4 Arti Culo Reverse FMEA

Proceedings of the ASME 2011 International Mechanical Engineering Congress & ExpositionIMECE2011 November 11-17, 2011, Denver, Colorado, USA IMECE2011-65159 APPLYING ADVANCED FMEA METHODS TO VEHICLE FIRE CAUSE DETERMINATIONS Kerry D. Parrott, BSME, CFI, CFEI/CVFI Sr. Engineer / Fire Investigation Analyst Stahl Engineering & Failure Analysis, LLC 3201 Stellhorn Road, Suite C149 Fort Wayne, Indiana 46815 [email protected] Pat J. Mattes Quality Tools Consultant 9732 Lafayette Center Road Yoder, Indiana 46464 [email protected] Douglas R. Stahl, PE, CFEI/CVFI Principal Engineer Stahl Engineering & Failure Analysis, LLC 3201 Stellhorn Road, Suite C149 Fort Wayne, Indiana 46815 [email protected] ABSTRACT following a systematic approach utilizing the scientific method for fire origin and cause determinations. The rFMEA methodology is proposed as a fire investigation tool that assists in that process. This “reverse FMEA” methodology will then be applied to a hypothetical, illustrative case study to demonstrate its application. This paper proposes that the advanced Failure Modes and Effects Analysis (FMEA) techniques and methodology currently used by the automotive industry for product and process design can be reversed and used as an effective failure/root cause analysis tool. This paper will review FMEA methodologies, explain the newest advanced FMEA methodologies that are now being used in the automotive industry, and will then explain how this methodology can be effectively reversed and used as a failure analysis and fire cause determination tool referred to as a “reverse FMEA” (rFMEA). This paper will address the application of these techniques and methodology to vehicle fire cause determination. This methodology is particularly suited to situations where multiple potential fire causes are contained within an established area of origin. NFPA 921 Guide for Fire & Explosion Investigations [1] and NFPA 1033 Standard for Professional Qualifications for Fire Investigator [2], often referenced by the fire investigation community, prescribe Key words: reverse FMEA, rFMEA, failure analysis, fire investigation, origin, cause, effect, vehicle, failure modes and effects analysis, FMEA, root cause analysis, RCA BACKGROUND Most modern motor vehicle and equipment manufacturers and their suppliers use a Quality Management System such as QS9000 promulgated by the Automotive Industry Action Group (AIAG) or ISO/TS 16949:2002, developed by the International Automotive Taskforce (IATF), as part of their product design processes. These systems provide a common 1 Copyright © 2011 by ASME Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 03/05/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use In this way. FMEA is integrated into the AIAG Advanced Quality Planning Process (APQP). DISCUSSION OF ADVANCED AND “REVERSE” FMEA CONCEPTS AND METHODOLOGY The fundamental premise of this paper is a two-fold proposal on modifications to the traditional. First. through reduction of design/manufacturing variation needed to accomplish the required system/vehicle functionality. it is a repository for product and process design and performance knowledge. and the relationship between function and failure. Ford. and the 5Why methodology favored by Toyota Motor Corp.Effect” model introduced in Advanced FMEA can be conducted in the reverse order. This sequence can be applied to the determination of cause in vehicle fires (and more generally. failure modes can be designed out of a product before they are ever produced [7]. through emphasis on the prevention of errors and defects in the design and manufacturing stages.. the ultimate. A “Cause and Effect” relationship really doesn’t exist. Finally. and Renewable Energy sectors. eliminate or reduce potential failures and their associated effects [5]. and originally developed by Sakichi Toyoda. The root cause is the first.org/about-asme/terms-of-use . Advanced FMEA methodology goes beyond the simple “Cause and Effect” relationship and teaches that there is an intermediate step.asmedigitalcollection. there was a prior-occurring cause [8].Failure . The AIAG also oversees the publication and distribution of QS-9000 and ISO/TS 16949:2009. this ever evolving tool has become a powerful technique helping designers to recognize and evaluate potential product failure modes early in the design and manufacturing processes and. The failure sequence then becomes “Effect . namely the failure itself.Failure .asme. and subsequently the associated supplier sector. It can also be thought of as the single event which. the newest standards for automotive quality system and customer specific requirements.Cause”. Failure Modes and Effects Analysis (FMEA) is one of the most widely accepted and commonly used quality product design (dFMEA) and process (pFMEA) tools in the automotive industry today. Common RCA techniques used in the automotive industry include 8-Disciplines. the failure has to be in the middle. the base. and also a foundation for continuous product and process improvement. AIAG was originally sponsored by GM. quality manuals. automotive industry today have been designed and developed using this methodology. hence. and it helps define and predict the possible effects of a potential failure while the design team is still in the design phase of the product. Ishikawa Diagrams. and Chrysler in 1982. Fault Tree Analysis. As such. Root Cause Analysis (RCA) is a general engineering term applied to a wide variety of reactive quality tools that have historically been used to analyze failures after they have occurred with the purpose of arriving at a “root” cause. hence the commonly referred to “cause and effect” relationship. let’s discuss and understand modern automotive FMEAs in more detail. Pareto Analysis. The common and widely accepted base presumption for all these different techniques is that for every effect. predictive FMEA style of analysis and also to the cause and effect relationship. and training [6]. FMEA was initially introduced in the 1940s by the US military and quickly gained acceptance in the growing aeronautical and aerospace fields [4]. Since its early introduction into the American automotive industry by Ford Motor Company. had it been prevented. It is the answer to the “why” question. and to date are gaining ground in Medical. and enhanced with 5-Why root cause analysis methods. occurrence. or the initiating cause that starts an unwanted sequence of events. FMEAs also assign severity. The first proposal introduces the concept of “Advanced FMEA” which addresses the sequence linearity hierarchy. Most products and processes involved in the modern The second proposal is that the “Cause . FMEA is an predictive engineering tool and technique that strives to drive a deeper understanding of the potential causes and effects in a design. Every effect that is noticed must have 2 Copyright © 2011 by ASME Downloaded From: http://proceedings. would have stopped a causal sequence of events. to other failure analysis investigations). Information Technology. all of this information is tabulated for future reference and updated as new information becomes available. and through consideration of potential customer or environmental impact on the intended functionality [3]. The tools and techniques gained favor in the automotive sector. and detection rankings that help to guide and prioritize the design process.org/ on 03/05/2016 Terms of Use: http://www. More specifically.asme. and now has expanded to include most all major vehicle OEMs and OEM suppliers in the automotive and truck industries.guideline for manufacturers to continually improve their products. Once a function or set of functions is established. all potential failure modes will then fall into one or more of just seven different categories listed below. and one which is typically promoted throughout the automotive industry. failures can also be precipitated by other failures and this is known as an error sequence or failure sequence.in promoting the concept of “Function Brainstorming”. The Cause . it focuses on failure in lieu of intended functions. Primary failure 1.org/ on 03/05/2016 Terms of Use: http://www. 3. 2. Causes of failure can be numerous. has been instrumental 3 Copyright © 2011 by ASME Downloaded From: http://proceedings. or “tank should not leak”. etc. “transfer energy”. concise pattern for the determination of potential failure modes against those functions. or “tank leaked”. the methodology misses a few critical points especially in terms of the linearity and sequencing of the analysis steps. 6. Using the previous example of “provide heat” as an established function.Effect model is illustrated in Figure 1 below. Unevenly provides heat (valid) 7. and therefore. and it tends to focus on failure modes that are extremely unlikely to ever occur even if numerous noncoincidental conditions spontaneously coincided. Similarly. This is in contrast with the traditional FMEA practices that involve the analysis team establishing the intended functions of the item being studied. Figure 1 Another key concept in Advanced FMEA is that function precedes failure. then offers a clean.org/about-asme/terms-of-use . the analysis team can then use the failure categorization described above to rationalize the validity of the potential failure modes:     During the analysis of functions to determine failure modes. for sake of simplicity in this paper. then it stands to reason that a singular failure can have a cause or a “cause of a cause”. followed by failure mode identification. and can even be thought of as a set of outcomes to be avoided. the establishment of potential causes of failure then becomes the focus.asme. and in parallel with methodologies first introduced by John L. 7. Functions are to be thought of as a set of intended outcomes. 1. However. a failure mode would be the inability to provide heat or light. The downfall of this activity is two-fold. Does not provide heat (valid) Range failure 2. the team will typically spend their energies brainstorming all of the potential ways a particular product could fail. One of the authors. subsystem. a common mistake that analysis teams make. in lieu of failure brainstorming. a preceding failure that occurred and for every failure that occurs there must have been a preceding cause..asmedigitalcollection. Does not function Functions insufficiently (too little) Functions excessively (too much) Functions too soon (too quickly) Functions too late (too slowly) Functions unevenly Functions erratically This methodology first ensures that the design team fully understands the functions the product or process needs to accomplish.Failure . Provides heat too slowly (valid) 5. 4. failures would be identified as “sound transmitted”. “provide light”. and are typically viewed as the immediate reasons for failure modes. 5. Erratically provides heat (valid) Once functions are determined. or system under development or review.asme. Since every failure has a cause. the potential effects of that failure. and then the potential causes of failure (controls and action-planning intentionally left out of the immediate discussion). In such activity. Lindland [10]. Indeed. which offers considerable alignment and focus on the tie-ins between function analysis and failure mode identification. is the concept of “Failure Brainstorming”. such as “provide heat”. a failure mode for outcomes to be avoided would be that they were not avoided. or transfer energy. Provides heat too quickly (perhaps invalid) Stability failure 6. Using the above examples. only singular levels are considered here. This is known as a cause sequence and is the The focus should be on brainstorming the functionality of the component. Excessively provides heat (valid) Time failure 4. A failure mode can then be thought of as unintended outcomes for those functions [9]. Pat Mattes. Insufficiently provides heat (valid) 3. the potential failure mode. While the traditional style is a practical and effective mentality. such as “avoid transmission of sound”. there are multiple effects and multiple causes of failure but. FMEA and RCA can be thought of as mirror opposites in time. based on the authors’ and industry experience. or maintenance process [12]. This chronology in the life cycle of a vehicle system or component through design.org/ on 03/05/2016 Terms of Use: http://www. So if we apply the new FMEA sequencing to RCA. these generalized categories can be customized to tailor an analysis to specialized markets. So from a practical application approach. a fire event. FMEA techniques are also currently in use and the basis for qualitative Fire Risk Analysis within the Fire Protection Engineering community [11]. this relationship is also true in the reverse direction for RCA.asmedigitalcollection. is associated with a failure. most all potential motor vehicle failure mode causes can be generally classified into five categories. and that every failure has a cause. rFMEA APPLICATION TO FIRE INVESTIGATION The National Fire Protection Association has estimated using National Incident Fire Reporting System data and their own fire department surveys that between 1999 and 2003 there were an average of 325. analyzes these effects to determine the functional failure or failures that precipitated the observed effects. Generally. The FMEA looks forward into the future to predict how a design will perform or possibly fail. manufacturing.asme. New causal information can then be added to previous FMEAs. Environment Figure 2 Variation can include variations from design. Some causes can also be some combination of these categories. as illustrated in Figure 2. This allows us to use a “reverse FMEA” (rFMEA) methodology to determine fire causation in motor vehicles and their systems. and because of the cause sequence. Effects are analyzed to determine Failures. manufacturing. and then deduces causes of the failures to determine cause of the fire.100 motor vehicle fires per year in this country with cars. providing real world feedback to the FMEA process for continuous product improvement at the design level. Therefore. for product performance. Variation Customer use Adjacent Systems Cause Categories Changes over time Figure 3 This figure also illustrates how the FMEA and RCA techniques can be procedural opposites of each other. such as an effect observed during a vehicle fire investigation. The RCA looks back into the past to see what went wrong during the design. 4 Copyright © 2011 by ASME Downloaded From: http://proceedings. every cause also has a cause. Causes lead to Failures and Failures lead to Effects.asme. enabling the same methodology to work in either direction. or assembly specifications. and the causal investigation can be symbolically expressed as shown in Figure 3 below. The fundamental insight is that in traditional FMEA. and Failures are analyzed to determine Causes. With knowledge and experience gained in various vehicle application segments. trucks. and other highway vehicles accounting for 95% of reported vehicle fires [13]. RCA techniques strive to determine how every effect can be traced back to its original cause. we can reverse the FMEA methodology to arrive at a root cause methodology. we can say that every effect. the fire investigation analyst starts by documenting the observable effects noted in the area of origin. since these sequences of events are mirror opposites. Application of the “reverse FMEA” technique also opens the possibility of referencing the original design and process FMEA(s) to determine if the cause was evaluated as an original design or process potential failure mode.foundation for the “5-Why” style of Root Cause Analysis (RCA) technique.org/about-asme/terms-of-use . During a vehicle fire investigation. The first step in a fire investigation failure analysis is always to systematically establish an area or point of origin by way of the traditional fire investigation tools such as fire pattern analysis. The second factor is the large number of potential ignition sources contained within a vehicle [1. Cause determination involves identifying the first fuel ignited. and by modifications or abuse by owners. to the interaction between different systems. an analyst must first understand the design and function of all the various automotive systems before their failure modes and their corresponding causes can be well understood [21]. and proximity of the many mechanical. and witness accounts [1. product use. 1. and electrical systems found on modern vehicles. Determining the cause of a vehicle fire is generally considered by the fire investigation community to be a challenging endeavor at best. It is especially useful in situations where multiple potential causes may exist and the true root cause is therefore difficult to establish. this methodology focuses on steps 3 through 7. but the improved current methods within Advanced FMEA are “reversed” to assist the fire investigation analyst in establishing a root cause in a more robust and better documented fashion and in accordance to the scientific method. In the proposed methodology. the cause must then be identified as undetermined. heat and flame vector analysis. 22]. 20]. There are several other main factors that make motor vehicle investigations so challenging. A vehicle fire occurred and we need to understand how and why the fire happened. In circumstances where all potential causes have been eliminated. First is the large number and variety of ignitable materials contained in a motor vehicle. These factors are important because the large amount of ignitable materials often results in a large amount of damage that eliminates the evidence. the standard method of establishing the origin of the fire is retained due to the maturity and stability and acceptance of the practice. as referenced for the fire investigation community in both NFPA 921 (Guide for Fire & Explosion Investigations) and NFPA 1033 (Standard for Professional Qualifications for Fire Investigator). modifications made to incomplete vehicles by up-fitters.org/ on 03/05/2016 Terms of Use: http://www. 6. damage survey. Effect Failure Cause Figure 4 5 Copyright © 2011 by ASME Downloaded From: http://proceedings. Each of these systems has its own failure modes inherent to the design of a particular system. 3. which is the essential element towards understanding the sequence of events in product design. In 2004. 7. 4.org/about-asme/terms-of-use . Since the specific cause of a failure is directly related to the function of that system. Additionally. and to the continual changes that occur to the systems over time as they operate. and the circumstances that resulted in the fire [1. 17]. and allows the fire to propagate at a rapid pace making the area or point of origin difficult to determine [9. the ignition source. it was estimated the typical passenger car contained 258 pounds of plastic materials [14.The usefulness of this “reverse FMEA” approach is that once an area or point of origin is determined. final stage manufacturers. 18]. 16. Recognizing the need Defining the problem Collection of data Analyzing the data Developing a causal hypothesis Testing this hypothesis Arrive at a final hypothesis This process is then repeated as new or additional information becomes available until a cause or list of potential causes is established. hydraulic. From a vehicle fire cause analysis standpoint. complexity. wear. 22]. Since this is generally always the same. repairs that may or may not have been properly done. 5. fuel load considerations. 15].asme.asme. 2. and we can do this by conducting a fire origin and cause investigation [23]. and prescribed for use in the determination of the cause of a fire. This reference denotes it as the seven step process noted below. or maintainers. The Scientific Method is generally well established. event sequencing. operators. The second step in fire investigation failure analysis is cause determination. Vehicle fires can be very difficult to investigate because of the multitude. This complexity is further complicated by the variations in systems from different manufacturers. this methodology provides a tool to help sort out the complexities of each system and interactions between the systems involved in a systematic and well documented approach that scientifically drives towards determining the root cause. and are maintained over time in a continually varying environment. steps one and two are given and always the same. and/or environmental conditions combined in unexpected ways to produce the fire. most fluids typically found in motor vehicles are ignitable by hot surfaces [1.asmedigitalcollection. The added advantage of this methodology is that all hypotheses that were considered are now well documented for future reference.org/ on 03/05/2016 Terms of Use: http://www. every may have happened. probable root cause should become apparent after no more than the 5th order cause according to the “5-Whys” methodology. Remember that failures can have more than one cause. and helps to assure that causes immediately succeed each other. This is our initial observable effect. The causal sequences that have to stop because they no longer make sense are the hypotheses that fail. The cause or alternate potential causes are listed in the third column of the form in appendix A.Cause. Using FMEA terminology. Think of it as a tool to help the analyst determine if events are linear succeeded causes. They can be thought of as the causes that might have occurred. This correlates to Step 3. but did not.Using the reversed “Effects . the methodology considers every cause that In NFPA 921 terminology. Cause of Cause.asmedigitalcollection. Another way to think of this “Effect . analyzing the data. This failure for each observable effect is listed in the second column.Cause” model described in the chronology of a product and highlighted in Figure 4.asme. failure cause sequence looks as follows. This information can be added to columns 4-7 of the form. how it is clipped to prevent chaffing. or preceding events. i. and relative motion cannot occur if the harness is properly secured. and the hypotheses that do not fail will identify the most probable root causes. Think of a cause as the immediate reason for the failure. and so on until the point where the most probable root cause is found or to the point where the analysis no longer makes sense and has to stop. A short circuit. Remember from the discussion section that every effect is associated with a failure. Another concept from advanced FMEA methodology of importance is that of hierarchical alignment. This step in the process correlates to step 4 of the scientific method.asme. so all potential causes have to be listed and then each one will be further evaluated later to determine its corresponding causes. and then the cause of the cause of the cause (3rd order cause). The next step in the methodology is to determine the cause of the cause (2nd order cause).Failure . the collection of data.org/about-asme/terms-of-use . etc” logic path is to think of it as a tool to test your causal hypothesis. It could be related to factors such the type and thickness of the insulation. Therefore the second step in the process is to analyze the observable effects and to consider what the failure was that caused the observable effect. This step in the procedure correlates to steps 5-7 of the scientific method. for example. Wear between surfaces generally does not occur without relative motion. the analyst has to consider that each failure had a cause. Let’s consider an example where a shorted and beaded wire has been found in the area of origin in a vehicle. This is the information that is then listed in the first column of the rFMEA form in Appendix A. The hypotheses that fail will have to stop. By doing this. is a lack of isolation or insufficient insulation of the conductor. the final hypothesis can be describes as the most probable root cause. father of the Toyota Production System. Collecting data on a vehicle that has been involved in a fire consists of noting all the observable effects of the fire within the area or point of origin. Therefore the effect. For the conductor to have been exposed to a ground and short it must have worn through the wire insulation. transmission fluid missing. The most 6 Copyright © 2011 by ASME Downloaded From: http://proceedings. Keep in mind during this stage that failures essentially constitute a lack of function. It therefore helps to differentiate between effects and causes. tested. and through the harness protective covering (if used). the 5-Why method is “the basis of Toyota’s scientific approach… by repeating why five times. To quote Taiichi Ohno. This is why it is so important that an investigator must be familiar with the design function of the components under evaluation in order to conduct an effective analysis. and arriving at the final hypothesis. we will now describe how this sequence can be applied to steps 3-7 of the scientific method as described above. Next. ruptured hoses. cracked or broken components. the nature of the problem as well as its solution becomes clear” [24].e. The first step in the “reverse FMEA” is to determine the observable effects of the fire in the area or point of origin. Since a beaded wire is an indication of a short circuit that cannot happen on a properly insulated wire. broken turbocharger shafts. etc.Failure . the failure is a lack of isolation of the conductor. Typical observable effects can be things such as shorted and beaded wires. developing and testing the hypothesis. or the appropriateness of the insulating material to its environment. hypothesis is being developed and evaluated. FMEA concepts were used as a tool to assist in analysis of the failure.Cause” template illustrated above can be shifted to the right and still make sense.wire / bracket Failure Wear through harness covering Effect One of the most common criticisms of a 5-Why technique incorporated in to this “reverse FMEA” is that it needs to be conducted by engineers’ familiar with the parts or components being studied and sometimes only identifies symptoms instead of a true root cause. The rFMEA methodology characterizes and formalizes the common application of FMEA and Advanced FMEA concepts and methodology to failure analysis by using them in a reverse analysis. and then causes. Harness loose Cause Relative motion . effect(s)." Failure Cause Wear through harness covering Relative motion . but actually working in the reverse direction.org/ on 03/05/2016 Terms of Use: http://www. leading to failures. FMEA concepts in failure analysis (including fire cause determination) have been utilized in two different ways. the very next immediate reason for the failure. and possible causes.wire / bracket Harness loose Effect Wear through wire insulation Failure to insulate conductor Conductor short to bracket Figure 5 Traditionally. Previous design and process FMEAs have been reviewed post-failure to see if the predictive analysis of the FMEA properly considered the cause(s). the engineer must understand how it worked and was manufactured in the first place. for example). Colin Gagg. England noted: "To recognize how a component or system failed. using the information discovered in analysis of the failure to construct a “FMEA” model for the failure. the hierarchical alignment also helps to assure the analyst that each step in the causal sequence is linear.Failure .asmedigitalcollection. Although this criticism is valid. However. since the new information is the effects. If the causal sequence is truly linear. then the “Effect . The rFMEA would include new failure information of the effect(s) and failure mode(s) provided by the specific fire investigation analysis including factors. circumstances. The analysis should be conducted by experienced and knowledgeable individuals. Forensic Engineering Lecturer at the Open University in Milton Keynes. This is illustrated in Figures 5-7 above.Conductor short to bracket Failure to insulate conductor Wear through wire insulation In this example. i.asme. and failure mode(s) found in the failure and possibly suggest variations in these characteristics which were not previously included.wire / bracket Figure 6 Figure 7 7 Copyright © 2011 by ASME Downloaded From: http://proceedings.e. that would be outside the scope of previous product design or process FMEAs (such as arson.asme. following the linear hierarchy methodology explained above helps the investigator to focus on immediately preceding causes of failures and not on symptoms of failures. Failure Cause Harness loose Wear through harness covering Wear through wire insulation Failure to insulate conductor Conductor short to bracket Effect Relative motion .org/about-asme/terms-of-use . whether distinctly recognized or not. Secondly. a sound understanding of the function of the components and systems being studied is still essential. which in turn caused a fire in the area of origin. 1. the failure is a short circuit to the bracket. and that the lights. it was determined to be the area of Following our Effect-Failure-Cause model for the first observable effect. Since one entire side of the engine compartment was substantially involved. should be used by trained. and the fire did not propagate into the cabin of the vehicle. The short circuit could only have happened if there is no insulation on the wire. Only two quarts remained from a sump capacity of 24 quarts. If the fire area or point of origin has been correctly determined. also consider that as this is a commercial vehicle.NFPA 921 discusses the use of FMEA as a potential fire analysis tool. An example would be an electrical short remote from the fire area of origin.org/about-asme/terms-of-use .Effect” concept of FMEAs as used in predictive automotive design and process FMEAs.asme. The inspection reports for prior days also did not reveal any electrical or mechanical issues with the truck. This is a SAE 2 gauge conductor running from the positive terminal on the alternator to the positive terminal on the starter solenoid. three significant observable effects have been identified. 2. it appears to be an attempt to fit fire investigation effects reactive information into a standard FMEA format. pose the right questions in the investigation. will not succeed if the analyst fails to understand the tool. hypothetical case in which the area of origin has been determined to be on right side of an engine compartment of a commercial DOT (Department of Transportation) class 8 truck that caught on fire while operating after several years of service. This is the same sequence as depicted in figures 5-7. For the purpose of this case study. The operator of this vehicle was required to hold a valid commercial driver’s license (CDL) and to abide by the license requirements. The rFMEA concept and methodology proposed is a tool to assist fire investigation analysts and engineers in the fire cause failure analysis process and.asme.Failure . that caused the current to be carried through a wire-reinforced hose transporting a flammable fluid. and that these reports must be kept on file. and electrical system were in good working order. The negative cable of the alternator charging circuit that also runs between the alternator and a ground stud on one side of the engine block was also found to exhibit signs of arcing and beading against the same steel bracket. Within this area of origin. The process of determining the area of origin for a fire in a commercial vehicle is outside the scope of this paper and therefore will not be discussed here.asmedigitalcollection. The inspection report for this truck on the day of the fire shows all the engine compartment fluids were full. Engine was excessively low on motor oil (SAE 15W40). correct hypotheses in a fire investigation failure analysis must contain a cause that provides failure(s) and effect(s) consistent with that point or area of fire origin – but the final root cause may be in another area of the vehicle and the rFMEA analysis should provide that cause of a cause using all of the information available to a fire investigation analyst or engineer. This is also a SAE 2 gauge conductor protected with nylon convoluted conduit. This area of origin could not be narrowed down any further. 3. knowledgeable persons familiar with the product design and fire investigation analysis and again.org/ on 03/05/2016 Terms of Use: http://www. it has undergone annual DOT inspections in addition to a well documented quarterly preventative maintenance program. Either the insulation was worn through in an area where it readily visible during a pre-trip inspection or it 8 Copyright © 2011 by ASME Downloaded From: http://proceedings. as any other tool. the final. and provide the correct information to the methodology. the fire damage was concentrated only on right side of the engine compartment with only minimal melting observed in other areas. gages. The positive cable of the alternator charging circuit was found to have signs of arcing and beading where it short circuited to a steel bracket. but the usage discussed and demonstrated there is not consistent with the “Cause . origin. let’s look at an illustrative. Rather. so we have two viable options for our first order cause. The primary requirement of interest here is that the vehicle must undergo a pre-trip inspection every day before it can be driven. as with any analysis tool. As background information. EXEMPLAR rFMEA FIRE INVESTIGATION CASE STUDY As an example. This circuit is covered with nylon convoluted conduit for abrasion protection. Further investigation into the manufacturing process revealed a recent design change to the thickness of the base plate material.melted off in as a result of the fire. the base plate and the seams for the cooling fins. this causal sequence makes no sense and has to stop (negative common ground design). There is no fifth order cause and this hypothesis does not provide a probable root cause. This means this circuit has made contact to a positive cable and is now energized. CONCLUSION The third observable effect was that the engine was low on motor oil. as well as all the reviewers for their helpful comments. Just like before. LLC for all the support. This information has been tabulated in a sample form in Appendix A. Again this sequence has to stop because if this circuit was already exposed to a fire long enough to burn through the harness covering and the wire insulations. Chafing means to wear down or rub away a surface by scraping. This causal sequence also stops. This crack allowed motor oil to be sprayed on either the turbocharger housing or on the exhaust manifold. At this point it no longer makes sense to follow this causal sequence as background investigations on the design of the harness determined that this harness is clipped at regular eight inch intervals. The engine block can only leak if it is cracked. The engine oil cooler was removed and found to have a cracked base plate. No cracks were found on the block. This in turn can only happen if the insulation on the ground wire and its harness covering were both worn or melted (second order cause). it is an effect and not a cause. it would first have to wear through the convoluted nylon conduit that covers and protects this circuit in the wiring harness. which is the third order cause. so this causal sequence stops.asme. This cannot happen unless the harness is loose. The second is that the ground cable was energized by a prior short circuit. If instead the insulation melted off in the fire. This is the second order cause. the short circuit is obviously an effect of the fire and not its cause. and this hypothesis fails. and the oil cooler has two potential leak points. This information was also verified with the pre-trip inspection reports and the preventative maintenance records. This is a third order cause. This is its second order cause. The engine components in this area that can leak hot motor oil are the turbocharger. The turbocharger in turn has three major potential leak points which are its second order causes.asmedigitalcollection. and also constitutes a systematic. Since either of these surfaces is sufficiently hot to allow for a hot surface ignition of the motor oil. It is particularly useful tool in situations where multiple potential root causes can be observed within the area of origin. well-documented application of the Scientific Method as prescribed in NFPA 921 and NFPA 1033. A harness that is well secured and has no relative motion cannot chafe. These are the first order causes.e. This is the forth order cause.asme. The failure mode here that causes a fire is if hot motor oils sprays on the hot surfaces of the turbocharger turbine housing or the exhaust manifold which are located in close proximity to each other. The first cause is that the ground cable short circuited. This failure allows for two potential first order causes. the ACKNOWLEDGEMENTS We would like to acknowledge Stahl Engineering & Failure Analysis. Effects involve Failures and Failures have Causes). The turbocharger was inspected and no problems were found. and no repairs had ever been made to the harness. The second observable effect is arcing and beading on the negative alternator cable to the same steel bracket as the positive cable. the failure here is a short circuit to a bracket. Other environmental issues such as rodents chewing on insulation are generally not an issue on vehicles where the engine compartment is inspected daily and are therefore not considered here. (i. This insight allows the rFMEA methodology to be an effective tool to aid in the determination of root cause in vehicle and equipment fires. engine block itself. 9 Copyright © 2011 by ASME Downloaded From: http://proceedings. and the engine oil cooler.org/about-asme/terms-of-use . This paper proposed that the advanced FMEA techniques and methodology currently used by the automotive industry for product and process design can be “reversed” and then used as an effective failure/root cause analysis tool to help determine the root cause of vehicle fires. The fundamental insight that Causes have Failures and Failures have Effects and that this relationship holds true in either direction.. but as it is a ground. Wearing through the harness cover requires relative motion between the harness and the bracket. We are calling this methodology “reverse FMEA” denoted as rFMEA. so this sequence stops as well. this is a probable root cause for the fire and we have arrived at a final hypothesis in compliance with NFPA 921 and 1033. For the insulation to have worn through.org/ on 03/05/2016 Terms of Use: http://www. 2002. 16 Nov.] Parker. [S. Jr. [7. [3. 16 Nov. MA: National Fire Protection Association. PA: Society of Automotive Engineers for Advancing Mobility Land Sea Air and Space. 2010. L. 1988. Print. REFERENCES [1. 2008.. [9.. and David Purser. Chapter 2: Fire Safety in Commercial Vehicles. Print. McGraw-Hill Dictionary of Scientific and Technical Terms. MIL-P-1629 [17. Warrandale. 1949.] "Quality. Fort Wayne.] Digges. and Robert Strassburger. Quincy.] Tewarson. Powell. "Hot Surface Ignition of Automotive and Aviation Fluids. Print. [11.] Colwell. Vol. Web. 1998. [10. Print. [6. 2008. "Section 21. MVFRI Research Summary." Automotive Industry Action Group.] Senders. Warrendale. Vol. Print. SP-1939. Print. The National Fire Investigator. San Fransisco: 8th International Fire and Materials Conference. Quintiere. Vol. Print. Print. 2008. [5. Print. and R. I. Ben Thomas. Potential Failure Mode and Effects Analysis in Manufacturing and Assembly Processes (process FMEA). J. MA: Productivity." Fire Protection Handbook 2008. W. Paul Leland. <http://www. Sudbury. [21. Second Quarter 2005. and Ali Reza. Jeff D. System and Design Failure Mode and Effects Analysis. Lecture. Chapter 1: Passenger Vhicle Fires. 1989.] Tewarson. 2010.] "NFPA 1033: Standard for Professional Qualifications for Fire Investigator. AIAG.] (R) Potential Failure Mode and Effects Analysis in Design (design FMEA). 2003. Print. Grant. John L. Kirk's Fire Investigation.NFPA is a registered trademark of the National Fire Protection Association. "Vehicle Fire Problem. MA: National Fire Protection Association. 2008 ed.] Procedure for Performing a Failure Mode Effect and Criticality Analysis.asme.] Nicholson. 1995. 2012.org>. AIAG is a registered service mark of the Automotive Industry Action Group. NJ: Brady. 2005. Tech. John Raymond Hall. Grossman. [15. [14.org/ on 03/05/2016 Terms of Use: http://www. 1997. New York: McGraw-Hill Book.. Ford Motor Company and General Motors.l. Pat.] Mattes." NFPA.asmedigitalcollection.] Lindland." NFPA Journal Jan/Feb 2007. PA: SAE International. 2011." FMEA Methods Seminar.aiag. Solomon. Upper Saddle River.] "NFPA 921: Guide for Fire and Investigations. "Section 3. Jeff D. [18. Rose Ray. "FMEA and RCA: the Mantras of Modern Risk Management. 2005.3. Tech.] Mifsud.. MA: National Fire Protection Association. Print." NFPA. Brian. [8.org/about-asme/terms-of-use . Print. [20. MI: Automotive Industry Action Group. Casey C. 2008 ed. [12. R.] Potential Failure Mode and Effects Analysis: Reference Manual. Print. Archibald. Print. Fire Behavior of Materials in Vehicle Crash Fires and Survivability of the Passengers. [19. Fire and Toxicity Properties of Underhood Fluids and Plastics. 2005-01-1555.] Routhier. Arthur E. SAE is a registered trademark of SAE International.] Cote. November 9. Q-25. 1." Fire Technology 41. John. Sybil P." Qual. DeHaan.8 Fire Risk Analysis. 20 Apr. [22. Kennerly H." Fire Protection Handbook 2008. Tech. 2001. Pamela A. and John D. Print. Quincy. Print. James G.] Chrysler Corporation." Fire Protection Handbook. T. Helene L. I.]: Bella Group.] Long. [13. [4.] no. Print.asme. 10 Copyright © 2011 by ASME Downloaded From: http://proceedings. 2007. 2010. "Section 21.] Kirk. 26 Oct. "FMEA Methods Seminar. [23. NAFI. Taiichi. Southfield. Heath Care 13 2004: 249-50. 7fm: the Seven Failure Modes.] Fire Investigator: Principles and Practice to NFPA 921 and 1033. Explosion [2. Colwell. Archibald. The Scientific Method. Rhoads Stephenson. and Robert E. Hypersonic Technologies. Print. Quincy.] Lindland. United States Military Procedure. 3135. Toyota Production System: beyond Large-scale Production. [24. Fire Behavior of Automotive Polymers. AIAG [16. Cambridge. MA: Jones & Bartlett Learning. Saf. Quality System Requirements QS-9000 3rd Edition. no. Ann Arbor: QualSAT. Web. John. Web. Block found OK a. Turbocharger OK Stop. not cause) a. Leak at seam 11 relative motion between harness and bracket Exposed to a fire Stop. Leak at oil supply c. Environmental causes Harness covering melted in fire Stop. Environmental causes 3 Engine low on oil 3rd Order Cause Stop. Cracked oil cooler base plate b. Leak at oil return 2. (effect not cause) NO NO Stop. Leak at shaft seal b.asme. Wire insulation melted in fire Harness covering melted in fire Stop. Ground not energized 2. (effect. Turbocharger OK Stop. Ground energized by prior short 1.org/ on 03/05/2016 Terms of Use: http://www.APPENDIX A: rFMEA / CASE STUDY # Effect Observed Alternator positive 1 cable short Alternator 2 negative cable short Failure Short to bracket Short to bracket 1st Order Cause 2nd Order Cause Oil spray on turbocharger or exhaust manifold 4th Order Cause 5th Order Cause Stop. (vehicle inspected daily) 1. Wear through wire insulation Wear through harness covering relative motion between harness and bracket Harness loose 2. Wire insulation melted in fire 3. Harness tied down in 8" incrementsgood repair Stop. Seams are OK YES NO Copyright © 2011 by ASME Downloaded From: http://proceedings.asme. Turbocharger OK NO NO NO NO Design change in material thickness Stop. Leak from engine block 3. Stop. Harness tied down in 8" increments good repair 1. (vehicle inspected daily) Exposed to fire Stop. Leak at turbocharger a.asmedigitalcollection. Wear through wire insulation Wear through harness covering b. Leak from oil cooler Probable Root Cause NO NO NO NO c.org/about-asme/terms-of-use .