane solution. Of course, whenever high-rises surround a construction site a tower luffer is ideal but they have many other applications as well.”

“New York has stringent environmental and regulatory requirements. We studied what we needed to do to achieve compliance and found that we were in a good place, so getting approval was relatively straightforward. We have built up a good relationship with the regulators.”

A peculiarity of some large New York luffers is the fly jib. Wolffkran offer their 700B in a base version, without fly-jib, and in a US version with one. Liebherr’s 710HC-L can be optionally equipped with one, for loads of up to 19.7t. “We wanted to complement our luffing-jib crane range and recognised the need for this size of crane” says Frech. “The feedback from our partners from different markets was incorporated into the development and resulted in the fly-jib.”

Their intended use is for turning large components such as wall panels. When delivered, the panels arrive flat on the back of a truck or low-loader; for installation, they need to be vertical. In restricted ground-spaces, the theory is that the luffing jib and the fly-jib together lift them from the truck in a horizontal orientation, then the fly-jib gently lowers one edge of it to swing it to vertical in mid-air. In practice, Salt sees the fly-jib more commonly put to other uses - in particular, for topping and tailing in tight spaces at height.

“Typically the luffing jib will lift a stack of steel, and once it is at height the fly will be used to install it. If you have a huge winch for the main jib capable of lifting 100t and a small 10t winch for the fly jib, it makes sense to use the latter for the more intricate smaller jobs. We have had enquiries for the fly-jib version from markets outside New York—including Australia at the moment. It is an easy add-on that needs little additional work, so it makes sense.”

A tower crane designed for the particular conditions of New York might seem an over-specialised niche market. Have manufacturers found other geographical markets for these luffers? “We have one in our rental division in Seattle now” says Felchlin. It is working on Amazon’s new headquarters.

“Three or four are going to Korea.” It is not geography so much as city congestion that counts. “Texas has plenty of land and cities in Texas have plenty of space” he says. “We don’t see them going there.”

But Seoul, London, Bangkok, Mexico City, Shanghai, Paris, Melbourne, Frankfurt are all cities that Linden Comansa has named as sharing New York’s congestion and constraints—and its possible need for suitable cranes.

New York is indeed the main area of use for these very large luffers, says Hans-Martin Frech of Liebherr’s marketing division, but it is by no means the only one. “The Middle East, Asia and metropolitan cities in Europe have all seen them at work.” Three of Liebherr’s 710 HC-L Lictronic luffing jib cranes are currently engaged in St Petersburg, on what will be the highest building in Europe. The Lakhta Tower, designed by British architects RMJM as headquarters for the energy group Gazprom, will also contain sport facilities, a planetarium, a panoramic restaurant and a technical park for children and stands 462m high.

The 710 HC-Ls at the site have 2x110kW Dual Drive shift hoist units which give hoist speeds of up to 176m/min. They are using radii of 45m, 50m and 60m, which enables them to cover the site to erect the heavy steel skeleton of the tower. All three are climbing the outside of the building; a smaller 357 HC-L 12/24 luffer is climbing inside it.

All three manufacturers are seeing demand for their large luffers from outside New York, and for applications other than skyscrapers. “Any normal building construction with heavy pre-cast elements in densely-built-up areas suits them” says Frech—again because they need less air-space than top-slewers. “In stockyards they offer fast handling of heavy elements—useful also in industrial plant and power-station construction.”

“In the UK, one of our 700s was used on Tottenham Hotspur’s new football arena” says Salt. “It was the 70m reach that gave the advantage. That in itself gives opportunities— lifting roof panels across distances literally the size of a football pitch.”

The new London Bridge Station was another UK use for the Wolffkran. “Reach was key here” he says, “And the ability to use it to erect a similar crane in an inaccessible site 50m away. They were leapfrogging cranes from south to north across the whole space. People are using them now in Northern Europe; one is going to Holland shortly. An adapted 700B is being used for wind technology power-plants, for 95t lifts at great reach, lifting large nacelles to 140m.”

“We have requests for large luffers—sometimes 64t might even be a bit small—to be used for the erection of wind farms,” echoes Echávarri. “Our main markets at the moment are North America, Singapore and North Korea but it is not confined to large cities for tall buildings. It is also where they need to lift heavy prefab or steel beams in construction. Right now we are involved in a project for a semiconductor plant in Korea that is requiring this type of crane.”

“But it is true that building skyscrapers in large cities is one of the main applications for this type of crane,” he says, “so we think congested metropolises in other markets will start demanding the LCL700. This is already happening with the rest of our range of luffers, whose demand is increasing as they are the best solution in jobsites with narrow spaces.”

Salt adds: “As construction methods change people begin to see the advantages. The 700B has a 20t line pull in single fall. That is huge. When the hook is coming down for the next load it can be travelling at 200m a minute. And that is very fast. There are lots of cranes that can lift 20t on four falls, but four falls of course makes them four times slower.” Speed on a construction site translates to money.

It boils down to power, Salt explains. “Our cranes tend to use a larger winch capable of lifting heavy loads on single line pull, which results in fewer rotations of the drum, thus creating less wear and greater reliability.”

“The market for these large luffers is growing,” says Salt. “Enquiries have increased over the past three years; people are seeing the benefits. They are not too expensive. Our cranes are easy to ship globally: the whole thing fits into containers with just two flat-racks, and for such a large machine that is an advantage.

On-site the footprint is small, just 2.3m, and it is easy to erect: our climbing system uses a singlepush ram: in other words it takes just one cycle of the ram to raise the tower enough to fit in the next section, and that makes it quicker and safer. Really what people are realising is that these are not huge monsters that are hard to set up and maintain.”

“There are lots of advantages in pre-casting concrete rather than casting in situ; and as pre-cast elements get bigger, you need bigger cranes to lift them,” says Salt. Frech agrees: “Throughout the world construction components are getting heavier,” he says, “and not only in high-rise construction.”

“The trend in both luffers and hammerhead cranes is to go larger and with more capacity” says Echávarri. “The large cities in North America, South America, Europe, Asia and Oceania are beginning to feel the need for high-capacity luffing-jib cranes in some of their projects. We see that as an important market for the LCL700.”

“We believe that the time for this size of luffer has just started, and hope to keep up with orders for a long time. The fact that other manufacturers are also adding to this size of crane to their range is also a sign of the increasing demand for the 700tm luffer.” It would seem that where New York leads, the rest of the world follows; and the market for very heavy-duty luffers will continue to grow.