‘Runaway’ is a dangerous phenomenon where the running diesel engine draws extra energy from low concentrations of any hydrocarbons in the surrounding air. This causes uncontrolled overspeed beyond the safe design limits and can lead to an explosion or ignition of the external air-fuel mixture.
Independent third-party tests performed by a leading engine OEM show that a diesel engine can start to run away within 3 to 9 seconds of a gas being drawn in, at a concentration as low as 22% LEL. Once this begins, turning off the ignition key will not stop a diesel engine There is very little margin for error if engine shutdown is dependent on human intervention!
Understanding the lessons learned from the Texas City Refinery accident and the Deepwater Horizon explosion are useful for addressing this safety related issue. Areas designated for no ignition sources are places where diesel engines must have appropriate upgrades to mitigate their potential for ignition.
The key recommendation is to ensure that these risks are understood, all employees understand the risks and that this message is reinforced periodically. As regulations change and new standards and guidance are developed, consideration should be given to periodic updates to maintain operator awareness. Oil & gas company safety policy, international standards and accident history prove diesel overspeed is both real and fatal
A critical aspect of contract work is the contractor safety agreement or policy that is established between the contracted company and the E&P company. While these contracted companies typically have internal safety policies of their own, a safety agreement helps establish accountability and responsibility between both parties and sets a precedent for the level of occupational safety that is expected on site. Contractor safety policies should bring attention to all recognized dangers, even if the probability of occurrence is low.
In summary, Diesel engines that are not properly controlled or protected present a dangerous source of ignition when used in areas where combustible vapours may exist. A resulting explosion often leads to significant consequences for people, refineries, and the environment. Common preventative measures found on site do not always work.