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First the Question:
Fred,
Early in the FMEA lecture you worked through a homework problem and you mentioned that a cdf may not be linear (hence the reason for giving three points in a reliability goal). Can you give an example of two of things you’ve seen with non-linear cdf’s? I’ve only done limited reliability testing at this point, but everything I’ve done and every example I’ve ever seen have had linear cdf’s.
Thanks,
John
And, my response: [Read more…]
In a recent LinkedIn post a fellow Reliability Engineer is asking the Reliability Engineering community in how to prepare for the CRE exam. Rapidly everyone is recommending books, study groups, and training courses. My recommendation to anyone taking the CRE exam is to be very familiar with your approved ASQ calculator. Here is a link that I found in [Read more…]
EAM & CMMS Systems, 10 times more data in the system or 10 time less done with the data available?.
A nice short article about the problem of data, data, too much data.
The CRE_Errata_9-26-2011_revised document is in pdf format and contains a couple of typos noted by John Cooper in the Indiana Council CRE prep materials – he has taught the CRE Prep course for Ops A La Carte and is a pretty good teacher and a CRE. [Read more…]
Recently a colleague sent me a published copy of the first CRE exam. Scanning through the document suggests that a few things have changed and many have not changed at all. I often comment my enjoyment of the reliability engineering profession, as it doesn’t change too fast and even I can keep up. [Read more…]
A reliability block diagram (RBD) for a product that has no redundancy or complex use profile is often very simple. A series system (reliability wise) implies that any one part or element of the product that fails the entire product fails. One might ask if an RBD is even necessary. [Read more…]
This is provided courtesy of Amanda at
Egerton Consulting Ltd
Visit our website at www.egertonconsulting.co.uk
<They have a great newsletter and worth subscribing. Fred> [Read more…]
Let’s say we have a product that most often fails for one major component. Let’s say a fan (it could be anything, and while I don’t have anything against fans, it’s easy to picture).
Ok, this fan has a data sheet with the classic reliability claim of 50,000 hours MTBF. For those that know about my disdain for MTBF (www.nomtbf.com) rest assured I’m not going to get into it here. The basic approach for estimating the number of failure during any [Read more…]
A part of the preparation for the ASQ CRE is experience and education. These, in my simple way of thinking, means applying what you have learned to solve problems and provide value. Reliability engineering is about two questions: [Read more…]
Hi Fred,
I would take this opportunity to ask the reliability guru about bathtub curve for hardware reliability. I am running 27 units for life test for a million cycles around 555 hours. I have one failure at 300,000 cycles, and the rest of the units are running fine. Would this be classified as an early life failure? Also, how do I make a determination of when the early life failure time interval ends and constant failure rate starts in this example based on failure rate of remaining units? Thanks. [Read more…]
Update:
I forwarded the note below to QCI for comment and asked if they have an errata available. They do.
The QCI errata is posted on [the] website. [Read more…]
Reading a datasheet to determine a reliability value may take some investigative work. Whenever I see a fit rate based on failure-free testing, I am curious about how they did the testing and the calculations. [Read more…]
During design and development, Reliability Engineers often receive reliability parameters in many forms. The most common reliability parameter is the mean time to failure (MTTF), which can also be specified as the failure rate (this is expressed as a frequency or Conditional Probability Density Function (PDF)) or the number of failures during a given period. [Read more…]
Speaking reliability-wise, parallel, means any of the elements in parallel structure permit the system to function. This does not mean they are physically parallel (in all cases), as capacitors in parallel provide a specific behavior in the circuit and if one capacitor fails that system might fail.
In this simple drawing, there are n components in parallel and any one component is needed for the system to function. [Read more…]
The annual salary survey done by American Society for Quality (ASQ) is summarized in the December 2011 issue. And, the good news is a CRE certification provides approximately a $21k salary premium over those in similar positions without the certification. Based on Table 2. salary premiums for certification holders in the article, Land the Big One, indicated the largest premium is [Read more…]
