Purpose of FMEA

The FMEA is used primarily for doing subsystem and system hazard analyses, but a functional FMEA can also be useful in performing preliminary hazard analyses and operating hazard analyses. It helps to identify critical items in terms of safety and reliability. 

The functional FMEA requires less detail and can be performed with the upper branches of an analytical tree. The requirement is to identify subsystems and their functions, not details of subsystem configuration or design. 

Failure rates or similar reliability statistics are required to quantify the analysis. This information may be difficult to obtain and even more difficult to validate. 

---

In this connection one may note that ISO 9001 2000 para 8.5.3 requires a documented procedure for preventive action. It also demands that preventive actions must be in proportion to the effect of the failure. The FMEA/FMECA approach satisfies ISO 9001 para 8.5.3, so for ISO 9001 2000 FMEA/FMECA may be applied, but it is not a specific ISO 9001 requirement, since the basic purpose of FMEA or FMECA is the same and the procedures are similar. However, one should note that there are some differences between them, which are listed in Table IV/2.0.3-l. There are different types of FMEA/FMECA, discussed next. 

The object and collaboration diagrams are input to the OF-FMEA method. From this input we develop formal specification of component interactions. For this purpose we use CSP. Each component of the collaboration diagram becomes a CSP process with input and output channels as shown in the diagram. In addition to this we develop formal models of safety requirements of the system. The requirements are derived from the railway safety regulations. Each requirement is modeled as a CSP process and imposes some restrictions on the ordering of events in the system. The requirements refer to the events that are visible on Level 4 of our decomposition. 

An FMEA team, usually put together for the purpose of the analysis, will work through a series of steps to apply the tool. At least one member of the team is usually an FMEA expert experienced in using the technique. A typical approach to an assessment might look like this ... 

Note A piece-part FMEA is often only effectively conducted by the design authority of the part being considered. For the purposes of supporting a 2X.1309 System Safety Assessment, the piece-part FMEA is thus seldom applied above System Level 3 and is only conducted(ARP4761 para G.3.2.2) when necessary (eg, when the more conservative results of a functional FMEA will not meet the ETA probability of failure budget). 

For the purpose of this example, we will assume that the previous FMEA on the elevator system did not examine the plunger components in particular and, therefore, that no prior hazard analysis information is available for evaluation. 

Critical items List The purpose of the FMEA is to identify and evaluate failure modes and the possible system effects of those failures. Since the potential for undesirable effects must be eliminated or controlled, the FMEA also provides recommended actions that must be taken to accomplish this goal. As part of this analysis process, the FMEA identifies any and all items within the system that, if a failure were to occur, would have a critical effect on the operation of that system. Therefore, to facilitate evaluation and analysis of these system effects, a critical items list is developed. The list provides detailed descriptive information on each item. It will explain its overall function within the system, as well as the function of any components that may make up that item. The failure mode determined as critical is then listed along with the potential effect(s) of such a failure. If an item on the critical items list is to be accepted as is, then acceptance rationale must be provided. Such rationale may include an explanation of any existing or planned design limitations that will prevent the failure during actual system operations, or the provision of excessive factors of safety that will render such fail-ure(s) extremely improbable. Another area for evaluating acceptance is the history, or lack thereof, and any known failures of systems similar in nature and operation. 

For the purpose of this example, the following components of the 10/1.5-ton overhead bridge crane are considered passive and will not be analyzed in the FMEA ... 

Application of FMEA/FMECA FMEA/FMECA contributes to improve product and production process to achieve better quality, better reliability, enlarged efficiency with increased safety, and enhanced customer satisfaction at comparatively lower cost. Therefore FMEA/FMECA is a tool that has been adapted in various ways for different applications and purposes, some of which are listed here ... 

Scope and boundary For defining the scope and boundaries of FMEA/FMECA the major questions are Is it for conceptual, design, process, or software and services Also the purpose of the study shall be questioned. The scope of analysis shall take into account the physical boundaries, operating phases (operational or startup/shutdown phase, etc.), and any other assumptions considered in the referendum. In brief the following points shall constitute the scope and boundary of analysis. It is worth noting that all interface points should be included in the scope even if these are beyond the physical boundaries defined. 

Introductory Information The analyst should provide basic information in this section of the report which describes the purpose and scope of the FMEA along with any limitations imposed on the analysis as a result (i.e., items not specifically within the scope of the analysis). The scope will also identify the type of FMEA (i.t., functional or hardware). Also included in the introduction section is an explanation of the methodology used to perform the analysis such as, but not limited to drawing reviews, examination of previous analyses (if applicable), evaluation of lessons learned, use of Preliminary Hazard List and/or Preliminary Hazard Analysis, and so on. Finally, any preestablished ground rules that may have been agreed upon should be provided here. Such ground rules typically limit or further narrow the scope of the FMEA, or just a portion of it, and should therefore be explained in the introductory pages of the report. 

The purpose of this article is to present preliminary estimates of the causes and effects of risks occurring in the international intermodal transport, as well as evaluation of possibilities to avoid potential risks. Structure of the article is as follows the next section presents logistical operations occurring in the international supply chain. Than the article includes a discussion on the choice of a suitable risk analysis process. Sequentially presented in the table descriptions associated with the FMEA analysis. The last part is a summary and set out the next stages of work. 

For the purpose of mechatronic systems risk assessment, it is possible to utilize a modified version of FMEA (see also Chapter 4.3). Following consultation with experts in the field of specific application of a lifting machine, the particular functional structures are assigned points in the range 1-10. For mechatronic systems, it is possible to apply the ME (mechanics and electronics) structure identification coefficient, also within a 1-10 range the coefficient is directly dependent on a number of electronic components. If an element of the mechanical part of the machine is dealt with, ME =... 

The traditional FMEA has been a well-accepted safety analysis method, however, it suffers from several weaknesses. One of the critically debated weaknesses, is the method that the traditional FMEA employs to achieve a risk ranking. The purpose of ranking risk in order of importance is to assign the limited resources to the most serious risk items. Traditional FMEA uses an RPN to evaluate the risk level of a component or process. The RPN is obtained by finding the multiplication of three factors, which are the probability of failure (5/), the severity of the failure S) and the probability of not detecting the failure (Sj). Representing this mathematically will give ... 

It is generated to support the safety assessment, so it is important to understand the expectations and requirements of the FMEA before any work on it commences (e.g. its sole purpose may be to support verification of the FTA through a comparison of FMEA failure modes with the basic events of the fault tree). 

Failure Modes and Effects Analysis. Failure modes and effects analysis (FMEA) is applied only to equipment. It is used to determine how equipment could fail, the effect of the failure, and the likelihood of failure. There are three steps in an FMEA (4) (7) define the purpose, objectives, and scope. Large processes are broken down into smaller systems such as feed or cooling. At first, the failures are only considered to affect the system. In a more general study, the effects on a plant-wide basis can be considered. (2) Define the problem and boundary conditions. This includes identifying the system to be studied, establishing the physical boundaries, and labeling the equipment with a unique identifier for use in the FMEA procedure. (3)... 

The failure mode and effect analysis (FMEA) is generally applied to a specific piece of equipment in a process or a particularly hazardous part of a larger process. Its primary purpose is to evaluate the frequency and consequences of component failures on the process and surroundings. Its major shortcoming is that it focuses only on component failure and does not consider errors in operating procedures or those committed by operators. As a result, it has limited use in the chemical process industry. 

Before mistake proofing can be applied, potential mistakes must first be identified. FMEA can be used for this purpose. It identifies different failure modes along with their potential causes and consequences. For each potential failure mode, a risk evaluation is performed based on the likelihood of a defect to occur, the likelihood of it being detected, and the severity of its consequences. One of the columns in an FMEA is titled Control Plan. This column must be filled out before performing the risk assessment. Both the likelihood of occurrence and likelihood of detection are affected by the controls that are currently in place. 

Column 8 is used to list the failure rate of the particular component failure mode. The use of this column is optional when FMEAs are being done for qualitative purposes. When quantitative failure rates are desired and... 

If we are conducting an FMECA, then column 10 in Table 5.10 has been reserved for this purpose (where it should be evident that the severity depends on the worst-case aircraft-level effect defined in Column 7). fii some cases the Level 4 system integrator might feel that the Level 3 designer does not have the required system knowledge to justify this effect, in which case their participation needs to be solicited to ensure the objective of the FMEA is satisfied. 

ABSTRACT On the strength of experience with risk analysis methodology in IT-operating enterprises, an approach has to be able to deal with limited resources. This prompts an analyst to perform a heuristic and biased approach, which is typically a questiomiaire structured by a IT security standard. The difficulty is to draw up a limited set of concise IT security related questions, which result in meaningful outcomes for IT risk analysis purposes. In the proposed approach, the Code of Practice ISO/IEC 27002 is used to structure the analysis and to restrict the number of questions. The Code s recommendations are rephrased and a Guttman scale is introduced for an IT security FMEA-like risk analysis approach. For frequency assessments it is assumed that an implemented high-level security measurement resiilts in low frequencies of imdesired events. The paper pictures the adapted IT-FMEA approach and presents the results of a feasibihty study at Switzerland s leading telecom provider. 

This example will develop a hardware FMEA for a proposed system that is well into the design phase of the product life cycle. For informational purposes, it is assumed that a preliminary hazard analysis was previously performed during the early stages of the design phase of this system. The information from the PHA will be used to assist in the development of the hardware FMEA. It should also be noted that the nature of a FMEA requires evaluation of subsystems, subassemblies, and/or components. For this reason, more detailed and specific descriptive information is provided here than that supplied for previous examples discussed in this text. 

Note that the EMEA process described here requires the entry of probability, severity, and risk codes. The example of a risk assessment matrix shown in Table 13, and the Risk Category Codes, given in the nearby text fulfill the needs for traditional FMEA purposes. A Eailure Modes and Effects Analysis form on which those codes would be entered is provided in Addendum C at the end of this chapter, courtesy of A-P-T Research, Inc. 

As discussed earlier in Clause 2.0.4, there are two different approaches for FMEA/ FMECA with different purposes. One approach is top down, while the other is bottom up. Complexity of design, development stages, and amount of data availability actually determine which approach is better suited. In some complex laige systems it is not uncommon to use both in tandem. These approaches can he applied at any level. Functional analysis may be considered as an input for determining failure mode in both approaches. The top-down approach is better suited for functional analysis. 

---