Alexander Kielland disaster

North Sea five-legged pentagon rig built at French Dunkirk shipyard in the 1970s. Crack started at a fillet weld attaching a sonar flange plate (a vestigial appendage from when the rig was a drilling ship; never used in its hotel-conversion role). Maintenance crew (loose procedures) versus fabrication crew (strict procedures) — the maintenance weld killed the rig. Heat-affected zone hardness 350 (Rockwell C35); flange plate ductility one to seven percent.

Extended case study (sustained across §2). Maintenance welders welding without proper procedure controls created a hydrogen crack at a hydrophone-mount weld; the crack grew by fatigue to 50 feet over ~18 months until one of five legs separated and the platform capsized in a North Sea storm. Source attribution: Easterling textbook.

And I suspect in one of the two modules you'll read, I do a case study right out of Easterling on the Alexander Kielland disaster. Anybody know what the Alexander Kielland was? About 1980, in the North Sea, they were drilling for oil — this is sort of the beginning days of drilling for oil in the North Sea. They had a production platform that was supposed to be a drilling platform, but they converted it to a hotel. It was a 250-bed hotel in the middle of the North Sea. And one night in a North Sea storm — which they're famous for — it had five legs, each about 20 feet in diameter. Think of a mini-submarine leg — not the same thickness because it didn't have to go to the same depth, but nonetheless. They had a fatigue crack that started at a weld defect. It was all made in the shipyard in France.

Catch-up follow-up to prior session. Tom returns to the dimensions of the platform, the 1060-steel hydrophone bracket weld that initiated failure, and the Norwegian commission's focus on inadequate life rafts after conversion from drilling platform to hotel. 220 fatalities.

I wanted to catch up on a couple of things. I have to apologize — I was using my old lecture notes, and I found my newer lecture notes this morning. I talked about the Alexander Kielland disaster. This is the Alexander Kielland offshore platform. It's 50 meters across — half a football field — and 81 meters in the other direction, almost 90 percent of a football field. If you looked at the legs a little closer, this was the hydrophone. You have big columns of legs, then cross braces, and they put this piece on. It was 325 millimeters, about 10 inches in diameter. So that's 10 inches in diameter, and it looks like a little thing on this structure, so you can tell these things are pretty good size. At the time it was one of the largest offshore oil rigs — this was probably early '70s. It's not the largest anymore.

Extended case on why non-critical welds matter. A 16-inch sonar-bracket pipe welded to a 24-foot-diameter leg, with a thumbnail-sized crack in high-carbon steel, grew by fatigue to 20+ feet before a storm snapped the structure. Over 200 dead.

There are some huge failures that cost a billion dollars or take lots of lives. There's an offshore oil platform called the Alexander Kielland, about 1980 in the North Sea. This was supposed to be a production platform for oil in the North Sea, and they changed it to a hotel. A great big storm comes by — these things should have been safe in a storm — but the whole thing capsized, and over 200 people died.