Mechanical Technology February 2015

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⎪ Proactive maintenance, lubrication and contamination management ⎪
or pie-in-the-sky?
is extended and consequential dam-
ages usually contained, but the time
to failure remains unknown. Risk is
therefore partially managed.
Predictive maintenance means main-
tain when necessary. Special tools and
techniques are used to acquire knowl-
edge of asset condition. Maintenance
is selectively performed in time and
appropriately scoped when a threat to
asset health is detected. Unexpected
failures are fewer and consequential
damage greatly reduced. Risk is there-
fore substantially managed.
Proactive maintenance combines
preventative with predictive. The best
of both means time before failure is
extended while unexpected failures
and consequential damage are mini-
mised. Risk is very well managed.
But what is risk in this context? It
will mean different things to different
people, but encompasses the threat to
the asset owner in terms of reputation
and financial, safety and environmental
consequences. For most organisations,
by far the greatest financial implication
is due to the loss of productivity.
Reading the above, anyone seeking
to improve maintenance might assume
that proactive maintenance must be the
best strategy to adopt. Unfortunately it is
not so simple – life never is. If reliability
improvement at any cost were the only
objective, then it would be true. However,
this is rarely the case. It must almost
always be balanced with cost consider-
ations. When this is done it will be seen
that every one of the maintenance strate-
gies has a place. A good example is what
we do in maintaining the average car:
• Passive maintenance – for lamp re-
placements.
• Reactive maintenance – in respect of
punctured tyres.
• Preventative maintenance – engine oil
changes.
• Predictive maintenance – engine oil
pressure monitoring.
We don’t keep spares for headlamps and
brake lights because the risk of failure
and the associated consequences are
small. We do keep a spare tyre because
the risk of becoming stranded is high. We
change the engine oil to extend engine life
and we monitor oil pressure because it is
a prime indicator of engine condition. If
it drops below an acceptable threshold
we know we must do maintenance on
the engine.
A key point to note is that most assets
today are complex, with multiple com-
ponents that require different strategies.
The costs and benefits associated with
implementing the strategies also differ
according to the asset. The real challenge
for the responsible maintenance manager
is therefore to decide which strategy to
adopt for a particular asset in order to
balance the benefit of asset reliability
with the cost of maintenance. A holistic
view is essential for an optimised system.
The rapid rise in popularity of predic-
tive techniques is mainly based on cost
benefits. However, keeping pace with
the rapid growth in this field is challeng-
ing. Future discussions in this series will
examine the exciting new technologies
that have become available and how
maintenance strategies are evolving to
take advantage of them.
So proactive maintenance is not a
panacea of all ills in maintenance, but
it is certainly worth including in your
organisation’s daily constitutional. q