Mechanical Technology may 2015

⎪ Proactive maintenance, lubrication and contamination management ⎪

Progressive strategies in proactive maintenance

In this issue’s maintenance column, Mario Kuisis describes the importance of categorising assets into appropriate maintenance strategies and to progressively introduce new approaches as maintenance maturity grows.

Mario on maintenance:

T he first article in this series dis- cussed the evolution of mainte- nance strategies as we see them today, broadly described under the terms passive, reactive, preventative, predictive and proactive. It was shown that an optimised asset management system would invariably incorporate all of these strategies, in a mix to suit the type and criticality of the asset as it pertains to the owner. It sounds perfectly logical, but how to go about it practically? A good place to start is to categorise assets in terms of the strategy to be adopted. Just like planning, it needs some time out to take in the big picture. This is beneficial for many reasons, but the following are important in the context of proactive maintenance: • It will bring focus to the assets that really matter. • At a later stage, when considering predictive maintenance, it minimises the investment needed. Let’s consider the kind of thinking that goes into categorising assets by mainte- nance strategy. Any asset or component that is low

way with appropriate specifications and quality processes in place. The internal resources could include trained per- sonnel, strategic spares, special tools, handling equipment, etc. Typically, no operational costs are incurred, other than possibly the holding of strategic spares. Preventative maintenance becomes attractive when the consequences of fail- ure justify it. This can be due to high cost and complexity of repair or replacement and/or when significant loss of production is a likely result. Safety, environmental, reputational and other consequential risks associated with failure are also increasingly important. If these outweigh the costs of conducting reactive mainte- nance, then it is an appropriate strategy for the asset in question. The important point is to think about these factors and make the best business decision, but there are no hard and fast rules and the process also needs repeat- ing every few years as circumstances change. The extent and frequency of preventative maintenance can of course also be adapted. Usually, the OEM will provide all the information necessary for internal preventative maintenance or for outsourcing to third parties. For some specialised equipment, the OEM may be engaged to advantage. If one were to stop here, life for the maintenance practitioner would be rela- tively easy. Unfortunately, it is no longer good enough for most industrial plants and utilities because the unplanned outages that would result thrust to the heart of competitiveness, quality of supply and reputation. Often safety and the environment are also at play. In the end, business sustainability itself can be threatened. Hence, a more proactive approach is required. The next step in the chain of progres- sion is, therefore, to consider which as- sets would benefit from predictive main- tenance . This is a crucial step in many ways and more complex than it would appear. But what do we mean by predic- tive maintenance? In this discussion the

cost, quick and easy to repair or replace and has no significant production, safety, environmental, consequential or reputa- tional risk associated with its failure is eligible for passive maintenance. Passive maintenance requires no further con- sideration in respect of the categorised asset, as there is nothing to do. It only requires a decision to identify which assets are appropriate choices for this maintenance strategy. Reactive maintenance is a good option when there are no significant production, safety, environmental, conse- quential or reputational risks associated with failure, but repair or replacement is a moderate cost and/or not straightfor- ward. In this case, foresight is required to prepare for the eventuality, so that when failure does occur (as it will), there is a known process to repair or replace the faulty asset in as short a time frame as the situation demands. This may mean ensuring availability of internal resources and establishing a relationship with a preferred service pro- vider so as to affect repair or replacement without undue delay in a cost effective

An SDT ultrasound detector is being used here to determine the optimum lubrication level for a bearing. This exemplifies how predictive maintenance tools and techniques can be added to a preventative mainte- nance strategy to further failure.

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Mechanical Technology — May 2015