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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Steve
Date posted: Thu May 10 10:05:49 US/Eastern 2001
Subject: Calculated Failure Rate vs. Field Failure Rate
Message:
Hello, I performed a reliability prediction based on TR-332, and the failure rate looks high. We believe that the real failure rate should be better. Since the product is brand-new, no field data available yet. Is there a ratio of calculated failure rate to field one? Or are there any references addressed this issue? BTW, the product is a telecomunication switch used in central office. Thanks in advance! Steve


Reply:

Subject: Calculated Failure Rate vs. Field Failure Rate
Reply Posted by: Gary Sunada (gsunada@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Fri May 11 10:47:20 US/Eastern 2001
Message:
Hello Ė Theoretically, performing a prediction using TR-332 (also known as Telecordia GR-332) should give you failure rates that approximate your future field data, so no factor adjustment should be necessary. However, this is dependent on a fairly large assumption: is the model based on current, accurate data? If you believe that there are unique circumstances that may not apply itself to the TR-332 model, you may prefer an alternative, such as RACís PRISM software, which is based on MIL-HDBK-217.


Reply:

Subject: Calculated Failure Rate vs. Field Failure Rate
Reply Posted by: Gary Sunada (gsunada@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Mon May 14 9:36:54 US/Eastern 2001
Message:
Allow me to make a correction on that last statement: to say that PRISM is based on the 217 is incorrect. It would be more proper to say that PRISM is the successor to the 217. I quote from PRISM's description: PRISM is the new Reliability Analysis Center (RAC) software tool that ties together several tools into a comprehensive system reliability prediction methodology. The PRISM concept accounts for the myriad of factors that can influence system reliability, combining all those factors into an integrated system reliability assessment resource. PRISM was developed to overcome inherent limitations in MIL-HDBK-217 that is no longer being actively maintained or updated by the Department of Defense (DoD). PRISM fills this void by providing a superior approach for reliability modeling under a broad range of applications.


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