Rate of Failure, Median Time Between Failures: power plant has 200 control valves....

Sparky91

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Apr 14, 2018
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Hello, first time posting so I hope I'm in the right spot.
I think I have the calculations correct, it's the interpretation of the the mean time between failure I'm having trouble with.

A coal fired powered plant has 200 control valves in service. After a period of five (5) years there are fifteen (15) failures. Five (5) years is well within the useful life of these control valves, none of the failures will be due to wear-out, but rather to random causes.

  1. Calculate the failure rate (λ)
  2. Calculate the mean time between failures (MTBF) for these control valves. MTBF is the reciprocal of (λ) lambda i.e. 1/ (λ)
Failure rate formula for the purpose of this calculation is
λ = (Nf/t) (1/No)

Where,
λ = Failure rate
Nf = Number of components failed during testing period
No = Total number of components in operation during test period
t = Time


My Working :-
1. (15/5)(1/200) = 0.015 Failure rate
2. 1/0.015 = 66.7 (66.6666666667) MTBF

Iv'e been pulling my hair out as how to convert the 66.7 to a usable time frame.

Any help is greatly appreciated.
 
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