One is to deal with this blowout preventer stack and to take -- to use every capability to try to get it -- the rams to close.

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Then there was the blowout preventer, a huge stack of valves on the sea floor.

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The primary culprit behind the explosion appears to be the blowout preventer, a two-story-tall stack of valves on the seafloor that was built by Cameron in 2001 and designed to guillotine shut an out-of-control well.

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As a prelude to permanently shutting down the well, crews are trying to withdraw drill pipe hanging below the bottom of the blowout preventer and remove it from the well, so they can then remove the capping stack that's kept oil from leaking since July 15 and replace the old blowout preventer with a new one.

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