According to a report in the Wall Street Journal, the Deepwater Horizon oil rig lacked a device called an acoustic switch that could have shut off the flow of oil. The remote controlled device sends acoustic impulses through the water that can trigger an underwater valve to shut down the well.
All offshore rigs have one main switch to shut off the flow of oil by closing a valve located on the ocean floor. There is also supposed to be a backup, a so-called “dead man,” that will shut down the well in the event of a catastrophe on the rig. Apparently neither of these devices worked on the Deepwater Horizon rig. The crew members who would have been closest to the shutoff switch are among those missing and presumed dead.
With an acoustic trigger a crew can shut down a well even if the rig is damaged or evacuated.
However, BP, which reported profits of $5.598 billion for the first quarter of 2010, vigorously resisted changes to US regulations that would have required acoustic triggers on deep sea rigs, citing effectiveness and costs, about $500,000 per unit.
Compliant US regulators agreed, saying other backup plans were sufficient. They called the acoustic triggers unreliable and prone to causing unnecessary shutdowns.
However, according to a spokesman for Norway’s Petroleum Safety Authority quoted by the Journal, acoustic triggers are “the most successful and effective option.” Norway has used acoustic triggers on almost all its oil rigs since 1993.