Oil Analysis for Hydraulic Systems

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

The core test slate for hydraulic systems 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.

Baseline is quarterly sampling on critical assets. Adjust based on duty cycle: assets running near rated capacity 24/7 get tighter intervals; intermittent-duty units can stretch the interval by 50 percent. The general rule for Industrial Hydraulic Systems specifically is that PdM cadence should be no more than half the dominant failure mode's P-F interval. For most Industrial Hydraulic Systems populations that lands at monthly fluid sampling and quarterly cleanliness check.

The Industrial Hydraulic Systems failure population is dominated by contamination-driven valve wear, pump degradation, seal failures. Each leaves a different signature: cycle time creep, particle count rise, pump amp drift. Oil Analysis captures these via ICP wear metals, viscosity at 40°C and 100°C, ISO 4406 cleanliness, FTIR oxidation and trends them over the quarterly sampling on critical assets schedule. Early-stage indicators appear before functional failure — the lead time runs 60-180 days on most modes.