Securing floodgates for two centuries

Tampere, the largest inland city in the Nordics, was established in 1775 by king Gustav III of Sweden. Thanks to its location around the Tammerkoski rapids, the city has grown to become Finland’s third largest. The Tammerkoski rapids are a unique natural phenomenon, a stretch of water connecting the two lakes of Näsijärvi and Pyhäjärvi that drops by 18 meters (59 feet). The rapids have served an important role in the city’s development as an industrial hub over the last century; four hydroelectric power plants have gone up on the Tammerkoski rapids to supply energy to the area.

In 2009, the Finnish energy company Tampereen Energiantuotanto Oy, undertook the task of upgrading the hydropower generation by rebuilding the structures used in the rapid channels.

 

Redesigned for new life

Until the upgrade, which was finished in 2012, the sluice and flood gates were largely made of wood and would take hours to open. While the technology and materials worked well over one hundred years ago when they were installed, they had reached the end of their service lives.

The channel design needed to be modernized to last another 200 years and enhanced to meet the safety standards for the power plants’ fault scenarios. At the same time, the city of Tampere and specifically the location of the Tammerkoski rapids is culturally significant – a heritage site and therefore all of the new structures and equipment had to meet aesthetic standards that matched the area’s venerable look. They also needed to be of the highest quality and durable. By all aspects this project presented an optimal application for our lean duplex stainless steel Forta LDX 2101.

 

The major benefits of Forta

In using high-strength lightweight Forta duplex, which is nearly twice as strong as austenitic stainless steel, the new gates were lighter and required less hydraulic force to be operated. Likewise, with high corrosion resistance, the duplex stainless steel stands up to use in a marine environment with a sub-arctic climate. Though no paint was required to stand up to corrosion and therefore no maintenance is needed, the gates were painted to match with the stone structures and retain the aesthetic of the heritage site.

With stainless steel’s high surface hardness, the gates will stay protected against the wear and tear of use during months of freezing temperatures and against the impact of ice floes. Duplex stainless steel has proven the sustainable choice for the Tampere sluice and flood gates not only because it is maintenance free but also due to its price stability and recyclability. Even after retaining its integrity throughout its service life, stainless steel is fully recyclable.