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is to preserve system function rather than to keep an asset in service.
Applications of RCM require a full understanding of the function of
physical asset, and the nature of failures related to these functions. It
recognizes that the not all failure are created equal, and some failures
cannot be prevented by overhaul or preventive replacement. Thus,
maintenance actions that are not cost-effective in preserving system
function will not be performed [3].
The RCM methodology develops the appropriate
maintenance tactics through a thorough and rigorous decision process,
as show in Figure 1 [4].
Select
Equipment
(Assess
Criticality)
Failure
Mode &
Effect
Criticality
Analysis
Failure Data
Analysis
Maintenance
Task
Analysis &
Selection
Figure 1 The RCM process.
Implement &
Refine the
maintenance
plan
3.1 Machines Criticality
Criticality of each machine (MC) was calculated based on
the following four criteria: effect of the machine downtime on the
production process (EM), utilization rate of the machine (Bottleneck or
not) (UR), safety and environmental incidence of machine failure
(SEI), technical complexity of the machine and need of external
maintenance resources (MTC) [5].
Each of the criteria was given a weight showing its
importance relative to the criticality indices. The weight of each
criterion ranges from zero (no effect) to three (very important effect).
Machine criticality was then calculated using the following formula:
MC = 3*EM + 2*UR + 3*SEI + 1*MTC (1)
3.2 Failure Mode and Effect Criticality Analysis
FMEA techniques were used to calculate the risk priority
number (RPN) to rank the causes and consequences of failure or
frustration. Including the severity (S), occurrence (O) and detection (D)
by the following formula [6]:
RPN = (S) × (O) × (D) (2)
RPN can be used to make risk evaluations as follows: the
risk is slightly (RPN