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Basic calculations |
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Basic calculations |
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Basic calculations
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Basic calculations |
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Basic calculations |
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The following formulas are used to calculate reliability and availability of basic RBD models:
Configuration |
Reliability R, Unreliability UR |
Availability A, Unavailability UA |
|---|---|---|
Serial configuration
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R = Ra*Rb UR = URa+URb - URa*URb |
A = Aa*Ab UA = UAa+UAb - UAa*UAb |
Parallel configuration
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R = 1-(1-Ra)*(1-Rb) UR = URa*URb |
A = 1-(1-Aa)*(1-Ab) UA = UAa*UAb |
Reliability and Availability calculation of individual blocks is explained in previous paragraphs - Reliability Distributions.
For complex model RBD diagrams, diagram breakdown to basic models described above is performed and calculation is done using the same principles and formulas.
Consider for example the following diagram:
First, the serial segment containing blocks A and C is calculated, resulting in Rac = Ra*Rc.
Then serial segment is considered a single block AC which is parallel to block B, and reliability of the whole system R is calculated as reliability of two parallel blocks AC and B, so R = 1-(1-Rac)*(1-Rb).
