FMECA analysis

One hazards analysis technique used to analyze equipment items is FMEA. The method examines the ways in which an equipment item can fail (its failure modes) and examinees the effects or consequences of such failures. If the criticality of each failure is to be considered, then the method becomes a Failure Modes, Effects and Criticality (FMECA) Analysis. The consequences can be to do with safety, reliability, or environmental performance. 

The development of the model of the degradation process is based on the identification of the IPs influencing the degradation of the component. In the present case study, this has been done by resorting to a FMECA analysis performed by safely analysis. The identified IPs are the following ... 

One of the main characteristics of the traditional FMECA analysis is the RPN calculation which, as explained before, is the result of a simple multiplication of three risk factors (S, O, D). Despite of being simple, this procedure presents some criticalities, which can be summarized as follows ... 

FMEA and FMECA analysis present some important limits, mainly related to RPN evaluation. Many authors have developed different methodologies in order to overcome these disadvantages and improve the failure mode prioritization process, most of them using a fuzzy approach. 

Information/documentation requirements For a successful FMEA/FMECA analysis a number of documents are necessary. The variety of information/ documentations necessary for DFMEA/DFMECA and PFMEA/PFMECA will be different. Also there wiU be variations in documentations for functional and hardware FMEA/FMECA approaches ... 

FMECA results a team of scientists performed a systematical risk analysis of the most important components using the FMECA method. In total, 29 potential failures were identified and their relative priorities for applying measures were determined. Seven of these failure modes are only influencing the operability itself and are not relevant form a safety point of view. From the remaining 22 failure modes, 6 are related to mechanical operations and the remaining 16 are indirectly related to the hazardous properties of the solvents. Since those properties are not directly evaluated by the procedure, the relative importance and magnitude of the effects remain unclear after the FMECA analysis. 

We previously encountered failure modes and effects (FMEA) and failure modes effects and criticality analysis (FMECA) as qualitative methods for accident analysis. These tabular methods for reliability analysis may be made quantitative by associating failure rates with the parts in a systems model to estimate the system reliability. FMEA/FMECA may be applied in design or operational phases (ANSI/IEEE Std 352-1975, MIL-STD-1543 and MIL-STD-1629A). Typical headings in the F.Mld. A identify the system and component under analysis, failure modes, the ef fect i>f failure, an estimale of how critical apart is, the estimated probability of the failure, mitigaturs and IHissihiy die support systems. The style and contents of a FMEA are flexible and depend upon the. ilitcLiives of the analyst. 

The assembly process (Figure 10-1) brings together all of the assessment tasks to provide the risk, its significance, how it was found, its sensitivity to uncertainties, confidence limits, and how it may be reduced by system improvements. Not all PSAs use fault trees and event trees. This is especially true of chemical PSAs that may rely on HAZOP or FMEA/FMECAs. Nevertheless the objectives are the same accident identification, analysis and evaluation. Figure 10-1 assumes fault tree and event tree techniques which should be replaced by the equivalent methods that are used. 

FMECA - Failure Modes, Effects and Criticality Analysis. 

All of these factors determine the stress experienced by the workers and the extent to which operational errors will be recovered before disastrous consequences have ensued. In this context, hazard identification techniques, such as hazard and operability studies (HAZOP), failure modes and effects and criticality analysis (FMECA), fault trees, and others are useful in making the process environment more forgiving. 

FMECA Failure Modes and Effects of Criticality Analysis... 

Failure modes effects criticality analysis (FMECA)... 

Perhaps the key to detcrnuiiiiig die consequences of an accident is die study of accident mininiization/prcvendon. This topic receives extensive treatment in Section 17.2. The estimation (not calculadon) of consequences is treated in Section 17.3, which is followed by evacuation procedures (Section 17.4). The next section e.xaniiiies failure modes, effects and critical analysis (FMECA). The cluipter concludes with vulnerability analysis (Section 17.6) and event tree analysis (Section 17.7). 

Failure mode, effects, and criticality analysis (FMECA) This method tabulates a list of equipment in the process along with all the possible failure modes for each item. The effect of a particular failure is considered with respect to the process. 

In the FMECA procedure [2,3,256], an exhaustive list of the equipment is first made. Every item on the list is then reviewed for possible ways in which it can fail (the failure modes are open, closed, leaks, plugged, on, off, etc.). The effects of each failure mode are then recorded and a criticality ranking of every item of equipment is calculated. A limitation of this procedure is that combinations of failures which may cause an incident are not really identified. Failure modes and effects analysis (FMEA) is the same procedure without the criticality analysis. 

From those techniques given in Table 1 my personal preference is for failure mode, effects, and criticality analysis (FMECA). This technique can be applied to both equipment and facilities and can be used to methodically break down the analysis of a complex process into a series of manageable steps. It is a powerful tool for summarizing the important modes of failure, the factors that may cause these failures, and their likely effects. It also incorporates the degree of severity of the consequences, their respective probabilities of occurrence, and their detectability. It must be stressed, however, that the outcome of the risk assessment process should be independent of the tool used and must be able to address all of the risks associated with the instrument that is being assessed. 

The next section e. aniines failure m es, effects and critical analysis (FMECA). The cliapter concludes with xaihierability analysis (Section 17.6) and event tree analysis (Section 17.7). 

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