Safety valve at heart of BP Gulf oil spill

A trapped piece of drill pipe prevented a fail-safe device from stopping last year’s massive BP Gulf oil spill, a US government investigation has found.

Its report said the device, known as a blow-out preventer, failed to work properly because the piece of drill pipe kept its blind shear rams from sealing the well around the time of the April 20 oil rig explosion off the coast of Louisiana. Shear rams are components in a blow-out preventer that cut, or shear, through drill pipe and form a seal against well pressure. The Norwegian firm hired by the government to test the blow-out preventer said the way the drill pipe was positioned within the well bore caused it to buckle and bow when the well lost control, impeding the rams.

Det Norske Veritas’s report does not assign blame to any one company, but does find fault with the performance and design of the blow-out preventer. The device was made by Cameron and maintained by Transocean.

The firm made several recommendations for the industry in its report, including changing the design of blow-out preventers.

The firm’s tests also indicated that some back-up control system components did not perform as intended. It recommended the industry revise its procedures for periodic testing and verification of the back-up control systems to assure they will function properly at all times.

Blow-out preventers sit at the wellhead of exploratory wells and are supposed to lock in place to prevent a spill in case of an explosion.

The 300-ton device that was used with BP’s Macondo well was raised from the sea floor on September 4.

Representatives for Cameron and Transocean were among an army of interested parties that were allowed to monitor DNV’s examination of the device.

BP, the Justice Department and lawyers for plaintiffs in lawsuits over the disaster were also allowed to monitor. None of them was allowed to have any hands-on involvement.

The official testing ended earlier this month. BP has asked a federal judge for permission to conduct additional testing on its own. Cameron has objected, saying that if further testing is done, a neutral third-party should do it.