MISCONCEPTION: MORE FREQUENT MAINTENANCE LEADS TO INCREASED RELIABILITY
It is a fallacy that increasing frequency of invasive maintenance leads to better reliability. In many situations, opening
up a system to perform invasive maintenance may actually increase the chances of failure through the introduction of iatrogenic
Unfortunately, many preventive maintenance (PM) programs set maintenance frequencies using generic industry practices without
consideration of the asset and the operating environment. Worse still, time-based intervals are often arbitrarily tightened
in a knee-jerk response to failures and deviations.
Such actions can, in fact, worsen the situation by inadvertently introducing premature failure. A far more effective approach
is to understand the failure modes and develop specific strategies to address them, such as less invasive condition-based
MISCONCEPTION: ASSET FAILURE MEANS THE MAINTENANCE STRATEGY IS INEFFECTIVE
Asset failure could signal a failing in the maintenance strategy, but not necessarily. Further analysis and investigation
is required before a maintenance strategy is deemed to be ineffective.
The effectiveness of a maintenance strategy should be evaluated against targets such as quality, health and safety, environmental
integrity, production output, operating costs, etc. A preventive maintenance strategy cannot completely eliminate the risk
of failure. Failure with a low probability of occurrence may still occur, even under the most robust maintenance strategy.
This is not to say that we give up trying to improve reliability; on the contrary, periodic maintenance effectiveness reviews
are used to identify root causes of recurring failures and drive continuous improvement in reliability that are quantifiable
to the business.
An effective maintenance strategy manages asset failure to a tolerable risk, aligned with the business objectives. If you
are meeting your objectives, then the asset maintenance strategy is effective with respect to your business objectives.
MISCONCEPTION: ALL BIOPHARMACEUTICAL MAINTENANCE IS CRITICAL
If failure impacts product quality, then maintenance is critical, but if it doesn't have product impact, then it need not
be. In practice, only a small percentage of maintenance tasks are critical to product quality, the rest being there for business
The ISPE Good Practice Guide on Maintenance cites, "The maintenance program should help to ensure that the equipment is continually maintained in a qualified state and
is suitable for intended use" (3). The primary goal of maintenance in the biopharmaceutical industry is to reduce the risk
of a failure that may impact product drug quality. Not all functional failures of an asset, however, impact drug quality.
Differentiating between those failure modes that do and those that do not enables effort to be focused where it is needed
Having a maintenance strategy of run-to-failure is perfectly acceptable when a failure mode cannot be detected and the equipment
is deemed to be non-critical. Conversely, monitoring the condition of critical equipment provides constant assurance that
the equipment is safely operating in its qualified state, while providing early signals of wear that may lead to a failure
that affects product quality.
MISCONCEPTION: ANY DEVIATION FROM A PM SCHEDULE WILL LEAD TO EQUIPMENT NOT FIT FOR USE
The misconception that any deviation from a PM schedule will lead to equipment not fit for use is perhaps the most dangerous.
Performing critical maintenance outside the optimum time interval may increase the risk of a functional failure that impacts
the qualified state. Execution of PM outside of the optimum interval, however, does not in itself cause the asset to be no
longer qualified or suitable for intended use, unless the qualified state or suitability for use is dependent upon the execution
of the PM task at a specific point. In the majority of circumstances, this condition does not apply.
So, apart from a very small number of specific exceptions, deviation from a PM schedule increases risk, but does not directly
cause the asset to be no longer fit for use. This is not to say that PM tasks are unimportant; they are important because
they reduce risk and save money.
If an organization falls behind with its maintenance schedule, it is important to prioritize work so that the bigger risks
are still addressed and slippage is allowed only on the lower risk items. Schedule-adherence at an aggregate level, therefore,
provides a leading indicator on the risks that the business is running. When organizations fall behind, the most important
priority is to clear the backlog to get back on track.
Gerard Clarke is reliability engineer at Pfizer; James Baillargeon is instruments and control manager at MedImmune; Paul Boles is senior technical manager GMP manufacturing at Genentech; Rob Christman is associate director global Reliability engineering at Genzyme; and Steve Jones is director at BioPhorum Operations Group.
1. BPOG, Misconception of Maintenance and Reliability,
2. J. Moubray, Reliability Centered Maintenance, 2nd edition (Industrial Press Inc., 1997).
3. ISPE, Good Practice Guide on Maintenance (ISPE, March 2009).