What's inside a platform leg?

Each of the four legs of the Visund platform is equipped with an aluminium spiral staircase designed and manufactured by the Jotne Group. Each staircase is approximately 40 meters high, which compares to a 14 floor building on land.

"It is an unusual solution and the delivery was a challenge. The requirements are much tougher offshore than onshore when it comes to stress calculations," explains Jon Ketil Mathisen, who manages Jotne Ankers' department for construction and building.

Aluminium was chosen as the material because of its relatively low weight and high strength. Most other platforms have straight stairs as a back-up to the lifts. The stairs are for emergency and maintenance purposes.

Jotne Ankers delivered the staircases to Marine Aluminium in Haugesund. The Visund platform was built by Umoe Haugesund for operation by Norsk Hydro.

Onshore, most of Jotne Ankers' stairs are in steel, although brass, aluminium, wood, glass and other materials are also used. The company is one of Norway's leading manufacturers of stairs.