Overview
EN ISO 23581:2024 - "Petroleum products and related products - Determination of kinematic viscosity - Method by Stabinger type viscometer" - is a CEN-endorsed ISO standard that describes how to determine kinematic viscosity (ν) for transparent and opaque liquid petroleum products and crude oils. The method calculates kinematic viscosity from measured dynamic viscosity (η) and density (ρ) using a Stabinger-type viscometer. The procedure is primarily intended for liquids with Newtonian flow behaviour (shear stress proportional to shear rate) and includes updated scope covering base oils, formulated oils, jet fuels and residual fuel oils.
Key topics and requirements
- Method principle: kinematic viscosity derived from dynamic viscosity and density measured by a Stabinger-type viscometer.
- Applicability: transparent and opaque petroleum liquids and crude oils; predominantly Newtonian fluids. Results for non-Newtonian fluids are comparable only at similar shear rates.
- Calibration and verification: instrument calibration, verification procedures and traceability requirements are specified.
- Apparatus and preparation: detailed description of the viscometer, sample handling tools, automatic sample changers and cleaning methods.
- Sampling and sample handling: guidance on sampling, conditioning (including residual fuel oils), storage and pre-test conditioning.
- Measurement procedures: manual and automatic filling, cleaning, and temperature scanning options for multi-temperature determinations.
- Calculations and reporting: formulas for kinematic viscosity, dynamic viscosity, density extrapolation, viscosity index and standardized expression of results.
- Precision and bias: repeatability (r), reproducibility (R) and interlaboratory study findings for the test materials and ranges reported in Clause 13; note that precision has been determined only for the listed materials and conditions.
- Safety: users must follow appropriate safety measures for hazardous materials and equipment.
Practical applications
- Quality control and acceptance testing in petroleum refining, fuel distribution and lubricants manufacturing.
- Routine laboratory viscosity testing for crude oils, base oils, finished fuels and industrial lubricants.
- Research and development where accurate viscosity vs. temperature profiles are required.
- Regulatory or commercial testing where harmonized, traceable viscosity data are needed.
Who should use this standard
- Petroleum and petrochemical laboratory managers
- QC/QA teams in fuel and lubricant production
- Test laboratories and third-party certifiers
- Equipment manufacturers and calibration service providers
- Standards and regulatory bodies
Related standards
- ISO 23581:2024 (base text)
- Cross-references and comparisons with other viscosity methods (e.g., ASTM D7042, ASTM D445) are addressed in the standard’s precision and bias sections.
Keywords: EN ISO 23581:2024, kinematic viscosity, Stabinger type viscometer, dynamic viscosity, density, petroleum products, Newtonian flow, viscosity measurement, crude oil viscosity.