ISO 13357-2:2025

Overview

ISO 13357-2:2025 - "Petroleum products - Determination of the filterability of lubricating oils - Part 2: Procedure for dry oils" specifies a laboratory test method to evaluate the filterability of dry, mineral-based lubricating oils. The standard is intended primarily for hydraulic fluids up to ISO viscosity grade (VG) 100 (ISO 3448), and it can be extended to heavier oils (VG 150, 220, 320) using coarser membranes. The procedure quantifies how an oil passes through a membrane filter under controlled pressure and is used to predict potential filtration problems in service.

Key Topics and Requirements

• Scope: Applies to mineral oils in a dry state; not suitable for fluids that damage test membranes (e.g., some fire‑resistant fluids) or oils containing insoluble/partially soluble large additives (certain viscosity-index modifiers and friction modifiers).
• Test principle: Filter the oil through a specified membrane and record times/volumes; calculate filterability as percentage ratios reflecting flow-rate changes during filtration.
• Two-stage measurement:
  • Stage I - compares early mean flow to an initial theoretical rate to screen for gross plugging.
  • Stage II - compares initial flow rate to the flow rate near 200–300 ml; more sensitive to gels and fine silts and predictive of performance with fine (sub‑5 µm) filtration.
• Apparatus and consumables:
  • Stainless-steel lidded funnel assembly with an effective filtration area of approx. 1130 mm² ± 60 mm².
  • 47 mm mixed cellulose ester membranes: 0.8 µm mean pore size for oils ≤ VG 100; 3.0 µm for higher VG oils.
  • Measuring cylinder (250 ml, ISO 4788), compressed dry/filter gas (air or N2) with regulator (50–200 kPa), water (ISO 3696 grade 3), isopropyl alcohol and light aliphatic hydrocarbon wash solvent.
• Alternatives and precision: Annex B permits gravimetric techniques; Clause 12 updates precision, repeatability and reproducibility criteria.
• Test report: Specifies required test conditions and reporting elements.

Practical Applications and Users

• Who uses it: Test laboratories, lubricant manufacturers, hydraulic system designers, maintenance engineers, and quality assurance teams.
• Why use it:
  • Predict filter plugging risk and system wear due to particulate, gels or silts.
  • Compare lubricant batches and formulations for suitability with fine filtration systems.
  • Support specification, acceptance testing and troubleshooting of hydraulic and heavy‑duty lubrication systems (e.g., paper machines, rolling mills).

Related Standards

• ISO 13357-1 - Filterability: effects of water and temperature (complements Part 2 for wet conditions)
• ISO 3448 - ISO viscosity classification
• ISO 3170 - Manual sampling of petroleum liquids
• ISO 3696 - Water for analytical laboratory use
• ISO 4788 - Laboratory graduated measuring cylinders

Keywords: ISO 13357-2:2025, filterability test, lubricating oils, hydraulic fluids, membrane filtration, VG 100, Stage I filterability, Stage II filterability, gravimetric measurement.