Development of algorithms for predicting ignition probabilities and explosion frequencies

Abstract

This article covers the development of algorithms for predicting the frequencies of explosions based on a variety of design, operating and environmental conditions. Algorithms were developed for estimating unit‐based explosion frequencies, such as those reported in API, but in more detail and covering a much broader range of chemical process types. This article also shows the developed methods for predicting scenario‐based explosion frequencies, using frequencies of initiating events and conditional probabilities of immediate ignition and delayed ignition resulting in explosion. The algorithms were based on a combination of published data and expert opinion. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2010

One company's observations on the implementation of LOPA

“…Probability of Ignition-Ignition of flammables is a complex topic, since it needs to consider immediate and delayed ignition (where consequences may be different), area classifications, ignition sources, and so forth. While generalized values based on research and experiments are available [6], these values are often misapplied due to lack of understanding. For that reason, our guidance specifies a value of 1 (certain ignition) for any release within the battery limits of a process unit.…”

Hazards for syngas fires and explosions

“…Moosemiller [5] provided a failure frequency of 3 × 10 −4 /year (“medium frequency”) for VCEs resulting from reformer units with a range of factors that can be used to account for larger or smaller units, area classification, PSM system effectiveness, and other factors. Ignition probabilities in this article show that a default assumption is that ignition occurs in 56% of releases, and explosions are the minority of cases at ∼ 5% of releases.…”