Reliability:
The probability that a system/equipment will perform its intended function for a specific period of time, under specific conditions.
Availability:
The probability that a system/equipment will be available when it is required. Both of these are key to customer satisfaction
and cost control. Both can be improved but the first step is to estimate and/or measure your system's predicted or current Reliability and Availability.
What is the difference between a FMEA and a FMECA?
A FMEA is qualitative, whereas a FMECA is a quantitative analysis. In a FMECA, the probability of a specific failure occurring is given as a numerical prediction. FMEAs employ probability of failure categories based on probability ranges. The proper category is determined by the experience and expertise of the analyst, instead of a mathematical probability calculation involving actual component failure rates.
Do I need a FMEA or a FMECA? |
FMEAs require less time and effort to prepare, and therefore cost less to perform. The answer to this question depends on what you want out of the analysis and what requirements you have to meet. Check your contracts; do they specifically ask for a FMECA? Many just want to ensure that you have done the best you possibly can to provide a reliable, safe, and cost-effective product.
What level of depth is necessary? Should we examine each and every component or should we "black box" as much as we can?
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The depth of analysis is directly proportional to its complexity. The level of depth will play a major role in costs associated with the analysis. If this system in question has already been designed, and design changes are not feasible, an individual component level analyses is probably not recommended.
Do you employ any National Standards to perform your analyses?
FMECAs are based on MIL-STD-1629, "Procedures for Performing a Failure Mode, Effects and Criticality Analysis". This document is approved for use by all Departments and Agencies of the Department of Defense (DOD). Safety Analyses are based on MIL-STD-882, "Department of Defense Standard Practice for System Safety" and its various Data Item Descriptions (DIDs). This standard provides uniform requirements for system safety to identify the hazards of a system and to recommend design requirements and management controls to prevent mishaps. It was designed to apply to all DOD systems and facilities.
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