Viewpoint: modern maintenance is a game of strategy

Damaged equipment and compromised safety are the all-too-common outcomes of cutting back maintenance budgets in the wrong places.

So, in order to remain competitive, plant managers are now turning to new maintenance strategies that are more closely matched to their own operations.

To ‘tailor’ a plan to a specific location, managers must be very familiar with their system, with a deep understanding of its weak points. This approach contrasts with traditional strategies such as ‘failure recovery’ and ‘condition monitoring’.

Failure recovery means that plant managers run plant components without engaging in any proactive maintenance. In this situation, the plant is operated until failure or a defect makes maintenance measures necessary.

To ‘tailor’ a plan to a specific location, managers must be very familiar with their system, with a deep understanding of its weak points

These plant managers may save on maintenance costs, but have no way of predicting unscheduled downtime.

Prevention of such unscheduled downtime is the objective of conditionbased and predictive maintenance strategies, which seek to carry out measures before a problem occurs.

Condition-based maintenance is based on continuous monitoring of the plant, with specialists preparing failure forecasts to ensure timely scheduling of necessary maintenance measures.

However, these strategies can result in excessive maintenance, as run levels of components and parts are not fully utilised.

Predictive maintenance also applies conceptual fault diagnosis to identify a plant’s weak points, which can be very time-intensive for personnel.

Risk-based approaches

Two alternative approaches experts are beginning to explore are risk-based maintenance (RBM) and reliability-centred maintenance (RCM).

RBM ranks possible risks that may result in plant failure, focusing on areas where it is highly probable that an incident might occur with very severe consequences.

As some plants – particularly large-scale locations with a high number of linked components – can be highly complex structures, systematic and practice-focused analysis is imperative.

An RCM approach examines plant components for malfunctions and provides an assessment of the possible consequences.

The dedicated use of these types of methods can improve plant availability while reducing costs, and by involving operating personnel, managers can also raise their awareness of the plant’s features.

Two alternative approaches experts are beginning to explore are risk-based maintenance (RBM) and reliability-centred maintenance (RCM)

These approaches often go hand-in-hand with total productive maintenance (TPM), a strategy that can be highly effective when choosing how to address quality losses caused by possible wear or malfunctions.

A fundamental question in choosing a maintenance strategy is whether operational experts prefer ‘deterministic’ or ‘probabilistic’ methods.

Deterministic methods are based on causal relationships and the ‘if-then’ principle. They rely on detailed knowledge of the individual components and therefore require extensive expertise, and have proved their worth in safety technology.

Probabilistic methods, by contrast, extend the ‘if-then relationships’ of the deterministic methods to include probabilities. This approach gives preference to certain maintenance measures and can ultimately reduce costs.

People power

So, is there such a thing as the perfect strategy? Improving efficiency while also maintaining a high level of safety is only possible where experts deploy maintenance strategies that take into account the plant’s particular features and characteristics.

For example, defects such as cracks, identified in non-destructive testing, only need to be repaired if fracture mechanics and risk analysis demonstrate that they cannot be tolerated under the defined service parameters.

The more sophisticated the maintenance strategies, the higher the importance that qualified personnel support their realisation by conducting integrated analysis of plants and systems

But the more sophisticated the maintenance strategies, the higher the importance that qualified personnel support their realisation by conducting integrated analysis of plants and systems.

Plant managers who wish to stay competitive in the long run need to take a practice-focused and solution-oriented approach and analyse the possibilities that modern maintenance strategies offer for the respective plant.

This is only possible with knowledge of the individual operating behaviour and reliable data.

• Hans Christian Schröder is the senior expert for power plants at TÜV SÜD Industrie Service.