Guidelines for Evaluating the Likelihood of Ignition of Released Flammable Masses

摘要

Almost since the beginning of time, and certainly since the beginning of structured riskanalyses, a core question in studies involving flammable releases has been, "Will therelease ignite?" Technology has been developed to predict consequences of ignition withvaring degrees of precision. However, the "Will it actually ignite" question has receivedmuch less attention and technical development. We know that when a flammablematerial is released from process equipment, the result may be a fire, an explosion, or therelease may simply dissipate with no apparent effect other than a minor environmentalimpact. Depending on the circumstances, the probability (likelihood) of ignition canrange from 0 to 1. Most of the current methods used for estimating the likelihood ofignition are rather crude, and in many or most cases are not based on actual processindustry data. For anyone performing a risk-based analysis of any type (QRAs, LOPAs,risk-based facility siting studies, or even the application of a PHA risk matrix), thisresults in overly conservative or overly optimistic expectations of ignition. In otherwords, the current methods are often not much better than a guess and can be misleading,with potentially catastrophic results.It is not difficult to find situations in which the probability of ignition for a given set ofconditions varies widely from source to source. There are also some variables that areknown to be important to the likelihood of ignition that have not yet been rigorouslyquantified. This results in uncertainty in risk-based studies, limiting the ability of therisk manager to justify spending for appropriate projects that would reduce the likelihoodof ignition as a way of managing risk.