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292879 Guidelines for Evaluating the Likelihood of Ignition of Releasaed Flammable Masses
ABSTRACT:
“Guidelines for Evaluating the Likelihood of Ignition of Released Flammable Masses”
By
Bob Stack (Dow Chemical), Adrian Sepeda (CCPS Staff Consultant) and Mike Moosemiller (BakerRisk)
When a flammable material is released from process equipment, the result may be a fire, an explosion, or the release may simply dissipate with no apparent effect other than a minor environmental impact. Depending on the circumstances, the probability (likelihood) of ignition can range from 0 to 1. 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) two things are of importance—the probability the event will occur and the likely consequences if it does. Of the two, consequences have been the subject of much more extensive development work. Ignition probability/likelihood, however, is an equally critical input that requires objective evaluation and to date has had less technologically sound approaches developed. The result is that most of the methods for estimating the likelihood of ignition are rather crude, and in many or most cases not based on actual process industry data. This results in overly conservative or overly optimistic expectations of ignition.
As a result, it is not difficult to find situations where the probability of ignition for a given set of conditions varies widely from source to source. There are also some variables that are known to be important to the likelihood of ignition that have not, as of yet, been quantified rigorously. This results in uncertainty in risk-based studies, and also limits the ability of the risk manager to justify spending on appropriate projects to reduce the likelihood of ignition as a way of managing risk.
For this reason CCPS commissioned a book, expected to be released in the fall of 2012 that consolidates the available information on this subject and proposes ignition probability algorithms that advance the art. The book is accompanied by a data source that codifies the algorithms for those who want to utilize the book concepts as is, and provides a list of citations that can be expanded upon if desired. The intended audiences for the book are Process Safety Subject Matter Experts (SMEs) involved in risk assessments and hazard evaluations. The timing of the book’s release is after the release of the revision to the CCPS book “Guidelines for Evaluating Process Plant Buildings for External Fires, Explosions, and Toxic Releases”, and near the release time of” the CCPS book “Guidelines for Conditional Modifiers and Enabling Conditions” in order to support risk-based analyses that will be described in those references.
The algorithms proposed in this book represent the state of the art, but the reader must recognize that the art is still evolving. There is an expectation that updates to the software will occur periodically, so that people who purchase the book complete with the Calculation Tool will be able to benefit from updates that result from user feedback from the initial version of the Calculation Tool. Therefore the goal of this project is not only to provide a ‘snapshot’ of the current technology in an effort to manage risk, but to promote its continued improvement via user involvement and feedback.
The presentation describes the contents of the book as well as some of the key concepts and algorithms. Example cases from the book are illustrated through a demonstration of the Calculation Tool that is provided with the book.
See more of this Group/Topical: Global Congress on Process Safety