A flowline jumper failure that led to a subsea leak in the Gulf of Mexico in 2020, according to a U.S. Bureau of Safety and Environmental Enforcement (BSEE) study, was brought on by hydrogen embrittlement.
A subsea jumper released roughly 479 barrels of oil into the Gulf of Mexico in the incident that took place in July 2020. According to the BSEE analysis, this was brought on by a failed flange connection on the jumper between the multiphase flowmeter (MPFM) and Blind Tee.
The BSEE claims that hydrogen embrittlement, which resulted in the fracture of four of the eight fasteners (studs) at the flange connection, was to blame for the breakdown. The shattered studs’ corrosion-resistant nickel-based alloy (Inconel 718) is not alloy steel.
Because Inconel 718 fasteners are said to be susceptible to hydrogen embrittlement when installed in cathodic-protected subsea environments, they must abide by certain American Petroleum Institute (API) guidelines.
The U.S. Bureau came to the conclusion that the failure to follow management of change (MOC) procedures, the absence of API 6ACRA compliance for subsea flange fasteners in the engineering documentation used for procurement, and the failure to install API 6ACRA compliant studs in the jumper flange connection were the main contributors to the incident.
As a result, BSEE is advising operators and contractors to use a metallurgist with industry experience to evaluate all current and upcoming subsea fasteners to make sure they are fit for service and not susceptible to hydrogen embrittlement or any other environmental cracking failures, to share industry learnings about subsea leak detection systems, and to emphasize that company, contract, and sub-contract personnel implement MOC when there are modifications related to equi
The recommendations also call for the verification and documentation of flange fastener make-up torque values, the careful monitoring of SSLD notification system alarms during shut-in, transient, and steady-state production operating conditions, and the consideration of subsea leak potential when analyzing significant subsea flowline pressure drops even when the trends in pressure are higher than the sea’s ambient pressure.
The Bureau panel urges the market to develop a standardized technique for determining the shear and torsional capacity of API flange connectors.