We use HALT here at Schweitzer Engineering Labs to help improve the reliability of power protection relays (devices that among other things control circuit breakers on power lines, using measured currents and voltages to detect faults). We want to have MTBF times in hundreds of years, so that if the lights go out in Los Angeles, it was caused by something besides our relays. In my previous life at Hewlett-Packard/Agilent Technology, we used HALT, sometimes HASS, and MTBF calculations to improve product reliability. One engineer did a comparison of the failures of a certain product predicted using MTBF calculations on components vs. actual field failures. The correlation was suprisingly good. I can't exactly remember the sorting technique, but the conclusion was that 85% of the component failures in the field were found at the top of the components list sorted by MTBF. My observation is that MTBF calculations help you design out the worst offenders, and pay special attention to those potentially high failure rate parts that cannot be designed out. HALT helps catch those things that fall through the cracks, either because their life characteristics are not known, someone made a mistake, or there are process problems (either at the manufacturer or in your own plant) which cause higher than expected failure rates. The last cause if the most problematical. You can have a component that has a low predicted failure rate, has been tested over and over, even in your own HALT program, and later becomes a big problem when the manufacturer loses the recipe. Don Borowski Schweitzer Engineering Labs "Brian O'Connell" <[email protected]> on 08/01/2002 06:53:59 AM Please respond to "Brian O'Connell" <[email protected]> To: "[email protected]" <[email protected]> cc: (bcc: Don Borowski/SEL) Subject: RE: HALT and HAAS Interesting observations from all. I would appreciate if the good people that posted on this subject could reveal the item, or product category being tested. It would be interesting to see the "relative relevance" of each test or analysis technique (e.g., MH217, HALT, HASS, ESS, etc) to the product's short and long-term performance. In my current job, I apply HALT and MTBF calculations to component power supplies. HALT seems to quickly reveal a physical or electronic design weakness. But once (manager-selected) design flaws have been removed, HALT does not seem to predict which component is likely to fail over the power supply's life. I have researched some of my employer's MTBF reports and found most to accurately predict failure modes. Brian ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" This e-mail may contain SEL confidential information. The opinions expressed are not necessarily those of SEL. Any unauthorized disclosure, distribution or other use is prohibited. If you received this e-mail in error, please notify the sender, permanently delete it, and destroy any printout. Thank you. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
