An Approach to the Quantitative Assessment of Risk due to Major Accidents Triggered by Lightning

Abstract

An extended analysis of past accident data indicated that lightning events may cause significant damage to process equipment handling dangerous substances, often leading to an extended loss of containment followed by fires, explosions or toxic releases. Data reported in the literature show that lightning caused 150 out of 480 tank fires reported in industrial accident databases between 1951 and 2003. The industrial accident databases indicate that lightning impacting on chemical plants is among the most important causes of the technological accidents triggered by natural events that are usually referred to as NaTech accidents. Considering specifically storage and processing activities, lightning events account for 61% of the accidents initiated by natural events. Even though different lightning protection measures, such as grounding and lightning rods, are usually implemented to avoid the direct lighting impact on storage tanks, recent studies have shown that these are unable to protect the flammable materials from the ignition when coming into contact with lightning sparks. Moreover, due to the increasing frequency and intensity of severe storms, the frequency of such accidents may grow in the future. Nevertheless, limited work has been dedicated to the development of quantified assessment procedures for the industrial risk generated by lightning phenomena in sites were relevant quantities of hazardous substances are present. The present study focused on the assessment of the lightning hazard and on the development of a detailed methodology for the quantitative assessment of the industrial risk due to loss of containment events triggered by lightning in the chemical and process industry. The procedure takes advantage of the progress made in recent years in the assessment of the expected frequency due to lightning. The methodology was developed within a common framework for the quantitative assessment of risk due to external hazard factors in chemical and process plants.