Blowing in the wind

11 April 2008

Renewable energy is experiencing massive growth. Wind turbine parks are popping up all over the world. Danes have been at the forefront of the technology for manufacturing and installation since the early 20th Century and Scandinavia remains central to developments.

Leading turbine manufacturers include Vestas, Siemens Windpower, GE Wind and Enercon. Their experience, and that of specialist wind turbine installation contractors, for example, A2Sea and Transbiaga, have accumulated over the years and resulted in practical solutions for new projects, along with improved lifting technologies.

The fast movement of machines and equipment between wind turbines is crucial in saving time and money when it comes to installation and maintenance. Norwegian lifting company Vest Kran has developed its own time-saving solution, using an all terrain Terex Demag AC 600. The eight axle crane, rigged with Superlift and fly jib, is moved on site between turbines under its own power. In this configuration it weighs 140 tonnes and stands 12 m tall, but still manages to negotiate the narrow dirt roads typical on wind farms.

Power plant

There are several wind power parks along the coast of Norway. Midway up the coast are the islands of Smøla and Hitra, where Siemens Windpower is refining its turbine technology. Smøla is the largest onshore wind farm project in Europe, with 68 turbines, producing 450 GW-h annually.

The 60 tonne wind turbine hubs are mounted on the masts 80 m above ground level and have to be removed for maintenance to replace gear boxes and other parts vital for power production.

Norwegian crane services company Vest Kran is carrying out lifting work at both parks and has developed its own way of cutting down time on rigging and transportation between the mills. Using its Terex Demag AC 600, an uprated AC 500 all terrain telescopic crane with superlift and fly jib, Vest Kran can hoist the heavy parts without having to dismantle the crane between turbines.

Flexible giant

AC 600 operator, Raymond Michelsen, says the Terex Demag is perfect for Vest Kran on sites like Smøla and Hitra. “At these parks the roads are not designed for extreme vehicles. The steep, narrow and curvy dirty roads stretch 24 kilometres and are often not more than four metres wide. Big crawlers are too wide and take a lot of time to rig and transport and, therefore, cost much more than our solution. The 140 tonne vehicle is more than 12 m high and saves valuable time and money.”

The risk of damage to any vehicle driveline is substantial when driving in that type of environment, Michelsen says.

“If the wheels start spinning and suddenly grab, the drive axles can snap like matches. On top of that there is the potential of weak shoulders on the dirt roads. Having 140 tonnes on wheels, with a lot of the weight mounted pretty high over the wheels, there is, of course, even greater risk of rolling the crane if the road shoulder is not strong enough. Therefore, I inspect the road carefully and plan the driving route before I even start moving.”

Morten Kristensen is Siemens Windpower site leader for maintenance at Smøla. “Efficient rigging and transportation is crucial in this business. Time is the key because the weather conditions can change so rapidly. Although wind is what it takes to turn our business, it can also ruin the maintenance budget if we can't do our job. It costs a lot of money to have these guys just hanging out here.”

Tougher than the rest

Vest Kran CO, Trond Emblem, says he is pleased with the way the company has developed efficient use of machinery following its experience in the wind turbine field.

“Based on these experiences Vest Kran saves 40% rigging and transportation time. That means quite a lot for our customers who have a fairly tight schedule. And I believe that is good news for our customers.”

Emblem explains that Vest Kran has been working with wind turbines for a decade or so in Norway's harsh geographical environment and climate. “Even if I consider us to be pioneers in Norway in this field, a decade is not a long time. But the environment here in Norway is dramatically different from the flat land in central Europe and, therefore, we face many challenges on these jobs.”

He continues, “Often we have fierce conditions with strong wind, biting temperatures and frozen tundra on top of the icy, steep and winding narrow dirt roads, sometimes as steep as 30 degrees. That can be a serious challenge, both for the equipment and logistics, not to mention the guys who face theelements.”

Emblem adds that finding the right lifting and transport equipment has been a challenge for Vest Kran.

“To serve our customers the way we wanted to, Vest Kran had to evaluate the equipment we had at our disposal. To transport the mills, sectioned in pieces we had to get special trailers for the tower sections, the blades of the mill and the heavy gearboxes and engine houses. Therefore, we bought new trailers.”

This included Faymonville Telemax trailers, up to 36 m long, for loads up to 60 tonnes. For heavier loads, up to 200 tonnes, Vest Kran bought Goldhofers.

Quick repair

Working at such a fast pace means damage to equipment can occur at the most inconvenient times. Emblem tells how, during one job at night, a transport wire snapped off while mounting the AC 600's jib, prompting a quick fix.

“When the wire broke the jib fell a couple of metres and slammed on the ground, breaking and bending some of the tubes in the structure. This happened on a Monday night when the guys were at the wind park replacing a gearbox, and time was, of course, of the essence. Our guys in the workshop here in Bergen flew up there and inspected the damage. By phone they consulted with specialists in Holland and ordered new parts. Sunday night the crane was re-certified and ready for the job. That is remarkable when accidents like this happen in the middle of nowhere.”

Vest Kran has ordered two new Terex Demags, the AC 350 with superlift, due for delivery in December. The company will then await the arrival of the 1,000 tonne lifting capacity AC 1000/9 in the third quarter of 2009.

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