Depending on ROV's for isolation is bad design

An accident in a refinery in 2007 that killed 4 contract workers highlights the dangers of depending only on ROV's (remotely operated valves) for isolation. A maintenance job was being carried out on a hot oil line. Operators closed a ROV in the line and issued the permit to remove a blind on the downstream flange of the ROV. Instrument air to the ROV was left open. (ROV is a fail to close valve) When the maintenance workers were fixing the chain block to remove the blind, it inadvertently hit the switch on the ROV control field panel and opened the valve, causing hot pressurised oil to spray, ignite and kill the 4 workers.  

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