LNG carrier tail shaft fracture

Used as a scale comparator in Tom's exchange with Pelloux. Possibly an instance of the canonical "LNG carrier tail shaft fracture" or "SS Libra LNG vessel tail shaft failure" — flagged in editorial register for confirmation.

I once had a fracture in a 33-inch diameter propeller shaft on a liquid natural gas tanker. I was kind of teasing Professor Pelloux — Professor Pelloux is still alive, he's retired, his specialty was fatigue and fracture — I said I bet I've got a bigger fracture than you've seen, because a 33-inch diameter shaft fracturing is pretty good size. He said, I don't think so. I said, what do you have? He said he had an anvil base to a big forging press, and the fracture was like 10 feet by 20 feet. That's a big fracture. If you had to pull it in two at 50,000 pounds per square inch, there are a lot of square inches in 10 by 20 feet.

Mid-1980s, Philippine Sea. One of the Quincy-built LNG ships had its tail shaft fail mid-voyage between Indonesia and Japan with a full LNG cargo. Offloaded onto a returning empty ship; Learjets flew fittings halfway around the world; out-of-the-way Philippine harbor; nobody hurt. Fatigue crack grew from a casting flaw the Seattle steel shop's inspector had found and the manager had suppressed by throwing him out of the office. Crack grew over five years until shaft broke in two. Pelloux brought in for forensic analysis.

There are entire books written about fracture analysis, and it helps to have someone who's been looking at it for ten or fifteen years show you how to do it. Professor Pelloux, who passed away, came from France, got his PhD in this department, went to work at Boeing, came back after three or four years, became a faculty member here, and taught fatigue and fracture. I remember in the mid '80s I had a tail shaft fracture on a liquid natural gas carrier, one of these same ships that was built down at Quincy, that I worked on the steel for the skirts twelve years before. They had a tail shaft fail in the middle of the Philippine Sea. They were going from Indonesia to Japan, full of LNG. When you've got a container ship full of a hundred thousand tons of LNG, that LNG is going to be boiling off, and you would like to have power so that it doesn't blow up. They had to offload it on a ship that was coming back from Japan that was empty, and they had Learjets flying halfway around the world with the right type of fittings. They did the transfer in an out-of-the-way harbor in the middle of the Philippines, and nobody got hurt. It took them a couple of days to offload the cargo. They wanted to know why the tail shaft fractured. I remember bringing in Professor Pelloux because he had a lot more experience.

Illustration of an internal forging defect originating in the as-cast structure of a great-big forging blank: solidification weakness at the centerline gets carried through forging, then propagates as a fatigue crack. Ship stopped dead with a full cargo of LNG in the Philippine Sea.

I've seen them. We know how to prevent them. In 1985, I saw one. In one of the other lectures on my welding course, I describe it. I think I describe it on the lectures you'll see this last summer. It's about a tail shaft of a liquid natural gas cargo tanker that stopped dead full of liquid natural gas in the Philippine Sea, because the tail shaft failed in fatigue. It had a defect right in the center of the casting. It wasn't a casting — it started out as a casting, and it got forged into the shaft, but they had a defect right in the center. It's a little more complex than that, but this is the type of thing that can happen.