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Topic 69: The essence of performing FMEA and FMECA in Safety and Risk Management

Abiaziem Davidson's picture

Failure Modes and Effects Analysis (FMEA) is an inductive method of performing a system reliability or safety analysis from a low to a high level. It is a Bottom Up approach in which the analyst looks in turn at each system component, assesses the effects of its failure on system behaviour.
The basic FMEA technique is to:
i. Examine each component in turn
ii. Identify ways in which it can fail (Failure Modes)
iii. Identify the consequence of these failures (failure Effects)
FMEA is generally a qualitative technique, but may be partly quantified by evaluating the Criticality of each failure. Criticality is a measure of importance which is based on the probability of a failure occurring and the severity of the resulting consequences. If criticality is included then the study becomes a Failure Modes, Effect and Criticality Analysis, or FMECA
The reasons for performing an FMEA may include:
i. To identify failures that can have effects on safety, Reliability and Availability.
ii. To allow improvement to the safety, reliability and maintainability of the system
iii. To improve understanding of the system
iv. To produce aids to fault diagnosis and operating instructions.
v. To quantify system reliability/ safety (where appropriate)
vi. To meet contractual requirement

Comments

Abiaziem Davidson's picture

FMECA is an extension of FMEA which aims to establish the relative importance of each failure effect so that priorities for action may be set. It does this by evaluating the criticality of each failure. The criticality of a failure is a measure of importance which considers both the severity of the consequence and the probability of these occurring.
As such an FMECA is a sample form of risk assessment. However, its limitation must be recognised, and it should not be used as a substitute where a full quantified risk assessment is needed for a high risk system.
The reasons for performing an FMECA may include:
i. Examine each component in turn
ii. Identify ways in which it can fail (Failure Modes)
iii. Identify the consequences of these failures (Failure Effects)
iv. Determine severity of final consequence
v. Determine probability (or frequency) of final consequence
vi. Comparison of criticalities
Abiaziem D.U

Ikechukwu Onyegiri's picture

FMEA and FMECA are methodologies designed to identify potential failure modes for a product or process before the problems occur, to assess the risk ideally [1]. These methodologies yield greater benefits when conducted in the product design or process development stages rather than in the already existing process span.

Risk Management via the FMEA method involves three components: Severity, Occurrence and Detection; all having a 10 point scale (with 10 being the highest). These component values are multiplied to yield the Risk Priority Number (RPN) which gives an indication to the potential of such risks. The FMEA approach is carried out such that no threshold RPN value exists and as such there is no value above which it is mandatory to take a recommended action or below which the team is automatically excused from the action.

FMEA/FMECA have various benefits such as:

1. Contribution to improved designs (upper reliability, better quality, enlarged safety) for product and processes

2. Improved consumer satisfaction as relates to cost savings, reduced development time and re-design costs, decreased warranty costs and waste (Lean Management)

3.Contributes to the development of control plans, testing requirements, optimum maintenance plans, reliability growth analysis and related activities. All these benefits also yield cost benefits in form of failure ode detection before occurrence.

On the other hand FMEA/FMECA come with some setbacks too which include [2]:

 . Though a reliable top-down and bottom-up analysis tool, it is not able to discover complex failure modes involving multiple failures within a subsystem or to report expected failure intervals of particular failure modes up to the upper level subsystem or system.

2. Due to the RPN correlation, multiplication of the three components may result in rank reversals, where a less serious failure mode receives a higher RPN than a more serious failure mode. This is so because the RPN works by ordinal rankings which state that one ranking is better or worse than the other but not by how much.

Regardless FMEA/FMECA are great tools which requires a thorough knowledge base plus collective brainstorming by a design team to optimise the risk severity, occurrence and detection. This makes it cumbersome to implement and as such isn't the industry favourite approach to risk and safety management.

[1]  Risk analysis method: FMEA/FMECA in the organizations. Lefayet Sultan Lipol & Jahirul Haq, IJBAS-IJENS Vol 11, No. 5

[2]  A new approach for evaluation of risk priorities of failure modes in FMEA Fiorenzo Franceschini, IJPR 2001, Vol 39, No. 13, 2991-3002

 

Ikechukwu Onyegiri

51126081

Oil and Gas Engineering

Agba A. Imbuo's picture


FMECA and FMEA are tools used to identify the failure mode of product and processes, assess the effect of the various modes of failure, ranking them according to the most serious and then identifying ways of correcting them according to the most critical ones. In Carrying out FMEA or FMECA, we must ensure that they comply with quality and safety requirements such as ISO/TS 16949, Six Sigma, ISO 9001 or QS 9000. The reasons for carrying out failure mode analysis are:
• It helps increase safety and reliability, quality, customer satisfaction and improves design for processes of products.
• Contribute to optimizing maintenance plan and reliability analysis
• Decrease waste and prevent unplanned cost that could arise from failure of components.
• Forms a basis for prioritizing risk which could be achieved using the criticality rating.
• Provide data used  for future analysis when a change in design is to be considered.

AMBROSE AGBA SUBSEA ENGINEERING (51227054)

Etienne Gunter's picture

I agree with you guys, but regarding the implementation of this tool, I have to say that the difficulty is to get the right mix of “focus and timing” when performing a FMECA.

What I mean is, some companies do this as an afterthought just to have such a document available (if by chance asked for it) and others completely overdo it, thereby ending up with a system that costs ten times to what was budgeted. You must get your focus and timing right, of when to do this in your development process in order to get the right inputs for your design.

Furthermore, the FMECA can be very subjective if reliable component data (often the case) is not available.

Olamide s Ajala's picture

 Ensuing from the disscussion above, I will like to draw our attention to the draw backs of this method.
There are quite a number of limitations to any risk analysis method including FMEA/FMECA. Qualitative draw backs include bias, ability to predict failure modes, and general inability to account for system dependencies or common mode failures.
A large number of studies have shown that items which have been shown to have low risk are often over emphasized and given higher risk values and conversely items which have a much higher risk are given lower risk values( Cohrssen, J.J. et al, 1989; Bye, R. Et al 2007).
One thing to take away from this discussion is that, there is always a qualitative aspect to risk/reliability analysis because someone has to interpret the risk and direct the analysis. It is not the problems that you know about that are important. It is the problems that you do not know about that are vital.
The Apollo space program exploited extensive risk analysis and a variety risk analysis tool throughout the program, the engineer at NASA worked to envisage every possible failure and the consequence of each failure using this information in detailed failure simulation cases.. However none of the analysis fully prepared NASA engineers for the event which occurred on Apollo 13.
Conclusively, A risk/reliability analysis provides a frame work that will aid the user in identifying and managing unexpected problems as they occur throughout the product life cycle and not prevent the event from occuring.
References
Tom moore,(2011). FMECA & COMMISIONING. SPE/ IADC Drilling Conference and Exhibition.
 Yuzhong, S, Seniichi, S .(2004) Reliability-based Classification Criteria and Their Application Procedures. SPE conference paper

Olamide Sherifah Ajala
Student ID:51230562
Course:Sub sea Engineering
olamide.sherifah.ajala@aberdeen.a.uk

Ojo Oluwayimika Joseph's picture

Failure Modes and Effects Analysis/Criticality(FMEA/FMECA) are reliability  analyses that can be used to identify potential hardware and software design deficiencies. The FMEA is a documented procedure of all probable failures in a system within specified ground rules. It is determined by the failure mode analysis that affects each failure on system operation, and classifies each by how extremely bad it was. The FMECA is an FMEA combined with a criticality analysis. The criticality analysis is an analysis procedure for associating failure probabilities with each failure mode. The FMEA/FMECA can help an organization in the following ways:·          Provide the organization with another viewpoint on a design·         Aid in projecting warranty and quality costs·         Aid the designers in producing a product with a lower MTBF·         Aid Customer Service in writing a field repair manual·         Aid Software Engineering in more complete diagnostic software·         Provide the designers with an undetectable failure list·         Provide the designers with a ranked critical parts list

·         Provide the designers with a single point failures list

Ojo Oluwayimika Joseph

Oil and Gas Engineering

SanjayVyas's picture

Failure Mode and Effects Analysis (FMEA) or FMECA is an analysis technique which facilitates the identification of potential problems in the design or process by examining the effects of lower level failures. Recommended actions or compensating provisions are made to reduce the likelihood of the problem occurring, and mitigate the risk.

In design stage, FMEA aids the objective evaluation of design requirements and design alternatives. It increases the probability that potential failure modes and their effects have been considered in the initial development process. It also develops a list of potential failure modes ranked according to their effects and establishes a priority system for design improvements.

FMEA in process identifies potential product related process failure modes. It identifies the potential process causes, identifies process variables on which to focus controls or monitoring, and develops a ranked list of potential failure modes, establishing a priority system for corrective action considerations. It also identifies process deficiencies, confirmed critical characteristics and/or significant characteristics and operator safety concerns.

References

Failure Modes and Effects Analysis (FMEA) and Failure Modes, Effects and Criticality
Analysis (FMECA)

Guidance on Failure Modes & Effects Analyses (FMEAs)

Sanjay Vyas-51234203

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