200-meter-high tower
NKT HV Cable's factory is located on Verkö Island, just outside Karlskrona. Several construction projects are happening simultaneously here. Skanska is building a brand-new facility for producing high-voltage cables. Upon completion, this will be the world's largest factory for high-voltage submarine cables, supplying everything from wind turbines to solar parks.
Skanska's project includes constructing several production halls. A major challenge is the 200-meter-high-cable tower that now stands tall at the NKT site. This third tower was built using slipform technology, which requires ongoing concrete work 24/7 until the tower has reached its final height of 200 meters.
Early involvement in the project
Skanska have completed several successful projects for NKT over the years. In the summer of 2022, NKT approached Skanska to conduct a feasibility study for an expansion, leading to a Partnering Agreement. Intensive work on the groundwork and foundations for the tower and production halls began in 2023. By spring 2024, work on the frames and preparations for slipforming had started. Slipforming of the tower began on July 30 and was completed in October 2024.
Planning and precision with slipform technology
Building a tower this high with slipform technology demands meticulous planning and precision. The technique is typically used for smaller structures built within weeks. This construction extended over three months for our project, with day and night shifts in four rotations. Two shuttle trucks delivered concrete to the pours.
Slipforming involves pouring concrete into a mold that is slowly raised by hydraulic jacks. As the concrete cures, the mold moves upward at a steady pace. This time-efficient solution allows for uninterrupted construction, enabling the tower to grow by an average of 2.6 meters per day.
However, there are challenges. This technology is sensitive to weather and wind, so monitoring weather forecasts closely is crucial. Production management checked the forecasts at least three days ahead and updated them at minimum three times a day. Fortunately, there are ways to adjust the concrete curing process to either accelerate or slow down depending on weather conditions.
Internal finishes and MEP
The tower has now reached its full height of 200 meters. Seven meters taller than the Turning Torso in Malmö, the NKT tower is now the tallest structure cast using slipform technology, in Sweden. After slipforming was completed, the installation of steelbeams and concrete slabs for the 29 floor plans begins. Shortly hereafter internal finishes and MEP (Mechanical, Electrical and Pluming) works starts. To meet the February 2026 deadline, machinery installations will proceed in parallel.
Skanska's assignment also includes several huge production buildings scheduled for completion in 2025, with work continuing alongside machine installations. All buildings are closely connected to the tower. In 2027 NKT:s production of high-voltage cables will commence. The cables will during the production process, get their insulating sheath in the tower.
An exciting project involving many skills
Building this third tower and the large production buildings is both exciting and challenging. The foundation works of the tower and the halls have been demanding and the high production rate requires extensive collaboration and coordination. To meet these requirements of the project, coworkers across several regions within Skanska have been involved.
The construction of the large production halls is demanding, with many activities occurring simultaneously in confined spaces. This project involves many parts of Skanska's operations as well as other parties, fostering a strong team spirit and mutual understanding of each other's challenges.
About NKT
- Founded in 1891, NKT operates globally.
- Manufactures and installs cable solutions for power transmission
- The Karlskrona facility will be the world's largest factory for high-voltage offshore cables. The new production section, partly built by Skanska, will be completed in 2026. NKT's total investment in Karlskrona includes additional industrial buildings and a new cable-laying vessel, to be completed in 2027.