Effect Analysis

Cause and effect analysis is useful in any kind of process capability analysis, not just as the result of attributes inspection and Pareto analysis. The focus of cause and effect analysis is on attacking a problem rather than on fixing blame. Once a nonconformity has been isolated for further study, attention shifts to analyzing how the deviation from specifications was caused. Sometimes the reason is obvious sometimes a considerable amount of investigation is required to uncover the cause or causes. The Japanese have developed and used cause and effect analysis, and the resulting diagram, as a formal structure for uncovering problem areas. The steps in a cause and effect analysis are (Ishikawa 1982,18)  

Determine the quality characteristic. Pareto diagrams can be used to identify the characteristic one would like to improve. 

Determine the main factors that may be causing lower than expected levels of the quality characteristic. Main factors can be identified through data analysis (i.e., highest frequencies), job analyses, etc. 

On each branch item, or main factor, determine the detailed factors. Defining and linking the relationships of the possible causal factors should lead to the source of the quality characteristic. 

There are various methods for arranging cause and effect diagrams. These methods 

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Methods for performing hazard analysis and risk assessment include safety review, checkhsts, Dow Fire and Explosion Index, what-if analysis, hazard and operabihty analysis (HAZOP), failure modes and effects analysis (FMEA), fault tree analysis, and event tree analysis. Other methods are also available, but those given are used most often. 

Failure Mode and Effects Analysis. The system design activity usually emphasizes the attainment of performance objectives in a timely and cost-efficient fashion. The failure mode and effects analysis (FMEA) procedure considers the system from a failure point of view to determine how the product might fail. The terms design failure mode and effects analysis (DFMEA) and failure mode effects and criticaUty analysis (EMECA) also are used. This EMEA technique is used to identify and eliminate potential failure modes early in the design cycle, and its success is well documented (3,4). 

End Effects Analysis of the mass-transfer efficiency of a packed cohimn should take into account that transfer which takes place outside the bed, i.e., at the ends of the packed sections. Inlet gas may veiy weU contact exit liquid below the bottom support plate, and exit gas can contact liquid from some types of distributors (e.g., spray nozzles). The bottom of the cohimn is the more hkely place for transfer, and SU-vey and KeUer [Chem. Eng. Prog., 62(1), 68 (1966)] found that the... 

Eailure Mode and Effects Analysis (EMEA) A failure identification methodology where the failure modes of a component sub-system are identified. An analysis of these failure modes on the safety of the entire system is performed. 

Chrysler Corporation, Ford Motors, General Motors Corporation 1995 Potential Failure Mode and Effects Analysis (FMEA) - Reference Manual, 2nd Edition. 

Today there are many tools available to aid in problem solving or f ure analysis. These include the Weibull Analysis, Failure Mode i Effect Analysis, and Fault Tree Analysis, to name a few. One of the m widely accepted is the Weibull analysis. This method can provide accurate engineering analysis based on extraordinary small samples [1]. 

A risk assessment analyses systems at two levels. The first level defines the functions the system must perform to respond successfully to an accident. The second level identifies the hardware for the systems use. The hardware identification (in the top event statement) describes minimum system operability and system boundaries (interfaces). Experience shows that the interfaces between a frontline system and its support systems are important to the system cs aluaiion and require a formal search to document the interactions. Such is facilitated by a failure modes and effect analysis (FMEA). Table S.4.4-2 is an example of an interaction FMEA for the interlace and support requirements for system operation. 

A failure modes and effects analysis delineates components, their interaction.s ith each other, and the effects of their failures on their system. A key element of fault tree analysis is the identification of related fault events that can contribute to the top event. For a quantitative evaluation, the failure modes must be clearly defined and related to a numerical database. Component failure modes should be realistically and consistently postulated within the context of system operational requirements and environmental factors. 

Table 15.3.4-1 Failure Modes Effects Analysis for Valve A in Figure 3.4.4-6...

How do you then design an effective system There are several techniques you can use. Failure Modes and Effect Analysis (FMEA), Fault Tree Analysis (FTA), and Theory of Constraints (TOC) are but three. The FMEA is a bottom-up approach, the FTA a top-down approach, and TOC a holistic approach. 

There is one technique widely used in the automotive industry for detecting and analyzing potential nonconformities Failure Modes and Effects Analysis (FMEA). There are Design FMEAs and Process FMEAs. The technique is the same - it is only the focus that is different. As clause 4.14 addresses potential nonconformities, the subject of FMEAs is treated in Part 2 Chapter 14. 

The lists of critical items that were described under Identifying controls in Part 2 Chapter 2, together with Failure Modes and Effects Analysis and Hazard Analysis, are techniques that aid the identification of characteristics crucial to the safe and proper functioning of the product. 

A failure modes and effects analysis is a systematic analytical technique for identifying potential failures in a design or a process, assessing the probability of occurrence and likely effect, and determining the measures needed to eliminate, contain, or control the effects. Action taken on the basis of an FMEA will improve safety, performance, reliability, maintainability and reduce costs. The outputs are essential to balanced and effective quality plans for both development and production as it will help focus the controls upon those products, processes, and characteristics that are at risk. It is not the intention here to give a full appreciation of the FMEA technique and readers are advised to consult other texts. 

Guidelines to failure modes and effects analysis (SMMT)... 

Potential failure mode and effects analysis (FMEA) (GM, Ford, Chrysler)... 

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