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Material fatigue sunk first mission of Ocean Cleanup

An analysis of the broken ocean cleanup system that came apart in the Great Pacific Garbage Patch indicates material fatigue coupled with stress concentration from a weld caused a section of the high density polyethylene floater to crack and break.

Made of 3-inch thick HDPE pipe, the 2,000-foot long floater is the backbone of the contraption designed by the Dutch non-profit group called Ocean Cleanup to gather marine debris. A tapered polyester skirt that hung below the pipe gave the system a U-shape to collect plastic from the ocean’s surface to a depth of 10 feet.

However, a 26-foot end section of the floater detached, with the break discovered Dec. 29. The piece was recovered, and the entire system was towed to Hawaii for study.

The system’s developers also have been analyzing what went wrong with “System 001,” because the ocean cleaner did retain garbage but not at the rate expected.

“Even though the system has only been out here four months it has been through more than a million [load] cycles [on the material] already. We have modeled everything we could have modeled, but there’s always reality,” Fedde Poppenk, an Ocean Cleanup mechanical engineer, says in video released Feb. 28 about the scrapped mission.

The floater pipe is made of PE 100-RC resin.

“We are using materials and we are in an environment that has hardly been modeled. so there are a lot of things that you just have to try out for the first time and simple see what happens,” Poppenk said.

After completing 116 days of offshore tests, the system’s design is being upgraded and Ocean Cleanup expects to return it to the ocean in a few months.

Credit: Plastics News