xj25
Electrical
- May 7, 2011
- 110
Hi,
I am looking for a closed formulae or method for getting the composed MTBF of m redundant equipments of N total.
I.e. 8 pumps, I need 6 working to do the job.
MTBF of 1 pump is X, What is the MTBF_6_of_8_pumps_working?
I got this formula from "introduction to reliability engineering" of E.E.Lewis, John Wiley & Sons but just for 1 of N redundant equipments:
MTBF= Sum_from_1_to_N[ (-1)^(n-1) * C_N_n / (n*Lambda) ]
where C_N_n is de binominal coeficient, Lambda the failure rate, and n the summing variable.
in the same book there is a discussion about m/N redundancy and it gets to a probability of failure (p.o.f.) method stimation,
i.e. for the pumps:
if 1 pump has p.o.f. of 1% so with this method I get 99.994% of probability of at least 6 pumps running
Where I am lost is in how to change from this p.o.f. values to MTBF (if it is possible using i.e. the MTBF of 1 pump)
Thanks for reading!
I am looking for a closed formulae or method for getting the composed MTBF of m redundant equipments of N total.
I.e. 8 pumps, I need 6 working to do the job.
MTBF of 1 pump is X, What is the MTBF_6_of_8_pumps_working?
I got this formula from "introduction to reliability engineering" of E.E.Lewis, John Wiley & Sons but just for 1 of N redundant equipments:
MTBF= Sum_from_1_to_N[ (-1)^(n-1) * C_N_n / (n*Lambda) ]
where C_N_n is de binominal coeficient, Lambda the failure rate, and n the summing variable.
in the same book there is a discussion about m/N redundancy and it gets to a probability of failure (p.o.f.) method stimation,
i.e. for the pumps:
if 1 pump has p.o.f. of 1% so with this method I get 99.994% of probability of at least 6 pumps running
Where I am lost is in how to change from this p.o.f. values to MTBF (if it is possible using i.e. the MTBF of 1 pump)
Thanks for reading!