Gulf of Mexico oil pipeline defect

Seamless pipe with a 3/4-inch × 3/8-inch surface flaw 80% through-wall, made in Ohio, passed two factory hydro tests, failed third hydro test after installation in Gulf. Cause: piece of fatigued piercing mandrel embedded in pipe surface. Defect was on pipe end, where eddy current couldn't reach; magnetic particle inspection (manual) missed it.

Another one was actually not strictly a forging lap. It was a piece of pipe that had been laid in the Gulf of Mexico underwater, and they were doing the final hydro test before they started using it to bring oil from the well onshore. This thing had been hydro tested twice at the plant in Ohio where it had been made, and it passed the hydro test, and then it got down and they had to coat it with a plastic compound to give it corrosion resistance in the ocean. Then they put it in the ocean and they hydro tested it again, and when they hydro tested it, it opened up. It had a flaw 80% of the way through.

Extended forensic case study. Seamless pipe sold under API standard, manufactured at American steel mill, defect (broken-off mandrel fragment rolled into hot steel) survived hydrostatic test at mill but failed in service buried in Gulf. Used to teach: (1) hydrostatic proof testing per ASTM A106, (2) limits of all NDT methods (probability never 1), (3) compositional fingerprinting for proving origin when markings stripped, (4) finite element analysis vs. infinite-crack approximation.

We've talked a couple of times about ASTM A106, and I finally have the sample to discuss some of the hydrostatic testing — not the one that occurred at the oil refinery where they bought six hundred lengths of pipe. If you remember, ASTM A106 for a piece of pipe allows hydrostatic testing. You can pressurize the pipe with water to fifty, sixty, seventy percent of the yield strength of the material. If it doesn't burst open, it's good. That's actually called proof testing. If you do it on every piece of pipe, which they do according to ASTM A106 — you have to do it according to the standard unless you as the purchaser say you don't want it, and then they have to mark it that it hasn't been done. Most of the pipe gets done.

Seamless pipe from a northeast Ohio mill, embedded mandrel fragment rolled into the surface, passed two pressure tests and failed the third after seabed installation. $5 million retrieval cost. Tom fingerprints the steel to one-part-in-100-million confidence using composition statistics from the AISI variability data.

[Tom holds up a section of seamless steel pipe.] Here we have a piece of steel pipe. We cut through it. There's a big missing piece here. This is seamless steel pipe. It's been painted on the outside. It was buried in the Gulf of Mexico to carry oil from a production platform to shore. This never carried any oil, because what happened is the steel mill that made it — which will remain nameless, but it's in northeast Ohio and it's been there for 100 years — produced a piece of steel and sold it, and they shipped it to Houston to be used in building this pipeline under the ocean, or on the floor of the ocean.