Failure Modes & Effects Analysis (FMEA) and Failure Modes, Effects & Criticality Analysis (FMECA) [Suggest Change]
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Primary Functional Area : Life Cycle Logistics
The FMEA systematically identifies the likely modes of failure and the possible effects of each failure on mission completion(MIL HDBK 502A, Product Support Analysis) The FMECA addresses the same features as the FMEA; however, the FMECA additionally addresses the criticality of each effect on mission completion, environmental impacts, health hazards, and system safety (MIL HDBK 502A, Product Support Analysis).
Purpose
The FMEA/FMECA is a reliability evaluation/design technique which examines potential failure modes within a system and its equipment, in order to determine the effects on equipment and system performance. Each mode is classified according impact on mission success and safety to personnel and equipment. It should be noted that the FMECA is composed of three separate analyses, the Failure Mode and Effects Analysis (FMEA), the Criticality Analysis (CA) and Risk Priority Analysis (RPA), and Critical Item Analysis (CIA) and Failure Compensation Analysis (FCA) (MIL HDBK 502A, Product Support Analysis).
On its own, the FMEA aids in:
- determining the effect of each failure mode on performance
- root cause identification and development of corrective actions
- investigation of design alternatives
- development of test methods and troubleshooting techniques
- qualitative reliability and maintainability analyses
- locating single point failures
By adding the Criticality Analysis (to include the RPA, CIA, and FCA), the FMEA becomes a FMECA which additionally aids in:
- providing data for developing the Reliability Block Diagram and Fault Tree Analysis
- qualitative safety and supportability analyses
- ranking failure according to severity classification
- estimating system critical failure rates
- Identifying reliability and safety critical components.
A primary tenet regarding the FMEA/FMECA is its relationship with the Logistics Product Data (LPD) database. LPD is the detailed data pertaining to the identification of Product Support resource requirements of a product. LPD requirements are addressed in TechAmerica GEIA-STD-0007. There are numerous different applications for maintaining and transferring LPD, many of which can be located on the Product Support Analysis Tools database (https://acc.dau.mil/psa-tools). Early analyses are utilized to populate the LPD which should be later updated with the results of each subsequent analysis, to include the FMEA/FMECA.
Analysis Steps
The FMEA or FMECA should be scheduled and completed concurrently with design of the system. According to MIL-HDBK-502A it is an iterative process; therefore, as the design matures, the analyses should become more detailed. MIL-HDBK-502A highlights that FMEA/FMECA planning begins as early as the Materiel Solution Analysis phase, though it may be deferred to the Technology Maturation and Risk Reduction phase. Since the process is iterative in nature, MIL-HDBK-502A states the FMEA/FMECA activity iterates in order to update the LPD through the Engineering and Manufacturing Development phase. Note that this activity is reserved for design changes once in the Production and Deployment phase and later.
The process below fits both the FMEA and FMECA, with the exception that when conducting a FMEA, step six would be omitted.
- Define the System—the system definition should include the identification of all internal and interface functions, the performance of the system at each indenture level, any system restraints, and any failure definitions
- Define the Ground Rules and Assumptions—these aid in better understanding the results of the analysis. Some examples include: mission of the item, operating time, source of source of failure rate data
- Build System Block Diagrams—Functional Diagrams and Reliability Block Diagrams (RBDs) should represent operations, interrelationships, and interdependencies. They allow traceability through each level of indenture
- Identify Failure Modes—all item and interface failure modes must be identified, understanding that any effects upon function, mission, or system must be determined
- Analyze Failure Effects/Causes—accomplished on each item in the RBD. Consequences of each failure mode on operation and the next higher level should be identified.
- Classify by Severity—severity provides qualitative measures of consequence. Severity is typically labeled as Catastrophic, Critical, Marginal, or Minor
- Identify means of failure Detection, Isolation, and Compensation—answer how the failure is by the operator, how the failure isolated, and how is it compensated for (redundancy, monitor, back up)
- Recommendations-design modifications or Fault Tree Analysis (FTA)
Source: Reliability Information Analysis Center (CRTA-FMECA)
The activities involved with identification of operations, maintenance, and support functions that must be performed in the intended environment, which includes the FMEA/FMECA, require a multifunctional effort. Expect that personnel specializing in design engineering, reliability, maintainability, human engineering, safety, and Product Support Element management will be involved. While MIL-HDBK-502A states that the contractor assumes responsibility for this activity during Materiel Solution Analysis phase and all subsequent phases, note that there is a requirement for substantial government input, which would include coordination with the engineering and product support communities.
Summary
The FMEA/FMECA requirements will generally be included under the Reliability Program. However, FMEA/FMECA requirements for a system should be developed in conjunction with the Product Support Analysis program requirements due to the necessity of having FMEA/FMECA results to conduct some PSA activities. In particular, the FMEA/FMECA provides the basis for built-in and external test specification and evaluation. This coordination should consider the timing of the FMEA/FMECA, level of detail, and documentation requirement.
A FMEA/FMECA helps identify the ways in which systems can fail, performance consequences, and serve as basis in the identification of Critical Safety Items as well as potential areas for preventative maintenance for the system. When conducted in a timely fashion, the FMEA/FMECA can be used to support trade-offs between performance and life-cycle costs to drive design improvements (DAG, para 5.4.2).
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Page Information
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Page Views
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12,082
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Created on
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11/29/2010
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Modified on
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3/16/2016
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Last Reviewed
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3/16/2016
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