In recent years, wind energy has become one of the most common renewable energy sources, leading the transition away from fossil fuels. The industry has been moving forward relentlessly through innovation and change, thus improving its competitive cost, and an assertive policy of developing renewable energies by governments.

So much so that wind turbine prices have fallen by almost a third since 2009 due to enhancements in turbine technology and onshore wind is now a competitive source of electricity compared to nuclear, coal or gas. Moreover, wind power costs are expected to decline even further, averaging 26 per cent to 35 per cent by 2025, according to Eng Federico Bonfogo, Senior Technical Sales Manager at Faccin, a world leading plate rolling manufacturer.

Demand for wind power is rapidly rising in practically every corner of the world, pushing the wind towers to evolve in size and type, from onshore to offshore towers, increasing the electrical capability from 4 MW up to 15 MW.

Consequently, a big share of the electricity will most likely be produced by facilities located offshore, where winds are stronger and more reliable. “One of the main differences between onshore and offshore towers, besides the diameters and thicknesses of the sections, is the need to connect the offshore tower to the seabed using a dedicated foundation system, a basement made of different designs, which anchor the tower to the seabed. As a result, bigger and safer structures must be built, turning the foundations fabrication into one of the key production processes related to the wind tower market,” Bonfogo said.

WIND TOWER FOUNDATIONS

In the wind power industry, there are different kinds of foundation types and the choice of the structure usually depends on the water depth and the seabed composition, such as rock and sand.

“Foundation types are either determined by the specific resistance of the seabed (usually a sandy seabed requires more complex structures) or by minimising the impact on the ocean ecosystem (some foundations have higher impact, during the installation phase, on the ocean flora and fauna),” he explained.

The most common foundation types currently used in the wind tower business are monopiles, which represent approx. 81.7 per cent of all installed substructures in Europe, followed by jackets at 6.9 per cent and gravity base foundations with almost 6 per cent.

DIFFERENT BENDING NEEDS

Bonfogo: providing a customised package

According to Faccin, one of the most common assumptions made in this business is to consider that the rolling of wind tower cans, can be done with one single rolling machine. Production requirements, however, show a different scenario. “The rolling capacity demanded for tower production, for instance, is different compared to foundations production; additionally, different foundation types also have different requirements,” Bonfogo said.

WHICH BENDING SYSTEM?

Bending hundreds of cans per month can ONLY be accomplished with a rolling package which combines a powerful super-sized plate rolling machine with key components like a strong side support, a sturdy top support and a feeding table with alignment device, all accessories controlled by a highly advanced fully-programmable CNC designed to automate the most complex rolling projects.

“Reliability, speed and accuracy must go hand to hand with costs reduction, and the job should be accomplished by a single operator through the use of a CNC capable of controlling automatically not only the machine but also the handling system,” he recommended.

HANDLING DEVICES

The feeding table can be horizontal or tilting type and its function is to support the plate during the first pre-bending. The table then feeds the roller through the use of multiple pushers that move forward and align the plate with the machine. Cutting production time is possible by using a Smart Feeding Table. This table works independently from the rolling machine and is capable of aligning the next plate to be rolled all while the rolling phase of the previous one is taking place. Thus, it is possible to save about five minutes per each can to be rolled, saving substantial time considering the entire cycle time is about 15 to 20 min.

The table is also used to realign conical plates during cone rolling. When connected to the CNC, this will be capable to calculate the plate misalignment and to reposition the plate during the rolling cycle in order to have an automatic cone bending.

When the initial part of the plate is bent, particularly when rolling thin plates, it has to be supported in order to avoid that it reopens due to its own weight. For this reason, at the machine side, it is possible to install one or two side supports.

Rolling conical shapes is not an easy operation and having the plate edge aligned at the end of the rolling process is very important for a fast track-welding operation. The best plate rolls manufacturers install additional clamps on the side supports that can pull together the plate edges while correcting the misalignment due to the cone shape.

The plate is aligned then over one of the side rolls and the help of the supports which are also equipped with pulling fingers and an additional arm capable of slightly open and close the can in order to get the perfect match of the plate edges.

Another major device, part of the Automation System, is the top support, fundamental to support the plates and to prevent the can from collapsing because of its weight. The top support must be tilt able in order to have perfect contact with both conical and cylindrical shapes.

All these powerful handling devices must be connected to the CNC which synchronizes them together by creating a unique system optimised to roll wind towers with the maximum accuracy in the shortest time possible.

Further than just controlling over 20 axis, CNCs nowadays must be capable of supporting the companies with different functions. The CNC PGS-Ultra supports operators with graphical simulations of the rolling process, a feature that gives certainty to the operation by seeing before what is going to happen.

“The CNC should also provide real time information for the maintenance and the monitoring of the production, a key point of Industry 4.0, that allows top managers get access to reporting apps now available on ITunes or Android like Faccin’s Management Control,” Bonfogo said.

In addition, the use of Wireless Controls is becoming a common practice when rolling plates in high capacity machines due to the flexibility it gives.

THE ROLLING MACHINE

Faccin Wind Tower Line: powerful devices

A reliable plate roll must always perform under heavy loads, Faccin spokesperson emphasised. “It must have an oversized structure with wide frames connected by heavy tie-rods and robust basement. Top brand components, an efficient cooling system together with centralised lubrication guarantee long life and no downtime on top level plate rolls,” he added. 

Last but not least, in a field where speed is as important as accuracy, the rolling machines, must have a super-fast hydraulic system like the Faccin Advantage Package that consists in +50 per cent movements speed, simultaneity of the movements and micro-positioning in order to reach the floor-to-floor production time of 20 min per rolled tube with the best accuracy.

A good rolling also means time saving in the subsequent steps of the wind tower assembly and welding. Rolling machines with great bending force can perform a top-quality rolling and pre-bending of the plates supplying perfect rolled cones to the welding stations. The rolling machines’ geometry and controls must be planned to reach the tightest tolerances and to minimise the re-rolling percentage of the cones that is a common problem on the lower quality plate rolls.

Thanks to its long experience, Faccin provides a customised package for every requirement related to the rolling of cans for towers and foundations: its Wind Tower Automation System, is a purpose-designed package available for the most exigent producers looking for reliability, speed, accuracy and costs reduction.

Learn more about Faccin and discover its latest developments by visiting its website www.faccin.com n