Investigation tracks failure of subsea bolts


WASHINGTON — The failure of a bolt used to affix emergency equipment to a subsea well in the Gulf of Mexico should spur the oil industry to write new standards for fasteners and the oversight of contractors working offshore, investigators say.

At issue is the Dec. 18, 2012 separation of the Transocean Discoverer India’s lower marine riser package from a blowout preventer at the top of a Chevron well in the Gulf of Mexico. The incident was quickly traced back to failed H4 connector bolts manufactured by GE Oil and Gas and prompted the replacement of more than 10,000 of the fasteners.

Read more: Regulators order drillers to replace faulty bolts

But according to a newly completed probe conducted for offshore energy regulators at the Interior Department, the underlying problems may be more far-reaching.

The investigation concurred with a separate analysis by Transocean, Chevron and GE that the root cause of the 2012 disconnect was hydrogen-induced stress corrosion cracking from brittle bolts.

According to the investigation report, a GE subcontractor relying on an older set of equipment standards did not give the bolts a required post-electroplating treatment that could have helped prevent the problem. An inadequate coat of paint on one portion of the bolt heads also was a contributing factor.

But the problems weren’t caught by a GE quality management system in place because it audited only first-tier level suppliers, such as GE contractors, and did not extend to subcontractors, including the one performing the electroplating coating of the bolts.

The investigators advised the Bureau of Safety and Environmental Enforcement to encourage the industry to improve its quality management standards to address the use of manufacturers’ subcontractors.

And it said the industry should develop “a consistent set of standards for connections and connection fasteners” used in subsea oil and gas equipment, with clear guidance on material hardness.

“Existing industry standards do not adequately address bolting/connector performance in subsea marine applications,” the report said. An API standard that provides requirements for blowout prevent connectors “does not contain material property requirements for the connection bolting used for subsea applications.”

The report was conducted by the bureau’s Quality Control-Failure Incident Team.

Bureau Director Brian Salerno said in a statement that a joint industry research project could examine “issues involving material hardness, coatings and cathodic protection for subsea equipment.”

“This is an important area for research, particularly for materials being utilized in operations in high temperature and high pressure settings and in other frontier areas such as the Arctic,” he said.

Salerno also said he would highlight “the need for enhanced equipment reliability through better quality control standards and data sharing.”

The American Petroleum Institute, which writes industry standards, said it was reviewing the report.

Jennifer Dlouhy

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