White Paper by Exida: Some of the significant process industries incidents occurred by overflowing vessels, including BP Texas City and Buncefield. In many overflow incidents, alarms were designed to signal the need for operator intervention. These alarms may have been identified as safeguards or layers of protection, but they did not succeed in preventing the incident. This paper reviews several overflow incidents to consider the alarm management and human factors elements of the failures.
Alarms are often cited as safeguards or independent protection layers to prevent hazardous events, yet incidents continue to occur where the alarm did not prompt action to prevent the consequence. The investigation of these incidents focuses on the root causes, but there is an opportunity to also examine the contributing factors that allowed the protection layers to fail. A set of failure mechanisms for alarms can map the failure to the activities of the alarm management lifecycle and the operator feedback model from ANSI/ISA -18.2  . Many of the failures can be related to human factors failure mechanisms, or situational awareness demons. A set of similar overflow incidents are analyzed using this methodology to develop recommendations.