Your Reliability Engineering Professional Development Site
A structured process or procedure to determine the most underlying or fundamental factor or reason for a failure.RCA is used to gather the necessary information to identify suitable short-term and long-term solutions to avoid similar failures in the future.
In my last article, RCA Templates Use or not?, I discussed templates and suggested that while beneficial for many things, they may not provide as much value for those doing RCA’s. This is because for any specific effect, the variability in the cause tree is significant and difficult to predict. This doesn’t mean that there are no options to utilize templates to help speed up the process, but perhaps not in the way that people might be used to. [Read more…]
A Crisis in the Home IT departmentIf you are the head of your home IT department, you may relate to this tale
Last night my wonderful wife Stacy was riddled with angst over the disruption of her binge watching a spy series, a mild crisis with our own IT hardware.
The cause of her disappointment was the failure of our new large screen Ultra High Definition (UHD) Smart TV to deliver a drama series with a reasonable picture and sound quality. [Read more…]
Recently there was a power outage, that caused approximately 2,000 homes to lose power during a very cold day. The paper headline read, “All-day outage caused by worn wiring”.
This seems like a reasonable comment and probably like many other newspaper headlines also seems to go a long way to explain what caused the 2,000 homes and business to lose power for 5 ½ hours, and the 300 that lost power for a total of 11 ½ hours. [Read more…]
Occasionally, I like to step back and reflect on reliability in basic terms.
In that spirit, the basic premise of reliability is usually stated as “The probability that an item will perform a required function, without failure, under stated conditions, for a stated period of time.”
To use the reliability equation, the definition of failure must be defined, so you can tell if your equipment has indeed failed. This way you can include it in the MTBF (Mean Time Between Failure) calculation.
After you have defined a failure and recorded them appropriately, you can plug the numbers into the reliability equation, R = e ^-(λ*t) where λ is the failure rate which is defined as λ= 1/MTBF and come up with an objective value for the reliability. [Read more…]
Historically Reliability Engineering of Electronics has been dominated by the belief that 1) The life or percentage of complex hardware failures that occurs over time can be estimated, predicted, or modeled and 2) Reliability of electronic systems can be calculated or estimated through statistical and probabilistic methods to improve hardware reliability. The amazing thing about this is that during the many decades that reliabilityengineers have been taught this and believe that this is true, there is little if any empirical field data from the vast majority of verified failures that shows any correlation with calculated predictions of failure rates.
[Read more…]
The Failure Reporting and Corrective Action System (FRACAS) is a closed-loop process whose purpose is to provide a systematic way to report, organize and analyze failure data. Implementation of a FRACAS has increasingly become commonplace within an industry. The requirement for implementation of some type of FRACAS within a DoD program was first established in 1985 with MIL-STD-2155. However, in 1995 that standard was reestablished with no changes to content as a handbook, MIL-HDBK-2155, and was recommended as guidance. Today, multiple software solutions exist that provide all the functionality required of a FRACAS. [Read more…]
Two short questions to evaluate your knowledge of failure mechanisms (root causes) and common reliability models. The answers will be posted in a comment, later.
Which of the following failure root causes is most likely NOT due to power line variation (electronic-based product)?
A. Circuit design margin exceeded
B. Power dissipation
C. In-rush current response
D. Mechanical fatigue [Read more…]
