Making light of lengthy loads

Materials handling provider, Combilift, and Danish manufacturer Andresen Towers have pooled expertise to address the logistical challenges involved in manufacturing and moving extreme lengths of product which form the basis of Andresen's new tower construction

Andresen Towers is part of the IAI Group which has more than 25 years of experience in the production of bended and bolted steel towers. The company has taken its original concept a stage further with the design of its patented shell towers and has secured a long term contract with Siemens Wind Power who will sell its products. Production and warehouse facilities have been set up at Andresen's HQ in Nyborg and nearby Langeskov.

Tom Andresen, CEO, says: "To make wind energy a more competitive alternative to fossil energy sources we have harnessed our technology to build the next generation of much higher towers. These can exploit the better wind conditions to generate a larger output which in turn reduces costs. For example, an increase in hub-height from 80 to 125m will decrease the price/KWh by 25%." The increased height of the steel shell towers compared to those currently available is due to the larger diameter and the reduced material thickness allows them to be produced from steel coils. These are cheaper than traditional steel plates and result in lighter towers. No welding of the structure is required as it is held together by tension controlled bolts, which do not need any retightening after installation.

Traditional tubular welded structures are limited to a diameter of 4.3m governed by road infrastructure (such as bridge heights) when it comes to transportation. As Andresen's shell tower sections are designed to be bolted together on site, they can be easily carried on ordinary trucks or in 45ft containers. Not only does this avoid extra costs for special transport and reduce disruption to traffic, it enables the shipment of towers to previously inaccessible areas.

Having solved the problem of moving the sections to their destination, a further issue was how to safely and efficiently handle and store loads which can be almost 14m long, 3.3m in diameter and weigh up to 30t. This is where Combilift came in and a two way dialogue with Andresen's management led to the choice of a Combilift Straddle Carrier (SC) as the one machine solution for each of the two sites. The design of each SC was adapted to take into account the slightly differing loads at Nyborg and Langeskov, the latter being built with a larger frame to cope with double-stacked high cube containers.

Ulrick Staudal of Combilift Denmark, explains: "There were a number of options, such as a combination of mobile cranes and traditional counterbalance forklifts or reach stackers, but Tom Andresen did not want to invest in pieces of equipment that could only carry out one specific job. He also focused on the total cost of ownership, which is becoming more of an issue for customers than just the initial investment." With a weight of just 18t, the combined weight of the SC and load is just 58t, which has cut out the need for expensive foundation work at Andresen's sites. "Our calculations, based on a 10-year operating lifetime took in initial capital outlay, fuel consumption, service costs and reduction in wear and tear on the surfaces and proved Andresen could achieve major operational savings compared to using any other type of equipment," says Staudal.

"The dimensions of Combilift's SC and its three-wheel manoeuvrability enable it to access the production area to load crates containing up to seven steel shells, weighing from 1.3 to 3.25t each," says Tom Andresen.

"The sheer physical size of a counterbalance truck would have made this nigh on impossible. We can then load onto HGV's without the need for a crane. In addition the SC handles incoming containers of components we manufacture elsewhere. The spreader beam attachment with different lift points also enables us to lift varying sizes of loads. Inside and out, the SC has been ideal for our needs and was a lot more economical than any other options we looked at." Combilift's Logistic Services assisted with layout diagrams showing best use of space for the storage of finished shells. Andresen sums up: "By combining our expertise with that of Combilift we have achieved all we set out to, and within an impressively short time frame."