Oil Analysis for Variable Speed Drives

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

The core test slate for variable speed drives 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.

Yes. Oil Analysis measurements use ICP wear metals, viscosity at 40°C and 100°C, ISO 4406 cleanliness, FTIR oxidation which capture at the bearing housing, terminal box, or sampling point without disrupting operation. The Variable Speed Drives stay online during the route. Only deep diagnostic work or repairs that follow from findings require taking the equipment offline.

Value rises with age. New Variable Speed Drives rarely show developing faults during the first 1,000 to 3,000 operating hours. The middle of the asset life (years 2-7 typically) is where Oil Analysis catches the most actionable findings. Late-life equipment — past the 10 to 15 years mark — shows higher fault frequency and benefits from tighter monitoring intervals than the program baseline.