Metallurgy and Fire Investigation

Elizabeth C. Buc, PhD, PE, CFI
Fire and Materials Research Laboratory, LLC, USA

Presented at International Symposium on Fire Investigation, 2012

ABSTRACT

NFPA 921 Guide for Fire and Explosion Investigations recognizes the need for specialists for certain aspects of fire cause investigations. One such area is metallurgical failure analysis. Examples of metallurgical aspects that overlap the fire investigation field include vessel and pipeline failures from corrosion or welded joint failures causing loss of containment (i.e., natural gas); wear and mechanical breaks or failures that generate sparks or frictional heating that cause ignition; and elucidation of heat or fire versus electrical arc damage to current carrying components, such as conductors, motor windings, contacts, and fuses. Equally important, metallurgy can be used to determine the effects of fire on low-melting temperature alloys, such as brass and brazed joints, to determine when damage occurred and if it contributed to the cause of a fire or was a result of fire exposure. Like fire investigation, metallurgical root-cause failure analyses are performed according to a recognized professional standard methodology that meets the criteria for admissibility. Here, key elements of a metallurgical-based failure analysis are highlighted with specific metallurgical-based fire cause investigation case studies.

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Fitting a Square Peg into a Round Hole

Fitting a Square Peg Into a Round Hole – Fire Classification Under NFPA 921

Brian P. Henry and Andrew L. Smith

This article will be presented at ISFI 2016

Introduction
This article will explore an important, but largely ignored, topic in NFPA 921 – should fire investigator experts classify fires? Does a classification of a fire as incendiary serve a purpose? Why did the NFPA implement authoritative guidelines permitting fire investigators the ability to separate fires into one of four distinctly defined categories? These important questions will be explored in detail below.

To begin, we must first ask ourselves why we investigate fires. As a society, we investigate a fire to find the root cause to prevent the fire from happening again. Public welfare and safety are huge concerns. Fire investigation implicates potential criminal responsibility. Some say the purpose of fire and explosion investigations is much broader than just determining the cause of a fire or explosion incident. The goal of any particular fire investigation is to come to a correct conclusion about the features of a particular fire or explosion incident that resulted in death, injury, damage, or other unwanted outcome.

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Fires Involving Air Conditioning Fan Coil Units

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

Yazeed Abdul Rahman, B.Eng(EEE)(Hons), CFEI, CVFI
Singapore Civil Defence Force, Singapore

Soh Seok Yuen, B.Eng(Mech)(Hons)
Singapore Civil Defence Force, Singapore

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT
Air conditioning is common in Singapore households due to the hot and humid tropical weather all year round. The typical air conditioning found in Singapore homes is the multi-split system which comprises a condensing unit (CU) and a number of wall-mounted fan coil units (FCU). From 2008 to 2013, there were 168 reported multi-split air conditioning fires of which 74 involved the wall-mounted FCU.

Fires involving the wall-mounted FCU are of greater concern than fires involving other parts of the multi split system as they have the propensity to cause significant property damage. There is also a lack of awareness on such fires in some local communities.

This paper details the observations made in a study on fires involving the multi-split air conditioning system in Singapore from 2008 to 2013. The intent of this study is to present investigative evidence that wall-mounted FCU fires can happen. The study also seeks to debunk the myth that wall-mounted FCU fires cannot happen when the FCUs are on standby mode. Additionally, the study will discuss how the burn patterns can possibly mislead investigators and highlights the value in scrutinising fires which are localized to the wall-mounted FCU.

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Explosion Severity: Propane Versus Natural Gas

Alfonso Ibarreta, Ph.D., PE, CFEI, Timothy Myers, Ph.D., PE, CFEI, CFI, James Bucher, Ph.D., CFEI and Kevin Marr, Ph.D., CFEI Exponent, USA

Presented at International Symposium on Fire Investigation, 2012

ABSTRACT
Natural gas, composed mainly of methane, is in some ways similar to propane gas. Both fuels have similar energy densities per unit mass, and similar laminar premixed flame burning velocities. However, propane explosions have been shown to produce higher overpressures in unconfined explosion tests when compared to methane. In vapor cloud explosion modeling, methane is considered to be a “low” reactivity fuel, while propane is listed as a “medium” reactivity fuel. In closed vessel explosion testing, the maximum rate of pressure rise for propane is almost twice than that for methane (based on KG  values reported in NFPA 68 (2007) Standard for Explosion Protection by Deflagration Venting , table E.1).

This study provides a direct comparison of the explosion severity between commercial propane and natural gas. Empirical correlations available for vented vessel explosions and unconfined Vapor Cloud Explosions (VCEs) are used to predict the difference in overpressure expected for a commercial propane explosion versus natural gas explosion. Although the maximum laminar burning velocity associated with propane is only about 15% higher than that associated with methane, commercial propane explosions are expected to result in overpressures that are about 40% higher than that of a natural gas explosion under identical conditions with a perfectly-mixed nearstoichiometric fuel-air mixture, based on empirical correlations.

In addition to the laminar burning velocity, other fundamental differences in the fuels may also play an important role in the explosion severity. Propane has a slightly higher expansion ratio than methane when undergoing combustion. The mass diffusivity of propane and methane are also quite different, making the premixed propane flame more prone to wrinkling under turbulent conditions. Future testing in the 20-L explosion chamber is suggested.

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Which toy was one of the fastest and most complete recalls in the history of CPSC?

The recall of all Hoverboards (a self-balancing 2 wheeled cross between a skateboard and a Segway) may be the fastest and most complete recall in the history of the CPSC (Consumer Product Safety Commission).  In addition to the numerous fires attributed to the lithium-ion battery powered device, there have been numerous injuries due to users falling off their hover boards. (Source: CNN, CPSC, TheVerge.com )


Are you a fire investigation expert?

Abstract deadline extended for 2016 International Symposium on Fire Investigation Science and Technology.

Deadline extended!


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