Complex Explosion Development in Mines: Case Study

Complex Explosion Development in Mines: Case Study – 2010 Upper Big Branch Mine Explosion

Scott David, Ph.D., P.E., CFEI
Derek Engel, CFEI
Kees van Wingerden, Ph.D.
GexCon, US, USA

ABSTRACT
On April 5th, 2010 a methane explosion occurred within the Upper Big Branch mine south of Charleston, WV. Twenty-nine men lost their lives as a result of a flammable concentration of methane that built up in the enclosed space and ignited, resulting in a methane explosion that transitioned into a coal dust explosion. This study used the FLACS CFD solver to conduct a detailed explosion analysis to evaluate the complex overpressure development throughout the mine as a result of the flammable cloud ignition. As a result of the accident investigation, unique explosion patterns were found in the mine where certain “blast indicators” within the mine shafts were deformed in such a manner that was inconsistent with the likely flow of the expanding blast wave. The FLACS analysis will analyze the explosion dynamics and shed light on the damage observations made after the blast.

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Fire Effects on Receptacles

Matthew E. Benfer, Daniel T. Gottuk
Hughes Associates Inc., USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2012

ABSTRACT

Although significant casualties and damage are attributed to electrical fires, there is still much uncertainty in clearly identifying forensic indicators of electrical components post-fire to be able to justify whether the component damage was a result of the fire (i.e., a fire victim) or whether it signifies a cause. The objective of this study was to assess the damage and potential forensic signatures of a range of electrical receptacle configurations exposed to two types of fires in order to provide a technical basis for realistic electrical fire scenarios, improving fire scene interpretation, and evaluating the utility of forensic analysis techniques. Specifically, the approach was to, first, characterize the damage (e.g., location of damage, melt, arcing, etc.) to receptacle configurations that have been the source of overheating and compare this to data for receptacles exposed to fire. A second objective was to characterize the similarities and differences between arcing and melting in receptacle components and wiring.

Laboratory testing evaluated the impact of a wide range of variables on the formation of overheating connections in residential duplex receptacles. Two types of receptacle configurations have been evaluated: 1) those focused on terminal connections and 2) those focused on plug connections. Testing included 528 receptacle trials, 408 trials with various terminal connections and 120 trials with various plug connections. Thirteen pre-fabricated wall assemblies of 36 receptacles were placed in 8 compartment fire tests and 5 furnace fire tests. The variables evaluated in the fire exposure testing included: the receptacle material, materials of the receptacle faceplate and box, terminal torque, and energized state of the receptacle. A portion of receptacles in the fire exposure testing had overheated connections that were created in the laboratory testing. These receptacles were used to assess whether evidence of overheating would persist after a fire exposure. All receptacles were documented for damage to the receptacle, faceplate, and outlet box including any arcing, overheating, and/or melting.

The results of laboratory testing indicate that only the loosest connections tend to form significant overheated connections irrespective of other variables such as receptacle materials and installation. Characteristics of damage to receptacles as a result of overheating have been identified and have been found to persist even after fire exposure. In addition, locations of arcing within receptacles as a result of fire exposures were identified and characterized. The location of arcing is primarily dependent on the duration and intensity of the fire exposure, as well as the construction and materials of the receptacle, outlet box, and faceplate.

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Observations on Two Fires

Observations on Two Fires in Which the Spill of Flammable Liquids Led to Deflagration and/or Flash Fire in a Stratified Heavy Vapor/Air Mixture

Giovanni Cocchi, P.E., Ph.D.
ARSON Fire, Safety and Environmental Investigations S.r.l., Italy

Presented at the International Symposium on Fire Investigation Science and Technology, 2014

ABSTRACT

The most common kind of diffuse phase explosions investigated by fire investigators involve methane or LPG, either accidentally or willingly allowed to accumulate in the confined volume of the room(s) of a building. Many volatile ignitable liquids can form a flammable vapor/air mixture when spilled on the floor and let evaporate for enough time. Upon ignition, flash fire or deflagration will take place, possibly followed by the development of a compartment fire. This work reviews the relevant literature about evaporation of volatile ignitable liquids, heavy gas dispersion and propagation of flame front in stratified heavy vapor/air mixtures. Subsequently, two cases in which the author was asked to provide its technical opinions will be discussed. The first one is a massive semi-confined deflagration in a large storage room that eventually vented through the weakest brick wall of the building. The building was not equipped with natural gas lines and no LPG can was retrieved at the scene. Subsequent fire debris analysis demonstrated the use of volatile accelerants. The second one is a flash fire that was caught on CCTV camera. Around four minutes before, a person was taped while pouring a liquid…After the flash fire, the puddles of liquid of what was intended to be a trailer were observed to burn as pool fires, until smoke obscured the camera. The flame front of the flash fire shows all the relevant features that other authors have previously shown to be peculiars of flash fires in a stratified heavy vapor/air mixture. Fire investigator should consider that when an explosion or a flash fire take place before fire development and natural gas or LPG sources can be legitimately ruled out, use of highly volatile accelerants should be regarded as a legitimate hypothesis and tested according to the scientific method of NFPA 921-2014 .

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Measuring the Impact of Cognitive Bias

Measuring the Impact of Cognitive Bias in Fire Investigation

Paul Bieber, CFEI, B.S., M.L.S.
Director of the Arson Research Project, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2012

ABSTRACT

Cognitive bias has been found to shape decision making in a wide variety of fields. Criminal investigation and the forensic sciences are no exception.  Fire investigation, part criminal investigation, part forensic examination, is uniquely positioned to be influenced by the affects of cognitive bias.

The 2009 report from the National Academy of Science, Strengthening Forensic Science in the United States; A Path Forward (NAS Report) , recognizes conceptual bias as a factor in all forensic disciplines.  The National Fire Protection Association Guide for Fire and Explosion Investigation (NFPA 921)  acknowledges these biases as a concern in fire investigation.3

This report will explore the most common forms of cognitive bias found in the field of fire investigation, review past research and give recommendations on how these biases might be minimized. It will also present the results of new research which sought to measure the influence of expectation and role bias in fire investigation. A companion report, “Case Study Review of Contextual Bias in Fire Investigation” is available at www.Thearsonproject.org.

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The Differences Between the North American Building Constructions and the Southern European Building Constructions

The Differences Between the North American Building Constructions and the Southern European Building Constructions Affects the Type of Fire Pattern That Are Most Commonly Found in a Fire Scene

Giovanni Cocchi, P.E., Ph. D.
ARSON Fire, Safety, and Environmental Investigations S.r.l., Italy

Presented at the International Symposium on Fire Investigation Science and Technology, 2014

ABSTRACT

Fire pattern analysis is a fundamental step in any fire investigation, since it provide the basis for the heat and flame vector analysis onto which the reconstruction of fire spread and the identification of the area of origin of the fire are based. Fire patterns formation depends on the fire effects being produced by the fire. This works discuss some of the differences between building construction in North America and Southern Europe, on the basis of the example of Italy, and try to tackle the problem if such differences may affects the type of fire patterns that are found in a fire scene.

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Analysis of Post-Fire Characteristics of Portable Oil Filled Room Heaters

Analysis of Post-Fire Characteristics of Portable Oil Filled Room Heaters to Determine Pre-Fire Orientation

K. Scott Barnhill, PE
Investigative Forensic Specialists, PLLC

Presented at the International Symposium on Fire Investigation Science and Technology, 2014

ABSTRACT
A portable oil filled room heater is a steel vessel typically with 5 to 8 fins containing approximately 3 to 4 liters of mineral oil. The mineral oil acts as the heat transfer fluid that is heated by an immersed electric heating element. The outward appearance of an oil filled heater is that of an old steam radiator.

An oil filled heater (OFH) exposed to full room involvement conditions will commonly display fire effects to include: rupture of the vessel’s spot welds, localized wavy deformations to the fins in the unwetted regions of the vessel, and differential deformation of the vessel’s fins. This study addresses the post-fire characteristics of oil filled heaters exposed to full room involvement conditions in two burn cells. A primary focus of the study is to determine if the pre-fire orientation of the oil filled heater can be determined by analysis of the post-fire appearance. A description of the dynamics that occur between the wetted and unwetted surfaces when the vessel is exposed to full room involvement conditions is discussed.

Analysis of an OFHs’ post-fire characteristics, to include vessel dimensions and wavy deformations, compared to the burn cell experiment results, allows an investigator to accurately interpret the normal reaction of an OFH to full room involvement as well as to determine its pre-fire orientation (upright or otherwise).

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Distinguishing Between Arcing and Melting Damage

DISTINGUISHING BETWEEN ARCING AND MELTING DAMAGE IN ELECTRICAL RECEPTACLES

Matthew Benfer and Daniel Gottuk
Hughes Associates Inc., USA

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT

The majority of fire-investigation related literature on electrical arcing focuses on copper wiring, both stranded and solid, with some attention paid to steel (i.e., conduit), and relatively little mention of brass. This is despite the relatively equal presence of copper, steel, and brass in receptacles and similar electrical devices. Changes to NFPA 921 in the 2014 edition of the guide expand upon the characteristic traits which can be used to assess whether arcing or melting is present in a conductor. However, most of the characteristic traits of arcing and melting are qualitative and not well defined in NFPA 921, which leads to more subjective evaluations. In addition, a myopic examination of evidence with respect to the presence of one or two characteristic traits can lead to a false indication of arcing. In cases such as this, other evidence of melting (i.e., in close proximity to the area in question) could preclude confirmation of arcing.

The purpose of this work was to determine which characteristic traits are effective in assessing potential arcing damage on receptacle components and wiring. A total of 86 receptacles were evaluated in this study. Thirty-nine receptacles failed as a result of an overheating connection resulting in arcing damage; this included 95 individual conductors. Forty-seven receptacles with fire-induced arcing were also evaluated; this included 87 individual conductors. All of the evaluated receptacles with fire-induced arcing were energized or energized with a load during testing. In contrast, thirty-seven non-energized receptacles with fire induced melting were evaluated with 57 individual conductors.

The characteristic arcing traits which were evaluated include: corresponding damage on the opposing conductor; localized point of contact with a sharp line of demarcation between undamaged and damaged areas; round, smooth shape; resolidification waves; tooling marks visible outside the area of damage; internal porosity; spatter deposits; and small beads and divots over a limited area. The characteristic traits of melting which were evaluated include: visible effects of gravity; gradual necking of the conductor; and pitting, thinning, and presence of holes in the conductor. These traits were taken from the literature (e.g., NFPA 921) and from observations made during the forensic examinations of receptacles and wiring conducted as part of this work. For each characteristic, there were three possible outcomes: Yes, No, and Possible. Yes indicated that the characteristic was judged to be present on the particular conductor; no indicated that the characteristic was judged not to be present on the conductor. Possible indicated that confirmation could not be made either for or against the presence of the characteristic. All of the evaluations were conducted by the same person.

Corresponding damage on the opposing conductor, localized damage with a sharp line of demarcation, and tooling marks outside of the area of damage were observed on significant portions of arc damaged conductors and small numbers of conductors with melting damage; these characteristics were found to be strong indicators of arcing.

Using multiple characteristic traits and contextual information for determination of arcing vs. fire-melting provides greater confidence in the evaluation of damage. In addition, visual examinations were found to be reliable indicators of both arcing and fire-melting for most conductors. However, there are some cases which would benefit from more advanced examination techniques including SEM/EDS examinations, X-ray, CT scanning (X-ray computed tomography), cross-sectioning and polishing, or other metallurgical methods.

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Anatomy of a Wrongful Arson Conviction

ANATOMY OF A WRONGFUL ARSON CONVICTION: SENTINEL EVENT ANALYSIS IN FIRE INVESTIGATION

Paul Bieber, CFEI, B.S., M.L.S. The Arson Research Project

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT

Anatomy of a Wrongful Arson Conviction will discuss the first comprehensive review of U.S. arson exonerations and the first application of sentinel-event and root-cause analysis to the field of fire investigation. Its purpose is to expose and explain the common factors that contribute to wrongful arson convictions.

Sentinel-event analysis has been embraced by several industries as an objective method of identifying and explaining the root causes of errors that have led to harmful outcomes. By reviewing dozens of arson cases, the Arson Research Project has documented the common errors at the heart of many fire investigations where accidental, natural or undetermined fires have been misidentified as arson.

This paper will also highlight the presence and impact of various forms of cognitive bias in each case study and emphasize the importance of objectivity and independence in the reliable application of the scientific method.

The 27 cases being reviewed include 19 exonerations, 7 cases where charges were dropped or a jury returned a not- guilty verdict, and one case that resulted in an execution. Together they represent over 200 years of combined incarceration and several life sentences. Even in the cases where the defendant was acquitted or the charges were dropped, the financial cost and emotional toll to the wrongfully accused were enormous. It is only through a clear examination and better understanding of these common errors that we may hope to avoid similar errors. This case- study review will attempt to shed some light on the problem in an ongoing effort to improve the practice of fire investigation and avoid future wrongful arson convictions.

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Plasma Ashing as a Fire Investigative Tool

Mark Goodson PE
Lee Green PE
Michael Shuttlesworth PE
Goodson Engineering
Denton, Texas USA

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT
One of the difficulties that has faced engineers who examine electrical or mechanical items and / or devices after a fire is that of cleaning the item. The key adage in cleaning is essentially a medical command – primum non nocere, or “do no harm.” The cleaning technique will preferably cause no damage to the artefact being examined. Successful cleaning allows for both microscopic, visual, and SEM / EDX analysis.

In a fire, it is not uncommon for fire artefacts (wires, as an example) to require cleaning. Historical cleaning techniques have relied upon ultrasonic cleaning as a means for debris removal. Ultrasonic cleaning makes use of mechanical (sonic) energy to cause debris to dislodge from artefacts. How successful this technique is depends (in part) upon the energy imparted, the solvent used, and the interface between the wire and the debris. In the case of partially pyrolyzed PVC insulation, there are conditions that occur (depending upon the state or extent of pyrolysis) where no amount of mechanical agitation will remove the fire debris.

Oxides can be removed from wires by the use of surfactants or cleaners, some of which can have an etching effect on the metal. Treatments such as Alconox  or Simple Green  sometimes work sufficiently, while a more aggressive oxide remover (Branson OR)  relies on citric acid to help clean the wires. With more aggressive reagents, the user runs the risk of etching the metal and ruining the surface finish.

The writers describe a technique for removing fire debris from metal objects (wire, CSST) for use in removing fire debris. The technique is referred to as plasma ashing . In plasma ashing, a vacuum is created around the artefact, and a carrier gas is introduced (such as O2). An RF field (13.56 MHz) is applied, and the oxygen takes on a monatomic state. Essentially, a plasma i s created, and the monatomic O is free to react with organics associated with the fire debris. This process is also referred to as a glow discharge . The end result is that organics are removed from the artefact, and the ashing takes place at low temperatures – sufficiently low such that grain structure of the metal is not changed. This technique is essentially what is used in one of the manufacturing steps for making integrated circuits (ICs). As such, it imparts sufficiently low energy such that crystalline semiconductor structures are not damaged.

We compare and contrast plasma ashing with other modalities of cleaning. More particularly, we note (through visual microscopy) the efficacy of ashing and ultrasonic cleaning, as well as material removal rates. We show that despite its relative expensive capital costs, ashing represents a cleaning technique that does what other modalities fail to do – consistent removal of organic debris with no damage to the underlying substrate.

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The Application and Use of Digital Multimedia Evidence in Fire Investigations

 

James H. Shanley, Jr., PE, CFEI, CFI, MIFireE
Travelers Engineering Laboratory
and
James T. Noll
Travelers Engineering Laboratory

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT

Digital multimedia is created in many forms and with increasing frequency with digital security systems, monitoring cameras, smart phones and other devices. Digital equipment and media obtained from these investigations should be handled in a specific way to preserve its integrity as potential evidence. In addition, Digital Multimedia may contain embedded data that can be clarified or analyzed to increase its value in a fire investigation.

The paper will review best practices with respect to handling digital equipment and multimedia in the context of a fire investigation. It will describe recovery and retrieval techniques and will aid the fire investigator in properly utilizing this growing resource of evidence.

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