Oil Cleanliness and Dryness Target Advisor

Set an initial particle-cleanliness and dryness target with a transparent rule table, then reconcile it with equipment, lubricant, filtration, and sampling requirements.

Operating context

Optional 100%-saturation value for this oil at operating temperature.

Recommended initial targets

ISO 4406 cleanliness target

Rheologylab
—

≥4 / ≥6 / ≥14 µm(c)

Relative saturation—
Water target—

How to use
  1. Select the equipment profile for the most contamination-sensitive lubricated component.
  2. Choose failure criticality from the consequence of loss of function.
  3. Choose the contamination environment; use wet or dirty when recurring ingress is credible.
  4. Choose component sensitivity; reserve robust for justified, tolerant equipment.
  5. Optionally enter the oil’s 100%-saturation water concentration at operating temperature. Do not borrow a generic value from another oil or temperature.
  6. Select Calculate targets to update the ISO code, relative-saturation target, optional ppm value, and rule contributions.
  7. Select Reset to restore the worked example. Resolve any warning before interpreting the result.
  8. Reconcile the target with OEM limits, filtration and sampling capability, lubricant chemistry, temperature, and failure consequences. Do not use this screening model for regulated or safety-critical acceptance decisions.
Equations used

ISOtarget = ISOequipment + Δcriticality + Δenvironment + Δsensitivity

The integer shift is applied to all three ISO 4406 code numbers and clamped to the code range 0–28. Equipment baselines are servo hydraulic 16/14/11, general hydraulic 18/16/13, rolling bearing/circulating oil 17/15/12, industrial gearbox 18/16/13, and turbine/critical circulating oil 17/15/12. Criticality shifts: high −1, medium 0, low +1. Environment shifts: controlled 0, typical 0, wet/dirty −1. Sensitivity shifts: high −1, normal 0, robust +1. Lower codes mean cleaner oil; one code step is approximately a factor of two in the particle-count band.

RStarget = clamp(RSequipment + ΔRS, 20%, 60%)

Stle

Equipment dryness baselines in the same order are 30%, 40%, 40%, 45%, and 35% relative saturation. Criticality adjustments: −10, 0, +10 percentage points. Environment: +5, 0, −10. Sensitivity: −5, 0, +5.

water target (ppm) = saturation concentration (ppm) × RStarget / 100

Relative saturation has no sign. Saturation concentration must be positive and oil-specific at operating temperature. ppm is omitted when it is unknown because water solubility changes with oil chemistry, ageing, contamination, pressure, and temperature.

Assumptions, limits, and references

This disclosed rule table is a screening policy, not a limit prescribed by ISO 4406. It assumes representative sampling and steady operating conditions. Confirm targets against OEM requirements, clearances, filter capability, laboratory method, supplier data, temperature, environment, and sampling location.

Do not use this advisor as a warranty, safety, aviation, medical, nuclear, fire-resistant-fluid, or regulatory acceptance limit.

References: ISO 4406:2021 for the cleanliness-code convention and industry workflow background.