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Integrated Violence Model of 1.3 Events with Example Test Results
Robert T. Ford; Safety Management Services, Inc. (SMS
®
); West Jordan, Utah, United States of America
Clint G. Guymon, PhD, PE; Safety Management Service, Inc. (SMS
®
); West Jordan, Utah, United States of America
KEYWORDS
integrated violence model, pressure rate-of-rise, vent area, venting, choked flow, modeling
ABSTRACT
The Integrated Violence Model (IVM) has been successfully used to determine the necessary vent area to
prevent damage to process equipment and building structures from excessive pressure during deflagration
events. It has also been used to determine the potential effects (fragmentation and overpressure) from a lack
of sufficient venting that can result in an explosion. Accidental ignitions of 1.3 substances like propellants
can transition from a deflagration to an explosion if the gases generated by the substance are not properly
vented. This paper provides an overview of the Integrated Violence Model that is specific to 1.3 materials.
Application of the Integrated Violence Model to the test scenarios outlined in NAWCWD TM 8742 is
highlighted showing the relationship for predicted structural failure between vent area ratio and the loading
density for the tested conditions as well as multiple other conditions. The model predictions of structural
failure and internal pressures agree with the experimental results.
INTRODUCTION
Burning or 1.3 type reactions are characterized by a non-instantaneous consumption of the substance such that the
substance reacts and gives off heat and or gas. If that heated gas is produced in a sufficient quantity and is not vented
properly the confining medium will yield and potentially explode. The confining medium may be the processing
equipment or the building in which the substance is located. Ideally, the amount of substance allowed in the processing
equipment or building structure and the associated venting conditions necessary to prevent an explosion would be
determined experimentally; however, completing such a large amount of experimental test is cost and time prohibitive.
Modeling based on small-scale testing is an effective way to obtain accurate estimates of the necessary vent area to
prevent an explosion of a small or large structure containing 1.3-type substances.
There are multiple different methods to complete modeling of the pressurization of a structure based on critical
parameters including gas generation rate of the reacting substance, size and location of vent areas, vent panel mass,
vent opening pressure, internal volume, and strength of the structure. The modeling scale can range from including
the molecular interactions and reactions (e.g. molecular dynamics), to the treatment of collections of molecules in
defined volumes interacting with each other (e.g. computational fluid dynamics), and to the treatment of larger areas
of gases (e.g. ballistics-type codes including the Integrated Violence Model). Unfortunately, the time to complete
modeling evaluations at smaller and smaller sizes increases exponentially. The modeling methodology selected should
be the one that yields the most accurate result with the least number of parameters. The accuracy of the model is
evaluated on whether or not the model can predict pressures and impulses that correspond to those observed
experimentally. The Integrated Violence Model has been accurate in matching small-scale experimental results and in
accurately predicting large-scale experimental results. An example application of the Integrated Violence Model to
the test scenarios outlined in NAWCWD TM 8742 (Farmer, 2015) is highlighted below.
