Category Archives: ISFI Proceedings

Christopher B. Wood
Managing Member
FIRELINK, LLC
Tewksbury, MA USA

ABSTRACT

This analysis begins with an application of the Society of Fire  Protection Engineer’s (SFPE’s) Guide to Substantiating a Fire Model for a Given Application. The Guide recommends that a model user use a process to analyze the relevant physics, evaluate candidate models, and select a particular model to use. Selection of the model is closely related to NFPA 921’s, Guide to Fire and Explosion Investigation, preliminary steps in the scientific method to identify and define the problem.

Following a modeler’s selection of a model to investigate a problem, the frequently followed next steps are to identify and collect the appropriate data for model input. Often times, this data may require some manipulation or interpretation before direct input into the model. This development of model data requires the modeler to understand the sensitivity of model outputs to model inputs to concentrate efforts on getting the highest available certainty on those parameters having the largest effect on the model outputs.

These steps are illustrated with the examination of an actual fire incident. The results demonstrate the important characteristics of hypothesis testing through the use of fire modeling. A Fire Dynamics Simulator (FDS) model is analyzed and implemented. The implementation uses experimental data to develop critical input data.

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Scott Davis, PhD., P.E., CFEI
Tom DeBold, P.E., CFEI
and
John Pagliaro, Ph.D.
Gexcon US, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

When investigating a flash fire or explosion, it is common to test and evaluate the integrity of a fuel gas system – such as LPG systems. One common technique is to use a pressurized inert gas, such as nitrogen, to not only identify possible holes for propane to leak through but also quantify the flow rate of the leak. However, if the leak is located under the liquid level of the propane cylinder, there is a common misconception that the mass flow rate for a liquid propane release must be approximately 270 times larger than a vapor release through the same hole size. In a recent case, an investigator concluded that a small hole identified during a leak test using nitrogen gas would be more than sufficient to cause a large flash fire because the hole would have been below the liquid propane level and thus would be 270 times larger than a vapor propane leak through the same hole. This misconception regarding the magnitude of liquid propane leaks stemmed from the fact that liquid propane has a density that is approximately 270 times larger than the density of gaseous propane at atmospheric pressure and temperature. Under practical conditions, the mass flow rates of liquid propane will actually be much closer to those of vapor releases given identical hole sizes. In fact, the difference will be only approximately 6-8 times larger if both liquid and gaseous propane are stored at ambient temperatures of 20°C. This near 30-fold reduction in liquid flow is due to how propane is stored and the physics governing a compressible vapor release compared to an incompressible liquid release. More specifically, for propane at 20°C the vapor will exit a small hole at the speed of sound and due to the high storage pressure (e.g., approximately 105 psig at 20°C) the density of the vapor leaking will be much higher than atmospheric conditions. Conversely, an incompressible liquid will be limited by the pressure difference upstream and downstream of the hole. The present study demonstrates the differences in liquid and vapor propane release rates and shows that liquid releases are not 270 larger than vapor releases. This is accomplished by: (1) providing an overview of the theoretical orifice flow equations for pressurized vapor and liquid releases; (2) presenting results from actual releases of liquid and vapor propane from a 120-gallon water capacity tank and a 20 lb cylinder; and (3) presenting CFD results that highlight the importance of accurate estimates of leak rates when it comes to formulating origin and cause hypotheses.

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Scott Davis, PhD., P.E., CFEI
John Pagliaro, Ph.D.
and
Tom DeBold, P.E., CFEI
Gexcon US, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

On July 1, 2014, a propane cylinder catastrophically failed and exploded on the back of a food truck in Philadelphia, PA. The explosion led to a sudden release of pressurized propane vapor and superheated propane liquid, which rapidly evaporated resulting in a large white cloud that entered and engulfed the rear of the food truck. This cloud ultimately found an ignition source within the food truck and resulted in a significant fireball burning both inside and outside of the food truck. The explosion and ensuing fire fatally injured the food truck owner and her daughter, and also caused injuries to 11 other individuals. This paper will first present the results of our investigation into the cause and origin of the catastrophic failure and explosion event, which included: (1) analyzing video footage of the explosion and ensuing fire; (2) applying propane phase diagrams to determine the expansion and resulting pressures within the cylinder prior to failure; and (3) applying blast techniques to determine the post catastrophic blast and ignition during the event. These techniques included advanced computational fluid dynamic modeling. The paper will also discuss safety critical design features and processes in the propane industry that must be in place to ensure the safe use and filling of propane cylinders, which include: cylinder requalification; having a fixed maximum liquid level gauge; having a pressure relief valve; and filling cylinders by weight or volume.

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Scott Davis,Ph.D., P.E., CFEI
and
John Pagliaro, Ph.D. Gexcon US, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

On April 26, 2014 at the Georgia Pacific Corrigan plywood facility, a fire that originated at a plywood sander eventually propagated through the pneumatic dust conveying system and resulted in an explosion in the baghouse (dustcollector), fatally injuring two employees, and seriously injuring others who were responding to the incident. Sparks from the sander entered the extraction pipe, which was protected by an active suppression/isolation system (spark-sprinkler-abort gate) upstream of the baghouse. When the fire in the extraction pipe was discovered, the extraction blower downstream the baghouse (negative pressure system) was turned off and allowed smoldering and burning to continue within the pipe. The blower was subsequently turned back on, at which time a flame front developed that propagated into the baghouse which was not properly isolated. This incident occurred because of the improper design of a back-blast damper as an isolation device and operational errors associated with the blower being turned off and back on prior to extinguishing the burning material. More specifically, when designing handling and conveying equipment for combustible dusts, it is crucial to properly implement protective measures (e.g., deflagration venting, suppression, and isolation) capable of mitigating the potential consequences and avoiding escalation of the explosion event when the dust is ignited. This paper will analyze the root cause of the incident as well as key lessons learned related to: system design; performing a dust hazard analysis; required air stream flow rates; proper back blast designs; impeding deflagration vents; and exclusion zones in the path of a vented deflagration in the baghouse.

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Michael Rushton
Office of the Ontario Fire Marshal, Canada

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

The common methodology and approach to fire investigation is to determine an origin and then inventory potential ignition sources within that origin. One potential shortcoming of this approach is if the ignition source cannot be found or does not originate from within the fire origin area. One of such possible elusive ignition source could be related to solar radiation, which originates from the sun in the form of visible and invisible light.

This paper approaches the subject of the propensity of ignition of common combustible materials as a result of exposure to a concentration of radiation originating from the sun. The paper explores various test set-ups, designed to focus sunlight through the means of refraction and reflection in order to concentrate sunlight across a specific two-dimensional target surface ultimately resulting in significantly larger radiant heat fluxes than the surrounding environment.

A total of 282 tests were conducted with various setups, which allowed for sunlight radiation to be focused onto ignitable materials such as paper. Many of the tests resulted in successful ignition of the materials. To quantify the observations, a heat flux sensor was used to measure the power produced by these various setups.

Lastly, the factors and parameters that would be required for this kind of ignition scenario(s?) are discussed. Based on the empirical data collected in the experiments, a formula is derived to represent some of the variables and also to approximate the heat flux output which can be expected from an optic object or focusing device such as a magnifying glass.

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Joel Liebesfeld, MA, MAS, Post Grad Certs: Computer Sci., Elec. & Mech. Engineering
James F. Valentine & Associates, Inc.

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

Tribology is a study within the field of mechanical engineering that focuses on the use and study of lubricants and age, wear and tear, as a function of the frictional interaction of sliding surfaces. The degradation of components, machinery, devices, appliances, et al, from the processes associated with age, wear and tear can adversely affect the surfaces formed between layers of sliding materials.

Tribology focuses mainly on the studies of plastics and metals, although many of the principles may also be applicable to other structural materials as well.

This paper will attempt to convey this intensely mathematical area of study into a more universally understandable written form of technical or lay language, but in some instances, there may be the use of formulae to exemplify models of the way in which, for example, friction can be the cause of vehicular fires. These formulae may be presented in words rather than symbolically.

It was while in a post-graduate certificate program in Tribology at the Massachusetts Institute of Technology (MIT) that I became aware of the application that Tribology had in regard to the investigation and analysis of electrical and electromechanical fires.

This paper will examine faults often found in polymers used for electrical insulation. Polymers that result in a fault are often used for strapping, harnessing/mounting of assorted wiring, especially vehicular wiring. Rotational machinery utilized in or in conjunction with passenger vehicles/work vehicles and most everywhere else, degrade as a result of a lack of improper lubrication, as well as age wear and tear. The polymers used in rotational machinery are particularly useful as resins/materials for windings, gaskets, et al. Small, but considerably irksome faults may ubiquitously appear in many types of commercial and passenger vehicles, residences and commercial structures. Example, a faulted starter motor will totally disable most vehicles manufactured with an internal combustion engine.

The paper will use examples taken from losses that were actually investigated by this author. These losses were the result of catastrophic faults that had developed in electrically energized machinery. These specific losses were discovered where the age, wear and tear of assorted materials lead to substantial fire losses.

Tribology studies involve a variety of specific data that is inclusive of time, material qualities, studies of heat production, a surface analysis of materials, assorted forces, etc.

Tribology, like many other studies, has a somewhat unique vocabulary that will be noted and explained as these words or phrases appear, such as the word ‘asperities’ which refers to certain specific surface qualities of assorted materials.

Unlike many studies or research reports, in this particular paper, an attempt will be made to have the reader learn the answers to questions regarding many common material faults and failures. And just to whet the reader’s appetite, wouldn’t it be scientifically useful to know that the contents of this paper may help Expert Fire Investigators explain what led up to the specific cause of a particular type of fire?

There are TWO easily obtainable data sources readily available to most investigators such as the Materials Safety Data Sheets (MADS) and an OSHA safety poster that together helps ensure that people will know how to use MADS, as required. These and other research resources can be helpful in the development of a report’s hypothesis, especially where such information can be integrated into a logical sequence that may be applied to the final determination of the cause for a fire.

For the reader to learn about the study of tribology it should be understood that the subject matter, in many instances, is fairly intuitive and therefore permits a broad, diversely educated audience to be able to understand and utilize most of the information as written and cited herein.

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Joel Liebesfeld, MA, MAS, Post Grad Certs: Computer Sci., Elec. & Mech. Engineering
James F. Valentine & Associates, Inc.

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT
Torque is a physics term that has many applications. Torque is defined as a twisting force that tends to cause rotation. The point where the object rotates is known as the axis of rotation. In electrical power distribution, torque tightened connectors are fairly commonplace, especially where metal-to-metal connectors are utilized or, for example, where bare steel or aluminum conductors are constructed to connect overhead powerlines between high voltage towers, as well as at utility poles that are used for electrical power distribution.

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Richard Kovarsky, P.E., CFEI, CFI
Pyro-Technical Investigations, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

There have been many advances in fire investigation over the past 30 years. These advances have seen the profession grow from an art based upon unsupported and untested theories and guidelines to a more rigorous discipline rooted in science and objective, tested theories and methodologies. This has been evidenced by the progression of documents such as NFPA 921 and 1033 and by the latest texts, such as those by Lentini and Gorbett. The changes brought about by these documents have had a significant impact on the profession of fire investigation, the manner in which fires are investigated and the basis for determining the origin and cause of a fire. These are all welcome changes. However, fire investigation is not only a profession, it is also a business. One of the areas that has resulted in significant impact on the business side of fire investigation has been the concept of spoliation of evidence. It has progressed from a little known idea to becoming a driver for the manner in which fires are investigated. This paper will look at the ways that the concept of spoliation has affected the business side of the profession.

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Toh Qiu Ping, B.Sc(Mathematical Sciences)
CFEI Singapore Civil Defence Force, Singapore

Tan Kim Haw, M.Sc(HSE), B.Sc(Chem)(Hons)
CFEI Singapore Civil Defence Force, Singapore

Lim Beng Hui, M.Sc(FI)(Dist), B.Eng(Civil)(Hons)
CFEI, CFII Singapore Civil Defence Force, Singapore

Lim Lam Kwang, B.Eng(Mechanical)(Hons)
Singapore Civil Defence Force, Singapore

Anna Teo Li Li, Diploma (Applied Food Science & Nutrition)
Singapore Civil Defence Force, Singapore

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

On 27 June 2015, 15 people were killed and more than 500 people were injured in a blaze at the Colour Play Asia event at the Formosa Fun Coast Water Park, just outside Taiwan’s capital, Taipei. The fire was caused by an explosion of a dense cloud of coloured powder – a mixture of corn starch and food colouring – which was sprayed into the air at high velocity over crowds of party goers.

Arising from the incident, there were safety concerns on the use of such coloured powder in other similar events worldwide, including Singapore’s own version of the Colour Run. This paper summarises the fire investigation findings from the tragedy in Taipei, and shares insights on the fire safety assessment conducted by Singapore authorities prior to its own event. Details of a laboratory analysis of the powders used and a hazard evaluation of the event will be presented. The safety measures imposed to minimise the risks involved, for Singapore’s Colour Run and other similar events, will also be discussed.

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Hubert Biteau, Ph.D., P.E., CFEI
Exponent, Failure Analysis Associates; Atlanta, GA

Nicholas Nava, P.E., CFEI, CVFI
Exponent, Failure Analysis Associates; Bowie, MD

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

A tool which is of particular interest in fire and explosion investigations is the modeling of flammable gas concentrations. The use of computational fluid dynamics (CFD) modeling, particularly NIST’s Fire Dynamics Simulator (FDS) is well known in the fire protection engineering community. Considerable research has been performed by engineers and scientists from NIST and within the fire protection engineering community to validate this model.

The use of FDS in modeling gas dispersion for natural gas and propane gas leaks has been the focus of past work by others. Recent interest has surrounded the use of flammable and combustible liquids during cleaning and construction type activities. Flammable gas is produced due to evaporation of the liquid phase. The dispersion of this flammable gas throughout compartments above the Lower Explosive Limit (LEL) can result in a fire or explosion when in contact with a competent ignition source.

The scope of this paper is to demonstrate FDS’s ability to accurately model flammable gas concentration and dispersion. Experimental testing was conducted to determine the evaporation rate of frequently used flammable and combustible liquids. Combustible gas monitors were used to spatially measure the flammable gas concentrations in proximity of a flammable and combustible liquid spill in a controlled diked area. The experiment was then modeled using FDS. Experimental data and modeling results were compared.

This work is of particular interest for those individuals involved in fire investigations who consider using FDS to model flammable gas concentrations. First, results of this experimental work will be presented. Secondly, a comparison of the experimental and model results will demonstrate FDS’s ability to accurately depict flammable gas evaporation and dispersion. Finally, recommendations will be made for the critical input parameters needed to allow for the use of the model for fire origin and cause determinations.

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