Plant Services - August 2008 - (Page 50) WEB HUNTER to highlight here. You’ll need to explore it on your own. But, you might want to start by opening the home page and scrolling down to the section called “Handy Tools & Information” and click the entry titled “Problems of The Month.” This gives you links to a selection of articles that explain how Weibull analysis can be applied to pump seals, relief valves, process reliability and other practical concerns in the typical plant setting. Look for the article about NASA. It’s a study in the simplicity of two points determining a line on a Weibull chart. In spite of the fact that only two space shuttles have experienced fatal crashes, Weibull analysis uses that pair of data points to predict when the next will how this is done is operated by Quanterion Solutions Inc., Utica, N.Y. For a concise description of the input data and the interpretation of the analytical results, with none of those perhaps confusing, intervening mathematical machinations, go to http://quanterion.com/ReliabilityQues and click on the link to the article titled “Which Design is More Reliable? Weibull Provides Answers!” Be forewarned, the several offers of free stuff you’ll see on this site require you to register your e-mail address, if not your entire identity. Bedtime reading The concepts underlying Weibull analysis provide powerful, objective evidence about the efficacy of the current maintenance philosophy the plant is using. occur, assuming NASA keeps the craft flying while maintaining its current reliability trend. Then, check out the link to “Free (Or Low-Cost) Software” to investigate, among other things, the RAPTOR software he military that models reliability, availability and maintainability. Case in point A protocol related to Weibull analysis goes by the name CrowAMSAA. It was originally developed for the U.S. Army Materiel Systems Analysis Activity, hence the AMSAA acronym. And, it was Dr. Larry H. Crow who realized it could be represented as a Weibull process. Because you didn’t ask how to build a watch, I now direct your attention to a case study that used the Crow-AMSAA technique to analyze the forced outages and reliability at a New Zealand power-generating station. The first six pages of this 22-page presentation cover the background and justification for the work. It’s on that seventh page that the data analysis begins and continues through subsequent pages to explain how and why various conclusions became obvious. It might not be incredibly detailed, but it gives a flavor of the power of quantifying reliability gains or losses. The paper is posted at www.plant-maintenance.com/articles/ Crow-AMSAA.pdf for your edification. Weibull analysis is only one of many approaches to modeling your reliability data. The good folks at The Statistical Engineering Division of NIST’s Information Technology Laboratory, Gaithersburg, Md., know about all of them and is willing to impart its collective wisdom to those of us who fund their efforts through our taxes. In fact, the Laboratory has an online handbook that should serve you well if you’re into numbers and maintenance statistics. Put on your reading glasses and crack the cover on www.itl.nist.gov/div898. Listed under the “Products and Services” heading at the center of the page is a link to the “NIST/SEMATECH Engineering Statistics Handbook.” This is a biggie – you’ll wind up with more than 3,100 pages if you download the entire PDF version, an action definitely not recommended. Instead, use the search feature on the left side. Enter “Weibull” and look for the entry named “1.3.6.6.8. Weibull Distribution.” Then, read about Weibull and take advantage of the many links to cross-referenced pages. You’ll definitely want to investigate the software offerings also shown under the “Products and Services” heading. When the page opens, take a look at Dataplot, a software package for graphical analysis on data you furnish. When you get to the Dataplot home page, click on “Dataplot Summary” to see the 17 broad categories of analysis it will handle. And each category has a string of subcategories and finer gradations. Even if you have no practical application for the software, at least tell some college engineering undergrad about it. From your peers For product selection Weibull analysis helps if you need to choose the most reliable product, assuming that the competing vendors provide life cycle test data or you subject the designs to your own run-to-failure field testing. A Web resource that explains 50 The concepts underlying Weibull analysis provide powerful, objective evidence about the efficacy of the current maintenance philosophy the plant is using. Despite the fact that the technique has been available for some time, its reliance on heavy mathematics and the user’s uncertainty about its applicability to a given situation can be off-putting. Well, friends, there’s no sense trying to reinvent the Weibull wheel when many of your associates in industry have gone this way before you. How would you like to tap into an online forum dediAugust 2008 www.PLANTSERVICES.com http://quanterion.com/ReliabilityQues http://www.itl.nist.gov/div898 http://www.plant-maintenance.com/articles/Crow-AMSAA.pdf http://www.plant-maintenance.com/articles/Crow-AMSAA.pdf http://www.PLANTSERVICES.com
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.