III. Reliability in Design and Development
A. Reliability design techniques
3. FMEA and FMECA (Analyze)
Define and distinguish between failure mode and effects analysis and failure mode, effects, and criticality analysis and apply these techniques in product, processes, and designs.
It’s time to consider what potentially could go wrong and take action.
Additional References
10 steps of FMEA (article)
SOR 083 The Most Common FMEA Mistakes and How to Avoid Them – Part I (podcast)
SOR 084 The Most Common FMEA Mistakes and How to Avoid Them – Part II (podcast)
When to do FMEA (article)
Finding Value in FMEA (article)
Quick Quiz
1-83. Identify all the considerations that should be taken into account in a criticality analysis.
I. consequences of a failure
II. damage to the environment
III. consequential damage of a failure
IV. potential increase in efficiencies
(A) I and II only
(B) II and III only
(C) I, II, and III only
(D) I, II, III, and IV
(C) I, II, and III only
Criticality is a relative measure of failure mode consequence and its frequency. Thus all the options apply except efficiency. If “efficiencies” here apply to how well the failure manifests or to the manufacturing process, neither concept applies to the concept of FMECA or specifically the criticality element.
1-91. What is the very first step in a failure mode, effects and criticality analysis?
(A) Define the system requirements.
(B) Identify all the failure modes.
(C) Compile a critical items list.
(D) Determine the causes of the failures.
(A) Define the system requirements.
According to The Basics of FMEA by Robin E. McDermott, et. al. there are ten steps to FMEA:
- Review the product
- Brainstorm potential failure modes
- List potential effects of each failure mode
- Assign a severity rating for each effect
- Assign an occurrence rating for each failure mode
- Assign a detection rating for each failure mode and/or effect
- Calculate the risk priority number for each effect
- Prioritize the failure modes for action
- Take action to eliminate or reduce the top priorities
- Calculate the resulting RPN as improvements occur
Other references place the scoring after listing causes and detection elements related to each failure mode. All start with understanding the system or component or process under consideration.
1-101. Identify the principal measures of failure during hazard analysis among the following.
I. failure mode
II. failure severity
III. failure probability
IV. failure mechanism
(A) I and II only
(B) I and III only
(C) II and III only
(D) III and IV only
(C) II and III only
The quantification of a hazard does not consider detection as is done in FMEA. How often and the consequence of a failure to humans or environment are the primary factors in hazard analysis.
The failure mode is a symptoms presented when a failure occurs. The failure mechanism is the underlying event or series of events that manifest as a failure mode.
1-102. What does one analyze in a process FMEA?
(A) system design and the impact of failure modes
(B) the specific hardware details of a device
(C) the functional output of a device
(D) how manufacturing failures affect the product operation
(D) how manufacturing failures affect the product operation
Key word here is “process”. FMEA or FMECA are tools to analyze designs or processes from system to component level.
1-105. Conducting a hardware FMECA on a system requires knowledge of which of the following?
(A) the details of the system
(B) the details of the subsystems
(C) the black box functions
(D) the software to be used
(A) the details of the system
FMEAs/FMECAs are versatile tools to determine risks and prioritize improvement efforts. A system study focuses on the system. A common practice is to use the results to the system study to identify subsystems, components, or processes for a detailed FMEA/FMECA study.
1-142. In a failure modes and effects analysis, which of following does not have a risk priority number assigned to it?
(A) detection
(B) function
(C) probability
(D) severity
(B) function
An FMEA does include a listing and discussion of the function of the item or system. It is not scored or ranked. The severity of a failure mode, the probability of a cause, and the ability to detect a cause before the failure occurs are all scored and comprise elements to calculate the risk priority number (RPN).
Leave a Reply