Friday, March 11, 2011

Getting the bits right

Yesterday, I saw a report that Sweden must make serious, yet invisible repairs to her most famous tourist attraction--the warship Vasa.  Launched in 1628, Vasa sailed for couple of hundred meters before it rolled over and sank into the mud of the Stockholm harbor where she rested until 1961 when a major effort was launched to raise and preserve her.  Because the harbor is mostly freshwater, the ship's wood was unusually well-preserved but even so, finding all the pieces and reassembling them while arresting further damage would prove to be a monumental effort that required years of highly skilled work.

Now it has been discovered that the bolts used to reassemble Vasa are corroding and will need replacement.

Sweden's Vasa warship set for make over
Published: 11 Mar 11 07:31 CET
The 17th century royal warship Vasa, one of Stockholm and Sweden's most popular visitor attractions, began a major refurbishment on Thursday to arrest corrosion.
"We need to remove the iron and the rust from inside the wood and replace (the bolts) with stainless steel that will not leak into the wood," Vasa Museum head Marika Hedin said.
The Vasa's hull was weakened by the pollution it was exposed to during the 333 years it spent on the Baltic Sea seabed after sinking in the Stockholm harbour on its maiden voyage.
The pollution, combined with the iron of the original bolts and rust, provoke "a chemical reaction that destroys the wood," Hedin explained.
The 5,000 new bolts, made of an alloy of chrome and nickel, will take five years to replace. more
Here's where the story gets interesting.  The replacement bolts for Vasa are made of an especially high grade of stainless steel that has been developed for especially corrosive applications such as in warm sea water called Sandvik SAF 2707 HD hyper-duplex stainless steel.  Offshore wind turbines are not practical without such steels so 2707 is critical to any plans for sustainable electrical generation.

The history of this project is utterly fascinating.  The Vasa was built as the flagship for one of Sweden's more warlike kings--the "Lion of the North" Gustavus Adolphus.  Always looking for new reasons to go to war, Gustavus had decided to take on the task of defending Protestantism in Northern Europe and would become a major figure in the Thirty Years War (1618-1648).  One of the things he did was provide a haven for Protestants fleeing from Catholic attacks and one of the more interesting groups he welcomed to Sweden were the Walloons.

The Walloons hailed from what is now a part of Belgium where the border between the Protestants and Catholics changed often.  Gustavus not only sympathized with them because they were fellow Protestants, he liked the fact that they had grown a body of expertise in the making of steel.  Sweden had valuable iron deposits so anyone who could make better steel was most welcome. In fact, Gustavus would give land to any steelmaking Walloon who wished to relocate to Sweden.

The boost to Sweden's steelmaking capabilities was immediate and long-lasting.  Sweden's iron ore wasn't especially abundant but it was very high quality.  So she would specialize in high-quality steels over the years leading to perhaps Sweden's most famous invention--the self-aligning ball bearing in 1907.

Vasa>Gustavus Adolphus>Walloons>specialized steelmaking>new bolts for Vasa. This virtuous circle has led to steels that make off-shore wind generation practical.

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