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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: Jean-Marie Cloarec (Jean-Marie.cloarec@ligeron.com )
Organization:LIGERON S.A.
Date posted: Wed Mar 29 9:30:06 US/Eastern 2000
Subject: Maintainability Allocation
Message:
During reliability allocation, I understand that I need to know each component quantity. But for maintainability allocation, do I need this quantity. For example, there’s 4 wheels on a car, if I lost one wheel, I can allocate its MTTR, but if I take in account the 4 wheels, the MTTR will increase, but, in fact, for each wheel I must have the same MTTR. I made a simulation and I find, say, ½ hour for a wheel, but with the quantity 4, I find ¾ hour. So do I must take in account the quantity for the same component for maintainability allocation.


Reply:

Subject: Maintainability Allocation
Reply Posted by: Ned Criscimagna (ncriscimagna@alionscience.com )
Organization: IIT Research Institute (RAC)
Date Posted: Thu Mar 30 8:06:28 US/Eastern 2000
Message:
In allocating system-level maintainability requirements, such as MTTR, down to lower levels of indenture, it is necessary to account for the quantity of a given item. In his book "Logistics Engineering and Management," (Prentice-Hall, 4th Edition, 1991) Dr. Benjamin Blanchard provides a good example of how to allocate Mean Corrective Maintenance Time (the same parameter as MTTR). The system MTTR is a function of both the frequency with which repairs are required and the length of time needed to make each repair. Since the quantity of a given item is one factor that determines the frequency of system failure, you must account for the quantity in the allocation process.


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