s last line of defense against disaster a massive 300-ton blowout preventer sitting on the ocean floor was finally triggered. But it failed by inches.
No human was to blame for the blowout preventer's failure to stop the Gulf oil spill, according to a team of Norwegian undersea oil-equipment experts who spent six months investigating why the "fail-safe" device did not work.
Why the blowout preventer didnt work has been the subject of intense speculation and several congressional and private investigations. The primary cause for that failure, according to the Norwegian consulting firm Det Norske Veritas, was the blowout preventer's "blind-shear ram" a massive set of steel jaws intended to completely cut through the drill pipe, crimping it in the process and sealing the well.
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The reason the shear ram's jaws failed was because they encountered a situation for which they were not designed a "buckled" section of drill pipe, bowed sideways by the enormous pressure of oil thrusting upward from miles beneath the earth, the investigators said in their final report to the Interior Department and the US Coast Guard, which was released Wednesday.
At 7:30 a.m. on April 22 last year, less than an hour before the Deepwater Horizon sank to the bottom of the Gulf of Mexico, a remote-operated vehicle (ROV) finally was able to activate the shear ram's hydraulic system, the report says. At that point, a 25-second-long process began as the system's steel jaws began to close on the pipe.
But as those blades closed, "the drill pipe was positioned such that the outside corner of the upper [blind-shear ram] blade contacted the drill pipe slightly off center of the drill pipe cross section," investigators found. As a result, part of the pipe was not sheared through as expected. "As the [shear ram blades] closed, a portion of the drill pipe c
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