Forum: Reliability & Maintainability Questions and Answers
Posted by: Bryant Date posted: Fri Dec 6 8:51:22 US/Eastern 2002 Subject: MTBF for complex electromechanical system Message: I just want some advice on which distribution should i use to model complex electromechanical system for example army vehicle? Some advice me to use exponential distribution. Can advice? Secondly MTBF only applies to exponential distribution but in actual fact, the vehicle will wear out sooner or later. So for my spares provisioning model should i use MTBF or MTTF values to be more realistic?
Posted by: Andrew Rowland (darowland@aep.com ) Date posted: Wed Dec 4 12:26:23 US/Eastern 2002 Subject: Life Data Analysis Message: I am trying to perform life data analysis which I plan to roll-up to an RBD. I am doing this to provide examples in an attempt to convince management that these analyses are important for an organization concerned with reliability. Obviously, it will be more poignant if I use actual plant systems, but I want to ensure that my results are the best they can be. In light of this, I have a couple of questions. I thank you in advance for your input. The system I have chosen to model is comprised of four identical “channels” of electronics. System level functions are satisfied by a 2-out-of-4 arrangement of the channels. The system has been in service for 25 years (late 70’s). Use of a computerized failure reporting system began in May 1991. Thus, the date of failures and time taken to repair each failure after May 1991 are easy to obtain. However, there is no failure data for the system prior to May 1991. The only thing I know for certain is that each channel operated failure free from May 1991 until the first failure was reported. Intuitively, the first failure found in the computerized system for each channel would be a right censored data point. The time of suspension would be the date of failure minus May 1991. Is this the correct way to treat this situation when performing life data analysis? Would the model developed only be applicable to a channel during the 15-25 year portion of it’s life? That is, I couldn’t expect my model to describe the behavior of a channel that was “brand new”.
Posted by: Wayne Date posted: Fri Nov 29 10:37:21 US/Eastern 2002 Subject: MTBF or service life?? Message: I often see supplier's specifications on things like for example a motor having an MTBF of 150,000hrs with a service life of 10 yrs. The MTBF greatly exceeds its service life. Is that possible? I thought that MTBF should be lower than service to make sense? So which figure do i use as my input for my reliability analysis of a complete system? MTBF or service life?
Posted by: John Hoegbraathen (john.sigurd.hogbrathen@kongsberg-simrad.com ) Organization:Kongsberg Simrad AS Date posted: Mon Nov 25 9:24:04 US/Eastern 2002 Subject: Test for ESD failure Message: Is it any known test method, described by a standard or any other paper, to be sure of whether a electronic component or circuit is damaged by ESD or not.
Posted by: Wee Teck Hoon (wteckhoo@dso.org.sg ) Date posted: Fri Nov 22 1:41:47 US/Eastern 2002 Subject: Integrated Diagnostics Message: Appreciate anyone who can enlighten me and refer me to good references on the subject of Integrated Diagnostics.
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