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: Stefano Stanghellini (stefano.stanghellini@transport.alstom.com )
Organization:ALSTOM TRANSPORT IS
Date posted: Thu May 23 9:51:57 US/Eastern 2002
Subject: Reliability assumption
Message:
I performed a safety study where only some particulare failure modes can cause the hazardous situation. In particualar I have to evaluate what is the probability to have railway signal blinking due toa failure. The situation is dangerous only if the signal blinks with a frequency i a range between 0.1 to 10 Hz. In my analysis I identified some integrated circuit which can self oscillate due to a failure and cause the dangerous situation. The considered components are designed to work till a frequency of about some Mhz. Because I have no information available about the failure mode distribuition, in my analysis I consider that the probability to fail at a certain frequency is homogemeous. In this way for the hazardous failure rate I considered a ratio of the total failure rate. The ratio I took into account was equal to: (dangerous frequency)/1Mhz. Somebody ask me to justify this assumption because seems to be not conservative. Can anybody help me? Is there some data i leterature about this kind of failure?

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