3.2. Methods and tools for the calculation of the condition of technical systems and priority building
By using different data sources from which information can be obtained, the state of a considered object can be
assessed. However, in this step, a further comparative analysis has to be made. This is necessary because the technical
condition alone is not sufficient to achieve an optimal technical and economic order planning and control in the
whole socio-technical maintenance system. Assuming limited resources (i.e. technicians, vehicles or accessibility) a
priority, an assessment of maintenance orders has to be done. Existing processes tend to follow the execution of the
orders in the order of their occurrence (i.e. FIFO - First In First Out). Here, the available information is intended to
enable sound sequence planning based on priority criteria.
The available information from which a prioritization of maintenance activities can be done has to comprise
various factors:
x Condition-Monitoring Technology
The introduced condition monitoring technology combined with a variety of diagnostic and prognostic methods
allows the prediction of an expected failure point with a corresponding uncertainty of the calculation method. As
a result, an observed object gets more forecast values due to using different methods. This is in the first instance
desirable and may increase the prediction quality.
x Cyclic Maintenance
Under the assumption that cyclical maintenance will continue to be carried out to identify particular not technically
observable failure modes at an early stage, the maintenance plan provides a statistically calculated date or
one which has been derived by the manufacturer's specifications, including a maximum allowable tolerance.
x Unexpected Damage Reports
Damage reports of sudden events usually lead directly to a high priority when the system is no longer applicable.
Other aspects for a high prioritization are the potential of significant losses or the risk of failure of other components.
Minor damage in which the system nevertheless continues to be operated, get a lower priority.
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x Importance of Considered Components
Furthermore, detailed information on the importance of considered components with respect to consequential
damages, costs, etc. are indications for a prioritization.
In conclusion, different sources of information have to be included for the assignment of a priority. The following
basic priority relations could be considered in the prioritization:
x If the calculated date is close to today's date, the priority increases.
x If the uncertainty of the calculated date is very high, the priority increases.
x If the component has a high degree of importance in the system, the priority increases.
x If the maintenance schedule of a cyclic maintenance is close to the current date, the priority increases.
x If the tolerance of the calculated date is high, the priority is lowered.
x etc.
The main task now is to bring together the information and rules by means of appropriate valuation methods. Out
of this, there derives a priority number and the ability to build an order sequence. The constraints that will be applied
may have an influence on the calculation and make this task more difficult. For example, a weighting could be made
based on a pairwise comparison of all criteria. An important paradigm should also be that algorithms that provide a
similar and reproducible result, experience a higher weighting.