Technology Training that Works FMEA & FMECA Chapter-09

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Definition of FMEA A Failure modes and effects analysis (FMEA), is a procedure in product development and operations management for analysis of potential failure modes The FMEA identifies potential failure modes based on the past experience with similar products or processes. This will be useful for the RCM team to design those failures out of th system with minimum effort and expenditure. By this way, the development time and costs are reduced. “Failure modes are any errors or defects in a process, design or items that affect the customer and can be potential or actual”. “Effects analysis refers to studying the consequences of those failures”.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) FMEA can provide an analytical approach, when dealing with potential failure modes and their associated causes. When considering possible failures in a design – like safety, cost, performance, quality and reliability – we can get lot of information about how to alter the development/manufacturing process, in order to avoid these failures.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Types of FMEA 1.Concept: analysis of systems or subsystems in the early design concept stages-Concept FMEA 2.Design: analysis of products prior to production-Design FMEA 3.Process: analysis of manufacturing and assembly processes- Process FMEA

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Concept FMEA The Concept FMEA is used to analyze concepts in the early stages before hardware is defined (most often at system and subsystem). At the concept stage there may be some draft drawings or basic information produced, enough to have a brainstorming session with experts in the required design areas. Once the brain-storming secession is completed and the product is deemed viable, the permission is given to proceed with design stage. This type of FMEA includes the interaction of multiple systems and interaction between the elements of a system at the concept stages and identifies potential failure modes caused by interactions within the concept It helps select the optimum concept alternatives, or determine changes to design specifications and determine if hardware system redundancy may be required within a design proposal

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Design FMEA Design FMEA is an analytical technique utilized primarily by a Design FMEA team to ensure potential failure modes and their associated causes are identified, considered and addressed. This systematic approach parallels, formalizes and documents the mental discipline that an engineer normally goes through in any design process. The Design FMEA are normally done at three levels (a) System (b) Sub-system (c) Component

Technology Training that Works Failure Mode and Effect Analysis (FMEA) The benefits of design FMEA (1) Aids in the objective evaluation of design requirements and design alternatives (2) Aids in the initial design for manufacturing and assembly requirements (3) Increases the probability that potential failure modes and their effects have been considered in the design/development process (4) It focuses on potential failure modes of products caused by design inefficiencies. (5) It is used to analyze products before they are released to production. (6) It is used to analyze hardware, functions or a combination (7) It provides additional information to help plan thorough and efficient test programs. (8) It develops a list of potential failure modes ranked according to their effect on the customer. Establishes a priority system for design improvements. (9) Provides an open issue format for recommending and tracking risk reducing actions. (10) Provides future reference to aid in analyzing field concerns

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Process FMEA The Process FMEA identifies potential product related process failure modes that are caused by manufacturing or assembly process deficiencies. 1.It assesses the potential customer effects of the failures. 2.It identifies process variables on which to focus controls or monitoring. 3.It develops a ranked list of potential failure modes, establishing a priority system for corrective action considerations. 4.It identifies confirmed critical characteristics and/or significant characteristics 5.It identifies operator safety concerns 6.It feeds information on design changes required and manufacturing feasibility back to the designers.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Process FMEA 7. The Process FMEA identifies potential product related process failure modes that are caused by manufacturing or assembly process deficiencies. 8. It assesses the potential customer effects of the failures. 9. It identifies process variables on which to focus controls or monitoring. 10. It develops a ranked list of potential failure modes, establishing a priority system for corrective action considerations. 11. It identifies confirmed critical characteristics and/or significant characteristics 12. It identifies operator safety concerns 13. It feeds information on design changes required and manufacturing feasibility back to the designers.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Approaches of FMEA Analysis Two main types of failure mode and effect analyses are used. (A)Functional FMEA The top-down approach is mainly used in an early design phase before the whole system structure is determined. 1.The functional approach is typically used when individual items cannot be identified or a complex system exists. 2.This type of FMEA assumes a failure on the subsystem level on the top level and then proceed downwards, till the individual component levels are reached to identify how the subsystem failure could occur. 3.Evaluates risks that the function is not specified correctly or/and completely

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Approaches of FMEA Analysis (B) Hardware FMEA (1) The bottom-up approach is used when a system design has been decided already. (2) The hardware approach investigates individual components first on the lower level and proceed upwards towards sub-assemblies, subsystem etc till the entire system is studied. (3) Evaluates risks that the function is not specified correctly and that the components incorrectly implements its functional specification.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) The FMEA Process There are 10 steps to the FMEA process. Both DFMEA and PFMEA use the same 10 steps mentioned below

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Defining FMEA terms Severity (S) The Severity determine all failure modes based on the functional requirements and their effects. A failure effect is defined as the result of a failure mode on the function of the system. In this way it is convenient to write these effects down in terms of what the user might see or experience. Examples of failure effects are: degraded performance, noise or even injury to a user. Each effect is given a severity number (S) from 1 (no danger) to 10 (critical). These numbers help to prioritize the failure modes and their effects. If the severity of an effect has a number 9 or 10, actions are considered to change the design by eliminating the failure mode, if possible, or protecting the user from the effect.

Technology Training that Works Failure Mode and Effect Analysis (FMEA)

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Defining FMEA terms Occurrence (O) In this step it is necessary to look at the cause of a failure mode and how many times it occurs. This can be done by looking at similar products or processes and the failure modes that have been documented for them. A failure cause is looked upon as a design weakness. All the potential causes for a failure mode should be identified and documented. Occurrence (O) is the likelihood that a specific cause/mechanism will occur. Occurrence is estimated on a “1” to “10” scale.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Defining FMEA terms Occurrence (O)

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Defining FMEA terms Detection (D) When appropriate actions are determined, it is necessary to test their efficiency. In addition, design verification is needed. The proper inspection methods need to be chosen. First, look at the current controls of the system, that prevent failure modes from occurring or which detect the failure before it reaches the customer. Hereafter one should identify testing, analysis, monitoring and other techniques that can be or have been used on similar systems to detect failures. From these controls we can learn how likely it is for a failure to be identified or detected. Each combination from the previous 2 steps receives a detection number (D). This ranks the ability of planned tests and inspections to remove defects or detect failure modes in time.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) Defining FMEA terms Detection (D) DETECTION is estimated on a “1” to “10” scale.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) After these three basic steps, risk priority numbers (RPN) are calculated. Risk Priority Number (RPN) RPN do not play an important part in the choice of an action against failure modes. They are more threshold values in the evaluation of these actions. The RPN can be calculated by multiplying these three steps: RPN = Severity x Occurrence x Detection The RPN must be calculated for both Design FMEA and Process FMEA. Once this is calculated, we can determine the areas of greatest concern. The failure modes that have highest RPN should be given top priority for corrective action. Sometimes it is not the case always. We may have high RPN, but there could be less severe failures and are less detectible. Use the judgment for proper corrective action.

Technology Training that Works Failure Mode and Effect Analysis (FMEA) After the values of severity, occurrence and detection allocated, the further action such as fixing target implementation date, fixing responsibility of person shall be done. The actions may be a specific inspection, testing and quality procedures, redesign or replacement, adding redundancy in the system or component, limiting the environmental stresses or operating ranges, etc. Once these action are done, we have to calculate the new RPN to establish that the improvement has been done Each on a scale from 1 to 10. The highest RPN is 10x10x10 = This means that this failure is not detectable by inspection, very severe and the occurrence is almost sure. If the occurrence is very sparse, this would be 1 and the RPN would decrease to 100. So, criticality analysis enables to focus on the highest risks

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Failure modes, effects and Criticality analysis (FMECA) is an extension of failure mode and effects analysis (FMEA). FMECA extends FMEA by including a criticality analysis, which is used to chart the probability of failure modes against the severity of their consequences. The result highlights failure modes with relatively high probability and severity of consequences, allowing remedial effort to be directed where it will produce the greatest value. The FMECA is the result of two steps: Failure Mode and Effect Analysis (FMEA)Criticality Analysis (CA). FMECA = FMEA + CA

Technology Training that Works  An FMECA is essentially an FMEA, with an added criticality analysis. An additional section should be added to the tabular format for criticality.  A FMECA is performed to evaluate reliability and safety by identifying critical failure modes and their effects on the system.  The FMECA is performed on parts that are especially critical to the operation and well being of operators. A thorough knowledge of the system is required to complete an FMECA.  Failure data is necessary to complete the criticality portion of an FMECA. Failure Mode, Effect and Criticality Analysis (FMECA)

Technology Training that Works The FMECA Analysis Process: 1) Define the system 2) Define ground rules and assumptions 3) Construct system block diagrams 4) Identify failure modes 5) Analyze failure effects / causes 6) Feed results back into design process 7) Classify failure effects by severity 8) Perform criticality calculations 9) Rank failure mode criticality 10) Determine critical items 11) Feed results back into design process 12) Identify means of failure detection, isolation and compensating provisions 13) Document the analysis. Summarize uncorrectable design areas, identify special controls necessary to mitigate risk. 14) Make recommendations 15) Follow up on corrective action implementation / effectiveness Failure Mode, Effect and Criticality Analysis (FMECA)

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Failure modes may be ranked by the assigned criticality to determine which failure mode should be reduced in criticality by redesign or other abatement methods. System users should specify acceptable criticality levels. There are three ways to complete FMECA:  Use criticality indices.  The severity and probability indices are added together to yield the criticality index. It represents a measure of the overall risk associated with each combination of severity and probability. This method is commonly used in preliminary design when the failure probabilities are not known.  Failure Probability is another method, involves determining the criticality.

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) A failure mode, effects, and criticality analysis can be a starting point for many other types of analyses, including: 1.Production planning 2.Maintenance planning analysis 3.System safety analysis 4.Test planning 5.Logistics support analysis 6.Repair level analysis These additional analyses may also be used to update and improve the FMECA as new information evolves. 1.May be based on qualitative judgment or 2.May be based on failure rate data (most common

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Criticality Analysis Criticality is a measure of the frequency of occurrence of an effect. The MIL-STD-1629A document describes two types of criticality analysis: (a) Quantitative (b) Qualitative.

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Qualitative analysis: Because failure rate data is not available, failure mode ratios and failure mode probability are not used. The probability of occurrence of each failure is grouped into discrete levels that establish the qualitative failure probability level for each entry based on the judgment of the analyst. The failure mode probability levels of occurrence are:  Level A - Frequent  Level B - Reasonably Probable  Level C - Occasional  Level D - Remote  Level E - Extremely Unlikely

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Quantitative analysis: Used when sufficient failure rate data is available to calculate criticality numbers. To use the quantitative criticality analysis method, the analysis team must:  Define the reliability/unreliability for each item, at a given operating time.  Identify the portion of the items unreliability that can be attributed to each potential failure mode.  Rate the probability of loss (or severity) that will result from each failure mode that may occur.  Calculate the criticality for each potential failure mode by obtaining the product of the three factors. Failure Mode Criticality (CM) is the portion of the criticality number for an item, due to one of its failure modes, which results in a particular severity classification (e.g. results in an end effect with severity I, II, etc...).

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Mode Criticality = Item Unreliability x Mode Ratio of Unreliability x Probability of Loss  Calculate the criticality for each item by obtaining the sum of the criticalities for each failure mode that has been identified for the item. Item Criticality = SUM of Mode Criticalities  To use the qualitative criticality analysis method to evaluate risk and prioritize corrective actions, the analysis team must:  Rate the severity of the potential effects of failure.  Rate the likelihood of occurrence for each potential failure mode.  Compare failure modes via a Criticality Matrix, which identifies severity on the horizontal axis and occurrence on the vertical axis.

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Classification of Severity Level (FMECA) Classify the severity of the effects of each failure mode using the following four categories: Brief method 1. Category-IV-Negligible (Less than minor injury, occupational illness, or system damage) 2.Category-III- Marginal (Minor injury, occupational illness, or system damage) 3. Category-II-Critical (Severe injury, occupational illness, or system damage) 4. Category-I-Catastrophic (Death or system loss)

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Classification of Severity Level (FMECA) Detailed Method

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Classification of Failure Mode Probabilities Failure mode probabilities may be classified as follows: Brief Method: 1. Extremely Remote (Unlikely to occur) 2. Remote (Possible to occur in time) 3. Reasonably Probable (Probably will occur in time) 4. Probable (Likely to occur immediately or within a short period of time)

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Classification of Failure Mode Probabilities Detailed Method

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Severity and probability rankings will help the designer to identify the criticality of the potential failure and the areas of the design that need the most attention. When a criticality index is included, the analysis is called a Failure Modes, Effects, and Criticality Analysis, or FMECA. For each failure mode, either propose modifications to prevent or control the failure mode or justify the acceptance of the failure mode and its effects. The criticality index is often defined as the sum or product of the severity and probability indices. The higher the criticality index, the higher the priority for change. The actual categorization of criticality indices into specific change priorities is generally a management decision

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) 1. Safety valve relieves pressure before it reaches dangerous levels. 2. Thermostat opens circuit through heating coil when the temperature rises above 250° C. 3. Pressure gage is divided into green and red sections. “Danger” is indicated when the pointer is in the red section Pressure Cooker Safety Features

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Pressure Cooker FMECA (A)Define Scope: 1.Resolution - The analysis will be restricted to the four major subsystems (electrical system, safety valve, thermostat, and pressure gage). 2. Focus – Safety (B) Prepare Block Diagram

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA) Information gained from FMECA 1.Listing of potential failure modes and failure causes. These could help guide the system testing and inspection techniques. 2.Further designation (criticality) of potential failures that could affect overall system performance. 3.Detection and control measures for each failure mode. 4.Management information. 5.Input for further analysis. Limitations of FMECA 1.Failure modes must be foreseen by the designer. 2.FMECA does not account for multiple failure interactions. 3.FMECA does not analyze dangers or problems that may occur when the system is operating properly. 4.Human factors are not considered

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA)

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA)

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA)

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA)

Technology Training that Works Failure Mode, Effect and Criticality Analysis (FMECA)

Technology Training that Works MIL-P-1629 & MIL-STD-1629A SAE J1739 QS-9000 SAE ARP5580 BS 5760 FMECA, Process and Design FMEA Standards

Technology Training that Works MIL-P-1629 & MIL-STD-1629A In 1949, US Military initiated the procedure MIL-P-1629, titled as “Performing a failure mode, effects and criticality analysis”. This procedure used as a reliability evaluation technique to determine the effect of system and equipment failures classified according to their impact on mission success and personnel/equipment safety. In 1960, NASA formally developed and applied this procedure to improve and verify reliability of space program hardware. The procedures called out in MIL-STD-1629A are the most widely accepted methods throughout the military and commercial industry.

Technology Training that Works SAE J1739 (R) for Automobile Industry This FMEA Standard describes (a)Failure Mode and Effects Analysis in Design (Design FMEA or DFMEA) (a)Failure Mode and Effects Analysis in Manufacturing and Assembly Processes (Process FMEA or PFMEA). It assists users in the identification and mitigation of risk providing appropriate terms, requirements, ranking charts, and worksheets. As a Standard, this document contains requirements "must" and recommendations "should" to guide the user through the FMEA process.

Technology Training that Works QS 9000 is the name given to the Quality System Requirements of the automotive industry which were developed by Chrysler, Ford, General Motors and major truck manufacturers and issued in late QS-9000 replaces such quality system requirements as Ford Q-101, Chrysler's Supplier Quality Assurance Manual, GM's NAO Targets for Excellence and the Truck Manufacturer's quality system manuals. The influence of QS-9000 is being seen throughout the automotive industry as it has virtually eliminated varying demands and waste associated with redundant systems. Proof of conformance to QS-9000 is certification/registration by an accredited third party such as Underwriter's Laboratories (UL) or the American Bureau of Shipping (ABS). Companies that become registered under QS-9000 will be considered to have higher standards and better quality products. QS 9000

Technology Training that Works SAE ARP5580-Recommended Failure Modes and Effects Analysis (FMEA) Practices for Non-Automobile Applications It describes the basic procedures for performing a Failure Modes and Effects Analysis (FMEA). It encompasses functional, interface, and detailed FMEA, as well as certain pre-analysis activities (FMEA planning and functional requirements analysis), post-analysis activities (failure latency analysis, FMEA verification, and documentation), and applications to hardware, software, and process design. It is intended for use by organizations whose product development processes use FMEA as a tool for assessing the safety and reliability of system elements, or as part of their product improvement processes. SAE ARP5580

Technology Training that Works BS :2010 Reliability of systems, equipment and components. Guide to the demonstration of dependability requirements. The dependability case Dependability is a vital performance characteristic and will help your business ensure systems are reliable and performing effectively. A dependability case provides a convenient and convincing means of recording and presenting dependability performance. It is supported by evidence that the necessary dependability performance has been or will be achieved. The dependability performance of a system depends on all aspects of that system, including: Components Processes Hardware Software People Interfaces. BS :2010