+
−
−
+
−
−
=
k
k
n
n
fs
t
t
n
T
fs
fs
r
P
r
r
r
À
T
)
1
(
1
1
, (10)
Non-repairable system consists of irreplaceable non-repairable elements. Its
functional condition may be displayed, as shown in Fig. 6.
Figure 6. Functional condition alteration of non-repairable system throughout
operation period Т
where t
max
– maximum term of operation of the system corresponding to term of
operation of an element with minimum operation lifetime. The system’s functional
condition will be equal to summarized conditions of constructive and non-constructive
components:
=
i
T
fs
FS
,
(11)
These systems are run by consumers throughout their entire lifetime with only
initial components. Therefore such systems don’t require either maintenance, or
repairs, or replacement of any particular elements.
Alterations in repairable system’s functional condition with the course of time
have a non uniform structure, which, in its turn, may experience alterations depending
on operational conditions. It may be represented graphically in coordinates, as below
(Fig. 7).
System falling into this category are operated throughout their entire lifetime
provided periodical renewal of their non-constructive elements within various terms
and periodical replacement of a part of constructive elements within various terms are
performed. In essence, consumers carry on maintenance and repairs of the system
subject to a certain schedule. It should be also noted that replacement and repairs of
both constructive and non-constructive elements may take place either within terms of
Т
fs
0
FS
T
t
FS
t
max
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