Oil Analysis for Centrifugal Compressors

Sampling intervals for centrifugal compressors depend on criticality and operating severity. Most programs sample critical equipment monthly and non-critical equipment quarterly. Newly commissioned or recently repaired centrifugal compressors should be sampled more frequently during the first few operating cycles to confirm break-in conditions are normal.

The core test slate for centrifugal compressors includes spectrometric wear metal analysis, particle count per ISO 4406, moisture content, viscosity at 40C, and acid number. Analytical ferrography should be added when screening tests indicate abnormal wear. Additional tests such as RPVOT for oxidation stability may be warranted depending on lubricant type and operating temperature.

A-criticality units (process-stopping or safety-critical) get the full Oil Analysis treatment at quarterly sampling on critical assets with detailed reports per asset. B-criticality units get screening at the same frequency but lighter reporting. C-criticality units get exception-based monitoring — a route check at lower frequency with full diagnostic only when something shifts. The split at most plants is 20% A, 50% B, 30% C of the Centrifugal Compressors population.

60-180 days, depending on which failure mode is developing. Early-stage signatures on Centrifugal Compressors appear well before functional failure: rising axial position, shaft vibration drift. Catching the fault early means scheduling the repair into a planned outage — usually 6 to 16 hours of planned downtime instead of 24 to 72 hours of unplanned downtime when the asset fails on shift.