This is a complete sample module, given away in full. Use it, teach it, adapt it. It is the first unit of a predictive maintenance program, and it exists here so you can judge the quality of the work before any conversation about the rest.
In this module
Why this module comes first
Most people arrive at predictive maintenance believing it means better sensors. It doesn't. Predictive maintenance is a bet on time. You detect a developing fault early enough to act before the equipment fails, and everything downstream follows from understanding how a particular machine actually fails.
Get that wrong and the rest of the program becomes button-pushing: readings collected on a route, alarms nobody trusts, and a dashboard open on a monitor that no one looks at. This module is the conceptual keystone. Teach it properly and the technique modules land. Skip it and they don't.
On completion, a participant can
- Distinguish reactive, preventive, predictive and proactive maintenance, and say when each is the economically correct choice
- Read and construct a P-F curve, and explain why the P-F interval determines monitoring frequency
- Identify the dominant failure modes in rotating equipment and their early symptoms
- Map a given failure mode to the condition-monitoring technique most likely to catch it early
The four maintenance strategies
Every maintenance decision is a choice among four postures. None is universally right; the skill is knowing which the asset deserves.
| Strategy | What it means | When it's correct |
|---|---|---|
| Reactive | Run the asset until it fails, then repair. | Cheap, non-critical, redundant assets where failure costs less than monitoring. |
| Preventive | Service on a fixed calendar or runtime schedule. | Known wear-out patterns, regulatory requirements, low-cost interventions. |
| Predictive | Monitor condition, act when evidence of a developing fault appears. | Critical assets with a detectable, gradual failure path. |
| Proactive | Eliminate the root cause so the failure mode stops recurring. | Repeat failures where the underlying cause is fixable: alignment, lubrication, design. |
Teaching point
Participants often assume predictive is always superior. It isn't. Monitoring a $200 pump with a spare on the shelf is a waste of a route stop. Criticality drives the choice.
The P-F curve
Equipment rarely fails instantly. Condition degrades over a period, and somewhere along that decline the fault becomes detectable. That is point P. Later, the asset can no longer do its job. That is point F, functional failure. The time between them is the P-F interval, and it is the single most useful number in the discipline.
The rule that follows
Monitoring frequency
To catch a fault reliably, you must inspect more than once within the P-F interval. The common working rule is to monitor at roughly half the interval or less.
A bearing fault with a 30-day detectable window inspected quarterly will be found by the breakdown, not by the route.
This is where most programs quietly fail. The technique is fine, the sensor is fine, and the inspection frequency was set by tradition rather than by the interval.
Common failure modes and their early signs
| Failure mode | Earliest reliable signal | Technique that sees it first |
|---|---|---|
| Bearing degradation | High-frequency energy well before audible noise | Vibration; ultrasonic |
| Misalignment | Characteristic axial vibration pattern | Vibration |
| Imbalance | Elevated vibration at running speed | Vibration |
| Lubrication failure | Wear particles and contamination in the oil | Oil analysis |
| Electrical connection fault | Localised heat rise under load | Thermography |
| Compressed air / steam leak | Ultrasonic emission at the leak point | Ultrasonic |
| Motor winding / rotor fault | Sidebands in the current signature | Motor current analysis |
Teaching point
The right-hand column previews the rest of the program. Each technique exists because it sees something the others miss. That is the argument for a mixed program rather than buying one tool.
Lab exercise: "Diagnose the interval"
Participants work in pairs. For each scenario: name the likely failure mode, estimate where it sits on the P-F curve, choose a monitoring technique, and set an inspection frequency. Allow 35 minutes, then debrief as a group.
- Pairs
- 35 minutes
- Group debrief
1Process pump
A centrifugal pump on a critical line has been rebuilt twice in eighteen months, each time for bearing failure. Nothing else has changed.
2Motor and gearbox
A gearbox coupled to a 75 hp motor runs slightly warmer than its neighbours. Output is unchanged and there is no unusual noise.
3Conveyor drive
A packaging line conveyor has begun tripping its overload intermittently, roughly once a week, always in the afternoon.
4Air compressor
The plant's compressed air system now runs a duty cycle nearly 20% higher than a year ago. Production volume is flat.
5Exhaust fan
A rooftop exhaust fan, non-redundant but not process-critical, has a replacement cost of about $1,800 installed and a two-day lead time.
6Switchgear
A distribution panel serving three production cells has never been inspected beyond visual checks. It is fifteen years old.
Debrief: the point of the exercise
Several scenarios have more than one defensible answer, and that is deliberate. Scenario 5 is the trap: the correct answer is usually no monitoring at all. A cheap, quickly replaced, non-critical asset does not earn a route stop. Participants who monitor everything have missed the economics. Scenario 4 is a system-level symptom rather than a single failing machine, and rewards anyone who reasons about the whole air system rather than one compressor. The exercise teaches judgment, not lookup.
Assessment
Ten multiple-choice items plus one short-answer question. The short-answer item is the one that matters:
Short answer
A bearing on a critical pump has a P-F interval of approximately 30 days. Your current route inspects this asset quarterly. Explain what is wrong with the present arrangement and what you would change, including your reasoning about frequency.
Expected response
Quarterly inspection is roughly a 90-day cycle against a 30-day detectable window, so the fault will almost always progress to failure between inspections. The monitoring provides no useful warning and the cost of the route is wasted. Frequency must fall inside the interval, conventionally at half or less, so a fortnightly or monthly check is defensible. A stronger answer also raises continuous monitoring if the asset's criticality justifies the sensor cost.
Instructor notes
- Timing
- Roughly 40 minutes lecture, 35 minutes lab, 25 minutes debrief, 20 minutes assessment and review, with the balance for questions.
- Common misconceptions to correct
- That predictive maintenance is always the best strategy; that the P-F interval is a fixed property of a machine rather than of the failure mode and technique used; and that more sensors means more warning, when sensors nobody responds to produce no warning at all.
- The one thing to land
- If participants leave with only one idea, it should be that inspection frequency must be set by the P-F interval, not by tradition or convenience. Nearly every disappointing predictive maintenance program in the field can be traced back to that single error.
- Adapting the length
- For a two-hour block, drop scenarios 3 and 6 and shorten the debrief. For a full-day session, add a plant walk in which participants rank ten real assets by criticality before the lab.
Use this freely.
This module is yours to teach, copy and adapt. No registration, no follow-up sequence, no salesperson. If it's useful, the full PM-01 course runs six modules and can be licensed for your program, or taught.
Virdi Technical Services LLC DBA Pamisva. pamisva.com. info@pamisva.com. (262) 320-7143. Free to teach, copy, and adapt.