Environmental Engineering Reference
In-Depth Information
Figure 20. Reliability block diagrams of two-channel redundant system
Figure 21. Simplified structure of single-channel
three-track system
2
−
3
(
)
2
(
)
2
P
=
− −
P
P
3 1
1
2 1
− −
1
M
ph
ph
2
(
)
2
P
− −
P
P
1
1
M
dr
da
(11)
MVS reliability analysis:
If we express the
values of a reliability (probability of no-failure
operation) through failure rates as
P
=
e
-λt
, we
can calculate and compare the values of reliability
for certain values of
λ
ph
,
λ
d
,
λ
M
,
λ
dr
,
λ
da
and
β
(the
fraction of absolute design faults).
Dependence of
P
1D
,
P
2D
,
P
1M
and
P
2M
(Equations
8, 9, 10 and 11)) on the time is graphically shown
in Figure 23. In the calculations the following
values of the failure rate were used
λ
ph
=10
-4
1/h,
λ
d
=
λ
ph
/2,
λ
M
=
λ
ph
/100,
λ
dr
=(1-
β
)×
λ
d
,
λ
da
=
β
×
λ
d
,
where
β
=0,1.
Figure 24 shows how a fraction of absolute
design faults (FADF is
β
) effects on a reliability
of a single-channel divers system.
2
(
)
2
− −
P
−
3 1
1
ph
P
=
P
M d
(10)
1
M
3
(
)
2
− −
P
2 1
1
ph
In case of using two different versions for
T
1.i
and
T
2.i
, system has RBD, shown in Figure 22, b,
and a formula for reliability calculation:
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