Maintenance excellence and reliability have become prominent within the corporate agenda. This is particularly true of the
biopharmaceutical industry where such concepts are becoming more widely adopted in attempts to reduce risk and reduce costs.
Many techniques, however, are still in their infancy, and while leaders are pressing for wider adoption, organizations are
often slow to adopt these techniques because many of the new concepts are counter-cultural.
This article focuses on common misconceptions that can be encountered by those spear-heading the change and introduces some
of the key concepts behind reliability engineering. This article also summarizes a detailed white paper created by the authors
MISCONCEPTION: PREVENTIVE MAINTENANCE CAN PREVENT ALL FAILURES
Failure is an unfortunate fact of life. Systems have a natural tendency to break and wear out, and the components of any asset
are subject to the effects of wear and tear. Eventually, components fail. It is a common misconception that simply because
preventive maintenance is employed, the risk of failure can be eliminated. While preventive maintenance can reduce the risk
of failure, so long as the failure mode exists, the risk of failure remains.
Reliability is about managing the probability of failure over time. Contrary to popular belief, only a small percentage of
equipment ages or wears out at the end of its expected life (see Sidebar). In practice, most failures occur in early life—infant mortality—or completely randomly at any point in its life (2).
The reality of failure (2)
By understanding the failure mode, appropriate maintenance strategies can be established to help detect, prevent, or mitigate
failure and improve the reliability of a component. Nevertheless, 100% reliability can never be guaranteed in reality so long
as the failure mode still exists.
MISCONCEPTION: ALL PREVENTIVE MAINTENANCE IS TIME-BASED
Historically, the biopharmaceutical industry has adopted mainly time-based maintenance but, in fact, other more effective
strategies can often be used. Increasingly, the industry is adopting predictive and condition-based techniques to anticipate
failure ahead of time. These techniques enable repairs to be planned and scheduled in a controlled manner, well before failure.
Preventive maintenance can be divided into three categories:
- Time-based or age-related. This type of preventive maintenance applies where the failure rate increases over time. This pattern
applies only to a small percentage of failures in the real world. Clearly, it does not make sense for this to be a primary
approach to preventive maintenance.
- Run-based or usage-related. This type of preventive maintenance is a development of time-based approach and applies where
the failure rate increases with usage, for example a valve diaphragm deteriorating through thermal cycles.
- Predictive or conditioned-based. This type of preventive maintenance applies to situations in which failure rates appear randomly,
where neither time nor usage provides good early failure indicators. This is the most common pattern of failure and, to be
truly effective, preventive maintenance programs should reflect this fact.
In the biopharmaceutical industry, vibration monitoring of bearings, motors, and gearboxes in plant and equipment is increasingly
common practice, where an increase in detected vibration can be used to indicate failure. Such systems provide a step increase
in reliability compared to invasive time-based replacement. Similarly, thermography can be used to monitor the condition of
electrical controls to signal early onset of failure. On the manufacturing floor, visual inspections carried out by operators
provide early signals as part of a structured total productive maintenance system.