(129b) How Emergency Isolation Valves Can Effectively Mitigate the Consequences of Early Pool Fires

Uncontrolled releases of ignitable liquids present a severe hazard to industrial properties through the formation of large pool fires that can cause significant property damage and even loss of life. Emergency isolation valves (EIV) provide an effective means to reduce the severity, or even completely eliminate the consequences, of these events. Unfortunately, in many facilities these devices are not extensively deployed due to cost concerns or even due to the poor perception of process risk.

In this work, the effectiveness of emergency isolation valves is quantified in a representative ethanol distillery plant. To estimate the consequences of the event, the PHAST model for thermal radiation from an early pool fire and damage functions based on the TNO Green Book are used to evaluate the expected loss for a range of EIV response times. This study shows that an automatic EIV, capable of stopping an ethanol leak within the first twenty seconds of a full bore rupture of a 4 inch line, can reduce the loss expectancy of an early pool fire exposure by a factor of 11 compared to a scenario where the leak is not stopped in a timely manner. It also demonstrates that a robust operator training program in conjunction with effective emergency operating procedures can significantly reduce the risk from a pool fire in cases where Romote Operable Shut Off Valves (ROSOVs) are installed.

This work clearly demonstrates the effectiveness of emergency isolation valves to reduce the consequences of uncontrolled releases of ignitable liquids, and shows how this method can be used to quantify the benefit of their installation.