|BP Has claimed that changes to the blowout preventer made by the drilling contractor caused failure. Source|
BP's Gulf of Mexico oil spill was the result of many errors of omission and commission, none of which would have proved fatal except in the event of all the others. This is the first in a series of brief reports on failures of management not only by BP, but by BP contractors, TransOcean and Halliburton.
One error of omission was failure by the drilling rig operator, Transocean, to charge the battery on the 250-ton blowout preventer that stood 50 feet tall on the sea floor at the head of the well, and which, on command, should have shut off the flow of gas and oil. Uncharged for over two years, contrary to the manufacturer's recommendations, the battery lacked sufficient juice to operate the shears designed to cut the flow.
The certainty of failure was assured by a miswired switch.
For details, see the report of evidence given by Arthur Zatarain, a consulting engineer called as an expert witness by BP in the Gulf Oil spill trial in the New Orleans Times-Pic.
BP's Macondo Oil Spill: Captain of Drilling Rig "Lacked Authority" to Operate Safety Systems