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Reliability Glossary

FMEA and RCM Terms

Analysis plan
A plan used to keep track of team members, ground rules and assumptions, estimated completion dates, scheduled work sessions and other details to help an analyst plan and manage analysis projects.

Control plan
A plan used to keep track of characteristics that affect a product during the manufacturing process to ensure that the desired product specifications are met during the manufacturing process. It is often integrated with PFD worksheet and/or a process FMEA.

Criticality analysis
A method for prioritizing issues that takes into account the probability of failure for the item and the portion of the failure likelihood that can be attributed to a particular failure mode. The resulting prioritization is used to determine the sequence and time-frame for the corrective actions that will be performed.

Design FMEA
An FMEA performed with the objective of improving the design of a subsystem or component.

Design for reliability (DFR):
A process in which a set of reliability engineering practices are utilized early in a product's design and integrated into the entire product development cycle.

Design reviews based on failure mode (DRBFM)
A methodology used to evaluate proposed changes to an existing design. DRBFM uses a worksheet similar to the FMEA worksheet, but it typically focuses on the failure modes that might be introduced by a specific change to a product or process.

Detection ratings
Qualitative ratings used to estimate the likelihood of prior detection for each cause of failure (i.e., the likelihood of detecting the problem before it reaches the end user or customer).

Failure effect categorization (FEC)
A process whereby by the effects of a system’s functional failures are evaluated and categorized in order to help the analyst prioritize identified issues and choose the appropriate maintenance strategy to address them.

Failure mode and effects analysis (FMEA)
A methodology designed to identify potential failure modes for a product or process, to assess the risk associated with those failure modes, to rank the issues in terms of importance and to identify and carry out corrective actions to address the most serious concerns.

Failure mode criticality
see Criticality analysis

Failure modes and reliability analysis (FMRA)
A methodology that uses information from FMEAs as a starting point for other reliability/availability analyses and cost calculations.

Failure modes, effects and criticality analysis (FMECA)
Similar to the FMEA methodology, except that it includes a criticality analysis.

Functional failure analysis (FFA)
see Failure mode and effects analysis (FMEA)

Maintenance tasks
Activities intended to repair or maintain a system (e.g., inspections).

Mode ratio
The probability that the item's failure will be due to the failure mode under consideration. In other words, this represents the percentage of all failures for the item that will be due to the given mode.

Occurrence ratings
Qualitative ratings used to estimate the likelihood of occurrence for each cause of failure.

Process flow diagram (PFD)
A high level chart that helps the analyst visualize the steps that a product goes through in a manufacturing or assembly process.

Process flow diagram (PFD) worksheet
A worksheet that captures details about what happens to an item in each step of its manufacturing or assembly process, and it records the product and process characteristics that are important to keep under control. The information from this worksheet can be used as an input to the process FMEA (PFMEA) and control plan for the item.

Process FMEA
An FMEA performed with the objective of improving the design of a manufacturing process.

Reliability centered maintenance (RCM) analysis
A structured framework for analyzing the functions and potential failure modes for a physical asset (such as an airplane, a manufacturing production line, etc.) in order to develop a scheduled maintenance plan that will provide an acceptable level of operability, with an acceptable level of risk, in an efficient and cost-effective manner.

Risk discovery analysis
A preliminary analysis that often involves answering questions and/or assigning ratings about possible risks. It is used to help the analyst choose which items should receive more detailed consideration via a failure mode and effects analysis (FMEA) or reliability centered maintenance (RCM) analysis.

Risk priority number (RPN) system
A relative rating system that prioritizes issues by assigning numerical values to them in each of three different categories: Severity (S), Occurrence (O) and Detection (D). The three ratings are multiplied together to determine the overall RPN for each issue, where higher RPNs indicate higher risk priority.

Severity ratings
Qualitative ratings used to estimate the severity of each effect of failure.

System FMEA
An FMEA performed with the objective of improving the design of a system.