Referring to functional condition alteration constructive elements should be
classified into four groups, non-replaceable non-reparable (1), replaceable non-
reparable (2), non-replaceable reparable (3) and replaceable reparable (4).
Below alterations in system’s elements are reviewed from group to group and
their functional dependence is identified and formalized.
Non-replaceable and non-repairable elements are elements which cannot be
replaced or reconditioned throughout their entire lifetime due to their construction or
other features. Functional condition of such elements is the same and formed only at
plants or factories producing machinery or construction elements. For example, they
may include various basic parts with relatively large mass and cost, repairs of which
may be non-feasible from economic point of view [2].
Functional state of irreplaceable non-repairable elements decreases downwards
with decreasing rate depending on operation conditions prevailing with such an
element. Relation between functional condition and time is often displayed applying
either of distribution principle, whether normal, or exponential, or Waybull’s
distribution, or their modifications. However, application efficiency for either of
mentioned principles is positively related with a quantity of available data about the
relevant element. In other words, if the matter concerns an element only known as
irreplaceable and non-repairable, its functional condition may be sufficiently
forecasted applying a linear distribution principle. The above statement may be
displayed in coordinate system, as shown in Fig 2.
As shown in Fig. 2 fs
0
– element’s functional state at the beginning of its operation
in a system, fs
Т
– element’s functional condition upon expiration of a certain interval
T, t
s
– service time of an element.
Figure 2. Alteration in functional condition for irreplaceable non-repairable
element during operation period T
Т
fs
0
fs
T
t
FS
t
s
- 1644 -