‘Tribology’ And Its Application To Electrical And Electromechanical Faults That Often Result In Fire

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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Torque Tightened Electromechanical Connections

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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Spoliation and its Impact on Fire Investigation

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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The “Colour Run” and its Safety Concerns – Sharing of Singapore’s Experience

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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CFD Modeling of Flammable Gas Concentration Levels and Empirical Validation

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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Thermal Activation of Molded Case Circuit Breakers by External Heat Exposure

Yannick Alexis
Daniel Gottuk
Jensen Hughes
Baltimore MD USA
Christopher B. Wood
FireLink LLC
Tewksbury MA USA

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

ABSTRACT

This paper explores thermally induced activation of Molded Case Circuit Breakers (MCCBs) that are commonly found in residential, small office and commercial occupancies. A total of 81 MCCBs were put into an oven with no current (i.e. no-load), along with thermocouples that were connected to a data acquisition system to track trip status and air temperatures proximate to the breakers. Different types of MCCBs were tested and results tabulated based on the brand, number of poles, and amperage ratings of the breakers. All the MCCBs were activated thermally during the testing, and the trip temperatures of the different types of MCCBs are displayed graphically. The breakers tended to trip between 350°F (177°C) and 470°F (243°C) and between 16 to 22 minutes from when the oven reached 160°F (the MCCB’s maximum operating temperature) and then followed a linear temperature increase of 10°F/min (5.6°C/min). The changes in the breakers’ physical conditions were also noted. This experiment provides further evidence that thermal activation of circuit breakers exposed to fire conditions may be a consideration for the investigator of a fire. Recommendations for future work are also included.

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Total Station Surveying Technology for Forensic Mapping

Total Station Surveying Technology for Forensic Mapping of Fire and Explosion Incident Scenes

Brian C. Dunagan, CSP, CFEI, CFII
IFO Group, Inc. – Incident Free Operations, Inc., USA
Christopher F. Schemel, Ph.D.
IFO Group, Inc. – Delta Q Consultants, Inc., USA

ABSTRACT
Total stations (electronic surveying equipment) are frequently used in traffic accident investigations to collect data for reconstruction specialists. For more than 20 years these devices have dramatically reduced the time and labor required to document and map vehicle accident scenes. The data collected by a total station can be easily imported into modeling and sophisticated mapping software. This technology can be deployed in other forensic applications and can be readily used to assist investigators in systematically and accurately mapping fire and explosion incident scenes. This paper summarizes the role a total station plays in forensic mapping. First, an overview of forensic mapping using total stations and associated equipment such as prisms and data collectors is presented. Second, the constraints and the legal considerations of the technology are discussed. Third, a case study using forensic mapping of an explosion scene is presented. Finally, it will be demonstrated that the use of these techniques can assist the savvy investigator in building a compelling case narrative that builds on and complements other evidence collected while satisfying the ever increasing standards for reliable and accurate documentation of scenes.

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Misuse of Simple Explosion Tools in Complex Explosion Investigations

Misuse of Simple Explosion Tools in Complex Explosion Investigations

Scott Davis, Ph.D., P.E., CFEI
Derek Engel, CFEI
Tom DeBold
Peter Hinze, Ph.D., P.E., CFEI
And
Bryant Hendrickson
GexCon US, U.S.A.

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

ABSTRACT

There are numerous simple models that can be used to assist the investigation into fuel-air explosions. These models include simple equilibrium based unvented explosions, single and multiple vent equations for large vessels and rooms, constant flame speed models with completely unconfined and fixed congestion (e.g, TNO Multi-energy model, BST method), TNT equivalent models that compare explosion consequences for gas phase explosions with TNT, etc. Some of these simplified methods can help predict both the free-field blast pressure, as well as the dynamic effects due to the venting of the expanding cloud (e.g., drag forces resulting from the blast wind).

While these models may be appealing to assist in an investigation, extreme caution needs to be exercised when using these models outside their intended application. For example, asymmetries and non-uniform congestion, or partially confined structures can result in simple tools vastly over or under-predicting explosion loads and the associated dynamic effect. This data is oftentimes critical in an accident investigation. This paper will present a variety of case studies where simple tools were incorrectly applied to complex explosion investigations, resulting in incorrect opinions regarding the incident. In contrast, the paper will compare the simplified results with those obtained using more advanced CFD modeling.

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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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