Mechanical Technology February 2015

⎪ 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.

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

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

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

Mechanical Technology — February 2015

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