Time-Based Maintenance (TBM) has long been a fundamental approach in equipment maintenance across many industries. However, when maintenance intervals are adjusted based solely on individual judgment or isolated events, it introduces significant risks to long-term reliability.
In this article, I explain why simple cycle adjustments can be misleading, and why a broader perspective—incorporating historical data, operating conditions, and system-level thinking—is essential. I also share what distinguishes maintenance professionals who are truly trusted in the field.
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The Problem with Simplistic TBM Changes
Consider a gearbox managed under a 4-year TBM cycle. Preventive maintenance—such as oil replacement or gear inspection—is scheduled every four years, and historically, this has worked without major issues.
Then, unexpectedly, the equipment fails in the third year.
A common reaction is:
“Since it failed in year 3, let’s change TBM from 4 years to 3 years.”
At first glance, this seems reasonable. In reality, this kind of linear thinking is one of the most common—and most problematic—patterns in maintenance decision-making.
What’s Missing in TBM Adjustments
1. Ignoring Historical Context
A failure at year 3 means very different things depending on the equipment’s lifecycle:
- Failure after 3 years from installation → possible early failure
- Failure after 23 years → likely a specific degradation mechanism
- Failure after 43 years → probable end-of-life
Without understanding the full history, changing the interval is just guesswork. Reliable maintenance always starts with historical analysis.
2. No Benchmark Against Similar Equipment
Is 4-year TBM really standard across similar gearboxes?
In many plants, you’ll find variations—some at 1 year, others at 5 years. The issue is that the rationale behind these intervals is often undocumented.
Without comparing similar assets and understanding why differences exist, any adjustment lacks a solid foundation.
3. Overlooking Operating Conditions
Maintenance engineers often focus only on equipment, while operators focus only on operation. Rarely do both perspectives merge.
Yet operating conditions directly affect equipment life. For example:
- First 20 years: 50 rpm operation (Product A)
- After year 21: 100 rpm operation (Product B)
If failure occurs after the operating change, the cause is likely not “time,” but “conditions.”
Adjusting TBM without considering this is fundamentally flawed.
4. Lack of System-Level Perspective
Equipment does not operate in isolation—it is part of a process system.
For example, if the gearbox is used in a process handling:
- High temperature (120°C)
- Strong acids
Then other equipment in the same system—pumps, seals, piping—are exposed to the same stresses.
Focusing only on the gearbox misses the bigger picture. In such cases, maintenance strategies should be reviewed at the system level, not just for a single asset.
Why Multi-Perspective Thinking Matters
A proper TBM review should integrate:
- Historical performance
- Cross-equipment comparison
- Operating conditions
- System-wide impact
Without this, TBM becomes reactive and inconsistent, heavily dependent on individual experience rather than engineering logic.
Conclusion
Adjusting TBM intervals is not simply about changing numbers—it is about understanding the underlying reasons behind equipment behavior.
Short-term, experience-based decisions may seem practical, but they often degrade long-term reliability.
Maintenance professionals who can think across multiple perspectives—history, operation, and system—are the ones who truly add value.
Developing this mindset is what separates a routine maintenance engineer from a trusted expert.
About the Author – NEONEEET
A user‑side chemical plant engineer with 20+ years of end‑to‑end experience across design → production → maintenance → corporate planning. Sharing practical, experience‑based knowledge from real batch‑plant operations. → View full profile
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