Today's offshore turbines may be huge, but there is still very little margin for error when it comes to bending and pre-bending towers, and fabricating foundations. Stefano Santoni, wind energy division manager at Davi-Promau, tells World Wind Technology how its tried and tested plate-rolling system, now managed by a simple-to-use control system, can help customers ensure high quality and accuracy while lowering costs and manpower.
As offshore wind markets mature and turbines grow bigger, how can Davi-Promau help with the shifts in technique this requires from a manufacturing perspective?
Stefano Santoni: Previously, offshore wind farms were installed much closer to the coast and in shallower water. Today, turbines are installed in far deeper water, and the foundations are bigger, heavier and far more expensive. Bigger foundations normally require thicker and longer plates to be rolled at larger diameters, and handling these plates can be difficult and expensive. Davi has therefore engineered several technical solutions that allow the costs to be drastically reduced, while increasing productivity.
What is Davi-Promau's 'High Productivity Package' and the accompanying iRoll PLUS, and how were these developed?
The Wind Towers High Productivity Package (WT HPP) was developed more than 20 years ago in cooperation with prominent generator makers, at a time when the tower fabrication process was entirely manual. To create the conical shape of each section, it was necessary to adjust the plate position during the bending process, using cranes and chains to manipulate the plate so that it could slightly rotate to this shape. Four to eight people were required to complete this long and difficult process. It was also very easy for these manually rolled sections not to have the proper accuracy and tolerances, and so many of them needed to be scrapped, resulting in losses in time and money. We created our WT HPP to reduce the bending time, save labour and give a perfect shape to each section - something that nobody else was able to offer.
Later on, we applied our concept to the foundation-fabrication process, increasing the size and capacity of our machine and its handling accessories to match the different specifications. Central to achieving our solution has been the development of a high-performance CNC system, the iRoll PLUS, to manage the entire process, from plate loading and automatic positioning on the in-feed conveyor, to the completely rolled can and edge alignment for tack welding. The entire process sequence is automatically created by the iRoll PLUS simply by inserting basic parameters such as the thickness, diameters and steel yield.
Another crucial aspect in wind tower production is achieving a perfect pre-bend. In order to avoid the negative effect of the counter-bending moment that results from the weight of the plate, we designed an in-feed conveyor that can be tilted during the first pre-bending. This means that all the power of the plate roll can be used in that important phase, enabling the best pre-bending.
How user-friendly is the wind tower bending machine?
Our system is highly user-friendly because everything is managed by the iRoll PLUS. Once the programme has been created and saved, the operator just needs to run the system, and verify that the achieved radius and tolerances are in line with expected theoretical values. Naturally, the process must be carefully managed, with the operator verifying the diameter at regular intervals in case the steel used doesn't have the foreseen yield.
Our WT HPP is continuously updated following the suggestions of our customers, so the product we are selling today is totally different to the one we first sold 20 years ago.
What are some of the most significant developments this R&D has allowed you to make?
We've made significant improvements related to the capacity of the accessories and the accuracy in automatic repositioning of the plate during the cone-forming operation. The lifting table, used to support and incline the plate during the first pre-bending phase, has been optimised to keep the plate completely flat during the operation. Enhancements have also been made to make the system even more user-friendly and productive.
How else do you support your customers?
Davi customer service is always available, whether based in its headquarters in Cesena, Italy, or in the US. In the rare case of a major fault, Davi's dedicated technicians are there to receive calls and emails from customers, stepping into action immediately. For problems that can't be solved over the phone or with the remote service included in the iRoll PLUS, spare parts can be dispatched on the same day and a Davi engineer is ready to fly to the customer site and fix the problem in the shortest possible time - two or three days at the most.