How should a plant choose between vibration, ultrasound and oil analysis?
No condition monitoring technology detects every failure. Choose a method only after identifying the asset function, credible failure modes, detectable symptoms and consequence of failure. Vibration, ultrasound and lubricant analysis often complement one another because they observe different physical effects.
Match the measurement to the mechanism
- Vibration analysis: useful for many rotating machine problems such as unbalance, misalignment, looseness and certain bearing or gear defects. Machine speed, sensor placement and operating load affect interpretation.
- Ultrasound: useful for acoustic signatures from some developing bearing conditions, compressed air leaks and certain electrical defects, subject to instrument capability and approved safety practices.
- Oil analysis: useful for lubricant condition, contamination and wear debris in lubricated machinery. Sampling location, cleanliness and consistent operating conditions strongly affect results.
These are applications, not guarantees. A failure mode that develops too quickly or produces no detectable precursor may require a protective function, design change or different maintenance strategy instead.
Use the P-F interval correctly
Point P is potential failure, when a developing defect first becomes detectable by the selected method. Point F is functional failure, when the asset can no longer meet its required function. The interval between them is not a fixed number for every machine. Choose inspection frequency and response time with enough margin for detection, diagnosis, parts and repair, taking uncertainty and the consequence of missed detection into account.
Build a reliable baseline
Collect measurements when equipment is known to be healthy and under documented speed, load and process conditions. Record the instrument, sensor or sample point, technique and date. Trend comparable observations. A single high reading without operating context is not automatically a failure, and a low reading does not establish absence of every defect.
Example: critical gearbox
For a critical gearbox, vibration may identify changes in mesh or bearing behavior while oil analysis checks wear debris and contamination. If both trends deteriorate, the team can inspect operating context and develop a planned repair. If oil condition is poor but vibration remains stable, lubricant contamination control may be the immediate priority. The techniques provide different evidence.
Decide what action follows an alarm
Define who reviews findings, how duplicates are screened, what evidence is attached to the work request and when operations must be notified. Measure useful defects found and corrective actions completed, not simply the number of readings collected. The monitoring program succeeds when it changes maintenance decisions in time.
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Technical references
NASA Reliability Centered Maintenance Guide · NASA, RCM Implementation with Predictive Technologies · DOE O&M Best Practices