 |
|
The water utility company E.D.A.R. de Bens in the town of A Coruña in northwestern Spain faced growing needs in the first years of the 21 century: the company would need to expand to handle the municipal wastewaters of the 600,000 inhabitants of five towns – A Coruña, Cambre, Culleredo, Arteixo and Oleiros – at the same time meeting the EU regulations concerning effluents from treatment plants.
Confederación Hidrográfica del Norte of the Spanish Ministry of the Environment awarded the expansion to Cadagua S.A. of Spain, an engineering company specializing in water purification, wastewater treatment, and desalination. Cadagua has built 170 plants to date, with a total processing capacity of 8,000,000 cubic meters per day.
Stainless steel is still a relatively new material in wastewater treatment, but it is fast becoming the standard in plant hardware owing to needs to fight corrosion and abrasion while lowering maintenance needs and life cycle costs. Planning for a minimum plant life of 25 years, Confederación Hidrográfica del Norte specified the austenitic grade EN 1.4404 (ASTM 316L) for gates, suction precipitator bridges, sand removers and lamellas.
Between the time of initial planning and when Cadagua took over the project engineering in 2006, the price of 1.4404 had skyrocketed due to high nickel prices. To find an alternative, Cadagua approached Outokumpu. The engineering company was well familiar with Outokumpu from desalination projects, fully aware of Outokumpu’s extensive track record in desalination and unique capabilities in Duplex grades. |
|
Duplex grades have proven superior to austenitic grades in many applications. Owing to their low nickel content, these grades afford better price stability than austenitic grades. Further, Duplex grades feature 90 percent higher strength and as such allow for considerable weight savings.
Based on corrosion tests, Outokumpu convinced E.D.A.R de Bens, Cadagua and the project contractor that the right grade was Duplex 2304 (EN 1.4362). Outokumpu was awarded the contract to supply approximately 360 tons of Duplex 2304 sheet and plate to the wastewater treatment project.
Duplex 2304 offers the water utility company multiple benefits in addition to vast savings in the initial price compared to 1.4404. Thanks to its high surface hardness, 2304 will withstand better the abrasion caused by solid suspended particles. The thinner material gauges and consequently lighter structures allowed by the grade translate into less edge preparation, less need for welding consumables, fewer welding hours, lower-capacity cranes, and overall easier handling of structures. It promises even longer usable lives and lower life cycle costs. |