To approach maintenance performance improvement, it is useful to understand the relationships between the four quadrants within the model and what returns each provides in terms of improved machine performance. The best independent information known to the author comes from the DuPont model of Up-Time (Ledet. 1994) featured in the Manufacturing Game1. This model illustrates the relationships between the various elements of the Reliability Assurance four quadrant model. The table below illustrates how Ledet has modelled the relative effect of various strategies on plant uptime.
Table showing the effect of different reliability
engineering activities on plant availability taken from the
Manufacturing Game and subsequent work by Ledet.
Ledet’s analysis suggests that if
companies focus on planning only they will improve their uptime by
0.5%. If they focus only on maintenance scheduling, uptime will
improve by 0.8%. If they focus on preventive and predictive
maintenance only, uptime will actually get worse by 2.4%. If
organisations focus on all of these three aspects, they will gain a
5.1% improvement in availability.
These results may well sound appealing in their own right, but
subsequent to the report, Ledet found that by adding defect
elimination to the initiatives undertaken, a further 9.7% (taking
the total improvement to14.8%) improvement in availability may be
achieved in their plants. This information is provided in the
following table.
The relationships between the four quadrants of Reliability
Assurance and the process elements studied by
Ledet
This relationship suggests that
improving planning and scheduling by implementing a CMMS without a
having a focussed PM program will not generate significant returns.
Similarly, working hard at developing a focussed PM program without
a good planning and scheduling system will not generate significant
returns either. The suggestion is that organisations should work on
their CMMS planning and scheduling systems and their maintenance
strategy development as well.
The other important factor is that the defect elimination process
is the process that provides the most improvement opportunity. If
this is the case, then the intuitive approach to secure improvement
would be to focus on defect elimination first and then work on the
other elements.
This approach will not work without a strong foundation of
preventive maintenance. This is because without good preventive
maintenance, reactive maintenance will prevail. In reactive mode, a
high percentage of the failures will be cause by a lack of
maintenance, not inherent problems with machinery design or
operating problems. In this situation, any program to work on
defects will, in all likelihood, be unable to determine if the
failure was due to lack of maintenance or design.
In addition, the volume of defects to analyse will probably be too
high to cover, making the defect elimination program exhaustive and
ineffective. The proposed starting point therefore must be to get
the fundamentals of effective PM in place which means that the
first step in launching an Reliability Assurance program is to
review the maintenance strategy.
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