[ Duplex ]
The new sluice gates will be a central element of the redevelopment of the Slussen neighbourhood . Image courtesy of Foster + Partners .
at the eastern end of Stockholm , and their drinking water from inflows of brackish water . The lock is such a defining feature of the area that the neighbourhood itself is called ‘ Slussen .’ The neighbourhood is one of Stockholm ’ s busiest , and its heavily travelled , water-traversing infrastructure can be difficult to access for maintenance . A massive urban planning project is underway to widen Slussen ’ s discharge canals , transform its public transportation throughways , and install new sluice gates . The new gates , two for control of water level and two for boat traffic , are designed to withstand brackish flood waters for a century . That is a tough ask of steel , which wants to rust under such conditions . 2205 duplex stainless steel , however , is perfect for the job . Flooding around lake Mälaren is a major concern due to increased rainfall and warmer winters in recent years . The year 2000 was Sweden ’ s rainiest since 1860 . In that year , significantly more water flowed into lake than could be let out through the sluice gates . The flooding was so bad it almost reached the central underground station tunnel of Stockholm . Nearby , the train station of Gamla Stan ( i . e . the Old Town ) wasn ’ t so lucky ; water infiltrated its ticketing hall , leading it to close for a brief time . In the two decades that followed , climate modelling confirmed this event was not an anomaly . Rather , similar extreme flooding events are likely to increase in both frequency and intensity . Although Gamla Stan ’ s train tracks never flooded , the floods of 2000 are perhaps a warning for what is yet to come . Without improved capacity to drain floodwaters from lake Mälaren , the whole Stockholm region would be vulnerable to unprecedented disaster . The new duplex stainless steel sluice gates will be large and strong enough to release significantly more water than their forebears . Because duplex stainless steel is so much stronger than carbon steel , the gates are light enough to be fabricated off site and delivered . Being able to weld in a fabrication shop versus on site not only conserves costs and resources , but it also allows for better quality control . Stål and Rörmontage fabricated and supplied the behemoth flood gates – now the world ’ s largest at 70 tonnes . The gates will protect against the surges of
storms , which will increase in intensity and frequency throughout the lock ’ s service life . The entire Slussen project is expected to finish in 2025 .
Gårda Damme , Gothenburg Gothenburg , a Swedish port city , stretches over a series of islands intersected by canals and bridges . With so many waterways , rising sea levels pose a major flood risk to the community . In 2013 , the rotten wooden sluice gates that once controlled the water flows in and out of the archipelago were replaced . The old gates were in such bad condition that a temporary support structure was necessary to hold them together . The new gates are designed to withstand 120 years of rising tides . Though Gothenburg ’ s canals usually hold fresh water , sea water occasionally backwashes in and increases the chloride content . Outokumpu ’ s 2404 duplex stainless steel , containing 1.6 % molybdenum , was chosen for both its strength and enhanced resistance to salts . The structure could last several times its specified service life if the rubber seals used on the gates are properly maintained . There are five gates altogether , each measuring 3.1 by 2.2m and weighing roughly 7 tonnes . Rotten as they were , the original wood sluice gates were a beautiful landmark in the city , and residents wanted to emulate some of their character . The fabricators
The 2205 duplex stainless steel-clad sluice gates were fabricated off site in a machine shop and transported by barge to their destination . Image courtesy of Skanska .
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