"We already do preventive maintenance — so we're doing reliability engineering, right?" This is one of the most common misconceptions we encounter working with WA industrial operations. The answer is no. And understanding why matters — because the confusion leads operations to invest in the wrong things, measure the wrong outcomes, and wonder why their maintenance spend keeps rising without a corresponding improvement in equipment performance.
Preventive maintenance asks: "What do we maintain, and when?"
Reliability engineering asks: "What is the right way to maintain it — and why?"
Both are necessary. They serve fundamentally different purposes.
Preventive maintenance (PM) is the practice of performing maintenance activities on a defined schedule — before failure occurs. Oil changes at defined intervals. Bearing replacements at defined hours. Seal inspections at defined frequencies. It is task-based. It answers the operational question: what do we need to do, and when? It is essential. Without some form of planned maintenance, operations degrade into pure reactive mode — the most expensive and dangerous way to run plant.
But PM programs have a fundamental limitation: they don't tell you whether the tasks you are performing are the right ones, at the right frequency, for the right reasons. Most PM programs accumulate tasks over time — tasks added after failures, tasks inherited from previous operators, tasks recommended by OEM manuals written for generic applications. The result is often a program that is simultaneously over-maintaining some assets and under-maintaining others, with significant resources directed at low-value activities.
Reliability engineering is the discipline of understanding why assets fail, determining the appropriate maintenance strategy for each failure mode, and continuously improving asset performance over time. It answers a different set of questions:
Which failures actually matter to production, safety, and cost?
What causes this specific failure mode — and what is the most effective way to address it?
Is time-based maintenance the right strategy for this failure mode — or is condition-based monitoring more effective?
What is the optimal maintenance interval — based on failure characteristics, not convention?
How do we measure whether our maintenance program is actually working?
Reliability engineering uses tools like RCM (Reliability Centred Maintenance), RCA (Root Cause Analysis), FMEA (Failure Mode and Effects Analysis), and asset criticality assessment. It is methodology-based rather than task-based. And crucially, it generates the rationale for maintenance tasks — the 'why' behind what the PM program actually does.
Many PM programs were built historically — tasks added over time without systematic review. The result is often over-maintenance: significant time and cost spent on activities that deliver minimal reliability benefit. A rotating equipment bearing PM that was added after a failure 10 years ago may now be running at a frequency that bears no relationship to the actual failure characteristics of the bearing. Reliability engineering reviews what maintenance is actually necessary and why — eliminating waste while maintaining or improving reliability outcomes.
Conversely, without reliability analysis, critical failure modes may not be addressed by any PM task. The program looks comprehensive but has gaps where it matters most. This is particularly common for failure modes that are not visible to the human senses — early-stage bearing degradation, seal face wear, impeller erosion — where condition monitoring is the appropriate strategy but is not part of the PM program because nobody formally analysed what the failure mode required.
Time-based PM is not always the right strategy. For failure modes that don't follow a wear-out pattern — that are random or condition-dependent — time-based replacement provides no reliability benefit and wastes the remaining useful life of the component. Condition-based monitoring is more effective for these failure modes. For some non-critical components, run-to-failure is the economically correct strategy. RCM methodology selects the right maintenance strategy for each failure mode. A PM program built without this analysis applies one strategy uniformly — which means it is almost certainly wrong for a significant proportion of what it covers.
An effective maintenance program combines both disciplines. They are not alternatives — they are layers of a coherent system.
For most WA industrial operations looking to improve, the starting point is not a full RCM study — it is a pragmatic assessment of the current maintenance program and the failures driving the most cost. A focused analysis of your top ten reactive events from the past 12 months typically identifies the failure modes causing the most disruption, and provides enough information to determine whether those failure modes are currently addressed by any PM task, and whether the current PM frequency is appropriate.
This focused approach — applying reliability engineering principles to the specific failures that are hurting you most — delivers measurable improvement significantly faster than a comprehensive RCM study. It also builds organisational capability and understanding that makes a broader reliability program easier to implement subsequently.
The objective is not methodological purity. It is operational improvement. The discipline of reliability engineering provides the tools — but the outcome is equipment that runs, costs that are controlled, and a maintenance team that understands why they're doing what they do.
Preventive maintenance without reliability engineering is activity without strategy. Reliability engineering without effective PM execution is analysis without results. Both are necessary — and the combination, applied consistently, delivers maintenance outcomes that neither can achieve alone.
Our engineers can evaluate your current PM program and identify the highest-value reliability improvements for your operation.
