Reliability HotWire: eMagazine for the Reliability Professional
In this issue:

Issue 32, October 2003

*Hot Topics
*Reliability Basics
*Tool Tips
*Hot News
*From the Edge
*Contribute to HotWire

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Hot Topics  
The Limitations of Using the MTTF as a Reliability Specification
In order to track and improve the reliability of their products, manufacturing organizations must utilize an accurate and concise method to specify and measure that reliability. Although useful to some degree, the mean life function (often denoted as "MTTF" or "MTBF") is not a good measurement when used as the sole reliability metric. Instead, the specification of a reliability value with an associated time, along with an associated confidence requirement when possible, is a more versatile and powerful metric for describing a product's reliability.

To read more, see 

Reliability Basics  

Characterizing Your Product's Reliability

As awareness of product reliability increases, so does the responsibility of engineering organizations to insure that reliability requirements are met. As a result, engineers and managers who have had little experience with life data analysis or applied statistics may find themselves responsible for calculating and reporting on a product's reliability. This article offers background on elementary concepts of reliability and life data analysis that will hopefully prove to be of use to the novice analyst.

To read more, see 

Tool Tips  
  • When analyzing a system, what is the difference between the reliability block diagram (RBD) and fault tree diagram (FTD) approach?

  • In Weibull++, why doesn't the calculated MLE line track the data points on my probability plot?

To read more, see 

Hot News
* 1st Annual Applied Reliability Symposium (ARS) - ReliaSoft and the Reliability Analysis Center (RAC), along with ReliaSoft's corporate sponsors GE, Quantum and the US Army, are very excited to announce the 1st Annual Applied Reliability Symposium (ARS) scheduled for June 16 - 18, 2004 in San Diego, California. Please visit the Symposium Web site at for information on early registration, topics and presenting organizations.
* 2004 Public Training Dates are Posted - Planning next year's training schedule has never been easier as you can now view ReliaSoft's public training seminars by class, date and location. Please visit to find the class, date and location that work best for you.
* Xfmea Enterprise is Now Available - While the Standard edition of ReliaSoft's Xfmea is designed for individuals and small departments, ReliaSoft's Xfmea Enterprise includes the power and flexibility to address the FMEA / FMECA needs of an entire organization. Which Xfmea is right for you? An easy-to-read comparison chart is available at:
* Reliability-Related Military Handbooks and Standards on - The resources available on continue to expand with the addition of links to  U.S. Department of Defense handbooks and standards related to reliability practices. These handbooks and standards can be downloaded (or viewed and printed) in *.pdf format. To review this new resource, please visit:
* The Society of Reliability Engineers (SRE) - The SRE Huntsville, AL chapter is looking to expand their membership. This is an excellent opportunity to spend time with your peers discussing reliability issues. The chapter generally meets monthly at BAE SYSTEMS, 310 Voyager Way. The next meeting is scheduled for Tuesday, October 14, 2003. Please contact Shirley Hardy at for more information.
* Calendar of Public Events:


China - Master the Subject, Master the Tools Training Seminar (MSMT) - Life data analysis, accelerated life data analysis and system analysis: October 27 - 31, 2003 in Shanghai, China. This seminar is primarily in Chinese. For more information, see
November Master the Subject, Master the Tools Training Seminar (MSMT) - Life data analysis, accelerated life data analysis and system analysis: November 17 - 21, 2003 in Tucson, AZ. For more information, see
December QALT Boot Camp - December 10 - 12, 2003 in Tucson, AZ. This intensive three day course covers advanced topics, concepts and applications of quantitative accelerated life testing (QALT) analysis and ReliaSoft's ALTA PRO software. For more information, see
From the Edge

In addition to the monthly Reliability HotWire, ReliaSoft publishes Reliability Edge, a printed journal that includes articles and information related to the field of reliability engineering. Articles of interest in the current edition:

  • Examining Risk Priority Numbers in FMEA - The Risk Priority Number (RPN) methodology is a technique for analyzing the risk associated with potential problems identified during a Failure Mode and Effects Analysis (FMEA). This article presents a brief overview of the basic RPN method and then examines some additional and alternative ways to use RPN ratings to evaluate the risk associated with a product or process design and to prioritize problems for corrective action. See

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Contributions Welcomed
As always, your feedback and contributions are appreciated. ReliaSoft is able to provide the most user-friendly reliability software packages and support because we listen to our customers. This applies to our newsletters and publications as well. We welcome any suggestions or contributions you may have for Reliability HotWire. If you have a topic or article that you think would be useful to the readers of Reliability HotWire, feel free to contact us.

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