Winds Of Change

08 May 2008

Generating electricity using wind turbines was pioneered in Denmark in the early part of the 20th Century and the country remains a centre for it today. While turbines today are typically one or two megawatts, manufacturers are working on larger ones and five or even six megawatt units are set to become common. These largest turbines already have towers up to 120 m high and rotor diameters of more than 120 m, which presents significant challenges to transport and erection contractors.

Coupled with the component size, weight and height, wind farm sites on land are often in remote locations at high-altitude, which makes access difficult, both to the site and to travel between individual turbines.

Larger means more

Turbines are getting larger and the component loads are getting bigger in all dimensions, which means increasingly large and more specialized equipment is needed. In addition to towers getting taller, components such as the nacelles are getting heavier. Towers between 70 and 100 m for 1.5 to 3 MW turbines are now common but nacelles of 5 MW turbines weighing more than 200 tonnes on 100 m-plus towers are now being seen.

It used to be that 150 to 300 tonne hydraulic cranes were common for turbine installation and at the turn of the last century a 600 tonne hydraulic crane was considered huge for such projects. Now the smallest cranes in, for example, Sarens’ turbine erection fleet are six 400 tonne capacity Liebherr LR 1400 lattice crawlers, while the Demag CC/TC 2800, of which Sarens also has six, has become a common lattice boom crane for 2 to 3 MW turbines. Larger still are the Sarens fleet's two 1250 tonne capacity CC 8800 crawlers, which are its solution for 5 MW units.

Projects with 4 and 5 MW wind turbines have a different scope and need to be handled differently. In Hundhammerfjellet, Norway, Scanwind was first to use Sarens’ Sartower for turbine erection. An inaccessible site in the mountains and the need for a tailing operation meant Kamag self-propelled modular transporters (SPMTs) were used both for transporting and tailing the turbine.

Some turbine companies, for example Repower, opt for the nacelle to be lifted in separate parts, but there is a growing trend for erection of fully assembled units. German rental company Nolte erected a 5 MW Repower turbine last year with what is claimed to be a world record hub height of 120 m. Its 61.5 m rotor blades each weigh 18 tonnes. Nolte used its fleet flagship, the first Liebherr LG 1750 eight-axle lattice boom truck crane. This crane is designed to accommodate the requirements for erecting next-generation turbines into the future.

For the heaviest turbine component (170 tonnes), which had to be positioned at a 26 m radius and a height under hook of around 85 m, the crane was rigged with 105 m main boom and 42 m derrick boom.

For the last three big lifts - of the top tower section, machinery deck, and nacelle rotor hub assembly with blades - the boom was extended to 122 m and a 12 m offset jib was added. The LG 1750's slewing ring is nearly 5 m above the ground, which helps achieve a maximum pulley head height of 135 m. In the same configuration the 40 m top tower section was added to complete the 115 m tower.

Following assembly of the 18 m x 6 m x 6 m and 142 tonne machinery deck and its components, the 134 tonne and 126 m diameter rotor with blades was assembled on the ground. Late that evening, after dark, wind conditions allowed the hub with its three blades to be lifted to a height of 120 m. Illuminated by powerful spotlights, the hub and blades unit was bolted up and the record windmill completed.

Also in Germany, at Bremerhaven, Sarens installed the prototype 5 MW M5000 for Multibrid using one of its CC 8800 crawlers. In addition to lifting, the project scope included rolling parts in and out of the workshop, jacking it down for turbine assembly, weighing, land transportation of the heaviest components to the lifting area and later the erection of the nacelle pre assembled with blades (total 120 tonnes).

Again in Germany, last year for Enercon, Sarens installed 5 MW type E112 turbines in Emden. The work on land was similar to the Multibrid lifting work - towers taller than 100 m and nacelle weights of more than 200 tonnes - but the near-shore lift required more attention as Sarens had to engineer, with Enercon, the rigging procedures, ballasting and sea fastening, and the crane and parts positioning, before erection work could start with the CC 8800 from a barge near the shore. Good preparation counts here for more than 50 % of the success of the project, Sarens’ Dirk Verwimp says.

Dimensional limits

The dimensions of tower segments (now up to 5 m diameter) are approaching technical transport limits, so turbine manufacturer Enercon has designed a new concept where the tubular tower pieces are welded on the ground, at site, and then erected in one piece. To allow the erection of larger turbines Ulferts & Wittrock, a crane operator in northern Germany, has developed a tandem lifting procedure.

Two Liebherr LR 1400/2 crawlers, assisted by two LR 1130s were used. With 56 m main booms and 28 m derrick booms, the two larger machines were positioned to the left and right of the horizontal tower. Pins were attached to the 97 m tower close to its centre of gravity about 40 m from its base so during the lift the load tilted slowly to vertical. The tower was tailed from the bottom using an LR 1130.

To ensure precise vertical positioning before lowering the tower on to its foundation, crane control was switched from the cabs to a remote control system in a container 100 m away. A third monitor showed a front view of the lift, which allowed for visual control of the tower position, in addition to the test data. According to the manager of Energieanlagenmontage GmbH, Ludger Janssen, for Enercon, this erection of the four E-66 turbines was a trial run for the larger towers of the next generation turbines.

An additional advantage of the new procedure is that because the tower is erected in one lift (and on three hooks) instead of one for each separate section, only one suitable weather window is needed. It might sound obvious but this is a clear advantage when the very nature of wind farms means they are located where there is strong wind.

Full service

As turbines are getting larger and the component loads get bigger and heavier it becomes an increasingly specialized job, in terms of people and equipment, to transport and erect them. The increasingly complicated projects means contractors’ corresponding safety and experience of high level project management in handling heavy loads at height become even more important requirements.

Belgium-based Sarens is a long-established contractor in the wind turbine erection business, its companies around the world having worked on individual projects since the 1990s. Sarens’ De Kil company (now Sarens The Netherlands) has been the Netherlands contractor for turbine manufacturers Vestas and NEG Micon for more than 10 years and has gained much experience from this.

In the early days, particularly when turbines were smaller, contractors just rented cranes for turbine erection. Since then project managers have expanded their requirement of crane rental companies to include assistance in pre-engineering, logistics and site organization, for example, supervision of lifts. When a contractor has reached this level of competence, it is a small step to take full project responsibility “from workshop to foundation”, Sarens’ Dirk Verwimp explains. Projects where the crane rental company handles the project from unloading components from ships, through land transport, to erection and mechanical & electrical assembly (ready for testing and grid connection) have become normal practice in the last five years, Verwimp says.

Do the job

Major contractors prefer to work with one or two major lifting, transport and assembly suppliers that have extensive experience in wind turbine work, Verwimp explains, “With these partners they want to go all over Europe to install their turbines (mainly those where lattice boom cranes are needed) as experience in this domain and crane availability from a big fleet is critical for them. That's why we feel that positioning in strategic areas of lattice boom cranes like LR 1400 and TC/CC 2800 becomes of utmost importance.”

To this end, Verwimp says Sarens has a concentration of cranes in the booming markets of Spain, Italy, Greece, UK, France and Portugal, and is already looking further afield - to Poland, the former Yugoslavia, Morocco, Australia, Asia, and South Africa.

Sarens profiles itself as a major world player for wind turbine contracts.

Heavy lifting & transport and civil engineering services specialist Dufour, which covers France and Benelux, has also invested in developing a full wind turbine installation service from transport to erection. Dufour's fleet includes mobile cranes up to 700 tonnes; lattice cranes up to 800 tonnes; specialized transport equipment; and a range of man baskets up to 88 m. Its competitive advantage, according to Frederic Dufour, also includes technicians experienced in wind turbine erection.

The company's specialization in logistics and heavy transport includes permanent transport authorisation for crane elements and counterweight in Belgium and France, which means flexibility and the ability to react at short notice.

Kranringen Wind headquartered in Denmark is a 50:50 Enggaard-Mammoet joint venture set up in 2002 just for wind turbine work. It has erected more than 3500 turbines around the world. It has subsidiaries in Germany and Australia while the rest of the world is covered from around 60 Mammoet offices.

The KRW fleet includes Demag TC 2800, TC 2000 and Liebherr LG 1550 lattice mobiles, and Demag CC 2800 lattice crawlers. A Liebherr LTM 1500 telescopic mobile with its 84 m boom is used for maintenance work, for example, changing blades, as contracts are short notice (one week or less) and it is quick to mobilise, KRW says. Also in the fleet are trailers to move the cranes and turbine components.

Weldex, another specialist in wind turbine erection, has been expanding its fleet of crawler cranes to work on a range of projects. At the lower end of the capacity scale the company has Liebherr LR 1100 and LR 1160 crawlers. The LR 1160 and LR 1280 models from the Nenzing plant in Austria have narrow hydraulically retractable undercarriage.

Since Liebherr first showed the Weldex narrow track LR 1400/2-W crawler with two slewing rings at Bauma 2004, other users have taken up the concept for turbine erection. Spanish turbine manufacturer Gamesa's subsidiary Setylsa, responsible for crane and haulage operations, has two units. These cranes operate in the Spanish highlands with an extended boom system - 98 m main boom and 10.5 m fixed jib, in conjunction with the derrick system - so turbine components up to 88 tonnes can be assembled at tower heights of up to 100 m.

The LR 1400/2-W operates on 11.5 m wide star-type outriggers, which, in addition to the crawler travel gear and slewing gears, are operated by radio control. For easy transport of the lattice sections, special adapters with king journals, which can be coupled directly to the towing vehicle, were designed for Gamesa.

Turbines snowball

In the US, Doug Williams, president of Buckner Heavy Lift Cranes had the idea to offer a wind turbine erection service back in 1996 while on a trip to Europe. Williams saw the first Liebherr LR 1400 crawler crane two years later, at the Bauma exhibition in Germany, and began planning for at least one unit to join Buckner's fleet.

In 2000 Williams spent time in Germany with Wittrock, which uses LR 1400s for turbine erection. He saw that the LR 1400 could work with: reduced counterweight on 300 tonne crane jobs; with full counter weight; with fixed jib (Wittrock worked with Liebherr developing a special for turbines); and light and heavy luffing jibs in the 400 tonne crane range.

Buckner says this is a range that other US companies were covering by using costly and cumbersome heavy lift attachments on 300 tonne cranes. For larger and taller turbines in the future the LR 1400 could have either a floating tray or a ballast wagon heavy lift attachment to allow it to work in the 600 tonne range.

After the purchase of Buckner's first LR 1400, things “snowballed” and there are now eight within Buckner Heavylift Cranes, two in Buckner Burkhalter LLC (a joint venture with Burkhalter Rigging) and Burkhalter owns another.

Also in the US, Manitowoc's new Model 16000 crawler is designed for the demands of turbine installation - an optional detachable upper boom point with a capacity of 90 tonnes is available. The 400 tonne Model 16000 also has the capacity enhancing Max-Er attachment, which increases capacity at normal working radii. The company says this makes a better Dollar-per-ton investment than larger cranes, and that it also eliminates the time and expense of transporting and setting up a bigger unit.

Contractors and manufacturers are responding quickly to the very active and rapidly changing application sector and shaping the development onwards and upwards of an increasingly specialized and extensive service.

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