Hot dip galvanizing

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Corrosion protection XXL

Metal constructions with top-class dimensions: This is the métier of BV Anlagenbau. If the best corrosion protection possible is required, the Salzbergen company is happy to make use of the services of Feuerverzinkung Osnabrück.

"Perfect!" Thomas Brüggemann strokes over the bright, matt-grey surface, examining the angles and edges. He looks very content. "Rust no longer has a chance."

The surface is part of a giant welded construction with a length of more than six metres. It is fixed on the loading area of a flat-bed truck, which has just arrived at the factory premises of BV Anlagenbau in the Lower-Saxon town of Salzbergen. Mr Brüggemann, the production manager of the plant manufacturer, is now standing on this loading area. After all, it is "his" product: He monitored the process in which the raw steel beams were cut and welded to form a complex steel construction in hours of diligent manual labour. Now that the construction has returned from a one-day trip, Mr Brüggemann wants to receive it.

If you combine four of these steel constructions, you will receive a nacelle structure – that is, the skeleton of a machine nacelle on top of the tower of a wind power station. However, the customer wants to implement this last assembly step themselves, on site. For Mr Brüggemann and his colleagues, only a few last working steps remain to be done at the returned construction before it is transported to Bremerhaven for shipment and handed over to the customer.

„With Seppeler and Feuerverzinkung Osnabrück, we are happy to have a suitable partner for the corrosion protection of our products close-by. Their pot is one of the deepest, the quality is impeccable and the cooperation is perfect.“

600,000 tons of CO2 saved
"Wind power is one of our focal points here at BV Anlagenbaus," Mr Brüggemann explains. The Salzbergen company has specialised in large machine constructions with a great vertical range of manufacture. From the material procurement to the painting, BV Anlagenbau implements all working steps themselves. In a guaranteed and certified quality – and for top-class dimensions: The turning machine has a diameter of 6.20 metres, while the largest milling cutter covers 14 metres horizontally and 5.20 metres vertically.

This performance parameters match the requirements of wind power companies excellently. The nacelle structure order could also be secured this way. It is a large order for an offshore wind power station situated 30 kilometres in front of the island of Rügen, the Winkinger wind park. As of 2017, there, 70 wind turbines are to generate clean energy for more than 350,000 households, saving 600,000 tons of CO2 every year.

Stress over the decades
The nacelle of each Wikinger wind turbine alone is as high as a two-story building. And for each of the 70 nacelles, BV Anlagenbau delivers the skeleton, which weighs more than six tons. The construction on the flat-bed truck is part of nacelle no. 23.

"For offshore wind parks, naturally, corrosion protection is a central topic," Tobias Brüggemann added. The nacelle structures are exposed to enormous stresses. It is not seldom that hurricane-force winds - i.e. with speeds as of 117 kilometres per hour - hit the almost 70 metres long rotor blades. Then there is the humid, salty air: rather daunting conditions for decades of a low-maintenance functioning. However, this is exactly what we want to achieve.

Modified surface
Therefore, the nacelle structure has now paid a visit to Seppeler. More accurately: to Westerkappeln, Feuerverzinkung Osnabrück. Only yesterday, the construction was dark, almost black, when the flat-bed truck drove away with it. And first signs of rust were visible in many spots already. This is what happens to steel. Today, the structure returned with a modified surface. It has become immune towards the destructive pitting corrosion thanks to a mechanically robust layer: an iron-zinc alloy which forms if the steel is immersed into a 450 degree C molten zinc bath.

"Our products are definitely bulky," Tobias Brüggemann said. "Therefore, we are very happy that, with Feuerverzinkung Osnabrück, we have a suitable partner for corrosion protection close-by." Suitable can be taken quite literally here: With a working dimension of 3.50 metres, the galvanizing pot of the Seppeler location is one of the deepest in Germany – deep enough to be able to galvanize the roughly three metres high nacelle structures. The goods to be galvanized must be immersed completely.

Trapped vapours
However, "fitting" also applies in figurative sense: Apart from quality, for Feuerverzinkung Osnabrück, energy efficiency and environmental awareness also play an important role. This has been verified by the certifications according to ISO 9001, 14001 and 50001. And recently, the pre-treatment was converted and completely encapsulated. Thus, no vapours from pickling and flux tanks can leak into the environment. This is ideal for a "green" project such as the new wind park.

For BV Anlagenbau, another benefit of Feuerverzinkung Osnabrück is the physical proximity – only approximately 40 motorway kilometres separate the two companies. In connection with the customer-oriented service of Seppeler, this means: Orders are processed quickly. Even if the schedule is tight or changes at short notice.

The satisfied expression of Tobias Brüggemann when observing the freshly galvanized nacelle structure is therefore not a surprise. Moreover, it corresponds to an experience which BV Anlagenbau has had multiple times in the area of corrosion protection: "The cooperation with Seppeler works!"

Facts & Figures

The rotor blades, which are often exposed to hurricane-force winds, are approx. 70 METRES long. Here, the supporting structures of the wind turbine must resist immense mechanical loads.

Products with a height of 3.5 METRES like nacelle structures are not a problem at all for Feuerverzinkung Osnabrück – neither during the galvanization process itself nor in the pre-treatment: The steel constructions fit into the acid baths without any issues.

Structure of the nacelle
The "skeleton" of the nacelle consists of 15x15 cm steel struts. It is 3.2 metres high and 9 metres long.

Climatic stress
The conditions at sea are rough: In order to protect the nacelle structure against corrosion caused by the humid and salty air, it is galvanized in Osnabrück.

Further references of the Seppeler Group

Bilster Berg Drive Resort

Division: Hot dip galvanizing

Everything Under One Roof

Divisions: Hot dip galvanizing/Coating